1 <!doctype linuxdoc system>
4 <title>ca65 Users Guide
5 <author>Ullrich von Bassewitz, <htmlurl url="mailto:uz@cc65.org" name="uz@cc65.org">
6 <date>2000-07-19, 2000-11-29, 2001-10-02, 2005-09-08
9 ca65 is a powerful macro assembler for the 6502, 65C02 and 65816 CPUs. It is
10 used as a companion assembler for the cc65 crosscompiler, but it may also be
11 used as a standalone product.
14 <!-- Table of contents -->
17 <!-- Begin the document -->
21 ca65 is a replacement for the ra65 assembler that was part of the cc65 C
22 compiler, originally developed by John R. Dunning. I had some problems with
23 ra65 and the copyright does not permit some things which I wanted to be
24 possible, so I decided to write a completely new assembler/linker/archiver
25 suite for the cc65 compiler. ca65 is part of this suite.
27 Some parts of the assembler (code generation and some routines for symbol
28 table handling) are taken from an older crossassembler named a816 written
29 by me a long time ago.
32 <sect1>Design criteria<p>
34 Here's a list of the design criteria, that I considered important for the
39 <item> The assembler must support macros. Macros are not essential, but they
40 make some things easier, especially when you use the assembler in the
41 backend of a compiler.
42 <item> The assembler must support the newer 65C02 and 65816 CPUs. I have been
43 thinking about a 65816 backend for the C compiler, and even my old
44 a816 assembler had support for these CPUs, so this wasn't really a
46 <item> The assembler must produce relocatable code. This is necessary for the
47 compiler support, and it is more convenient.
48 <item> Conditional assembly must be supported. This is a must for bigger
49 projects written in assembler (like Elite128).
50 <item> The assembler must support segments, and it must support more than
51 three segments (this is the count, most other assemblers support).
52 Having more than one code segments helps developing code for systems
53 with a divided ROM area (like the C64).
54 <item> The linker must be able to resolve arbitrary expressions. It should
55 be able to get things like
62 <item> True lexical nesting for symbols. This is very convenient for larger
64 <item> "Cheap" local symbols without lexical nesting for those quick, late
66 <item> I liked the idea of "options" as Anre Fachats .o65 format has it, so I
67 introduced the concept into the object file format use by the new cc65
69 <item> The assembler will be a one pass assembler. There was no real need for
70 this decision, but I've written several multipass assemblers, and it
71 started to get boring. A one pass assembler needs much more elaborated
72 data structures, and because of that it's much more fun:-)
73 <item> Non-GPLed code that may be used in any project without restrictions or
74 fear of "GPL infecting" other code.
82 <sect1>Command line option overview<p>
84 The assembler accepts the following options:
87 ---------------------------------------------------------------------------
88 Usage: ca65 [options] file
90 -D name[=value] Define a symbol
91 -I dir Set an include directory search path
92 -U Mark unresolved symbols as import
93 -V Print the assembler version
94 -W n Set warning level n
95 -g Add debug info to object file
97 -i Ignore case of symbols
98 -l name Create a listing file if assembly was ok
99 -mm model Set the memory model
100 -o name Name the output file
102 -t sys Set the target system
103 -v Increase verbosity
106 --auto-import Mark unresolved symbols as import
107 --bin-include-dir dir Set a search path for binary includes
108 --cpu type Set cpu type
109 --create-dep name Create a make dependency file
110 --create-full-dep name Create a full make dependency file
111 --debug-info Add debug info to object file
112 --feature name Set an emulation feature
113 --forget-inc-paths Forget include search paths
114 --help Help (this text)
115 --ignore-case Ignore case of symbols
116 --include-dir dir Set an include directory search path
117 --listing name Create a listing file if assembly was ok
118 --list-bytes n Maximum number of bytes per listing line
119 --macpack-dir dir Set a macro package directory
120 --memory-model model Set the memory model
121 --pagelength n Set the page length for the listing
122 --smart Enable smart mode
123 --target sys Set the target system
124 --verbose Increase verbosity
125 --version Print the assembler version
126 ---------------------------------------------------------------------------
130 <sect1>Command line options in detail<p>
132 Here is a description of all the command line options:
136 <label id="option--bin-include-dir">
137 <tag><tt>--bin-include-dir dir</tt></tag>
139 Name a directory which is searched for binary include files. The option
140 may be used more than once to specify more than one directory to search. The
141 current directory is always searched first before considering any
142 additional directories. See also the section about <ref id="search-paths"
143 name="search paths">.
146 <label id="option--cpu">
147 <tag><tt>--cpu type</tt></tag>
149 Set the default for the CPU type. The option takes a parameter, which
152 6502, 65SC02, 65C02, 65816, sunplus, sweet16, HuC6280
154 The sunplus cpu is not available in the freeware version, because the
155 instruction set is "proprietary and confidential".
158 <label id="option-create-dep">
159 <tag><tt>--create-dep name</tt></tag>
161 Tells the assembler to generate a file containing the dependency list for
162 the assembled module in makefile syntax. The output is written to a file
163 with the given name. The output does not include files passed via debug
164 information to the assembler.
167 <label id="option-create-full-dep">
168 <tag><tt>--create-full-dep name</tt></tag>
170 Tells the assembler to generate a file containing the dependency list for
171 the assembled module in makefile syntax. The output is written to a file
172 with the given name. The output does include files passed via debug
173 information to the assembler.
176 <label id="option--feature">
177 <tag><tt>--feature name</tt></tag>
179 Enable an emulation feature. This is identical as using <tt/.FEATURE/
180 in the source with two exceptions: Feature names must be lower case, and
181 each feature must be specified by using an extra <tt/--feature/ option,
182 comma separated lists are not allowed.
184 See the discussion of the <tt><ref id=".FEATURE" name=".FEATURE"></tt>
185 command for a list of emulation features.
188 <label id="option--forget-inc-paths">
189 <tag><tt>--forget-inc-paths</tt></tag>
191 Forget the builtin include paths. This is most useful when building
192 customized assembler modules, in which case the standard header files should
196 <label id="option-g">
197 <tag><tt>-g, --debug-info</tt></tag>
199 When this option (or the equivalent control command <tt/.DEBUGINFO/) is
200 used, the assembler will add a section to the object file that contains
201 all symbols (including local ones) together with the symbol values and
202 source file positions. The linker will put these additional symbols into
203 the VICE label file, so even local symbols can be seen in the VICE
207 <label id="option-h">
208 <tag><tt>-h, --help</tt></tag>
210 Print the short option summary shown above.
213 <label id="option-i">
214 <tag><tt>-i, --ignore-case</tt></tag>
216 This option makes the assembler case insensitive on identifiers and labels.
217 This option will override the default, but may itself be overridden by the
218 <tt><ref id=".CASE" name=".CASE"></tt> control command.
221 <label id="option-l">
222 <tag><tt>-l name, --listing name</tt></tag>
224 Generate an assembler listing with the given name. A listing file will
225 never be generated in case of assembly errors.
228 <label id="option--list-bytes">
229 <tag><tt>--list-bytes n</tt></tag>
231 Set the maximum number of bytes printed in the listing for one line of
232 input. See the <tt><ref id=".LISTBYTES" name=".LISTBYTES"></tt> directive
233 for more information. The value zero can be used to encode an unlimited
234 number of printed bytes.
237 <label id="option--macpack-dir">
238 <tag><tt>--macpack-dir dir</tt></tag>
240 This options allows to specify a directory containing macro files that are
241 used instead of the builtin images when a <tt><ref id=".MACPACK"
242 name=".MACPACK"></tt> directive is encountered. If <tt>--macpack-dir</tt>
243 was specified, a <tt>.mac</tt> extension is added to the package name and
244 the resulting file is loaded from the given directory. This is most useful
245 when debugging the builtin macro packages.
248 <label id="option-mm">
249 <tag><tt>-mm model, --memory-model model</tt></tag>
251 Define the default memory model. Possible model specifiers are near, far and
255 <label id="option-o">
256 <tag><tt>-o name</tt></tag>
258 The default output name is the name of the input file with the extension
259 replaced by ".o". If you don't like that, you may give another name with
260 the -o option. The output file will be placed in the same directory as
261 the source file, or, if -o is given, the full path in this name is used.
264 <label id="option--pagelength">
265 <tag><tt>--pagelength n</tt></tag>
267 sets the length of a listing page in lines. See the <tt><ref
268 id=".PAGELENGTH" name=".PAGELENGTH"></tt> directive for more information.
271 <label id="option-s">
272 <tag><tt>-s, --smart-mode</tt></tag>
274 In smart mode (enabled by -s or the <tt><ref id=".SMART" name=".SMART"></tt>
275 pseudo instruction) the assembler will track usage of the <tt/REP/ and
276 <tt/SEP/ instructions in 65816 mode and update the operand sizes
277 accordingly. If the operand of such an instruction cannot be evaluated by
278 the assembler (for example, because the operand is an imported symbol), a
281 Beware: Since the assembler cannot trace the execution flow this may
282 lead to false results in some cases. If in doubt, use the .ixx and .axx
283 instructions to tell the assembler about the current settings. Smart
284 mode is off by default.
287 <label id="option-t">
288 <tag><tt>-t sys, --target sys</tt></tag>
290 Set the target system. This will enable translation of character strings and
291 character constants into the character set of the target platform. The
292 default for the target system is "none", which means that no translation
293 will take place. The assembler supports the same target systems as the
294 compiler, see there for a list.
296 Depending on the target, the default CPU type is also set. This can be
297 overriden by using the <tt/<ref id="option--cpu" name="--cpu">/ option.
300 <label id="option-v">
301 <tag><tt>-v, --verbose</tt></tag>
303 Increase the assembler verbosity. Usually only needed for debugging
304 purposes. You may use this option more than one time for even more
308 <label id="option-D">
309 <tag><tt>-D</tt></tag>
311 This option allows you to define symbols on the command line. Without a
312 value, the symbol is defined with the value zero. When giving a value,
313 you may use the '$' prefix for hexadecimal symbols. Please note
314 that for some operating systems, '$' has a special meaning, so
315 you may have to quote the expression.
318 <label id="option-I">
319 <tag><tt>-I dir, --include-dir dir</tt></tag>
321 Name a directory which is searched for include files. The option may be
322 used more than once to specify more than one directory to search. The
323 current directory is always searched first before considering any
324 additional directories. See also the section about <ref id="search-paths"
325 name="search paths">.
328 <label id="option-U">
329 <tag><tt>-U, --auto-import</tt></tag>
331 Mark symbols that are not defined in the sources as imported symbols. This
332 should be used with care since it delays error messages about typos and such
333 until the linker is run. The compiler uses the equivalent of this switch
334 (<tt><ref id=".AUTOIMPORT" name=".AUTOIMPORT"></tt>) to enable auto imported
335 symbols for the runtime library. However, the compiler is supposed to
336 generate code that runs through the assembler without problems, something
337 which is not always true for assembler programmers.
340 <label id="option-V">
341 <tag><tt>-V, --version</tt></tag>
343 Print the version number of the assembler. If you send any suggestions
344 or bugfixes, please include the version number.
347 <label id="option-W">
348 <tag><tt>-Wn</tt></tag>
350 Set the warning level for the assembler. Using -W2 the assembler will
351 even warn about such things like unused imported symbols. The default
352 warning level is 1, and it would probably be silly to set it to
360 <sect>Search paths<label id="search-paths"><p>
362 Normal include files are searched in the following places:
365 <item>The current directory.
366 <item>A compiled-in directory, which is often <tt>/usr/lib/cc65/asminc</tt>
368 <item>The value of the environment variable <tt/CA65_INC/ if it is defined.
369 <item>A subdirectory named <tt/asminc/ of the directory defined in the
370 environment variable <tt/CC65_HOME/, if it is defined.
371 <item>Any directory added with the <tt/<ref id="option-I" name="-I">/ option
375 Binary include files are searched in the following places:
378 <item>The current directory.
379 <item>Any directory added with the <tt/<ref id="option--bin-include-dir"
380 name="--bin-include-dir">/ option on the command line.
385 <sect>Input format<p>
387 <sect1>Assembler syntax<p>
389 The assembler accepts the standard 6502/65816 assembler syntax. One line may
390 contain a label (which is identified by a colon), and, in addition to the
391 label, an assembler mnemonic, a macro, or a control command (see section <ref
392 id="control-commands" name="Control Commands"> for supported control
393 commands). Alternatively, the line may contain a symbol definition using
394 the '=' token. Everything after a semicolon is handled as a comment (that is,
397 Here are some examples for valid input lines:
400 Label: ; A label and a comment
401 lda #$20 ; A 6502 instruction plus comment
402 L1: ldx #$20 ; Same with label
403 L2: .byte "Hello world" ; Label plus control command
404 mymac $20 ; Macro expansion
405 MySym = 3*L1 ; Symbol definition
406 MaSym = Label ; Another symbol
409 The assembler accepts
412 <item>all valid 6502 mnemonics when in 6502 mode (the default or after the
413 <tt><ref id=".P02" name=".P02"></tt> command was given).
414 <item>all valid 6502 mnemonics plus a set of illegal instructions when in
415 <ref id="6502X-mode" name="6502X mode">.
416 <item>all valid 65SC02 mnemonics when in 65SC02 mode (after the
417 <tt><ref id=".PSC02" name=".PSC02"></tt> command was given).
418 <item>all valid 65C02 mnemonics when in 65C02 mode (after the
419 <tt><ref id=".PC02" name=".PC02"></tt> command was given).
420 <item>all valid 65618 mnemonics when in 65816 mode (after the
421 <tt><ref id=".P816" name=".P816"></tt> command was given).
422 <item>all valid SunPlus mnemonics when in SunPlus mode (after the
423 <tt><ref id=".SUNPLUS" name=".SUNPLUS"></tt> command was given).
429 In 65816 mode several aliases are accepted in addition to the official
433 BGE is an alias for BCS
434 BLT is an alias for BCC
435 CPA is an alias for CMP
436 DEA is an alias for DEC A
437 INA is an alias for INC A
438 SWA is an alias for XBA
439 TAD is an alias for TCD
440 TAS is an alias for TCS
441 TDA is an alias for TDC
442 TSA is an alias for TSC
447 <sect1>6502X mode<label id="6502X-mode"><p>
449 6502X mode is an extension to the normal 6502 mode. In this mode, several
450 mnemonics for illegal instructions of the NMOS 6502 CPUs are accepted. Since
451 these instructions are illegal, there are no official mnemonics for them. The
452 unofficial ones are taken from <htmlurl
453 url="http://oxyron.net/graham/opcodes02.html"
454 name="http://oxyron.net/graham/opcodes02.html">. Please note that only the
455 ones marked as "stable" are supported. The following table uses information
456 from the mentioned web page, for more information, see there.
459 <item><tt>ALR: A:=(A and #{imm})*2;</tt>
460 <item><tt>ANC: A:=A and #{imm};</tt> Generates opcode $0B.
461 <item><tt>ARR: A:=(A and #{imm})/2;</tt>
462 <item><tt>AXS: X:=A and X-#{imm};</tt>
463 <item><tt>DCP: {adr}:={adr}-1; A-{adr};</tt>
464 <item><tt>ISC: {adr}:={adr}+1; A:=A-{adr};</tt>
465 <item><tt>LAS: A,X,S:={adr} and S;</tt>
466 <item><tt>LAX: A,X:={adr};</tt>
467 <item><tt>RLA: {adr}:={adr}rol; A:=A and {adr};</tt>
468 <item><tt>RRA: {adr}:={adr}ror; A:=A adc {adr};</tt>
469 <item><tt>SAX: {adr}:=A and X;</tt>
470 <item><tt>SLO: {adr}:={adr}*2; A:=A or {adr};</tt>
471 <item><tt>SRE: {adr}:={adr}/2; A:=A xor {adr};</tt>
476 <sect1>sweet16 mode<label id="sweet16-mode"><p>
478 SWEET 16 is an interpreter for a pseudo 16 bit CPU written by Steve Wozniak
479 for the Apple ][ machines. It is available in the Apple ][ ROM. ca65 can
480 generate code for this pseudo CPU when switched into sweet16 mode. The
481 following is special in sweet16 mode:
485 <item>The '@' character denotes indirect addressing and is no longer available
486 for cheap local labels. If you need cheap local labels, you will have to
487 switch to another lead character using the <tt/<ref id=".LOCALCHAR"
488 name=".LOCALCHAR">/ command.
490 <item>Registers are specified using <tt/R0/ .. <tt/R15/. In sweet16 mode,
491 these identifiers are reserved words.
