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>19.07.2000, 29.11.2000, 02.10.2001
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 Create a listing if assembly was ok
99 -o name Name the output file
101 -t sys Set the target system
102 -v Increase verbosity
105 --auto-import Mark unresolved symbols as import
106 --cpu type Set cpu type
107 --debug-info Add debug info to object file
108 --feature name Set an emulation feature
109 --help Help (this text)
110 --ignore-case Ignore case of symbols
111 --include-dir dir Set an include directory search path
112 --listing Create a listing if assembly was ok
113 --pagelength n Set the page length for the listing
114 --smart Enable smart mode
115 --target sys Set the target system
116 --verbose Increase verbosity
117 --version Print the assembler version
118 ---------------------------------------------------------------------------
122 <sect1>Command line options in detail<p>
124 Here is a description of all the command line options:
128 <label id="option--cpu">
129 <tag><tt>--cpu type</tt></tag>
131 Set the default for the CPU type. The option takes a parameter, which
134 6502, 65SC02, 65C02, 65816 and sunplus
136 The last one (sunplus) is not available in the freeware version, because the
137 instruction set of the sunplus CPU is "proprietary and confidential".
140 <label id="option--feature">
141 <tag><tt>--feature name</tt></tag>
143 Enable an emulation feature. This is identical as using <tt/.FEATURE/
144 in the source with two exceptions: Feature names must be lower case, and
145 each feature must be specified by using an extra <tt/--feature/ option,
146 comma separated lists are not allowed.
148 See the discussion of the <tt><ref id=".FEATURE" name=".FEATURE"></tt>
149 command for a list of emulation features.
152 <label id="option-g">
153 <tag><tt>-g, --debug-info</tt></tag>
155 When this option (or the equivalent control command <tt/.DEBUGINFO/) is
156 used, the assembler will add a section to the object file that contains
157 all symbols (including local ones) together with the symbol values and
158 source file positions. The linker will put these additional symbols into
159 the VICE label file, so even local symbols can be seen in the VICE
163 <tag><tt>-h, --help</tt></tag>
165 Print the short option summary shown above.
168 <tag><tt>-i, --ignore-case</tt></tag>
170 This option makes the assembler case insensitive on identifiers and labels.
171 This option will override the default, but may itself be overriden by the
172 <tt><ref id=".CASE" name=".CASE"></tt> control command.
175 <tag><tt>-l, --listing</tt></tag>
177 Generate an assembler listing. The listing file will always have the
178 name of the main input file with the extension replaced by ".lst". This
179 may change in future versions.
182 <tag><tt>-o name</tt></tag>
184 The default output name is the name of the input file with the extension
185 replaced by ".o". If you don't like that, you may give another name with
186 the -o option. The output file will be placed in the same directory as
187 the source file, or, if -o is given, the full path in this name is used.
190 <tag><tt>--pagelength n</tt></tag>
192 sets the length of a listing page in lines. See the <tt><ref
193 id=".PAGELENGTH" name=".PAGELENGTH"></tt> directive for more information.
196 <tag><tt>-s, --smart-mode</tt></tag>
198 In smart mode (enabled by -s or the <tt><ref id=".SMART" name=".SMART"></tt>
199 pseudo instruction) the assembler will track usage of the <tt/REP/ and
200 <tt/SEP/ instructions in 65816 mode and update the operand sizes
201 accordingly. If the operand of such an instruction cannot be evaluated by
202 the assembler (for example, because the operand is an imported symbol), a
205 Beware: Since the assembler cannot trace the execution flow this may
206 lead to false results in some cases. If in doubt, use the .ixx and .axx
207 instructions to tell the assembler about the current settings. Smart
208 mode is off by default.
211 <label id="option-t">
212 <tag><tt>-t sys, --target sys</tt></tag>
214 Set the target system. This will enable translation of character strings
215 and character constants into the character set of the target platform.
216 The default for the target system is "none", which means that no translation
217 will take place. The assembler supports the same target systems as the
218 compiler, see there for a list.