495 Please note that the assembler does neither supply the interpreter needed for
496 SWEET 16 code, nor the zero page locations needed for the SWEET 16 registers,
497 nor does it call the interpreter. All this must be done by your program. Apple
498 ][ programmers do probably know how to use sweet16 mode.
500 For more information about SWEET 16, see
501 <htmlurl url="http://www.6502.org/source/interpreters/sweet16.htm"
502 name="http://www.6502.org/source/interpreters/sweet16.htm">.
505 <sect1>Number format<p>
507 For literal values, the assembler accepts the widely used number formats: A
508 preceding '$' or a trailing 'h' denotes a hex value, a preceding '%'
509 denotes a binary value, and a bare number is interpreted as a decimal. There
510 are currently no octal values and no floats.
513 <sect1>Conditional assembly<p>
515 Please note that when using the conditional directives (<tt/.IF/ and friends),
516 the input must consist of valid assembler tokens, even in <tt/.IF/ branches
517 that are not assembled. The reason for this behaviour is that the assembler
518 must still be able to detect the ending tokens (like <tt/.ENDIF/), so
519 conversion of the input stream into tokens still takes place. As a consequence
520 conditional assembly directives may <bf/not/ be used to prevent normal text
521 (used as a comment or similar) from being assembled. <p>
527 <sect1>Expression evaluation<p>
529 All expressions are evaluated with (at least) 32 bit precision. An
530 expression may contain constant values and any combination of internal and
531 external symbols. Expressions that cannot be evaluated at assembly time
532 are stored inside the object file for evaluation by the linker.
533 Expressions referencing imported symbols must always be evaluated by the
537 <sect1>Size of an expression result<p>
539 Sometimes, the assembler must know about the size of the value that is the
540 result of an expression. This is usually the case, if a decision has to be
541 made, to generate a zero page or an absolute memory references. In this
542 case, the assembler has to make some assumptions about the result of an
546 <item> If the result of an expression is constant, the actual value is
547 checked to see if it's a byte sized expression or not.
548 <item> If the expression is explicitly casted to a byte sized expression by
549 one of the '>', '<' or '^' operators, it is a byte expression.
550 <item> If this is not the case, and the expression contains a symbol,
551 explicitly declared as zero page symbol (by one of the .importzp or
552 .exportzp instructions), then the whole expression is assumed to be
554 <item> If the expression contains symbols that are not defined, and these
555 symbols are local symbols, the enclosing scopes are searched for a
556 symbol with the same name. If one exists and this symbol is defined,
557 it's attributes are used to determine the result size.
558 <item> In all other cases the expression is assumed to be word sized.
561 Note: If the assembler is not able to evaluate the expression at assembly
562 time, the linker will evaluate it and check for range errors as soon as
566 <sect1>Boolean expressions<p>
568 In the context of a boolean expression, any non zero value is evaluated as
569 true, any other value to false. The result of a boolean expression is 1 if
570 it's true, and zero if it's false. There are boolean operators with extreme
571 low precedence with version 2.x (where x > 0). The <tt/.AND/ and <tt/.OR/
572 operators are shortcut operators. That is, if the result of the expression is
573 already known, after evaluating the left hand side, the right hand side is
577 <sect1>Constant expressions<p>
579 Sometimes an expression must evaluate to a constant without looking at any
580 further input. One such example is the <tt/<ref id=".IF" name=".IF">/ command
581 that decides if parts of the code are assembled or not. An expression used in
582 the <tt/.IF/ command cannot reference a symbol defined later, because the
583 decision about the <tt/.IF/ must be made at the point when it is read. If the
584 expression used in such a context contains only constant numerical values,
585 there is no problem. When unresolvable symbols are involved it may get harder
586 for the assembler to determine if the expression is actually constant, and it
587 is even possible to create expressions that aren't recognized as constant.
588 Simplifying the expressions will often help.
590 In cases where the result of the expression is not needed immediately, the
591 assembler will delay evaluation until all input is read, at which point all
592 symbols are known. So using arbitrary complex constant expressions is no
593 problem in most cases.
597 <sect1>Available operators<label id="operators"><p>
601 <bf/Operator/| <bf/Description/| <bf/Precedence/@<hline>
602 | Built-in string functions| 0@
604 | Built-in pseudo-variables| 1@
605 | Built-in pseudo-functions| 1@
606 +| Unary positive| 1@
607 -| Unary negative| 1@
609 .BITNOT| Unary bitwise not| 1@
611 .LOBYTE| Unary low-byte operator| 1@
613 .HIBYTE| Unary high-byte operator| 1@
615 .BANKBYTE| Unary bank-byte operator| 1@
617 *| Multiplication| 2@
619 .MOD| Modulo operator| 2@
621 .BITAND| Bitwise and| 2@
623 .BITXOR| Binary bitwise xor| 2@
625 .SHL| Shift-left operator| 2@
627 .SHR| Shift-right operator| 2@
629 +| Binary addition| 3@
630 -| Binary subtraction| 3@
632 .BITOR| Bitwise or| 3@
634 = | Compare operator (equal)| 4@
635 <>| Compare operator (not equal)| 4@
636 <| Compare operator (less)| 4@
637 >| Compare operator (greater)| 4@
638 <=| Compare operator (less or equal)| 4@
639 >=| Compare operator (greater or equal)| 4@
642 .AND| Boolean and| 5@
643 .XOR| Boolean xor| 5@
645 ||<newline>
649 .NOT| Boolean not| 7@<hline>
651 <caption>Available operators, sorted by precedence
654 To force a specific order of evaluation, parentheses may be used, as usual.
658 <sect>Symbols and labels<p>
660 A symbol or label is an identifier that starts with a letter and is followed
661 by letters and digits. Depending on some features enabled (see
662 <tt><ref id="at_in_identifiers" name="at_in_identifiers"></tt>,
663 <tt><ref id="dollar_in_identifiers" name="dollar_in_identifiers"></tt> and
664 <tt><ref id="leading_dot_in_identifiers" name="leading_dot_in_identifiers"></tt>)
665 other characters may be present. Use of identifiers consisting of a single
666 character will not work in all cases, because some of these identifiers are
667 reserved keywords (for example "A" is not a valid identifier for a label,
668 because it is the keyword for the accumulator).
670 The assembler allows you to use symbols instead of naked values to make
671 the source more readable. There are a lot of different ways to define and
672 use symbols and labels, giving a lot of flexibility.
674 <sect1>Numeric constants<p>
676 Numeric constants are defined using the equal sign or the label assignment
677 operator. After doing
683 may use the symbol "two" in every place where a number is expected, and it is
684 evaluated to the value 2 in this context. The label assignment operator causes
685 the same, but causes the symbol to be marked as a label, which may cause a
686 different handling in the debugger:
692 The right side can of course be an expression:
699 <sect1>Standard labels<p>
701 A label is defined by writing the name of the label at the start of the line
702 (before any instruction mnemonic, macro or pseudo directive), followed by a
703 colon. This will declare a symbol with the given name and the value of the
704 current program counter.
707 <sect1>Local labels and symbols<p>
709 Using the <tt><ref id=".PROC" name=".PROC"></tt> directive, it is possible to
710 create regions of code where the names of labels and symbols are local to this
711 region. They are not known outside of this region and cannot be accessed from
712 there. Such regions may be nested like PROCEDUREs in Pascal.
714 See the description of the <tt><ref id=".PROC" name=".PROC"></tt>
715 directive for more information.
718 <sect1>Cheap local labels<p>
720 Cheap local labels are defined like standard labels, but the name of the
721 label must begin with a special symbol (usually '@', but this can be
722 changed by the <tt><ref id=".LOCALCHAR" name=".LOCALCHAR"></tt>
725 Cheap local labels are visible only between two non cheap labels. As soon as a
726 standard symbol is encountered (this may also be a local symbol if inside a
727 region defined with the <tt><ref id=".PROC" name=".PROC"></tt> directive), the
728 cheap local symbol goes out of scope.
730 You may use cheap local labels as an easy way to reuse common label
731 names like "Loop". Here is an example:
734 Clear: lda #$00 ; Global label
736 @Loop: sta Mem,y ; Local label
740 Sub: ... ; New global label
741 bne @Loop ; ERROR: Unknown identifier!
744 <sect1>Unnamed labels<p>
746 If you really want to write messy code, there are also unnamed labels. These
747 labels do not have a name (you guessed that already, didn't you?). A colon is
748 used to mark the absence of the name.
750 Unnamed labels may be accessed by using the colon plus several minus or plus
751 characters as a label designator. Using the '-' characters will create a back
752 reference (use the n'th label backwards), using '+' will create a forward
753 reference (use the n'th label in forward direction). An example will help to
776 As you can see from the example, unnamed labels will make even short
777 sections of code hard to understand, because you have to count labels
778 to find branch targets (this is the reason why I for my part do
779 prefer the "cheap" local labels). Nevertheless, unnamed labels are
780 convenient in some situations, so it's your decision.
783 <sect1>Using macros to define labels and constants<p>
785 While there are drawbacks with this approach, it may be handy in some
786 situations. Using <tt><ref id=".DEFINE" name=".DEFINE"></tt>, it is
787 possible to define symbols or constants that may be used elsewhere. Since
788 the macro facility works on a very low level, there is no scoping. On the
789 other side, you may also define string constants this way (this is not
790 possible with the other symbol types).
796 .DEFINE version "SOS V2.3"
798 four = two * two ; Ok
801 .PROC ; Start local scope
802 two = 3 ; Will give "2 = 3" - invalid!
807 <sect1>Symbols and <tt>.DEBUGINFO</tt><p>
809 If <tt><ref id=".DEBUGINFO" name=".DEBUGINFO"></tt> is enabled (or <ref
810 id="option-g" name="-g"> is given on the command line), global, local and
811 cheap local labels are written to the object file and will be available in the
812 symbol file via the linker. Unnamed labels are not written to the object file,
813 because they don't have a name which would allow to access them.
817 <sect>Scopes<label id="scopes"><p>
819 ca65 implements several sorts of scopes for symbols.
821 <sect1>Global scope<p>
823 All (non cheap local) symbols that are declared outside of any nested scopes
827 <sect1>Cheap locals<p>
829 A special scope is the scope for cheap local symbols. It lasts from one non
830 local symbol to the next one, without any provisions made by the programmer.
831 All other scopes differ in usage but use the same concept internally.
834 <sect1>Generic nested scopes<p>
836 A nested scoped for generic use is started with <tt/<ref id=".SCOPE"
837 name=".SCOPE">/ and closed with <tt/<ref id=".ENDSCOPE" name=".ENDSCOPE">/.
838 The scope can have a name, in which case it is accessible from the outside by
839 using <ref id="scopesyntax" name="explicit scopes">. If the scope does not
840 have a name, all symbols created within the scope are local to the scope, and
841 aren't accessible from the outside.
843 A nested scope can access symbols from the local or from enclosing scopes by
844 name without using explicit scope names. In some cases there may be
845 ambiguities, for example if there is a reference to a local symbol that is not
846 yet defined, but a symbol with the same name exists in outer scopes:
858 In the example above, the <tt/lda/ instruction will load the value 3 into the
859 accumulator, because <tt/foo/ is redefined in the scope. However:
871 Here, <tt/lda/ will still load from <tt/$12,x/, but since it is unknown to the
872 assembler that <tt/foo/ is a zeropage symbol when translating the instruction,
873 absolute mode is used instead. In fact, the assembler will not use absolute
874 mode by default, but it will search through the enclosing scopes for a symbol
875 with the given name. If one is found, the address size of this symbol is used.
876 This may lead to errors:
888 In this case, when the assembler sees the symbol <tt/foo/ in the <tt/lda/
889 instruction, it will search for an already defined symbol <tt/foo/. It will
890 find <tt/foo/ in scope <tt/outer/, and a close look reveals that it is a
891 zeropage symbol. So the assembler will use zeropage addressing mode. If
892 <tt/foo/ is redefined later in scope <tt/inner/, the assembler tries to change
893 the address in the <tt/lda/ instruction already translated, but since the new
894 value needs absolute addressing mode, this fails, and an error message "Range
897 Of course the most simple solution for the problem is to move the definition
898 of <tt/foo/ in scope <tt/inner/ upwards, so it precedes its use. There may be
899 rare cases when this cannot be done. In these cases, you can use one of the
900 address size override operators:
912 This will cause the <tt/lda/ instruction to be translated using absolute
913 addressing mode, which means changing the symbol reference later does not
917 <sect1>Nested procedures<p>
919 A nested procedure is created by use of <tt/<ref id=".PROC" name=".PROC">/. It
920 differs from a <tt/<ref id=".SCOPE" name=".SCOPE">/ in that it must have a
921 name, and a it will introduce a symbol with this name in the enclosing scope.
930 is actually the same as
939 This is the reason why a procedure must have a name. If you want a scope
940 without a name, use <tt/<ref id=".SCOPE" name=".SCOPE">/.
942 <bf/Note:/ As you can see from the example above, scopes and symbols live in
943 different namespaces. There can be a symbol named <tt/foo/ and a scope named
944 <tt/foo/ without any conflicts (but see the section titled <ref
945 id="scopesearch" name=""Scope search order"">).
948 <sect1>Structs, unions and enums<p>
950 Structs, unions and enums are explained in a <ref id="structs" name="separate
951 section">, I do only cover them here, because if they are declared with a
952 name, they open a nested scope, similar to <tt/<ref id=".SCOPE"
953 name=".SCOPE">/. However, when no name is specified, the behaviour is
954 different: In this case, no new scope will be opened, symbols declared within
955 a struct, union, or enum declaration will then be added to the enclosing scope
959 <sect1>Explicit scope specification<label id="scopesyntax"><p>
961 Accessing symbols from other scopes is possible by using an explicit scope
962 specification, provided that the scope where the symbol lives in has a name.
963 The namespace token (<tt/::/) is used to access other scopes:
971 lda foo::bar ; Access foo in scope bar
974 The only way to deny access to a scope from the outside is to declare a scope
975 without a name (using the <tt/<ref id=".SCOPE" name=".SCOPE">/ command).
977 A special syntax is used to specify the global scope: If a symbol or scope is
978 preceded by the namespace token, the global scope is searched:
985 lda #::bar ; Access the global bar (which is 3)
990 <sect1>Scope search order<label id="scopesearch"><p>
992 The assembler searches for a scope in a similar way as for a symbol. First, it
993 looks in the current scope, and then it walks up the enclosing scopes until
996 However, one important thing to note when using explicit scope syntax is, that
997 a symbol may be accessed before it is defined, but a scope may <bf/not/ be
998 used without a preceding definition. This means that in the following
1007 lda #foo::bar ; Will load 3, not 2!
1014 the reference to the scope <tt/foo/ will use the global scope, and not the
1015 local one, because the local one is not visible at the point where it is
1018 Things get more complex if a complete chain of scopes is specified:
1029 lda #outer::inner::bar ; 1
1041 When <tt/outer::inner::bar/ is referenced in the <tt/lda/ instruction, the
1042 assembler will first search in the local scope for a scope named <tt/outer/.
1043 Since none is found, the enclosing scope (<tt/another/) is checked. There is
1044 still no scope named <tt/outer/, so scope <tt/foo/ is checked, and finally
1045 scope <tt/outer/ is found. Within this scope, <tt/inner/ is searched, and in
1046 this scope, the assembler looks for a symbol named <tt/bar/.
1048 Please note that once the anchor scope is found, all following scopes
1049 (<tt/inner/ in this case) are expected to be found exactly in this scope. The
1050 assembler will search the scope tree only for the first scope (if it is not
1051 anchored in the root scope). Starting from there on, there is no flexibility,
1052 so if the scope named <tt/outer/ found by the assembler does not contain a
1053 scope named <tt/inner/, this would be an error, even if such a pair does exist
1054 (one level up in global scope).
1056 Ambiguities that may be introduced by this search algorithm may be removed by
1057 anchoring the scope specification in the global scope. In the example above,
1058 if you want to access the "other" symbol <tt/bar/, you would have to write:
1069 lda #::outer::inner::bar ; 2
1082 <sect>Address sizes and memory models<label id="address-sizes"><p>
1084 <sect1>Address sizes<p>
1086 ca65 assigns each segment and each symbol an address size. This is true, even
1087 if the symbol is not used as an address. You may also think of a value range
1088 of the symbol instead of an address size.