221 <tag><tt>-v, --verbose</tt></tag>
223 Increase the assembler verbosity. Usually only needed for debugging
224 purposes. You may use this option more than one time for even more
228 <tag><tt>-D</tt></tag>
230 This option allows you to define symbols on the command line. Without a
231 value, the symbol is defined with the value zero. When giving a value,
232 you may use the '$' prefix for hexadecimal symbols. Please note
233 that for some operating systems, '$' has a special meaning, so
234 you may have to quote the expression.
237 <tag><tt>-I dir, --include-dir dir</tt></tag>
239 Name a directory which is searched for include files. The option may be
240 used more than once to specify more than one directory to search. The
241 current directory is always searched first before considering any
242 additional directores.
245 <tag><tt>-U, --auto-import</tt></tag>
247 Mark symbols that are not defined in the sources as imported symbols. This
248 should be used with care since it delays error messages about typos and such
249 until the linker is run. The compiler uses the equivalent of this switch
250 (<tt><ref id=".AUTOIMPORT" name=".AUTOIMPORT"></tt>) to enable auto imported
251 symbols for the runtime library. However, the compiler is supposed to
252 generate code that runs through the assembler without problems, something
253 which is not always true for assembler programmers.
256 <tag><tt>-V, --version</tt></tag>
258 Print the version number of the assembler. If you send any suggestions
259 or bugfixes, please include the version number.
262 <label id="option-W">
263 <tag><tt>-Wn</tt></tag>
265 Set the warning level for the assembler. Using -W2 the assembler will
266 even warn about such things like unused imported symbols. The default
267 warning level is 1, and it would probably be silly to set it to
274 <sect>Input format<p>
276 <sect1>Assembler syntax<p>
278 The assembler accepts the standard 6502/65816 assembler syntax. One line may
279 contain a label (which is identified by a colon), and, in addition to the
280 label, an assembler mnemonic, a macro, or a control command (see section <ref
281 id="control-commands" name="Control Commands"> for supported control
282 commands). Alternatively, the line may contain a symbol definition using the
283 '=' token. Everything after a semicolon is handled as a comment (that is, it
286 Here are some examples for valid input lines:
289 Label: ; A label and a comment
290 lda #$20 ; A 6502 instruction plus comment
291 L1: ldx #$20 ; Same with label
292 L2: .byte "Hello world" ; Label plus control command
293 mymac $20 ; Macro expansion
294 MySym = 3*L1 ; Symbol definition
295 MaSym = Label ; Another symbol
298 The assembler accepts
301 <item>all valid 6502 mnemonics when in 6502 mode (the default or after the
302 <tt><ref id=".P02" name=".P02"></tt> command was given).
303 <item>all valid 65SC02 mnemonics when in 65SC02 mode (after the
304 <tt><ref id=".PSC02" name=".PSC02"></tt> command was given).
305 <item>all valid 65C02 mnemonics when in 65C02 mode (after the
306 <tt><ref id=".PC02" name=".PC02"></tt> command was given).
307 <item>all valid 65618 mnemonics when in 65816 mode (after the
308 <tt><ref id=".P816" name=".P816"></tt> command was given).
309 <item>all valid SunPlus mnemonics when in SunPlus mode (after the
310 <tt><ref id=".SUNPLUS" name=".SUNPLUS"></tt> command was given).
316 In 65816 mode several aliases are accepted in addition to the official
320 BGE is an alias for BCS
321 BLT is an alias for BCC
322 CPA is an alias for CMP
323 DEA is an alias for DEC A
324 INA is an alias for INC A
325 SWA is an alias for XBA
326 TAD is an alias for TCD
327 TAS is an alias for TCS
328 TDA is an alias for TDC
329 TSA is an alias for TSC
332 Evaluation of banked expressions in 65816 mode differs slightly from the
335 Instead of accepting a 24 bit address (something that is difficult for
336 the assembler to determine and would have required one more special
337 .import command), the bank and the absolute address in that bank are
341 jsl 3.$1234 ; Call subroutine at $1234 in bank 3
344 <sect1>Number format<p>
346 For literal values, the assembler accepts the widely used number formats:
347 A preceeding '$' denotes a hex value, a preceeding '%' denotes a
348 binary value, and a bare number is interpeted as a decimal. There are
349 currently no octal values and no floats.