1090 Possible address sizes are:
1093 <item>Zeropage or direct (8 bits)
1094 <item>Absolute (16 bits)
1096 <item>Long (32 bits)
1099 Since the assembler uses default address sizes for the segments and symbols,
1100 it is usually not necessary to override the default behaviour. In cases, where
1101 it is necessary, the following keywords may be used to specify address sizes:
1104 <item>DIRECT, ZEROPAGE or ZP for zeropage addressing (8 bits).
1105 <item>ABSOLUTE, ABS or NEAR for absolute addressing (16 bits).
1106 <item>FAR for far addressing (24 bits).
1107 <item>LONG or DWORD for long addressing (32 bits).
1111 <sect1>Address sizes of segments<p>
1113 The assembler assigns an address size to each segment. Since the
1114 representation of a label within this segment is "segment start + offset",
1115 labels will inherit the address size of the segment they are declared in.
1117 The address size of a segment may be changed, by using an optional address
1118 size modifier. See the <tt/<ref id=".SEGMENT" name="segment directive">/ for
1119 an explanation on how this is done.
1122 <sect1>Address sizes of symbols<p>
1127 <sect1>Memory models<p>
1129 The default address size of a segment depends on the memory model used. Since
1130 labels inherit the address size from the segment they are declared in,
1131 changing the memory model is an easy way to change the address size of many
1137 <sect>Pseudo variables<label id="pseudo-variables"><p>
1139 Pseudo variables are readable in all cases, and in some special cases also
1142 <sect1><tt>*</tt><p>
1144 Reading this pseudo variable will return the program counter at the start
1145 of the current input line.
1147 Assignment to this variable is possible when <tt/<ref id=".FEATURE"
1148 name=".FEATURE pc_assignment">/ is used. Note: You should not use
1149 assignments to <tt/*/, use <tt/<ref id=".ORG" name=".ORG">/ instead.
1152 <sect1><tt>.CPU</tt><label id=".CPU"><p>
1154 Reading this pseudo variable will give a constant integer value that
1155 tells which CPU is currently enabled. It can also tell which instruction
1156 set the CPU is able to translate. The value read from the pseudo variable
1157 should be further examined by using one of the constants defined by the
1158 "cpu" macro package (see <tt/<ref id=".MACPACK" name=".MACPACK">/).
1160 It may be used to replace the .IFPxx pseudo instructions or to construct
1161 even more complex expressions.
1167 .if (.cpu .bitand CPU_ISET_65816)
1179 <sect1><tt>.PARAMCOUNT</tt><label id=".PARAMCOUNT"><p>
1181 This builtin pseudo variable is only available in macros. It is replaced by
1182 the actual number of parameters that were given in the macro invocation.
1187 .macro foo arg1, arg2, arg3
1188 .if .paramcount <> 3
1189 .error "Too few parameters for macro foo"
1195 See section <ref id="macros" name="Macros">.
1198 <sect1><tt>.TIME</tt><label id=".TIME"><p>
1200 Reading this pseudo variable will give a constant integer value that
1201 represents the current time in POSIX standard (as seconds since the
1204 It may be used to encode the time of translation somewhere in the created
1210 .dword .time ; Place time here
1214 <sect1><tt>.VERSION</tt><label id=".VERSION"><p>
1216 Reading this pseudo variable will give the assembler version according to
1217 the following formula:
1219 VER_MAJOR*$100 + VER_MINOR*$10 + VER_PATCH
1221 It may be used to encode the assembler version or check the assembler for
1222 special features not available with older versions.
1226 Version 2.11.1 of the assembler will return $2B1 as numerical constant when
1227 reading the pseudo variable <tt/.VERSION/.
1231 <sect>Pseudo functions<label id="pseudo-functions"><p>
1233 Pseudo functions expect their arguments in parenthesis, and they have a result,
1234 either a string or an expression.
1237 <sect1><tt>.BANKBYTE</tt><label id=".BANKBYTE"><p>
1239 The function returns the bank byte (that is, bits 16-23) of its argument.
1240 It works identical to the '^' operator.
1242 See: <tt><ref id=".HIBYTE" name=".HIBYTE"></tt>,
1243 <tt><ref id=".LOBYTE" name=".LOBYTE"></tt>
1246 <sect1><tt>.BLANK</tt><label id=".BLANK"><p>
1248 Builtin function. The function evaluates its argument in braces and yields
1249 "false" if the argument is non blank (there is an argument), and "true" if
1250 there is no argument. The token list that makes up the function argument
1251 may optionally be enclosed in curly braces. This allows the inclusion of
1252 tokens that would otherwise terminate the list (the closing right
1253 parenthesis). The curly braces are not considered part of the list, a list
1254 just consisting of curly braces is considered to be empty.
1256 As an example, the <tt/.IFBLANK/ statement may be replaced by
1264 <sect1><tt>.CONCAT</tt><label id=".CONCAT"><p>
1266 Builtin string function. The function allows to concatenate a list of string
1267 constants separated by commas. The result is a string constant that is the
1268 concatenation of all arguments. This function is most useful in macros and
1269 when used together with the <tt/.STRING/ builtin function. The function may
1270 be used in any case where a string constant is expected.
1275 .include .concat ("myheader", ".", "inc")
1278 This is the same as the command
1281 .include "myheader.inc"
1285 <sect1><tt>.CONST</tt><label id=".CONST"><p>
1287 Builtin function. The function evaluates its argument in braces and
1288 yields "true" if the argument is a constant expression (that is, an
1289 expression that yields a constant value at assembly time) and "false"
1290 otherwise. As an example, the .IFCONST statement may be replaced by
1297 <sect1><tt>.HIBYTE</tt><label id=".HIBYTE"><p>
1299 The function returns the high byte (that is, bits 8-15) of its argument.
1300 It works identical to the '>' operator.
1302 See: <tt><ref id=".LOBYTE" name=".LOBYTE"></tt>,
1303 <tt><ref id=".BANKBYTE" name=".BANKBYTE"></tt>
1306 <sect1><tt>.HIWORD</tt><label id=".HIWORD"><p>
1308 The function returns the high word (that is, bits 16-31) of its argument.
1310 See: <tt><ref id=".LOWORD" name=".LOWORD"></tt>
1313 <sect1><tt>.IDENT</tt><label id=".IDENT"><p>
1315 The function expects a string as its argument, and converts this argument
1316 into an identifier. If the string starts with the current <tt/<ref
1317 id=".LOCALCHAR" name=".LOCALCHAR">/, it will be converted into a cheap local
1318 identifier, otherwise it will be converted into a normal identifier.
1323 .macro makelabel arg1, arg2
1324 .ident (.concat (arg1, arg2)):
1327 makelabel "foo", "bar"
1329 .word foobar ; Valid label
1333 <sect1><tt>.LEFT</tt><label id=".LEFT"><p>
1335 Builtin function. Extracts the left part of a given token list.
1340 .LEFT (<int expr>, <token list>)
1343 The first integer expression gives the number of tokens to extract from
1344 the token list. The second argument is the token list itself. The token
1345 list may optionally be enclosed into curly braces. This allows the
1346 inclusion of tokens that would otherwise terminate the list (the closing
1347 right paren in the given case).
1351 To check in a macro if the given argument has a '#' as first token
1352 (immediate addressing mode), use something like this:
1357 .if (.match (.left (1, {arg}), #))
1359 ; ldax called with immediate operand
1367 See also the <tt><ref id=".MID" name=".MID"></tt> and <tt><ref id=".RIGHT"
1368 name=".RIGHT"></tt> builtin functions.
1371 <sect1><tt>.LOBYTE</tt><label id=".LOBYTE"><p>
1373 The function returns the low byte (that is, bits 0-7) of its argument.
1374 It works identical to the '<' operator.
1376 See: <tt><ref id=".HIBYTE" name=".HIBYTE"></tt>,
1377 <tt><ref id=".BANKBYTE" name=".BANKBYTE"></tt>
1380 <sect1><tt>.LOWORD</tt><label id=".LOWORD"><p>
1382 The function returns the low word (that is, bits 0-15) of its argument.
1384 See: <tt><ref id=".HIWORD" name=".HIWORD"></tt>
1387 <sect1><tt>.MATCH</tt><label id=".MATCH"><p>
1389 Builtin function. Matches two token lists against each other. This is
1390 most useful within macros, since macros are not stored as strings, but
1396 .MATCH(<token list #1>, <token list #2>)
1399 Both token list may contain arbitrary tokens with the exception of the
1400 terminator token (comma resp. right parenthesis) and
1407 The token lists may optionally be enclosed into curly braces. This allows
1408 the inclusion of tokens that would otherwise terminate the list (the closing
1409 right paren in the given case). Often a macro parameter is used for any of
1412 Please note that the function does only compare tokens, not token
1413 attributes. So any number is equal to any other number, regardless of the
1414 actual value. The same is true for strings. If you need to compare tokens
1415 <em/and/ token attributes, use the <tt><ref id=".XMATCH"
1416 name=".XMATCH"></tt> function.
1420 Assume the macro <tt/ASR/, that will shift right the accumulator by one,
1421 while honoring the sign bit. The builtin processor instructions will allow
1422 an optional "A" for accu addressing for instructions like <tt/ROL/ and
1423 <tt/ROR/. We will use the <tt><ref id=".MATCH" name=".MATCH"></tt> function
1424 to check for this and print and error for invalid calls.
1429 .if (.not .blank(arg)) .and (.not .match ({arg}, a))
1430 .error "Syntax error"
1433 cmp #$80 ; Bit 7 into carry
1434 lsr a ; Shift carry into bit 7
1439 The macro will only accept no arguments, or one argument that must be the
1440 reserved keyword "A".
1442 See: <tt><ref id=".XMATCH" name=".XMATCH"></tt>
1445 <sect1><tt>.MAX</tt><label id=".MAX"><p>
1447 Builtin function. The result is the larger of two values.
1452 .MAX (<value #1>, <value #2>)
1458 ; Reserve space for the larger of two data blocks
1459 savearea: .max (.sizeof (foo), .sizeof (bar))
1462 See: <tt><ref id=".MIN" name=".MIN"></tt>
1465 <sect1><tt>.MID</tt><label id=".MID"><p>
1467 Builtin function. Takes a starting index, a count and a token list as
1468 arguments. Will return part of the token list.
1473 .MID (<int expr>, <int expr>, <token list>)
1476 The first integer expression gives the starting token in the list (the first
1477 token has index 0). The second integer expression gives the number of tokens
1478 to extract from the token list. The third argument is the token list itself.
1479 The token list may optionally be enclosed into curly braces. This allows the
1480 inclusion of tokens that would otherwise terminate the list (the closing
1481 right paren in the given case).
1485 To check in a macro if the given argument has a '<tt/#/' as first token
1486 (immediate addressing mode), use something like this:
1491 .if (.match (.mid (0, 1, {arg}), #))
1493 ; ldax called with immediate operand
1501 See also the <tt><ref id=".LEFT" name=".LEFT"></tt> and <tt><ref id=".RIGHT"
1502 name=".RIGHT"></tt> builtin functions.
1505 <sect1><tt>.MIN</tt><label id=".MIN"><p>
1507 Builtin function. The result is the smaller of two values.
1512 .MIN (<value #1>, <value #2>)
1518 ; Reserve space for some data, but 256 bytes minimum
1519 savearea: .min (.sizeof (foo), 256)
1522 See: <tt><ref id=".MAX" name=".MAX"></tt>
1525 <sect1><tt>.REF, .REFERENCED</tt><label id=".REFERENCED"><p>
1527 Builtin function. The function expects an identifier as argument in braces.
1528 The argument is evaluated, and the function yields "true" if the identifier
1529 is a symbol that has already been referenced somewhere in the source file up
1530 to the current position. Otherwise the function yields false. As an example,
1531 the <tt><ref id=".IFREF" name=".IFREF"></tt> statement may be replaced by
1537 See: <tt><ref id=".DEFINED" name=".DEFINED"></tt>
1540 <sect1><tt>.RIGHT</tt><label id=".RIGHT"><p>
1542 Builtin function. Extracts the right part of a given token list.
1547 .RIGHT (<int expr>, <token list>)
1550 The first integer expression gives the number of tokens to extract from the
1551 token list. The second argument is the token list itself. The token list
1552 may optionally be enclosed into curly braces. This allows the inclusion of
1553 tokens that would otherwise terminate the list (the closing right paren in
1556 See also the <tt><ref id=".LEFT" name=".LEFT"></tt> and <tt><ref id=".MID"
1557 name=".MID"></tt> builtin functions.
1560 <sect1><tt>.SIZEOF</tt><label id=".SIZEOF"><p>
1562 <tt/.SIZEOF/ is a pseudo function that returns the size of its argument. The
1563 argument can be a struct/union, a struct member, a procedure, or a label. In
1564 case of a procedure or label, its size is defined by the amount of data
1565 placed in the segment where the label is relative to. If a line of code
1566 switches segments (for example in a macro) data placed in other segments
1567 does not count for the size.
1569 Please note that a symbol or scope must exist, before it is used together with
1570 <tt/.SIZEOF/ (this may get relaxed later, but will always be true for scopes).
1571 A scope has preference over a symbol with the same name, so if the last part
1572 of a name represents both, a scope and a symbol, the scope is chosen over the
1575 After the following code:
1578 .struct Point ; Struct size = 4
1583 P: .tag Point ; Declare a point
1584 @P: .tag Point ; Declare another point
1596 .data ; Segment switch!!!
1602 <tag><tt/.sizeof(Point)/</tag>
1603 will have the value 4, because this is the size of struct <tt/Point/.
1605 <tag><tt/.sizeof(Point::xcoord)/</tag>
1606 will have the value 2, because this is the size of the member <tt/xcoord/
1607 in struct <tt/Point/.
1609 <tag><tt/.sizeof(P)/</tag>
1610 will have the value 4, this is the size of the data declared on the same
1611 source line as the label <tt/P/, which is in the same segment that <tt/P/
1614 <tag><tt/.sizeof(@P)/</tag>
1615 will have the value 4, see above. The example demonstrates that <tt/.SIZEOF/
1616 does also work for cheap local symbols.
1618 <tag><tt/.sizeof(Code)/</tag>
1619 will have the value 3, since this is amount of data emitted into the code
1620 segment, the segment that was active when <tt/Code/ was entered. Note that
1621 this value includes the amount of data emitted in child scopes (in this
1622 case <tt/Code::Inner/).
1624 <tag><tt/.sizeof(Code::Inner)/</tag>
1625 will have the value 1 as expected.
1627 <tag><tt/.sizeof(Data)/</tag>
1628 will have the value 0. Data is emitted within the scope <tt/Data/, but since
1629 the segment is switched after entry, this data is emitted into another
1634 <sect1><tt>.STRAT</tt><label id=".STRAT"><p>
1636 Builtin function. The function accepts a string and an index as
1637 arguments and returns the value of the character at the given position
1638 as an integer value. The index is zero based.
1644 ; Check if the argument string starts with '#'
1645 .if (.strat (Arg, 0) = '#')
1652 <sect1><tt>.SPRINTF</tt><label id=".SPRINTF"><p>
1654 Builtin function. It expects a format string as first argument. The number
1655 and type of the following arguments depend on the format string. The format
1656 string is similar to the one of the C <tt/printf/ function. Missing things
1657 are: Length modifiers, variable width.
1659 The result of the function is a string.
1666 ; Generate an identifier:
1667 .ident (.sprintf ("%s%03d", "label", num)):
1671 <sect1><tt>.STRING</tt><label id=".STRING"><p>
1673 Builtin function. The function accepts an argument in braces and converts
1674 this argument into a string constant. The argument may be an identifier, or
1675 a constant numeric value.
1677 Since you can use a string in the first place, the use of the function may
1678 not be obvious. However, it is useful in macros, or more complex setups.
1683 ; Emulate other assemblers:
1685 .segment .string(name)
1690 <sect1><tt>.STRLEN</tt><label id=".STRLEN"><p>
1692 Builtin function. The function accepts a string argument in braces and
1693 evaluates to the length of the string.
1697 The following macro encodes a string as a pascal style string with
1698 a leading length byte.