352 <sect1>Conditional assembly<p>
354 Please note that when using the conditional directives (<tt/.IF/ and friends),
355 the input must consist of valid assembler tokens, even in <tt/.IF/ branches
356 that are not assembled. The reason for this behaviour is that the assembler
357 must still be able to detect the ending tokens (like <tt/.ENDIF/), so
358 conversion of the input stream into tokens still takes place. As a consequence
359 conditional assembly directives may <bf/not/ be used to prevent normal text
360 (used as a comment or similar) from being assembled. <p>
366 <sect1>Expression evaluation<p>
368 All expressions are evaluated with (at least) 32 bit precision. An
369 expression may contain constant values and any combination of internal and
370 external symbols. Expressions that cannot be evaluated at assembly time
371 are stored inside the object file for evaluation by the linker.
372 Expressions referencing imported symbols must always be evaluated by the
376 <sect1>Size of an expression result<p>
378 Sometimes, the assembler must know about the size of the value that is the
379 result of an expression. This is usually the case, if a decision has to be
380 made, to generate a zero page or an absolute memory references. In this
381 case, the assembler has to make some assumptions about the result of an
385 <item> If the result of an expression is constant, the actual value is
386 checked to see if it's a byte sized expression or not.
387 <item> If the expression is explicitly casted to a byte sized expression by
388 one of the '>', '<' or '^' operators, it is a byte expression.
389 <item> If this is not the case, and the expression contains a symbol,
390 explicitly declared as zero page symbol (by one of the .importzp or
391 .exportzp instructions), then the whole expression is assumed to be
393 <item> If the expression contains symbols that are not defined, and these
394 symbols are local symbols, the enclosing scopes are searched for a
395 symbol with the same name. If one exists and this symbol is defined,
396 it's attributes are used to determine the result size.
397 <item> In all other cases the expression is assumed to be word sized.
400 Note: If the assembler is not able to evaluate the expression at assembly
401 time, the linker will evaluate it and check for range errors as soon as
405 <sect1>Boolean expressions<p>
407 In the context of a boolean expression, any non zero value is evaluated as
408 true, any other value to false. The result of a boolean expression is 1 if
409 it's true, and zero if it's false. There are boolean operators with extrem
410 low precedence with version 2.x (where x > 0). The <tt/.AND/ and <tt/.OR/
411 operators are shortcut operators. That is, if the result of the expression is
412 already known, after evaluating the left hand side, the right hand side is
416 <sect1>Constant expressions<p>
418 Sometimes an expression must evaluate to a constant without looking at any
419 further input. One such example is the <tt/<ref id=".IF" name=".IF">/ command
420 that decides if parts of the code are assembled or not. An expression used in
421 the <tt/.IF/ command cannot reference a symbol defined later, because the
422 decision about the <tt/.IF/ must be made at the point when it is read. If the
423 expression used in such a context contains only constant numerical values,
424 there is no problem. When unresolvable symbols are involved it may get harder
425 for the assembler to determine if the expression is actually constant, and it
426 is even possible to create expressions that aren't recognized as constant.
427 Simplifying the expressions will often help.
429 In cases where the result of the expression is not needed immediately, the
430 assembler will delay evaluation until all input is read, at which point all
431 symbols are known. So using arbitrary complex constant expressions is no
432 problem in most cases.
436 <sect1>Available operators<label id="operators"><p>
438 Available operators sorted by precedence:
441 Op Description Precedence
442 -------------------------------------------------------------------
443 Builtin string functions 0
445 Builtin pseudo variables 1
446 Builtin pseudo functions 1
449 ~ Unary bitwise not 1
450 .BITNOT Unary bitwise not 1
451 < Low byte operator 1
452 > High byte operator 1
453 ^ Bank byte operator 1
457 .MOD Modulo operation 2
459 .BITAND Bitwise and 2
461 .BITXOR Bitwise xor 2
462 << Shift left operator 2
463 .SHL Shift left operator 2
464 >> Shift right operator
465 .SHR Shift right operator 2
472 = Compare operation (equal) 4
473 <> Compare operation (not equal) 4
474 < Compare operation (less) 4
475 > Compare operation (greater) 4
476 <= Compare operation (less or equal) 4
477 >= Compare operation (greater or equal) 4
479 && Boolean and 5
491 To force a specific order of evaluation, braces may be used as usual.
497 <sect>Symbols and labels<p>
499 The assembler allows you to use symbols instead of naked values to make
500 the source more readable. There are a lot of different ways to define and
501 use symbols and labels, giving a lot of flexibility.
504 <sect1>Numeric constants<p>
506 Numeric constants are defined using the equal sign or the label assignment
507 operator. After doing
513 may use the symbol "two" in every place where a number is expected, and it is
514 evaluated to the value 2 in this context. The label assignment operator causes
515 the same, but causes the symbol to be marked as a label, which may cause a
516 different handling in the debugger:
522 The right side can of course be an expression:
529 <sect1>Standard labels<p>
531 A label is defined by writing the name of the label at the start of the line
532 (before any instruction mnemonic, macro or pseudo directive), followed by a
533 colon. This will declare a symbol with the given name and the value of the
534 current program counter.
537 <sect1>Local labels and symbols<p>
539 Using the <tt><ref id=".PROC" name=".PROC"></tt> directive, it is possible to
540 create regions of code where the names of labels and symbols are local to this
541 region. They are not known outside of this region and cannot be accessed from
542 there. Such regions may be nested like PROCEDUREs in Pascal.
544 See the description of the <tt><ref id=".PROC" name=".PROC"></tt>
545 directive for more information.
548 <sect1>Cheap local labels<p>
550 Cheap local labels are defined like standard labels, but the name of the
551 label must begin with a special symbol (usually '@', but this can be
552 changed by the <tt><ref id=".LOCALCHAR" name=".LOCALCHAR"></tt>
555 Cheap local labels are visible only between two non cheap labels. As soon as a
556 standard symbol is encountered (this may also be a local symbol if inside a
557 region defined with the <tt><ref id=".PROC" name=".PROC"></tt> directive), the
558 cheap local symbol goes out of scope.
560 You may use cheap local labels as an easy way to reuse common label
561 names like "Loop". Here is an example:
564 Clear: lda #$00 ; Global label
566 @Loop: sta Mem,y ; Local label
570 Sub: ... ; New global label
571 bne @Loop ; ERROR: Unknown identifier!
574 <sect1>Unnamed labels<p>
576 If you really want to write messy code, there are also unnamed
577 labels. These labels do not have a name (you guessed that already,
578 didn't you?). A colon is used to mark the absence of the name.
580 Unnamed labels may be accessed by using the colon plus several minus
581 or plus characters as a label designator. Using the '-' characters
582 will create a back reference (use the n'th label backwards), using
583 '+' will create a forward reference (use the n'th label in forward
584 direction). An example will help to understand this:
606 As you can see from the example, unnamed labels will make even short
607 sections of code hard to understand, because you have to count labels
608 to find branch targets (this is the reason why I for my part do
609 prefer the "cheap" local labels). Nevertheless, unnamed labels are
610 convenient in some situations, so it's your decision.
613 <sect1>Using macros to define labels and constants<p>
615 While there are drawbacks with this approach, it may be handy in some
616 situations. Using <tt><ref id=".DEFINE" name=".DEFINE"></tt>, it is
617 possible to define symbols or constants that may be used elsewhere. Since
618 the macro facility works on a very low level, there is no scoping. On the
619 other side, you may also define string constants this way (this is not
620 possible with the other symbol types).
626 .DEFINE version "SOS V2.3"
628 four = two * two ; Ok
631 .PROC ; Start local scope
632 two = 3 ; Will give "2 = 3" - invalid!
637 <sect1>Symbols and <tt>.DEBUGINFO</tt><p>
639 If <tt><ref id=".DEBUGINFO" name=".DEBUGINFO"></tt> is enabled (or <ref
640 id="option-g" name="-g"> is given on the command line), global, local and
641 cheap local labels are written to the object file and will be available in the
642 symbol file via the linker. Unnamed labels are not written to the object file,
643 because they don't have a name which would allow to access them.
647 <sect>Scopes<label id="scopes"><p>
649 ca65 implements several sorts of scopes for symbols.
651 <sect1>Global scope<p>
653 All (non cheap local) symbols that are declared outside of any nested scopes
657 <sect1>A special scope: cheap locals<p>
659 A special scope is the scope for cheap local symbols. It lasts from one non
660 local symbol to the next one, without any provisions made by the programmer.