1702 .byte .strlen(Arg), Arg
1707 <sect1><tt>.TCOUNT</tt><label id=".TCOUNT"><p>
1709 Builtin function. The function accepts a token list in braces. The function
1710 result is the number of tokens given as argument. The token list may
1711 optionally be enclosed into curly braces which are not considered part of
1712 the list and not counted. Enclosement in curly braces allows the inclusion
1713 of tokens that would otherwise terminate the list (the closing right paren
1718 The <tt/ldax/ macro accepts the '#' token to denote immediate addressing (as
1719 with the normal 6502 instructions). To translate it into two separate 8 bit
1720 load instructions, the '#' token has to get stripped from the argument:
1724 .if (.match (.mid (0, 1, {arg}), #))
1725 ; ldax called with immediate operand
1726 lda #<(.right (.tcount ({arg})-1, {arg}))
1727 ldx #>(.right (.tcount ({arg})-1, {arg}))
1735 <sect1><tt>.XMATCH</tt><label id=".XMATCH"><p>
1737 Builtin function. Matches two token lists against each other. This is
1738 most useful within macros, since macros are not stored as strings, but
1744 .XMATCH(<token list #1>, <token list #2>)
1747 Both token list may contain arbitrary tokens with the exception of the
1748 terminator token (comma resp. right parenthesis) and
1755 The token lists may optionally be enclosed into curly braces. This allows
1756 the inclusion of tokens that would otherwise terminate the list (the closing
1757 right paren in the given case). Often a macro parameter is used for any of
1760 The function compares tokens <em/and/ token values. If you need a function
1761 that just compares the type of tokens, have a look at the <tt><ref
1762 id=".MATCH" name=".MATCH"></tt> function.
1764 See: <tt><ref id=".MATCH" name=".MATCH"></tt>
1768 <sect>Control commands<label id="control-commands"><p>
1770 Here's a list of all control commands and a description, what they do:
1773 <sect1><tt>.A16</tt><label id=".A16"><p>
1775 Valid only in 65816 mode. Switch the accumulator to 16 bit.
1777 Note: This command will not emit any code, it will tell the assembler to
1778 create 16 bit operands for immediate accumulator addressing mode.
1780 See also: <tt><ref id=".SMART" name=".SMART"></tt>
1783 <sect1><tt>.A8</tt><label id=".A8"><p>
1785 Valid only in 65816 mode. Switch the accumulator to 8 bit.
1787 Note: This command will not emit any code, it will tell the assembler to
1788 create 8 bit operands for immediate accu addressing mode.
1790 See also: <tt><ref id=".SMART" name=".SMART"></tt>
1793 <sect1><tt>.ADDR</tt><label id=".ADDR"><p>
1795 Define word sized data. In 6502 mode, this is an alias for <tt/.WORD/ and
1796 may be used for better readability if the data words are address values. In
1797 65816 mode, the address is forced to be 16 bit wide to fit into the current
1798 segment. See also <tt><ref id=".FARADDR" name=".FARADDR"></tt>. The command
1799 must be followed by a sequence of (not necessarily constant) expressions.
1804 .addr $0D00, $AF13, _Clear
1807 See: <tt><ref id=".FARADDR" name=".FARADDR"></tt>, <tt><ref id=".WORD"
1811 <sect1><tt>.ALIGN</tt><label id=".ALIGN"><p>
1813 Align data to a given boundary. The command expects a constant integer
1814 argument that must be a power of two, plus an optional second argument
1815 in byte range. If there is a second argument, it is used as fill value,
1816 otherwise the value defined in the linker configuration file is used
1817 (the default for this value is zero).
1819 Since alignment depends on the base address of the module, you must
1820 give the same (or a greater) alignment for the segment when linking.
1821 The linker will give you a warning, if you don't do that.
1830 <sect1><tt>.ASCIIZ</tt><label id=".ASCIIZ"><p>
1832 Define a string with a trailing zero.
1837 Msg: .asciiz "Hello world"
1840 This will put the string "Hello world" followed by a binary zero into
1841 the current segment. There may be more strings separated by commas, but
1842 the binary zero is only appended once (after the last one).
1845 <sect1><tt>.ASSERT</tt><label id=".ASSERT"><p>
1847 Add an assertion. The command is followed by an expression, an action
1848 specifier, and an optional message that is output in case the assertion
1849 fails. If no message was given, the string "Assertion failed" is used. The
1850 action specifier may be one of <tt/warning/, <tt/error/, <tt/ldwarning/ or
1851 <tt/lderror/. In the former two cases, the assertion is evaluated by the
1852 assembler if possible, and in any case, it's also passed to the linker in
1853 the object file (if one is generated). The linker will then evaluate the
1854 expression when segment placement has been done.
1859 .assert * = $8000, error, "Code not at $8000"
1862 The example assertion will check that the current location is at $8000,
1863 when the output file is written, and abort with an error if this is not
1864 the case. More complex expressions are possible. The action specifier
1865 <tt/warning/ outputs a warning, while the <tt/error/ specifier outputs
1866 an error message. In the latter case, generation of the output file is
1867 suppressed in both the assembler and linker.
1870 <sect1><tt>.AUTOIMPORT</tt><label id=".AUTOIMPORT"><p>
1872 Is followed by a plus or a minus character. When switched on (using a
1873 +), undefined symbols are automatically marked as import instead of
1874 giving errors. When switched off (which is the default so this does not
1875 make much sense), this does not happen and an error message is
1876 displayed. The state of the autoimport flag is evaluated when the
1877 complete source was translated, before outputting actual code, so it is
1878 <em/not/ possible to switch this feature on or off for separate sections
1879 of code. The last setting is used for all symbols.
1881 You should probably not use this switch because it delays error
1882 messages about undefined symbols until the link stage. The cc65
1883 compiler (which is supposed to produce correct assembler code in all
1884 circumstances, something which is not true for most assembler
1885 programmers) will insert this command to avoid importing each and every
1886 routine from the runtime library.
1891 .autoimport + ; Switch on auto import
1894 <sect1><tt>.BANKBYTES</tt><label id=".BANKBYTES"><p>
1896 Define byte sized data by extracting only the bank byte (that is, bits 16-23) from
1897 each expression. This is equivalent to <tt><ref id=".BYTE" name=".BYTE"></tt> with
1898 the operator '^' prepended to each expression in its list.
1903 .define MyTable TableItem0, TableItem1, TableItem2, TableItem3
1905 TableLookupLo: .lobytes MyTable
1906 TableLookupHi: .hibytes MyTable
1907 TableLookupBank: .bankbytes MyTable
1910 which is equivalent to
1913 TableLookupLo: .byte <TableItem0, <TableItem1, <TableItem2, <TableItem3
1914 TableLookupHi: .byte >TableItem0, >TableItem1, >TableItem2, >TableItem3
1915 TableLookupBank: .byte ^TableItem0, ^TableItem1, ^TableItem2, ^TableItem3
1918 See also: <tt><ref id=".BYTE" name=".BYTE"></tt>,
1919 <tt><ref id=".HIBYTES" name=".HIBYTES"></tt>,
1920 <tt><ref id=".LOBYTES" name=".LOBYTES"></tt>
1923 <sect1><tt>.BSS</tt><label id=".BSS"><p>
1925 Switch to the BSS segment. The name of the BSS segment is always "BSS",
1926 so this is a shortcut for
1932 See also the <tt><ref id=".SEGMENT" name=".SEGMENT"></tt> command.
1935 <sect1><tt>.BYT, .BYTE</tt><label id=".BYTE"><p>
1937 Define byte sized data. Must be followed by a sequence of (byte ranged)
1938 expressions or strings.
1944 .byt "world", $0D, $00
1948 <sect1><tt>.CASE</tt><label id=".CASE"><p>
1950 Switch on or off case sensitivity on identifiers. The default is off
1951 (that is, identifiers are case sensitive), but may be changed by the
1952 -i switch on the command line.
1953 The command must be followed by a '+' or '-' character to switch the
1954 option on or off respectively.
1959 .case - ; Identifiers are not case sensitive
1963 <sect1><tt>.CHARMAP</tt><label id=".CHARMAP"><p>
1965 Apply a custom mapping for characters. The command is followed by two
1966 numbers in the range 1..255. The first one is the index of the source
1967 character, the second one is the mapping. The mapping applies to all
1968 character and string constants when they generate output, and overrides
1969 a mapping table specified with the <tt><ref id="option-t" name="-t"></tt>
1970 command line switch.
1975 .charmap $41, $61 ; Map 'A' to 'a'
1979 <sect1><tt>.CODE</tt><label id=".CODE"><p>
1981 Switch to the CODE segment. The name of the CODE segment is always
1982 "CODE", so this is a shortcut for
1988 See also the <tt><ref id=".SEGMENT" name=".SEGMENT"></tt> command.
1991 <sect1><tt>.CONDES</tt><label id=".CONDES"><p>
1993 Export a symbol and mark it in a special way. The linker is able to build
1994 tables of all such symbols. This may be used to automatically create a list
1995 of functions needed to initialize linked library modules.
1997 Note: The linker has a feature to build a table of marked routines, but it
1998 is your code that must call these routines, so just declaring a symbol with
1999 <tt/.CONDES/ does nothing by itself.
2001 All symbols are exported as an absolute (16 bit) symbol. You don't need to
2002 use an additional <tt><ref id=".EXPORT" name=".EXPORT"></tt> statement, this
2003 is implied by <tt/.CONDES/.
2005 <tt/.CONDES/ is followed by the type, which may be <tt/constructor/,
2006 <tt/destructor/ or a numeric value between 0 and 6 (where 0 is the same as
2007 specifying <tt/constructor/ and 1 is equal to specifying <tt/destructor/).
2008 The <tt><ref id=".CONSTRUCTOR" name=".CONSTRUCTOR"></tt>, <tt><ref
2009 id=".DESTRUCTOR" name=".DESTRUCTOR"></tt> and <tt><ref id=".INTERRUPTOR"
2010 name=".INTERRUPTOR"></tt> commands are actually shortcuts for <tt/.CONDES/
2011 with a type of <tt/constructor/ resp. <tt/destructor/ or <tt/interruptor/.
2013 After the type, an optional priority may be specified. Higher numeric values
2014 mean higher priority. If no priority is given, the default priority of 7 is
2015 used. Be careful when assigning priorities to your own module constructors
2016 so they won't interfere with the ones in the cc65 library.
2021 .condes ModuleInit, constructor
2022 .condes ModInit, 0, 16
2025 See the <tt><ref id=".CONSTRUCTOR" name=".CONSTRUCTOR"></tt>, <tt><ref
2026 id=".DESTRUCTOR" name=".DESTRUCTOR"></tt> and <tt><ref id=".INTERRUPTOR"
2027 name=".INTERRUPTOR"></tt> commands and the separate section <ref id="condes"
2028 name="Module constructors/destructors"> explaining the feature in more
2032 <sect1><tt>.CONSTRUCTOR</tt><label id=".CONSTRUCTOR"><p>
2034 Export a symbol and mark it as a module constructor. This may be used
2035 together with the linker to build a table of constructor subroutines that
2036 are called by the startup code.
2038 Note: The linker has a feature to build a table of marked routines, but it
2039 is your code that must call these routines, so just declaring a symbol as
2040 constructor does nothing by itself.
2042 A constructor is always exported as an absolute (16 bit) symbol. You don't
2043 need to use an additional <tt/.export/ statement, this is implied by
2044 <tt/.constructor/. It may have an optional priority that is separated by a
2045 comma. Higher numeric values mean a higher priority. If no priority is
2046 given, the default priority of 7 is used. Be careful when assigning
2047 priorities to your own module constructors so they won't interfere with the
2048 ones in the cc65 library.
2053 .constructor ModuleInit
2054 .constructor ModInit, 16
2057 See the <tt><ref id=".CONDES" name=".CONDES"></tt> and <tt><ref
2058 id=".DESTRUCTOR" name=".DESTRUCTOR"></tt> commands and the separate section
2059 <ref id="condes" name="Module constructors/destructors"> explaining the
2060 feature in more detail.
2063 <sect1><tt>.DATA</tt><label id=".DATA"><p>
2065 Switch to the DATA segment. The name of the DATA segment is always
2066 "DATA", so this is a shortcut for
2072 See also the <tt><ref id=".SEGMENT" name=".SEGMENT"></tt> command.
2075 <sect1><tt>.DBYT</tt><label id=".DBYT"><p>
2077 Define word sized data with the hi and lo bytes swapped (use <tt/.WORD/ to
2078 create word sized data in native 65XX format). Must be followed by a
2079 sequence of (word ranged) expressions.
2087 This will emit the bytes
2093 into the current segment in that order.
2096 <sect1><tt>.DEBUGINFO</tt><label id=".DEBUGINFO"><p>
2098 Switch on or off debug info generation. The default is off (that is,
2099 the object file will not contain debug infos), but may be changed by the
2100 -g switch on the command line.
2101 The command must be followed by a '+' or '-' character to switch the
2102 option on or off respectively.
2107 .debuginfo + ; Generate debug info
2111 <sect1><tt>.DEFINE</tt><label id=".DEFINE"><p>
2113 Start a define style macro definition. The command is followed by an
2114 identifier (the macro name) and optionally by a list of formal arguments
2116 See section <ref id="macros" name="Macros">.
2119 <sect1><tt>.DEF, .DEFINED</tt><label id=".DEFINED"><p>
2121 Builtin function. The function expects an identifier as argument in braces.
2122 The argument is evaluated, and the function yields "true" if the identifier
2123 is a symbol that is already defined somewhere in the source file up to the
2124 current position. Otherwise the function yields false. As an example, the
2125 <tt><ref id=".IFDEF" name=".IFDEF"></tt> statement may be replaced by
2132 <sect1><tt>.DESTRUCTOR</tt><label id=".DESTRUCTOR"><p>
2134 Export a symbol and mark it as a module destructor. This may be used
2135 together with the linker to build a table of destructor subroutines that
2136 are called by the startup code.
2138 Note: The linker has a feature to build a table of marked routines, but it
2139 is your code that must call these routines, so just declaring a symbol as
2140 constructor does nothing by itself.
2142 A destructor is always exported as an absolute (16 bit) symbol. You don't
2143 need to use an additional <tt/.export/ statement, this is implied by
2144 <tt/.destructor/. It may have an optional priority that is separated by a
2145 comma. Higher numerical values mean a higher priority. If no priority is
2146 given, the default priority of 7 is used. Be careful when assigning
2147 priorities to your own module destructors so they won't interfere with the
2148 ones in the cc65 library.
2153 .destructor ModuleDone
2154 .destructor ModDone, 16
2157 See the <tt><ref id=".CONDES" name=".CONDES"></tt> and <tt><ref
2158 id=".CONSTRUCTOR" name=".CONSTRUCTOR"></tt> commands and the separate
2159 section <ref id="condes" name="Module constructors/destructors"> explaining
2160 the feature in more detail.
2163 <sect1><tt>.DWORD</tt><label id=".DWORD"><p>
2165 Define dword sized data (4 bytes) Must be followed by a sequence of
2171 .dword $12344512, $12FA489
2175 <sect1><tt>.ELSE</tt><label id=".ELSE"><p>
2177 Conditional assembly: Reverse the current condition.
2180 <sect1><tt>.ELSEIF</tt><label id=".ELSEIF"><p>
2182 Conditional assembly: Reverse current condition and test a new one.
2185 <sect1><tt>.END</tt><label id=".END"><p>
2187 Forced end of assembly. Assembly stops at this point, even if the command
2188 is read from an include file.
2191 <sect1><tt>.ENDENUM</tt><label id=".ENDENUM"><p>
2193 End a <tt><ref id=".ENUM" name=".ENUM"></tt> declaration.
2196 <sect1><tt>.ENDIF</tt><label id=".ENDIF"><p>
2198 Conditional assembly: Close a <tt><ref id=".IF" name=".IF..."></tt> or
2199 <tt><ref id=".ELSE" name=".ELSE"></tt> branch.
2202 <sect1><tt>.ENDMAC, .ENDMACRO</tt><label id=".ENDMACRO"><p>
2204 End of macro definition (see section <ref id="macros" name="Macros">).
2207 <sect1><tt>.ENDPROC</tt><label id=".ENDPROC"><p>
2209 End of local lexical level (see <tt><ref id=".PROC" name=".PROC"></tt>).
2212 <sect1><tt>.ENDREP, .ENDREPEAT</tt><label id=".ENDREPEAT"><p>
2214 End a <tt><ref id=".REPEAT" name=".REPEAT"></tt> block.
2217 <sect1><tt>.ENDSCOPE</tt><label id=".ENDSCOPE"><p>
2219 End of local lexical level (see <tt/<ref id=".SCOPE" name=".SCOPE">/).
2222 <sect1><tt>.ENDSTRUCT</tt><label id=".ENDSTRUCT"><p>
2224 Ends a struct definition. See the <tt/<ref id=".STRUCT" name=".STRUCT">/
2225 command and the separate section named <ref id="structs" name=""Structs
2229 <sect1><tt>.ENUM</tt><label id=".ENUM"><p>
2231 Start an enumeration. This directive is very similar to the C <tt/enum/
2232 keyword. If a name is given, a new scope is created for the enumeration,
2233 otherwise the enumeration members are placed in the enclosing scope.
2235 In the enumeration body, symbols are declared. The first symbol has a value
2236 of zero, and each following symbol will get the value of the preceding plus
2237 one. This behaviour may be overridden by an explicit assignment. Two symbols
2238 may have the same value.
2250 Above example will create a new scope named <tt/errorcodes/ with three
2251 symbols in it that get the values 0, 1 and 2 respectively. Another way
2252 to write this would have been:
2262 Please note that explicit scoping must be used to access the identifiers:
2265 .word errorcodes::no_error
2268 A more complex example:
2277 EWOULDBLOCK = EAGAIN
2281 In this example, the enumeration does not have a name, which means that the
2282 members will be visible in the enclosing scope and can be used in this scope
2283 without explicit scoping. The first member (<tt/EUNKNOWN/) has the value -1.
2284 The value for the following members is incremented by one, so <tt/EOK/ would
2285 be zero and so on. <tt/EWOULDBLOCK/ is an alias for <tt/EGAIN/, so it has an
2286 override for the value using an already defined symbol.
2289 <sect1><tt>.ERROR</tt><label id=".ERROR"><p>
2291 Force an assembly error. The assembler will output an error message
2292 preceded by "User error". Assembly is continued but no object file will
2295 This command may be used to check for initial conditions that must be
2296 set before assembling a source file.
2306 .error "Must define foo or bar!"
2310 See also: <tt><ref id=".FATAL" name=".FATAL"></tt>,
2311 <tt><ref id=".OUT" name=".OUT"></tt>,
2312 <tt><ref id=".WARNING" name=".WARNING"></tt>
2315 <sect1><tt>.EXITMAC, .EXITMACRO</tt><label id=".EXITMACRO"><p>
2317 Abort a macro expansion immediately. This command is often useful in
2318 recursive macros. See separate section <ref id="macros" name="Macros">.
2321 <sect1><tt>.EXPORT</tt><label id=".EXPORT"><p>
2323 Make symbols accessible from other modules. Must be followed by a comma
2324 separated list of symbols to export, with each one optionally followed by an
2325 address specification and (also optional) an assignment. Using an additional
2326 assignment in the export statement allows to define and export a symbol in
2327 one statement. The default is to export the symbol with the address size it
2328 actually has. The assembler will issue a warning, if the symbol is exported
2329 with an address size smaller than the actual address size.
2336 .export foobar: far = foo * bar
2337 .export baz := foobar, zap: far = baz - bar
2340 As with constant definitions, using <tt/:=/ instead of <tt/=/ marks the
2343 See: <tt><ref id=".EXPORTZP" name=".EXPORTZP"></tt>
2346 <sect1><tt>.EXPORTZP</tt><label id=".EXPORTZP"><p>
2348 Make symbols accessible from other modules. Must be followed by a comma
2349 separated list of symbols to export. The exported symbols are explicitly
2350 marked as zero page symbols. An assignment may be included in the
2351 <tt/.EXPORTZP/ statement. This allows to define and export a symbol in one
2358 .exportzp baz := $02
2361 See: <tt><ref id=".EXPORT" name=".EXPORT"></tt>
2364 <sect1><tt>.FARADDR</tt><label id=".FARADDR"><p>
2366 Define far (24 bit) address data. The command must be followed by a
2367 sequence of (not necessarily constant) expressions.
2372 .faraddr DrawCircle, DrawRectangle, DrawHexagon
2375 See: <tt><ref id=".ADDR" name=".ADDR"></tt>
2378 <sect1><tt>.FATAL</tt><label id=".FATAL"><p>
2380 Force an assembly error and terminate assembly. The assembler will output an
2381 error message preceded by "User error" and will terminate assembly
2384 This command may be used to check for initial conditions that must be
2385 set before assembling a source file.
2395 .fatal "Must define foo or bar!"
2399 See also: <tt><ref id=".ERROR" name=".ERROR"></tt>,
2400 <tt><ref id=".OUT" name=".OUT"></tt>,
2401 <tt><ref id=".WARNING" name=".WARNING"></tt>
2404 <sect1><tt>.FEATURE</tt><label id=".FEATURE"><p>
2406 This directive may be used to enable one or more compatibility features
2407 of the assembler. While the use of <tt/.FEATURE/ should be avoided when
2408 possible, it may be useful when porting sources written for other
2409 assemblers. There is no way to switch a feature off, once you have
2410 enabled it, so using
2416 will enable the feature until end of assembly is reached.
2418 The following features are available:
2422 <tag><tt>at_in_identifiers</tt><label id="at_in_identifiers"></tag>
2424 Accept the at character (`@') as a valid character in identifiers. The
2425 at character is not allowed to start an identifier, even with this
2428 <tag><tt>c_comments</tt></tag>
2430 Allow C like comments using <tt>/*</tt> and <tt>*/</tt> as left and right
2431 comment terminators. Note that C comments may not be nested. There's also a
2432 pitfall when using C like comments: All statements must be terminated by
2433 "end-of-line". Using C like comments, it is possible to hide the newline,
2434 which results in error messages. See the following non working example:
2437 lda #$00 /* This comment hides the newline
2441 <tag><tt>dollar_in_identifiers</tt><label id="dollar_in_identifiers"></tag>
2443 Accept the dollar sign (`$') as a valid character in identifiers. The
2444 dollar character is not allowed to start an identifier, even with this
2447 <tag><tt>dollar_is_pc</tt></tag>
2449 The dollar sign may be used as an alias for the star (`*'), which
2450 gives the value of the current PC in expressions.
2451 Note: Assignment to the pseudo variable is not allowed.
2453 <tag><tt>labels_without_colons</tt></tag>
2455 Allow labels without a trailing colon. These labels are only accepted,
2456 if they start at the beginning of a line (no leading white space).
2458 <tag><tt>leading_dot_in_identifiers</tt><label id="leading_dot_in_identifiers"></tag>
2460 Accept the dot (`.') as the first character of an identifier. This may be
2461 used for example to create macro names that start with a dot emulating
2462 control directives of other assemblers. Note however, that none of the
2463 reserved keywords built into the assembler, that starts with a dot, may be
2464 overridden. When using this feature, you may also get into trouble if
2465 later versions of the assembler define new keywords starting with a dot.
2467 <tag><tt>loose_char_term</tt></tag>
2469 Accept single quotes as well as double quotes as terminators for char
2472 <tag><tt>loose_string_term</tt></tag>
2474 Accept single quotes as well as double quotes as terminators for string
2477 <tag><tt>missing_char_term</tt></tag>
2479 Accept single quoted character constants where the terminating quote is
2484 <bf/Note:/ This does not work in conjunction with <tt/.FEATURE
2485 loose_string_term/, since in this case the input would be ambiguous.
2487 <tag><tt>org_per_seg</tt><label id="org_per_seg"></tag>
2489 This feature makes relocatable/absolute mode local to the current segment.
2490 Using <tt><ref id=".ORG" name=".ORG"></tt> when <tt/org_per_seg/ is in
2491 effect will only enable absolute mode for the current segment. Dito for
2492 <tt><ref id=".RELOC" name=".RELOC"></tt>.
2494 <tag><tt>pc_assignment</tt></tag>
2496 Allow assignments to the PC symbol (`*' or `$' if <tt/dollar_is_pc/
2497 is enabled). Such an assignment is handled identical to the <tt><ref
2498 id=".ORG" name=".ORG"></tt> command (which is usually not needed, so just
2499 removing the lines with the assignments may also be an option when porting
2500 code written for older assemblers).
2502 <tag><tt>ubiquitous_idents</tt></tag>
2504 Allow the use of instructions names as names for macros and symbols. This
2505 makes it possible to "overload" instructions by defining a macro with the
2506 same name. This does also make it possible to introduce hard to find errors
2507 in your code, so be careful!
2511 It is also possible to specify features on the command line using the
2512 <tt><ref id="option--feature" name="--feature"></tt> command line option.
2513 This is useful when translating sources written for older assemblers, when
2514 you don't want to change the source code.
2516 As an example, to translate sources written for Andre Fachats xa65
2517 assembler, the features
2520 labels_without_colons, pc_assignment, loose_char_term
2523 may be helpful. They do not make ca65 completely compatible, so you may not
2524 be able to translate the sources without changes, even when enabling these
2525 features. However, I have found several sources that translate without
2526 problems when enabling these features on the command line.
2529 <sect1><tt>.FILEOPT, .FOPT</tt><label id=".FOPT"><p>
2531 Insert an option string into the object file. There are two forms of
2532 this command, one specifies the option by a keyword, the second
2533 specifies it as a number. Since usage of the second one needs knowledge
2534 of the internal encoding, its use is not recommended and I will only
2535 describe the first form here.
2537 The command is followed by one of the keywords
2545 a comma and a string. The option is written into the object file
2546 together with the string value. This is currently unidirectional and
2547 there is no way to actually use these options once they are in the
2553 .fileopt comment, "Code stolen from my brother"
2554 .fileopt compiler, "BASIC 2.0"
2555 .fopt author, "J. R. User"
2559 <sect1><tt>.FORCEIMPORT</tt><label id=".FORCEIMPORT"><p>
2561 Import an absolute symbol from another module. The command is followed by a
2562 comma separated list of symbols to import. The command is similar to <tt>
2563 <ref id=".IMPORT" name=".IMPORT"></tt>, but the import reference is always
2564 written to the generated object file, even if the symbol is never referenced
2565 (<tt><ref id=".IMPORT" name=".IMPORT"></tt> will not generate import
2566 references for unused symbols).
2571 .forceimport needthisone, needthistoo
2574 See: <tt><ref id=".IMPORT" name=".IMPORT"></tt>
2577 <sect1><tt>.GLOBAL</tt><label id=".GLOBAL"><p>
2579 Declare symbols as global. Must be followed by a comma separated list of
2580 symbols to declare. Symbols from the list, that are defined somewhere in the
2581 source, are exported, all others are imported. Additional <tt><ref
2582 id=".IMPORT" name=".IMPORT"></tt> or <tt><ref id=".EXPORT"
2583 name=".EXPORT"></tt> commands for the same symbol are allowed.
2592 <sect1><tt>.GLOBALZP</tt><label id=".GLOBALZP"><p>
2594 Declare symbols as global. Must be followed by a comma separated list of
2595 symbols to declare. Symbols from the list, that are defined somewhere in the
2596 source, are exported, all others are imported. Additional <tt><ref
2597 id=".IMPORTZP" name=".IMPORTZP"></tt> or <tt><ref id=".EXPORTZP"
2598 name=".EXPORTZP"></tt> commands for the same symbol are allowed. The symbols
2599 in the list are explicitly marked as zero page symbols.
2607 <sect1><tt>.HIBYTES</tt><label id=".HIBYTES"><p>
2609 Define byte sized data by extracting only the high byte (that is, bits 8-15) from
2610 each expression. This is equivalent to <tt><ref id=".BYTE" name=".BYTE"></tt> with
2611 the operator '>' prepended to each expression in its list.
2616 .lobytes $1234, $2345, $3456, $4567
2617 .hibytes $fedc, $edcb, $dcba, $cba9
2620 which is equivalent to
2623 .byte $34, $45, $56, $67
2624 .byte $fe, $ed, $dc, $cb
2630 .define MyTable TableItem0, TableItem1, TableItem2, TableItem3
2632 TableLookupLo: .lobytes MyTable
2633 TableLookupHi: .hibytes MyTable
2636 which is equivalent to
2639 TableLookupLo: .byte <TableItem0, <TableItem1, <TableItem2, <TableItem3
2640 TableLookupHi: .byte >TableItem0, >TableItem1, >TableItem2, >TableItem3
2643 See also: <tt><ref id=".BYTE" name=".BYTE"></tt>,
2644 <tt><ref id=".LOBYTES" name=".LOBYTES"></tt>,
2645 <tt><ref id=".BANKBYTES" name=".BANKBYTES"></tt>
2648 <sect1><tt>.I16</tt><label id=".I16"><p>
2650 Valid only in 65816 mode. Switch the index registers to 16 bit.
2652 Note: This command will not emit any code, it will tell the assembler to
2653 create 16 bit operands for immediate operands.
2655 See also the <tt><ref id=".I8" name=".I8"></tt> and <tt><ref id=".SMART"
2656 name=".SMART"></tt> commands.
2659 <sect1><tt>.I8</tt><label id=".I8"><p>
2661 Valid only in 65816 mode. Switch the index registers to 8 bit.
2663 Note: This command will not emit any code, it will tell the assembler to
2664 create 8 bit operands for immediate operands.
2666 See also the <tt><ref id=".I16" name=".I16"></tt> and <tt><ref id=".SMART"
2667 name=".SMART"></tt> commands.
2670 <sect1><tt>.IF</tt><label id=".IF"><p>
2672 Conditional assembly: Evaluate an expression and switch assembler output
2673 on or off depending on the expression. The expression must be a constant
2674 expression, that is, all operands must be defined.
2676 A expression value of zero evaluates to FALSE, any other value evaluates
2680 <sect1><tt>.IFBLANK</tt><label id=".IFBLANK"><p>
2682 Conditional assembly: Check if there are any remaining tokens in this line,
2683 and evaluate to FALSE if this is the case, and to TRUE otherwise. If the
2684 condition is not true, further lines are not assembled until an <tt><ref
2685 id=".ELSE" name=".ESLE"></tt>, <tt><ref id=".ELSEIF" name=".ELSEIF"></tt> or
2686 <tt><ref id=".ENDIF" name=".ENDIF"></tt> directive.
2688 This command is often used to check if a macro parameter was given. Since an
2689 empty macro parameter will evaluate to nothing, the condition will evaluate
2690 to FALSE if an empty parameter was given.
2704 See also: <tt><ref id=".BLANK" name=".BLANK"></tt>
2707 <sect1><tt>.IFCONST</tt><label id=".IFCONST"><p>
2709 Conditional assembly: Evaluate an expression and switch assembler output
2710 on or off depending on the constness of the expression.
2712 A const expression evaluates to to TRUE, a non const expression (one
2713 containing an imported or currently undefined symbol) evaluates to
2716 See also: <tt><ref id=".CONST" name=".CONST"></tt>
2719 <sect1><tt>.IFDEF</tt><label id=".IFDEF"><p>
2721 Conditional assembly: Check if a symbol is defined. Must be followed by
2722 a symbol name. The condition is true if the the given symbol is already
2723 defined, and false otherwise.
2725 See also: <tt><ref id=".DEFINED" name=".DEFINED"></tt>
2728 <sect1><tt>.IFNBLANK</tt><label id=".IFNBLANK"><p>
2730 Conditional assembly: Check if there are any remaining tokens in this line,
2731 and evaluate to TRUE if this is the case, and to FALSE otherwise. If the
2732 condition is not true, further lines are not assembled until an <tt><ref
2733 id=".ELSE" name=".ELSE"></tt>, <tt><ref id=".ELSEIF" name=".ELSEIF"></tt> or
2734 <tt><ref id=".ENDIF" name=".ENDIF"></tt> directive.
2736 This command is often used to check if a macro parameter was given.
2737 Since an empty macro parameter will evaluate to nothing, the condition
2738 will evaluate to FALSE if an empty parameter was given.
2751 See also: <tt><ref id=".BLANK" name=".BLANK"></tt>
2754 <sect1><tt>.IFNDEF</tt><label id=".IFNDEF"><p>
2756 Conditional assembly: Check if a symbol is defined. Must be followed by
2757 a symbol name. The condition is true if the the given symbol is not
2758 defined, and false otherwise.
2760 See also: <tt><ref id=".DEFINED" name=".DEFINED"></tt>
2763 <sect1><tt>.IFNREF</tt><label id=".IFNREF"><p>
2765 Conditional assembly: Check if a symbol is referenced. Must be followed
2766 by a symbol name. The condition is true if if the the given symbol was
2767 not referenced before, and false otherwise.
2769 See also: <tt><ref id=".REFERENCED" name=".REFERENCED"></tt>
2772 <sect1><tt>.IFP02</tt><label id=".IFP02"><p>
2774 Conditional assembly: Check if the assembler is currently in 6502 mode
2775 (see <tt><ref id=".P02" name=".P02"></tt> command).
2778 <sect1><tt>.IFP816</tt><label id=".IFP816"><p>
2780 Conditional assembly: Check if the assembler is currently in 65816 mode
2781 (see <tt><ref id=".P816" name=".P816"></tt> command).