661 All other scopes differ in usage but use the same concept internally.
664 <sect1>Generic nested scopes<p>
666 A nested scoped for generic use is started with <tt/<ref id=".SCOPE"
667 name=".SCOPE">/ and closed with <tt/<ref id=".ENDSCOPE" name=".ENDSCOPE">/.
668 The scope can have a name, in which case it is accessible from the outside by
669 using <ref id="scopesyntax" name="explicit scopes">. If the scope does not
670 have a name, all symbols created within the scope are local to the scope, and
671 aren't accessible from the outside.
673 A nested scope can access symbols from the local or from enclosing scopes by
674 name without using explicit scope names. In some cases there may be
675 ambiguities, for example if there is a reference to a local symbol that is not
676 yet defined, but a symbol with the same name exists in outer scopes:
688 In the example above, the <tt/lda/ instruction will load the value 3 into the
689 accumulator, because <tt/foo/ is redefined in the scope. However:
701 Here, <tt/lda/ will still load from <tt/$12,x/, but since it is unknown to the
702 assembler that <tt/foo/ is a zeropage symbol when translating the instruction,
703 absolute mode is used instead. In fact, the assembler will not use absolute
704 mode by default, but it will search through the enclosing scopes for a symbol
705 with the given name. If one is found, the address size of this symbol is used.
706 This may lead to errors:
718 In this case, when the assembler sees the symbol <tt/foo/ in the <tt/lda/
719 instruction, it will search for an already defined symbol <tt/foo/. It will
720 find <tt/foo/ in scope <tt/outer/, and a close look reveals that it is a
721 zeropage symbol. So the assembler will use zeropage addressing mode. If
722 <tt/foo/ is redefined later in scope <tt/inner/, the assembler tries to change
723 the address in the <tt/lda/ instruction already translated, but since the new
724 value needs absolute addressing mode, this fails, and an error message "Range
727 Of course the most simple solution for the problem is to move the definition
728 of <tt/foo/ in scope <tt/inner/ upwards, so it preceeds its use. There may be
729 rare cases when this cannot be done. In these cases, you can use one of the
730 address size override operators:
742 This will cause the <tt/lda/ instruction to be translated using absolute
743 addressing mode, which means changing the symbol reference later does not
747 <sect1>Nested procedures<p>
749 A nested procedure is created by use of <tt/<ref id=".PROC" name=".PROC">/. It
750 differs from a <tt/<ref id=".SCOPE" name=".SCOPE">/ in that it must have a
751 name, and a it will introduce a symbol with this name in the enclosing scope.
760 is actually the same as
769 This is the reason why a procedure must have a name. If you want a scope
770 without a name, use <tt/<ref id=".SCOPE" name=".SCOPE">/.
772 <bf/Note:/ As you can see from the example above, scopes and symbols live in
773 different namespaces. There can be a symbol named <tt/foo/ and a scope named
774 <tt/foo/ without any conflicts (but see the section titled <ref
775 id="scopesearch" name=""Scope search order"">).
778 <sect1>Structs, unions and enums<p>
780 Structs, unions and enums are explained in a <ref id="structs" name="separate
781 section">, I do only cover them here, because if they are declared with a
782 name, they open a nested scope, similar to <tt/<ref id=".SCOPE"
783 name=".SCOPE">/. However, when no name is specified, the behaviour is
784 different: In this case, no new scope will be opened, symbols declared within
785 a struct, union, or enum declaration will then be added to the enclosing scope
789 <sect1>Explicit scope specification<label id="scopesyntax"><p>
791 Accessing symbols from other scopes is possible by using an explicit scope
792 specification, provided that the scope where the symbol lives in has a name.
793 The namespace token (<tt/::/) is used to access other scopes:
801 lda foo::bar ; Access foo in scope bar
804 The only way to deny access to a scope from the outside is to declare a scope
805 without a name (using the <tt/<ref id=".SCOPE" name=".SCOPE">/ command).