2784 <sect1><tt>.IFPC02</tt><label id=".IFPC02"><p>
2786 Conditional assembly: Check if the assembler is currently in 65C02 mode
2787 (see <tt><ref id=".PC02" name=".PC02"></tt> command).
2790 <sect1><tt>.IFPSC02</tt><label id=".IFPSC02"><p>
2792 Conditional assembly: Check if the assembler is currently in 65SC02 mode
2793 (see <tt><ref id=".PSC02" name=".PSC02"></tt> command).
2796 <sect1><tt>.IFREF</tt><label id=".IFREF"><p>
2798 Conditional assembly: Check if a symbol is referenced. Must be followed
2799 by a symbol name. The condition is true if if the the given symbol was
2800 referenced before, and false otherwise.
2802 This command may be used to build subroutine libraries in include files
2803 (you may use separate object modules for this purpose too).
2808 .ifref ToHex ; If someone used this subroutine
2809 ToHex: tay ; Define subroutine
2815 See also: <tt><ref id=".REFERENCED" name=".REFERENCED"></tt>
2818 <sect1><tt>.IMPORT</tt><label id=".IMPORT"><p>
2820 Import a symbol from another module. The command is followed by a comma
2821 separated list of symbols to import, with each one optionally followed by
2822 an address specification.
2828 .import bar: zeropage
2831 See: <tt><ref id=".IMPORTZP" name=".IMPORTZP"></tt>
2834 <sect1><tt>.IMPORTZP</tt><label id=".IMPORTZP"><p>
2836 Import a symbol from another module. The command is followed by a comma
2837 separated list of symbols to import. The symbols are explicitly imported
2838 as zero page symbols (that is, symbols with values in byte range).
2846 See: <tt><ref id=".IMPORT" name=".IMPORT"></tt>
2849 <sect1><tt>.INCBIN</tt><label id=".INCBIN"><p>
2851 Include a file as binary data. The command expects a string argument
2852 that is the name of a file to include literally in the current segment.
2853 In addition to that, a start offset and a size value may be specified,
2854 separated by commas. If no size is specified, all of the file from the
2855 start offset to end-of-file is used. If no start position is specified
2856 either, zero is assumed (which means that the whole file is inserted).
2861 ; Include whole file
2862 .incbin "sprites.dat"
2864 ; Include file starting at offset 256
2865 .incbin "music.dat", $100
2867 ; Read 100 bytes starting at offset 200
2868 .incbin "graphics.dat", 200, 100
2872 <sect1><tt>.INCLUDE</tt><label id=".INCLUDE"><p>
2874 Include another file. Include files may be nested up to a depth of 16.
2883 <sect1><tt>.INTERRUPTOR</tt><label id=".INTERRUPTOR"><p>
2885 Export a symbol and mark it as an interruptor. This may be used together
2886 with the linker to build a table of interruptor subroutines that are called
2889 Note: The linker has a feature to build a table of marked routines, but it
2890 is your code that must call these routines, so just declaring a symbol as
2891 interruptor does nothing by itself.
2893 An interruptor is always exported as an absolute (16 bit) symbol. You don't
2894 need to use an additional <tt/.export/ statement, this is implied by
2895 <tt/.interruptor/. It may have an optional priority that is separated by a
2896 comma. Higher numeric values mean a higher priority. If no priority is
2897 given, the default priority of 7 is used. Be careful when assigning
2898 priorities to your own module constructors so they won't interfere with the
2899 ones in the cc65 library.
2904 .interruptor IrqHandler
2905 .interruptor Handler, 16
2908 See the <tt><ref id=".CONDES" name=".CONDES"></tt> command and the separate
2909 section <ref id="condes" name="Module constructors/destructors"> explaining
2910 the feature in more detail.
2913 <sect1><tt>.LINECONT</tt><label id=".LINECONT"><p>
2915 Switch on or off line continuations using the backslash character
2916 before a newline. The option is off by default.
2917 Note: Line continuations do not work in a comment. A backslash at the
2918 end of a comment is treated as part of the comment and does not trigger
2920 The command must be followed by a '+' or '-' character to switch the
2921 option on or off respectively.
2926 .linecont + ; Allow line continuations
2929 #$20 ; This is legal now
2933 <sect1><tt>.LIST</tt><label id=".LIST"><p>
2935 Enable output to the listing. The command must be followed by a boolean
2936 switch ("on", "off", "+" or "-") and will enable or disable listing
2938 The option has no effect if the listing is not enabled by the command line
2939 switch -l. If -l is used, an internal counter is set to 1. Lines are output
2940 to the listing file, if the counter is greater than zero, and suppressed if
2941 the counter is zero. Each use of <tt/.LIST/ will increment or decrement the
2947 .list on ; Enable listing output
2951 <sect1><tt>.LISTBYTES</tt><label id=".LISTBYTES"><p>
2953 Set, how many bytes are shown in the listing for one source line. The
2954 default is 12, so the listing will show only the first 12 bytes for any
2955 source line that generates more than 12 bytes of code or data.
2956 The directive needs an argument, which is either "unlimited", or an
2957 integer constant in the range 4..255.
2962 .listbytes unlimited ; List all bytes
2963 .listbytes 12 ; List the first 12 bytes
2964 .incbin "data.bin" ; Include large binary file
2968 <sect1><tt>.LOBYTES</tt><label id=".LOBYTES"><p>
2970 Define byte sized data by extracting only the low byte (that is, bits 0-7) from
2971 each expression. This is equivalent to <tt><ref id=".BYTE" name=".BYTE"></tt> with
2972 the operator '<' prepended to each expression in its list.
2977 .lobytes $1234, $2345, $3456, $4567
2978 .hibytes $fedc, $edcb, $dcba, $cba9
2981 which is equivalent to
2984 .byte $34, $45, $56, $67
2985 .byte $fe, $ed, $dc, $cb
2991 .define MyTable TableItem0, TableItem1, TableItem2, TableItem3
2993 TableLookupLo: .lobytes MyTable
2994 TableLookupHi: .hibytes MyTable
2997 which is equivalent to
3000 TableLookupLo: .byte <TableItem0, <TableItem1, <TableItem2, <TableItem3
3001 TableLookupHi: .byte >TableItem0, >TableItem1, >TableItem2, >TableItem3
3004 See also: <tt><ref id=".BYTE" name=".BYTE"></tt>,
3005 <tt><ref id=".HIBYTES" name=".HIBYTES"></tt>,
3006 <tt><ref id=".BANKBYTES" name=".BANKBYTES"></tt>
3009 <sect1><tt>.LOCAL</tt><label id=".LOCAL"><p>
3011 This command may only be used inside a macro definition. It declares a
3012 list of identifiers as local to the macro expansion.
3014 A problem when using macros are labels: Since they don't change their name,
3015 you get a "duplicate symbol" error if the macro is expanded the second time.
3016 Labels declared with <tt><ref id=".LOCAL" name=".LOCAL"></tt> have their
3017 name mapped to an internal unique name (<tt/___ABCD__/) with each macro
3020 Some other assemblers start a new lexical block inside a macro expansion.
3021 This has some drawbacks however, since that will not allow <em/any/ symbol
3022 to be visible outside a macro, a feature that is sometimes useful. The
3023 <tt><ref id=".LOCAL" name=".LOCAL"></tt> command is in my eyes a better way
3024 to address the problem.
3026 You get an error when using <tt><ref id=".LOCAL" name=".LOCAL"></tt> outside
3030 <sect1><tt>.LOCALCHAR</tt><label id=".LOCALCHAR"><p>
3032 Defines the character that start "cheap" local labels. You may use one
3033 of '@' and '?' as start character. The default is '@'.
3035 Cheap local labels are labels that are visible only between two non
3036 cheap labels. This way you can reuse identifiers like "<tt/loop/" without
3037 using explicit lexical nesting.
3044 Clear: lda #$00 ; Global label
3045 ?Loop: sta Mem,y ; Local label
3049 Sub: ... ; New global label
3050 bne ?Loop ; ERROR: Unknown identifier!
3054 <sect1><tt>.MACPACK</tt><label id=".MACPACK"><p>
3056 Insert a predefined macro package. The command is followed by an
3057 identifier specifying the macro package to insert. Available macro
3061 atari Defines the scrcode macro.
3062 cbm Defines the scrcode macro.
3063 cpu Defines constants for the .CPU variable.
3064 generic Defines generic macros like add and sub.
3065 longbranch Defines conditional long jump macros.
3068 Including a macro package twice, or including a macro package that
3069 redefines already existing macros will lead to an error.
3074 .macpack longbranch ; Include macro package
3076 cmp #$20 ; Set condition codes
3077 jne Label ; Jump long on condition
3080 Macro packages are explained in more detail in section <ref
3081 id="macropackages" name="Macro packages">.
3084 <sect1><tt>.MAC, .MACRO</tt><label id=".MAC"><p>
3086 Start a classic macro definition. The command is followed by an identifier
3087 (the macro name) and optionally by a comma separated list of identifiers
3088 that are macro parameters.
3090 See section <ref id="macros" name="Macros">.
3093 <sect1><tt>.ORG</tt><label id=".ORG"><p>
3095 Start a section of absolute code. The command is followed by a constant
3096 expression that gives the new PC counter location for which the code is
3097 assembled. Use <tt><ref id=".RELOC" name=".RELOC"></tt> to switch back to
3100 By default, absolute/relocatable mode is global (valid even when switching
3101 segments). Using <tt>.FEATURE <ref id="org_per_seg" name="org_per_seg"></tt>
3102 it can be made segment local.
3104 Please note that you <em/do not need/ <tt/.ORG/ in most cases. Placing
3105 code at a specific address is the job of the linker, not the assembler, so
3106 there is usually no reason to assemble code to a specific address.
3111 .org $7FF ; Emit code starting at $7FF
3115 <sect1><tt>.OUT</tt><label id=".OUT"><p>
3117 Output a string to the console without producing an error. This command
3118 is similar to <tt/.ERROR/, however, it does not force an assembler error
3119 that prevents the creation of an object file.
3124 .out "This code was written by the codebuster(tm)"
3127 See also: <tt><ref id=".ERROR" name=".ERROR"></tt>,
3128 <tt><ref id=".FATAL" name=".FATAL"></tt>,
3129 <tt><ref id=".WARNING" name=".WARNING"></tt>
3132 <sect1><tt>.P02</tt><label id=".P02"><p>
3134 Enable the 6502 instruction set, disable 65SC02, 65C02 and 65816
3135 instructions. This is the default if not overridden by the
3136 <tt><ref id="option--cpu" name="--cpu"></tt> command line option.
3138 See: <tt><ref id=".PC02" name=".PC02"></tt>, <tt><ref id=".PSC02"
3139 name=".PSC02"></tt> and <tt><ref id=".P816" name=".P816"></tt>
3142 <sect1><tt>.P816</tt><label id=".P816"><p>
3144 Enable the 65816 instruction set. This is a superset of the 65SC02 and
3145 6502 instruction sets.
3147 See: <tt><ref id=".P02" name=".P02"></tt>, <tt><ref id=".PSC02"
3148 name=".PSC02"></tt> and <tt><ref id=".PC02" name=".PC02"></tt>
3151 <sect1><tt>.PAGELEN, .PAGELENGTH</tt><label id=".PAGELENGTH"><p>
3153 Set the page length for the listing. Must be followed by an integer
3154 constant. The value may be "unlimited", or in the range 32 to 127. The
3155 statement has no effect if no listing is generated. The default value is -1
3156 (unlimited) but may be overridden by the <tt/--pagelength/ command line
3157 option. Beware: Since ca65 is a one pass assembler, the listing is generated
3158 after assembly is complete, you cannot use multiple line lengths with one
3159 source. Instead, the value set with the last <tt/.PAGELENGTH/ is used.
3164 .pagelength 66 ; Use 66 lines per listing page
3166 .pagelength unlimited ; Unlimited page length
3170 <sect1><tt>.PC02</tt><label id=".PC02"><p>
3172 Enable the 65C02 instructions set. This instruction set includes all
3173 6502 and 65SC02 instructions.
3175 See: <tt><ref id=".P02" name=".P02"></tt>, <tt><ref id=".PSC02"
3176 name=".PSC02"></tt> and <tt><ref id=".P816" name=".P816"></tt>
3179 <sect1><tt>.POPCPU</tt><label id=".POPCPU"><p>
3181 Pop the last CPU setting from the stack, and activate it.
3183 This command will switch back to the CPU that was last pushed onto the CPU
3184 stack using the <tt><ref id=".PUSHCPU" name=".PUSHCPU"></tt> command, and
3185 remove this entry from the stack.
3187 The assembler will print an error message if the CPU stack is empty when
3188 this command is issued.
3190 See: <tt><ref id=".CPU" name=".CPU"></tt>, <tt><ref id=".PUSHCPU"
3191 name=".PUSHCPU"></tt>, <tt><ref id=".SETCPU" name=".SETCPU"></tt>
3194 <sect1><tt>.POPSEG</tt><label id=".POPSEG"><p>
3196 Pop the last pushed segment from the stack, and set it.
3198 This command will switch back to the segment that was last pushed onto the
3199 segment stack using the <tt><ref id=".PUSHSEG" name=".PUSHSEG"></tt>
3200 command, and remove this entry from the stack.
3202 The assembler will print an error message if the segment stack is empty
3203 when this command is issued.
3205 See: <tt><ref id=".PUSHSEG" name=".PUSHSEG"></tt>
3208 <sect1><tt>.PROC</tt><label id=".PROC"><p>
3210 Start a nested lexical level with the given name and adds a symbol with this
3211 name to the enclosing scope. All new symbols from now on are in the local
3212 lexical level and are accessible from outside only via <ref id="scopesyntax"
3213 name="explicit scope specification">. Symbols defined outside this local
3214 level may be accessed as long as their names are not used for new symbols
3215 inside the level. Symbols names in other lexical levels do not clash, so you
3216 may use the same names for identifiers. The lexical level ends when the
3217 <tt><ref id=".ENDPROC" name=".ENDPROC"></tt> command is read. Lexical levels
3218 may be nested up to a depth of 16 (this is an artificial limit to protect
3219 against errors in the source).
3221 Note: Macro names are always in the global level and in a separate name
3222 space. There is no special reason for this, it's just that I've never
3223 had any need for local macro definitions.
3228 .proc Clear ; Define Clear subroutine, start new level
3230 L1: sta Mem,y ; L1 is local and does not cause a
3231 ; duplicate symbol error if used in other
3234 bne L1 ; Reference local symbol
3236 .endproc ; Leave lexical level
3239 See: <tt/<ref id=".ENDPROC" name=".ENDPROC">/ and <tt/<ref id=".SCOPE"
3243 <sect1><tt>.PSC02</tt><label id=".PSC02"><p>
3245 Enable the 65SC02 instructions set. This instruction set includes all
3248 See: <tt><ref id=".P02" name=".P02"></tt>, <tt><ref id=".PC02"
3249 name=".PC02"></tt> and <tt><ref id=".P816" name=".P816"></tt>
3252 <sect1><tt>.PUSHCPU</tt><label id=".PUSHCPU"><p>
3254 Push the currently active CPU onto a stack. The stack has a size of 8
3257 <tt/.PUSHCPU/ allows together with <tt><ref id=".POPCPU"
3258 name=".POPCPU"></tt> to switch to another CPU and to restore the old CPU
3259 later, without knowledge of the current CPU setting.
3261 The assembler will print an error message if the CPU stack is already full,
3262 when this command is issued.
3264 See: <tt><ref id=".CPU" name=".CPU"></tt>, <tt><ref id=".POPCPU"
3265 name=".POPCPU"></tt>, <tt><ref id=".SETCPU" name=".SETCPU"></tt>
3268 <sect1><tt>.PUSHSEG</tt><label id=".PUSHSEG"><p>
3270 Push the currently active segment onto a stack. The entries on the stack
3271 include the name of the segment and the segment type. The stack has a size
3274 <tt/.PUSHSEG/ allows together with <tt><ref id=".POPSEG" name=".POPSEG"></tt>
3275 to switch to another segment and to restore the old segment later, without
3276 even knowing the name and type of the current segment.
3278 The assembler will print an error message if the segment stack is already
3279 full, when this command is issued.
3281 See: <tt><ref id=".POPSEG" name=".POPSEG"></tt>
3284 <sect1><tt>.RELOC</tt><label id=".RELOC"><p>
3286 Switch back to relocatable mode. See the <tt><ref id=".ORG"
3287 name=".ORG"></tt> command.
3290 <sect1><tt>.REPEAT</tt><label id=".REPEAT"><p>
3292 Repeat all commands between <tt/.REPEAT/ and <tt><ref id=".ENDREPEAT"
3293 name=".ENDREPEAT"></tt> constant number of times. The command is followed by
3294 a constant expression that tells how many times the commands in the body
3295 should get repeated. Optionally, a comma and an identifier may be specified.
3296 If this identifier is found in the body of the repeat statement, it is
3297 replaced by the current repeat count (starting with zero for the first time
3298 the body is repeated).
3300 <tt/.REPEAT/ statements may be nested. If you use the same repeat count
3301 identifier for a nested <tt/.REPEAT/ statement, the one from the inner
3302 level will be used, not the one from the outer level.
3306 The following macro will emit a string that is "encrypted" in that all
3307 characters of the string are XORed by the value $55.
3311 .repeat .strlen(Arg), I
3312 .byte .strat(Arg, I) ^ $55
3317 See: <tt><ref id=".ENDREPEAT" name=".ENDREPEAT"></tt>
3320 <sect1><tt>.RES</tt><label id=".RES"><p>
3322 Reserve storage. The command is followed by one or two constant
3323 expressions. The first one is mandatory and defines, how many bytes of
3324 storage should be defined. The second, optional expression must by a
3325 constant byte value that will be used as value of the data. If there
3326 is no fill value given, the linker will use the value defined in the
3327 linker configuration file (default: zero).
3332 ; Reserve 12 bytes of memory with value $AA
3337 <sect1><tt>.RODATA</tt><label id=".RODATA"><p>
3339 Switch to the RODATA segment. The name of the RODATA segment is always
3340 "RODATA", so this is a shortcut for
3346 The RODATA segment is a segment that is used by the compiler for
3347 readonly data like string constants.
3349 See also the <tt><ref id=".SEGMENT" name=".SEGMENT"></tt> command.
3352 <sect1><tt>.SCOPE</tt><label id=".SCOPE"><p>
3354 Start a nested lexical level with the given name. All new symbols from now
3355 on are in the local lexical level and are accessible from outside only via
3356 <ref id="scopesyntax" name="explicit scope specification">. Symbols defined
3357 outside this local level may be accessed as long as their names are not used
3358 for new symbols inside the level. Symbols names in other lexical levels do
3359 not clash, so you may use the same names for identifiers. The lexical level
3360 ends when the <tt><ref id=".ENDSCOPE" name=".ENDSCOPE"></tt> command is
3361 read. Lexical levels may be nested up to a depth of 16 (this is an
3362 artificial limit to protect against errors in the source).
3364 Note: Macro names are always in the global level and in a separate name
3365 space. There is no special reason for this, it's just that I've never
3366 had any need for local macro definitions.
3371 .scope Error ; Start new scope named Error
3373 File = 1 ; File error
3374 Parse = 2 ; Parse error
3375 .endscope ; Close lexical level
3378 lda #Error::File ; Use symbol from scope Error
3381 See: <tt/<ref id=".ENDSCOPE" name=".ENDSCOPE">/ and <tt/<ref id=".PROC"
3385 <sect1><tt>.SEGMENT</tt><label id=".SEGMENT"><p>
3387 Switch to another segment. Code and data is always emitted into a
3388 segment, that is, a named section of data. The default segment is
3389 "CODE". There may be up to 254 different segments per object file
3390 (and up to 65534 per executable). There are shortcut commands for
3391 the most common segments ("CODE", "DATA" and "BSS").
3393 The command is followed by a string containing the segment name (there are
3394 some constraints for the name - as a rule of thumb use only those segment
3395 names that would also be valid identifiers). There may also be an optional
3396 address size separated by a colon. See the section covering <tt/<ref
3397 id="address-sizes" name="address sizes">/ for more information.
3399 The default address size for a segment depends on the memory model specified
3400 on the command line. The default is "absolute", which means that you don't
3401 have to use an address size modifier in most cases.
3403 "absolute" means that the is a segment with 16 bit (absolute) addressing.
3404 That is, the segment will reside somewhere in core memory outside the zero
3405 page. "zeropage" (8 bit) means that the segment will be placed in the zero
3406 page and direct (short) addressing is possible for data in this segment.
3408 Beware: Only labels in a segment with the zeropage attribute are marked
3409 as reachable by short addressing. The `*' (PC counter) operator will
3410 work as in other segments and will create absolute variable values.
3412 Please note that a segment cannot have two different address sizes. A
3413 segment specified as zeropage cannot be declared as being absolute later.
3418 .segment "ROM2" ; Switch to ROM2 segment
3419 .segment "ZP2": zeropage ; New direct segment
3420 .segment "ZP2" ; Ok, will use last attribute
3421 .segment "ZP2": absolute ; Error, redecl mismatch
3424 See: <tt><ref id=".BSS" name=".BSS"></tt>, <tt><ref id=".CODE"
3425 name=".CODE"></tt>, <tt><ref id=".DATA" name=".DATA"></tt> and <tt><ref
3426 id=".RODATA" name=".RODATA"></tt>
3429 <sect1><tt>.SETCPU</tt><label id=".SETCPU"><p>
3431 Switch the CPU instruction set. The command is followed by a string that
3432 specifies the CPU. Possible values are those that can also be supplied to
3433 the <tt><ref id="option--cpu" name="--cpu"></tt> command line option,
3434 namely: 6502, 6502X, 65SC02, 65C02, 65816, sunplus and HuC6280. Please
3435 note that support for the sunplus CPU is not available in the freeware
3436 version, because the instruction set of the sunplus CPU is "proprietary
3439 See: <tt><ref id=".CPU" name=".CPU"></tt>,
3440 <tt><ref id=".IFP02" name=".IFP02"></tt>,
3441 <tt><ref id=".IFP816" name=".IFP816"></tt>,
3442 <tt><ref id=".IFPC02" name=".IFPC02"></tt>,
3443 <tt><ref id=".IFPSC02" name=".IFPSC02"></tt>,
3444 <tt><ref id=".P02" name=".P02"></tt>,
3445 <tt><ref id=".P816" name=".P816"></tt>,
3446 <tt><ref id=".PC02" name=".PC02"></tt>,
3447 <tt><ref id=".PSC02" name=".PSC02"></tt>
3450 <sect1><tt>.SMART</tt><label id=".SMART"><p>
3452 Switch on or off smart mode. The command must be followed by a '+' or '-'
3453 character to switch the option on or off respectively. The default is off
3454 (that is, the assembler doesn't try to be smart), but this default may be
3455 changed by the -s switch on the command line.
3457 In smart mode the assembler will do the following:
3460 <item>Track usage of the <tt/REP/ and <tt/SEP/ instructions in 65816 mode
3461 and update the operand sizes accordingly. If the operand of such an
3462 instruction cannot be evaluated by the assembler (for example, because
3463 the operand is an imported symbol), a warning is issued. Beware: Since
3464 the assembler cannot trace the execution flow this may lead to false
3465 results in some cases. If in doubt, use the <tt/.Inn/ and <tt/.Ann/
3466 instructions to tell the assembler about the current settings.
3467 <item>In 65816 mode, replace a <tt/RTS/ instruction by <tt/RTL/ if it is
3468 used within a procedure declared as <tt/far/, or if the procedure has
3469 no explicit address specification, but it is <tt/far/ because of the
3477 .smart - ; Stop being smart
3480 See: <tt><ref id=".A16" name=".A16"></tt>,
3481 <tt><ref id=".A8" name=".A8"></tt>,
3482 <tt><ref id=".I16" name=".I16"></tt>,
3483 <tt><ref id=".I8" name=".I8"></tt>
3486 <sect1><tt>.STRUCT</tt><label id=".STRUCT"><p>
3488 Starts a struct definition. Structs are covered in a separate section named
3489 <ref id="structs" name=""Structs and unions"">.
3491 See: <tt><ref id=".ENDSTRUCT" name=".ENDSTRUCT"></tt>
3494 <sect1><tt>.SUNPLUS</tt><label id=".SUNPLUS"><p>
3496 Enable the SunPlus instructions set. This command will not work in the
3497 freeware version of the assembler, because the instruction set is
3498 "proprietary and confidential".
3500 See: <tt><ref id=".P02" name=".P02"></tt>, <tt><ref id=".PSC02"
3501 name=".PSC02"></tt>, <tt><ref id=".PC02" name=".PC02"></tt>, and
3502 <tt><ref id=".P816" name=".P816"></tt>
3505 <sect1><tt>.TAG</tt><label id=".TAG"><p>
3507 Allocate space for a struct or union.
3518 .tag Point ; Allocate 4 bytes
3522 <sect1><tt>.WARNING</tt><label id=".WARNING"><p>
3524 Force an assembly warning. The assembler will output a warning message
3525 preceded by "User warning". This warning will always be output, even if
3526 other warnings are disabled with the <tt><ref id="option-W" name="-W0"></tt>
3527 command line option.
3529 This command may be used to output possible problems when assembling
3538 .warning "Forward jump in jne, cannot optimize!"
3548 See also: <tt><ref id=".ERROR" name=".ERROR"></tt>
3549 <tt><ref id=".FATAL" name=".FATAL"></tt>,
3550 <tt><ref id=".OUT" name=".OUT"></tt>
3553 <sect1><tt>.WORD</tt><label id=".WORD"><p>
3555 Define word sized data. Must be followed by a sequence of (word ranged,
3556 but not necessarily constant) expressions.
3561 .word $0D00, $AF13, _Clear
3565 <sect1><tt>.ZEROPAGE</tt><label id=".ZEROPAGE"><p>
3567 Switch to the ZEROPAGE segment and mark it as direct (zeropage) segment.
3568 The name of the ZEROPAGE segment is always "ZEROPAGE", so this is a
3572 .segment "ZEROPAGE", zeropage
3575 Because of the "zeropage" attribute, labels declared in this segment are
3576 addressed using direct addressing mode if possible. You <em/must/ instruct
3577 the linker to place this segment somewhere in the address range 0..$FF
3578 otherwise you will get errors.
3580 See: <tt><ref id=".SEGMENT" name=".SEGMENT"></tt>
3584 <sect>Macros<label id="macros"><p>
3587 <sect1>Introduction<p>
3589 Macros may be thought of as "parametrized super instructions". Macros are
3590 sequences of tokens that have a name. If that name is used in the source
3591 file, the macro is "expanded", that is, it is replaced by the tokens that
3592 were specified when the macro was defined.
3595 <sect1>Macros without parameters<p>
3597 In it's simplest form, a macro does not have parameters. Here's an
3601 .macro asr ; Arithmetic shift right
3602 cmp #$80 ; Put bit 7 into carry
3603 ror ; Rotate right with carry
3607 The macro above consists of two real instructions, that are inserted into
3608 the code, whenever the macro is expanded. Macro expansion is simply done
3609 by using the name, like this:
3618 <sect1>Parametrized macros<p>
3620 When using macro parameters, macros can be even more useful:
3634 When calling the macro, you may give a parameter, and each occurrence of
3635 the name "addr" in the macro definition will be replaced by the given
3654 A macro may have more than one parameter, in this case, the parameters
3655 are separated by commas. You are free to give less parameters than the
3656 macro actually takes in the definition. You may also leave intermediate
3657 parameters empty. Empty parameters are replaced by empty space (that is,
3658 they are removed when the macro is expanded). If you have a look at our
3659 macro definition above, you will see, that replacing the "addr" parameter
3660 by nothing will lead to wrong code in most lines. To help you, writing
3661 macros with a variable parameter list, there are some control commands:
3663 <tt><ref id=".IFBLANK" name=".IFBLANK"></tt> tests the rest of the line and
3664 returns true, if there are any tokens on the remainder of the line. Since
3665 empty parameters are replaced by nothing, this may be used to test if a given
3666 parameter is empty. <tt><ref id=".IFNBLANK" name=".IFNBLANK"></tt> tests the
3669 Look at this example:
3672 .macro ldaxy a, x, y
3685 This macro may be called as follows:
3688 ldaxy 1, 2, 3 ; Load all three registers
3690 ldaxy 1, , 3 ; Load only a and y
3692 ldaxy , , 3 ; Load y only
3695 There's another helper command for determining, which macro parameters are
3696 valid: <tt><ref id=".PARAMCOUNT" name=".PARAMCOUNT"></tt> This command is
3697 replaced by the parameter count given, <em/including/ intermediate empty macro
3701 ldaxy 1 ; .PARAMCOUNT = 1
3702 ldaxy 1,,3 ; .PARAMCOUNT = 3
3703 ldaxy 1,2 ; .PARAMCOUNT = 2
3704 ldaxy 1, ; .PARAMCOUNT = 2
3705 ldaxy 1,2,3 ; .PARAMCOUNT = 3
3708 Macro parameters may optionally be enclosed into curly braces. This allows the
3709 inclusion of tokens that would otherwise terminate the parameter (the comma in
3710 case of a macro parameter).
3713 .macro foo arg1, arg2
3717 foo ($00,x) ; Two parameters passed
3718 foo {($00,x)} ; One parameter passed
3721 In the first case, the macro is called with two parameters: '<tt/($00/'
3722 and 'x)'. The comma is not passed to the macro, since it is part of the
3723 calling sequence, not the parameters.
3725 In the second case, '($00,x)' is passed to the macro, this time
3726 including the comma.
3729 <sect1>Detecting parameter types<p>
3731 Sometimes it is nice to write a macro that acts differently depending on the
3732 type of the argument supplied. An example would be a macro that loads a 16 bit
3733 value from either an immediate operand, or from memory. The <tt/<ref
3734 id=".MATCH" name=".MATCH">/ and <tt/<ref id=".XMATCH" name=".XMATCH">/
3735 functions will allow you to do exactly this:
3739 .if (.match (.left (1, {arg}), #))
3741 lda #<(.right (.tcount ({arg})-1, {arg}))
3742 ldx #>(.right (.tcount ({arg})-1, {arg}))
3744 ; assume absolute or zero page
3751 Using the <tt/<ref id=".MATCH" name=".MATCH">/ function, the macro is able to
3752 check if its argument begins with a hash mark. If so, two immediate loads are
3753 emitted, Otherwise a load from an absolute zero page memory location is
3754 assumed. Please note how the curly braces are used to enclose parameters to
3755 pseudo functions handling token lists. This is necessary, because the token
3756 lists may include commas or parens, which would be treated by the assembler
3759 The macro can be used as
3764 ldax #$1234 ; X=$12, A=$34
3766 ldax foo ; X=$56, A=$78
3770 <sect1>Recursive macros<p>
3772 Macros may be used recursively:
3775 .macro push r1, r2, r3
3784 There's also a special macro to help writing recursive macros: <tt><ref
3785 id=".EXITMACRO" name=".EXITMACRO"></tt> This command will stop macro expansion
3789 .macro push r1, r2, r3, r4, r5, r6, r7
3791 ; First parameter is empty
3797 push r2, r3, r4, r5, r6, r7
3801 When expanding this macro, the expansion will push all given parameters
3802 until an empty one is encountered. The macro may be called like this:
3805 push $20, $21, $32 ; Push 3 ZP locations
3806 push $21 ; Push one ZP location
3810 <sect1>Local symbols inside macros<p>
3812 Now, with recursive macros, <tt><ref id=".IFBLANK" name=".IFBLANK"></tt> and
3813 <tt><ref id=".PARAMCOUNT" name=".PARAMCOUNT"></tt>, what else do you need?
3814 Have a look at the inc16 macro above. Here is it again:
3828 If you have a closer look at the code, you will notice, that it could be
3829 written more efficiently, like this:
3840 But imagine what happens, if you use this macro twice? Since the label
3841 "Skip" has the same name both times, you get a "duplicate symbol" error.
3842 Without a way to circumvent this problem, macros are not as useful, as
3843 they could be. One solution is, to start a new lexical block inside the
3857 Now the label is local to the block and not visible outside. However,
3858 sometimes you want a label inside the macro to be visible outside. To make
3859 that possible, there's a new command that's only usable inside a macro
3860 definition: <tt><ref id=".LOCAL" name=".LOCAL"></tt>. <tt/.LOCAL/ declares one
3861 or more symbols as local to the macro expansion. The names of local variables
3862 are replaced by a unique name in each separate macro expansion. So we could
3863 also solve the problem above by using <tt/.LOCAL/:
3867 .local Skip ; Make Skip a local symbol
3874 Skip: ; Not visible outside
3879 <sect1>C style macros<p>
3881 Starting with version 2.5 of the assembler, there is a second macro type
3882 available: C style macros using the <tt/.DEFINE/ directive. These macros are
3883 similar to the classic macro type described above, but behaviour is sometimes
3888 <item> Macros defined with <tt><ref id=".DEFINE" name=".DEFINE"></tt> may not
3889 span more than a line. You may use line continuation (see <tt><ref
3890 id=".LINECONT" name=".LINECONT"></tt>) to spread the definition over
3891 more than one line for increased readability, but the macro itself
3892 may not contain an end-of-line token.