807 A special syntax is used to specify the global scope: If a symbol or scope is
808 preceeded by the namespace token, the global scope is searched:
815 lda #::bar ; Access the global bar (which is 3)
820 <sect1>Scope search order<label id="scopesearch"><p>
822 The assembler searches for a scope in a similar way as for a symbol. First, it
823 looks in the current scope, and then it walks up the enclosing scopes until
826 However, one important thing to note when using explicit scope syntax is, that
827 a symbol may be accessed before it is defined, but a scope may <bf/not/ be
828 used without a preceeding definition. This means that in the following
837 lda #foo::bar ; Will load 3, not 2!
844 the reference to the scope <tt/foo/ will use the global scope, and not the
845 local one, because the local one is not visible at the point where it is
848 Things get more complex if a complete chain of scopes is specified:
859 lda #outer::inner::bar ; 1
871 When <tt/outer::inner::bar/ is referenced in the <tt/lda/ instruction, the
872 assembler will first search in the local scope for a scope named <tt/outer/.
873 Since none is found, the enclosing scope (<tt/another/) is checked. There is
874 still no scope named <tt/outer/, so scope <tt/foo/ is checked, and finally
875 scope <tt/outer/ is found. Within this scope, <tt/inner/ is searched, and in
876 this scope, the assembler looks for a symbol named <tt/bar/.
878 Please note that once the anchor scope is found, all following scopes
879 (<tt/inner/ in this case) are expected to be found exactly in this scope. The
880 assembler will search the scope tree only for the first scope (if it is not
881 anchored in the root scope). Starting from there on, there is no flexibility,
882 so if the scope named <tt/outer/ found by the assembler does not contain a
883 scope named <tt/inner/, this would be an error, even if such a pair does exist
884 (one level up in global scope).
886 Ambiguities that may be introduced by this search algorithm may be removed by
887 anchoring the scope specification in the global scope. In the example above,
888 if you want to access the "other" symbol <tt/bar/, you would have to write:
899 lda #::outer::inner::bar ; 2
912 <sect>Address sizes<label id="address-sizes"><p>
916 <sect>Pseudo variables<label id="pseudo-variables"><p>
918 Pseudo variables are readable in all cases, and in some special cases also
923 Reading this pseudo variable will return the program counter at the start
924 of the current input line.
926 Assignment to this variable is possible when <tt/<ref id=".FEATURE"
927 name=".FEATURE pc_assignment">/ is used. Note: You should not use
928 assignments to <tt/*/, use <tt/<ref id=".ORG" name=".ORG">/ instead.
931 <sect1><tt>.CPU</tt><label id=".CPU"><p>
933 Reading this pseudo variable will give a constant integer value that
934 tells which CPU is currently enabled. It can also tell which instruction
935 set the CPU is able to translate. The value read from the pseudo variable
936 should be further examined by using one of the constants defined by the
937 "cpu" macro package (see <tt/<ref id=".MACPACK" name=".MACPACK">/).
939 It may be used to replace the .IFPxx pseudo instructions or to construct
940 even more complex expressions.
946 .if (.cpu .bitand CPU_ISET_65816)
958 <sect1><tt>.PARAMCOUNT</tt><label id=".PARAMCOUNT"><p>
960 This builtin pseudo variable is only available in macros. It is replaced by
961 the actual number of parameters that were given in the macro invocation.
966 .macro foo arg1, arg2, arg3
968 .error "Too few parameters for macro foo"
974 See section <ref id="macros" name="Macros">.
977 <sect1><tt>.TIME</tt><label id=".TIME"><p>
979 Reading this pseudo variable will give a constant integer value that
980 represents the current time in POSIX standard (as seconds since the
983 It may be used to encode the time of translation somewhere in the created
989 .dword .time ; Place time here
993 <sect1><tt>.VERSION</tt><label id=".VERSION"><p>
995 Reading this pseudo variable will give the assembler version according to
996 the following formula:
998 VER_MAJOR*$100 + VER_MINOR*$10 + VER_PATCH
1000 It may be used to encode the assembler version or check the assembler for
1001 special features not available with older versions.
1005 Version 2.11.1 of the assembler will return $2B1 as numerical constant when
1006 reading the pseudo variable <tt/.VERSION/.
1010 <sect>Pseudo functions<label id="pseudo-functions"><p>
1012 Pseudo functions expect their arguments in parenthesis, and they have a result,
1013 either a string or an expression.
1016 <sect1><tt>.BANKBYTE</tt><label id=".BANKBYTE"><p>
1018 The function returns the bank byte (that is, bits 16-23) of its argument.
1019 It works identical to the '^' operator.
1021 See: <tt><ref id=".HIBYTE" name=".HIBYTE"></tt>,
1022 <tt><ref id=".LOBYTE" name=".LOBYTE"></tt>
1025 <sect1><tt>.BLANK</tt><label id=".BLANK"><p>
1027 Builtin function. The function evaluates its argument in braces and
1028 yields "false" if the argument is non blank (there is an argument), and
1029 "true" if there is no argument. As an example, the <tt/.IFBLANK/ statement
1037 <sect1><tt>.CONCAT</tt><label id=".CONCAT"><p>
1039 Builtin string function. The function allows to concatenate a list of string
1040 constants separated by commas. The result is a string constant that is the
1041 concatentation of all arguments. This function is most useful in macros and
1042 when used together with the <tt/.STRING/ builtin function. The function may
1043 be used in any case where a string constant is expected.
1048 .include .concat ("myheader", ".", "inc")
1051 This is the same as the command
1054 .include "myheader.inc"
1058 <sect1><tt>.CONST</tt><label id=".CONST"><p>
1060 Builtin function. The function evaluates its argument in braces and
1061 yields "true" if the argument is a constant expression (that is, an
1062 expression that yields a constant value at assembly time) and "false"
1063 otherwise. As an example, the .IFCONST statement may be replaced by
1070 <sect1><tt>.HIBYTE</tt><label id=".HIBYTE"><p>
1072 The function returns the high byte (that is, bits 8-15) of its argument.
1073 It works identical to the '>' operator.
1075 See: <tt><ref id=".LOBYTE" name=".LOBYTE"></tt>,
1076 <tt><ref id=".BANKBYTE" name=".BANKBYTE"></tt>
1079 <sect1><tt>.HIWORD</tt><label id=".HIWORD"><p>
1081 The function returns the high word (that is, bits 16-31) of its argument.
1083 See: <tt><ref id=".LOWORD" name=".LOWORD"></tt>
1086 <sect1><tt>.LEFT</tt><label id=".LEFT"><p>
1088 Builtin function. Extracts the left part of a given token list.
1093 .LEFT (<int expr>, <token list>)
1096 The first integer expression gives the number of tokens to extract from
1097 the token list. The second argument is the token list itself.
1101 To check in a macro if the given argument has a '#' as first token
1102 (immidiate addressing mode), use something like this:
1107 .if (.match (.left (1, arg), #))
1109 ; ldax called with immidiate operand
1117 See also the <tt><ref id=".MID" name=".MID"></tt> and <tt><ref id=".RIGHT"
1118 name=".RIGHT"></tt> builtin functions.
1121 <sect1><tt>.LOBYTE</tt><label id=".LOBYTE"><p>
1123 The function returns the low byte (that is, bits 0-7) of its argument.
1124 It works identical to the '<' operator.
1126 See: <tt><ref id=".HIBYTE" name=".HIBYTE"></tt>,
1127 <tt><ref id=".BANKBYTE" name=".BANKBYTE"></tt>
1130 <sect1><tt>.LOWORD</tt><label id=".LOWORD"><p>
1132 The function returns the low word (that is, bits 0-15) of its argument.
1134 See: <tt><ref id=".HIWORD" name=".HIWORD"></tt>
1137 <sect1><tt>.MATCH</tt><label id=".MATCH"><p>
1139 Builtin function. Matches two token lists against each other. This is
1140 most useful within macros, since macros are not stored as strings, but
1146 .MATCH(<token list #1>, <token list #2>)
1149 Both token list may contain arbitrary tokens with the exception of the
1150 terminator token (comma resp. right parenthesis) and
1157 Often a macro parameter is used for any of the token lists.
1159 Please note that the function does only compare tokens, not token
1160 attributes. So any number is equal to any other number, regardless of the
1161 actual value. The same is true for strings. If you need to compare tokens
1162 <em/and/ token attributes, use the <tt><ref id=".XMATCH"
1163 name=".XMATCH"></tt> function.