3894 <item> Macros defined with <tt><ref id=".DEFINE" name=".DEFINE"></tt> share
3895 the name space with classic macros, but they are detected and replaced
3896 at the scanner level. While classic macros may be used in every place,
3897 where a mnemonic or other directive is allowed, <tt><ref id=".DEFINE"
3898 name=".DEFINE"></tt> style macros are allowed anywhere in a line. So
3899 they are more versatile in some situations.
3901 <item> <tt><ref id=".DEFINE" name=".DEFINE"></tt> style macros may take
3902 parameters. While classic macros may have empty parameters, this is
3903 not true for <tt><ref id=".DEFINE" name=".DEFINE"></tt> style macros.
3904 For this macro type, the number of actual parameters must match
3905 exactly the number of formal parameters.
3907 To make this possible, formal parameters are enclosed in braces when
3908 defining the macro. If there are no parameters, the empty braces may
3911 <item> Since <tt><ref id=".DEFINE" name=".DEFINE"></tt> style macros may not
3912 contain end-of-line tokens, there are things that cannot be done. They
3913 may not contain several processor instructions for example. So, while
3914 some things may be done with both macro types, each type has special
3915 usages. The types complement each other.
3919 Let's look at a few examples to make the advantages and disadvantages
3922 To emulate assemblers that use "<tt/EQU/" instead of "<tt/=/" you may use the
3923 following <tt/.DEFINE/:
3928 foo EQU $1234 ; This is accepted now
3931 You may use the directive to define string constants used elsewhere:
3934 ; Define the version number
3935 .define VERSION "12.3a"
3941 Macros with parameters may also be useful:
3944 .define DEBUG(message) .out message
3946 DEBUG "Assembling include file #3"
3949 Note that, while formal parameters have to be placed in braces, this is
3950 not true for the actual parameters. Beware: Since the assembler cannot
3951 detect the end of one parameter, only the first token is used. If you
3952 don't like that, use classic macros instead:
3960 (This is an example where a problem can be solved with both macro types).
3963 <sect1>Characters in macros<p>
3965 When using the <ref id="option-t" name="-t"> option, characters are translated
3966 into the target character set of the specific machine. However, this happens
3967 as late as possible. This means that strings are translated if they are part
3968 of a <tt><ref id=".BYTE" name=".BYTE"></tt> or <tt><ref id=".ASCIIZ"
3969 name=".ASCIIZ"></tt> command. Characters are translated as soon as they are
3970 used as part of an expression.
3972 This behaviour is very intuitive outside of macros but may be confusing when
3973 doing more complex macros. If you compare characters against numeric values,
3974 be sure to take the translation into account.
3979 <sect>Macro packages<label id="macropackages"><p>
3981 Using the <tt><ref id=".MACPACK" name=".MACPACK"></tt> directive, predefined
3982 macro packages may be included with just one command. Available macro packages
3986 <sect1><tt>.MACPACK generic</tt><p>
3988 This macro package defines macros that are useful in almost any program.
3989 Currently defined macros are:
4024 <sect1><tt>.MACPACK longbranch</tt><p>
4026 This macro package defines long conditional jumps. They are named like the
4027 short counterpart but with the 'b' replaced by a 'j'. Here is a sample
4028 definition for the "<tt/jeq/" macro, the other macros are built using the same
4033 .if .def(Target) .and ((*+2)-(Target) <= 127)
4042 All macros expand to a short branch, if the label is already defined (back
4043 jump) and is reachable with a short jump. Otherwise the macro expands to a
4044 conditional branch with the branch condition inverted, followed by an absolute
4045 jump to the actual branch target.
4047 The package defines the following macros:
4050 jeq, jne, jmi, jpl, jcs, jcc, jvs, jvc
4055 <sect1><tt>.MACPACK cbm</tt><p>
4057 The cbm macro package will define a macro named <tt/scrcode/. It takes a
4058 string as argument and places this string into memory translated into screen
4062 <sect1><tt>.MACPACK cpu</tt><p>
4064 This macro package does not define any macros but constants used to examine
4065 the value read from the <tt/<ref id=".CPU" name=".CPU">/ pseudo variable. For
4066 each supported CPU a constant similar to
4078 is defined. These constants may be used to determine the exact type of the
4079 currently enabled CPU. In addition to that, for each CPU instruction set,
4080 another constant is defined:
4092 The value read from the <tt/<ref id=".CPU" name=".CPU">/ pseudo variable may
4093 be checked with <tt/<ref id="operators" name=".BITAND">/ to determine if the
4094 currently enabled CPU supports a specific instruction set. For example the
4095 65C02 supports all instructions of the 65SC02 CPU, so it has the
4096 <tt/CPU_ISET_65SC02/ bit set in addition to its native <tt/CPU_ISET_65C02/
4100 .if (.cpu .bitand CPU_ISET_65SC02)
4108 it is possible to determine if the
4114 instruction is supported, which is the case for the 65SC02, 65C02 and 65816
4115 CPUs (the latter two are upwards compatible to the 65SC02).
4119 <sect>Predefined constants<label id="predefined-constants"><p>
4121 For better orthogonality, the assembler defines similar symbols as the
4122 compiler, depending on the target system selected:
4125 <item><tt/__APPLE2__/ - Target system is <tt/apple2/
4126 <item><tt/__APPLE2ENH__/ - Target system is <tt/apple2enh/
4127 <item><tt/__ATARI__/ - Target system is <tt/atari/
4128 <item><tt/__ATMOS__/ - Target system is <tt/atmos/
4129 <item><tt/__BBC__/ - Target system is <tt/bbc/
4130 <item><tt/__C128__/ - Target system is <tt/c128/
4131 <item><tt/__C16__/ - Target system is <tt/c16/
4132 <item><tt/__C64__/ - Target system is <tt/c64/
4133 <item><tt/__CBM__/ - Target is a Commodore system
4134 <item><tt/__CBM510__/ - Target system is <tt/cbm510/
4135 <item><tt/__CBM610__/ - Target system is <tt/cbm610/
4136 <item><tt/__GEOS__/ - Target system is <tt/geos/
4137 <item><tt/__LUNIX__/ - Target system is <tt/lunix/
4138 <item><tt/__NES__/ - Target system is <tt/nes/
4139 <item><tt/__PET__/ - Target system is <tt/pet/
4140 <item><tt/__PLUS4__/ - Target system is <tt/plus4/
4141 <item><tt/__SUPERVISION__/ - Target system is <tt/supervision/
4142 <item><tt/__VIC20__/ - Target system is <tt/vic20/
4146 <sect>Structs and unions<label id="structs"><p>
4148 <sect1>Structs and unions Overview<p>
4150 Structs and unions are special forms of <ref id="scopes" name="scopes">. They
4151 are to some degree comparable to their C counterparts. Both have a list of
4152 members. Each member allocates storage and may optionally have a name, which,
4153 in case of a struct, is the offset from the beginning and, in case of a union,
4157 <sect1>Declaration<p>
4159 Here is an example for a very simple struct with two members and a total size
4169 A union shares the total space between all its members, its size is the same
4170 as that of the largest member.
4172 A struct or union must not necessarily have a name. If it is anonymous, no
4173 local scope is opened, the identifiers used to name the members are placed
4174 into the current scope instead.
4176 A struct may contain unnamed members and definitions of local structs. The
4177 storage allocators may contain a multiplier, as in the example below:
4182 .word 2 ; Allocate two words
4189 <sect1>The <tt/.TAG/ keyword<p>
4191 Using the <ref id=".TAG" name=".TAG"> keyword, it is possible to reserve space
4192 for an already defined struct or unions within another struct:
4206 Space for a struct or union may be allocated using the <ref id=".TAG"
4207 name=".TAG"> directive.
4213 Currently, members are just offsets from the start of the struct or union. To
4214 access a field of a struct, the member offset has to be added to the address
4215 of the struct itself:
4218 lda C+Circle::Radius ; Load circle radius into A
4221 This may change in a future version of the assembler.
4224 <sect1>Limitations<p>
4226 Structs and unions are currently implemented as nested symbol tables (in fact,
4227 they were a by-product of the improved scoping rules). Currently, the
4228 assembler has no idea of types. This means that the <ref id=".TAG"
4229 name=".TAG"> keyword will only allocate space. You won't be able to initialize
4230 variables declared with <ref id=".TAG" name=".TAG">, and adding an embedded
4231 structure to another structure with <ref id=".TAG" name=".TAG"> will not make
4232 this structure accessible by using the '::' operator.
4236 <sect>Module constructors/destructors<label id="condes"><p>
4238 <em>Note:</em> This section applies mostly to C programs, so the explanation
4239 below uses examples from the C libraries. However, the feature may also be
4240 useful for assembler programs.
4243 <sect1>Module constructors/destructors Overview<p>
4245 Using the <tt><ref id=".CONSTRUCTOR" name=".CONSTRUCTOR"></tt>, <tt><ref
4246 id=".DESTRUCTOR" name=".DESTRUCTOR"></tt> and <tt><ref id=".INTERRUPTOR"
4247 name=".INTERRUPTOR"></tt> keywords it it possible to export functions in a
4248 special way. The linker is able to generate tables with all functions of a
4249 specific type. Such a table will <em>only</em> include symbols from object
4250 files that are linked into a specific executable. This may be used to add
4251 initialization and cleanup code for library modules, or a table of interrupt
4254 The C heap functions are an example where module initialization code is used.
4255 All heap functions (<tt>malloc</tt>, <tt>free</tt>, ...) work with a few
4256 variables that contain the start and the end of the heap, pointers to the free
4257 list and so on. Since the end of the heap depends on the size and start of the
4258 stack, it must be initialized at runtime. However, initializing these
4259 variables for programs that do not use the heap are a waste of time and
4262 So the central module defines a function that contains initialization code and
4263 exports this function using the <tt/.CONSTRUCTOR/ statement. If (and only if)
4264 this module is added to an executable by the linker, the initialization
4265 function will be placed into the table of constructors by the linker. The C
4266 startup code will call all constructors before <tt/main/ and all destructors
4267 after <tt/main/, so without any further work, the heap initialization code is
4268 called once the module is linked in.
4270 While it would be possible to add explicit calls to initialization functions
4271 in the startup code, the new approach has several advantages:
4275 If a module is not included, the initialization code is not linked in and not
4276 called. So you don't pay for things you don't need.
4279 Adding another library that needs initialization does not mean that the
4280 startup code has to be changed. Before we had module constructors and
4281 destructors, the startup code for all systems had to be adjusted to call the
4282 new initialization code.
4285 The feature saves memory: Each additional initialization function needs just
4286 two bytes in the table (a pointer to the function).
4291 <sect1>Calling order<p>
4293 The symbols are sorted in increasing priority order by the linker when using
4294 one of the builtin linker configurations, so the functions with lower
4295 priorities come first and are followed by those with higher priorities. The C
4296 library runtime subroutine that walks over the function tables calls the
4297 functions starting from the top of the table - which means that functions with
4298 a high priority are called first.
4300 So when using the C runtime, functions are called with high priority functions
4301 first, followed by low priority functions.
4306 When using these special symbols, please take care of the following:
4311 The linker will only generate function tables, it will not generate code to
4312 call these functions. If you're using the feature in some other than the
4313 existing C environments, you have to write code to call all functions in a
4314 linker generated table yourself. See the <tt/condes/ and <tt/callirq/ modules
4315 in the C runtime for an example on how to do this.
4318 The linker will only add addresses of functions that are in modules linked to
4319 the executable. This means that you have to be careful where to place the
4320 condes functions. If initialization or an irq handler is needed for a group of
4321 functions, be sure to place the function into a module that is linked in
4322 regardless of which function is called by the user.
4325 The linker will generate the tables only when requested to do so by the
4326 <tt/FEATURE CONDES/ statement in the linker config file. Each table has to
4327 be requested separately.
4330 Constructors and destructors may have priorities. These priorities determine
4331 the order of the functions in the table. If your initialization or cleanup code
4332 does depend on other initialization or cleanup code, you have to choose the
4333 priority for the functions accordingly.
4336 Besides the <tt><ref id=".CONSTRUCTOR" name=".CONSTRUCTOR"></tt>, <tt><ref
4337 id=".DESTRUCTOR" name=".DESTRUCTOR"></tt> and <tt><ref id=".INTERRUPTOR"
4338 name=".INTERRUPTOR"></tt> statements, there is also a more generic command:
4339 <tt><ref id=".CONDES" name=".CONDES"></tt>. This allows to specify an
4340 additional type. Predefined types are 0 (constructor), 1 (destructor) and 2
4341 (interruptor). The linker generates a separate table for each type on request.
4346 <sect>Porting sources from other assemblers<p>
4348 Sometimes it is necessary to port code written for older assemblers to ca65.
4349 In some cases, this can be done without any changes to the source code by
4350 using the emulation features of ca65 (see <tt><ref id=".FEATURE"
4351 name=".FEATURE"></tt>). In other cases, it is necessary to make changes to the
4354 Probably the biggest difference is the handling of the <tt><ref id=".ORG"
4355 name=".ORG"></tt> directive. ca65 generates relocatable code, and placement is
4356 done by the linker. Most other assemblers generate absolute code, placement is
4357 done within the assembler and there is no external linker.
4359 In general it is not a good idea to write new code using the emulation
4360 features of the assembler, but there may be situations where even this rule is
4365 You need to use some of the ca65 emulation features to simulate the behaviour
4366 of such simple assemblers.
4369 <item>Prepare your sourcecode like this:
4372 ; if you want TASS style labels without colons
4373 .feature labels_without_colons
4375 ; if you want TASS style character constants
4376 ; ("a" instead of the default 'a')
4377 .feature loose_char_term
4379 .word *+2 ; the cbm load address
4384 notice that the two emulation features are mostly useful for porting
4385 sources originally written in/for TASS, they are not needed for the
4386 actual "simple assembler operation" and are not recommended if you are
4387 writing new code from scratch.
4389 <item>Replace all program counter assignments (which are not possible in ca65
4390 by default, and the respective emulation feature works different from what
4391 you'd expect) by another way to skip to memory locations, for example the
4392 <tt><ref id=".RES" name=".RES"></tt> directive.
4396 .res $2000-* ; reserve memory up to $2000
4399 Please note that other than the original TASS, ca65 can never move the program
4400 counter backwards - think of it as if you are assembling to disk with TASS.
4402 <item>Conditional assembly (<tt/.ifeq//<tt/.endif//<tt/.goto/ etc.) must be
4403 rewritten to match ca65 syntax. Most importantly notice that due to the lack
4404 of <tt/.goto/, everything involving loops must be replaced by
4405 <tt><ref id=".REPEAT" name=".REPEAT"></tt>.
4407 <item>To assemble code to a different address than it is executed at, use the
4408 <tt><ref id=".ORG" name=".ORG"></tt> directive instead of
4409 <tt/.offs/-constructs.
4416 .reloc ; back to normal
4419 <item>Then assemble like this:
4422 cl65 --start-addr 0x0ffe -t none myprog.s -o myprog.prg
4425 Note that you need to use the actual start address minus two, since two bytes
4426 are used for the cbm load address.
4431 <sect>Bugs/Feedback<p>
4433 If you have problems using the assembler, if you find any bugs, or if
4434 you're doing something interesting with the assembler, I would be glad to
4435 hear from you. Feel free to contact me by email
4436 (<htmlurl url="mailto:uz@cc65.org" name="uz@cc65.org">).
4442 ca65 (and all cc65 binutils) are (C) Copyright 1998-2003 Ullrich von
4443 Bassewitz. For usage of the binaries and/or sources the following
4444 conditions do apply:
4446 This software is provided 'as-is', without any expressed or implied
4447 warranty. In no event will the authors be held liable for any damages
4448 arising from the use of this software.
4450 Permission is granted to anyone to use this software for any purpose,
4451 including commercial applications, and to alter it and redistribute it
4452 freely, subject to the following restrictions:
4455 <item> The origin of this software must not be misrepresented; you must not
4456 claim that you wrote the original software. If you use this software
4457 in a product, an acknowledgment in the product documentation would be
4458 appreciated but is not required.
4459 <item> Altered source versions must be plainly marked as such, and must not
4460 be misrepresented as being the original software.
4461 <item> This notice may not be removed or altered from any source