1167 Assume the macro <tt/ASR/, that will shift right the accumulator by one,
1168 while honoring the sign bit. The builtin processor instructions will allow
1169 an optional "A" for accu addressing for instructions like <tt/ROL/ and
1170 <tt/ROR/. We will use the <tt><ref id=".MATCH" name=".MATCH"></tt> function
1171 to check for this and print and error for invalid calls.
1176 .if (.not .blank(arg)) .and (.not .match (arg, a))
1177 .error "Syntax error"
1180 cmp #$80 ; Bit 7 into carry
1181 lsr a ; Shift carry into bit 7
1186 The macro will only accept no arguments, or one argument that must be the
1187 reserved keyword "A".
1189 See: <tt><ref id=".XMATCH" name=".XMATCH"></tt>
1192 <sect1><tt>.MID</tt><label id=".MID"><p>
1194 Builtin function. Takes a starting index, a count and a token list as
1195 arguments. Will return part of the token list.
1200 .MID (<int expr>, <int expr>, <token list>)
1203 The first integer expression gives the starting token in the list (the
1204 first token has index 0). The second integer expression gives the number
1205 of tokens to extract from the token list. The third argument is the
1210 To check in a macro if the given argument has a '<tt/#/' as first token
1211 (immidiate addressing mode), use something like this:
1216 .if (.match (.mid (0, 1, arg), #))
1218 ; ldax called with immidiate operand
1226 See also the <tt><ref id=".LEFT" name=".LEFT"></tt> and <tt><ref id=".RIGHT"
1227 name=".RIGHT"></tt> builtin functions.
1230 <sect1><tt>.REF, .REFERENCED</tt><label id=".REFERENCED"><p>
1232 Builtin function. The function expects an identifier as argument in braces.
1233 The argument is evaluated, and the function yields "true" if the identifier
1234 is a symbol that has already been referenced somewhere in the source file up
1235 to the current position. Otherwise the function yields false. As an example,
1236 the <tt><ref id=".IFREF" name=".IFREF"></tt> statement may be replaced by
1242 See: <tt><ref id=".DEFINED" name=".DEFINED"></tt>
1245 <sect1><tt>.RIGHT</tt><label id=".RIGHT"><p>
1247 Builtin function. Extracts the right part of a given token list.
1252 .RIGHT (<int expr>, <token list>)
1255 The first integer expression gives the number of tokens to extract from
1256 the token list. The second argument is the token list itself.
1258 See also the <tt><ref id=".LEFT" name=".LEFT"></tt> and <tt><ref id=".MID"
1259 name=".MID"></tt> builtin functions.
1262 <sect1><tt>.SIZEOF</tt><label id=".SIZEOF"><p>
1264 <tt/.SIZEOF/ is a pseudo function that returns the size of its argument. The
1265 argument can be a struct/union, a struct member, a procedure, or a label. In
1266 case of a procedure or label, its size is defined by the amount of data
1267 placed in the segment where the label is relative to. If a line of code
1268 switches segments (for example in a macro) data placed in other segments
1269 does not count for the size.
1271 Please note that a symbol or scope must exist, before it is used together with
1272 <tt/.SIZEOF/ (this may get relaxed later, but will always be true for scopes).
1273 A scope has preference over a symbol with the same name, so if the last part
1274 of a name represents both, a scope and a symbol, the scope is choosen over the
1277 After the following code:
1280 .struct Point ; Struct size = 4
1285 P: .tag Point ; Declare a point
1286 @P: .tag Point ; Declare another point
1298 .data ; Segment switch!!!
1304 <tag><tt/.sizeof(Point)/</tag>
1305 will have the value 4, because this is the size of struct <tt/Point/.
1307 <tag><tt/.sizeof(Point::xcoord)/</tag>
1308 will have the value 2, because this is the size of the member <tt/xcoord/
1309 in struct <tt/Point/.
1311 <tag><tt/.sizeof(P)/</tag>
1312 will have the value 4, this is the size of the data declared on the same
1313 source line as the label <tt/P/, which is in the same segment that <tt/P/
1316 <tag><tt/.sizeof(@P)/</tag>
1317 will have the value 4, see above. The example demonstrates that <tt/.SIZEOF/
1318 does also work for cheap local symbols.
1320 <tag><tt/.sizeof(Code)/</tag>
1321 will have the value 3, since this is amount of data emitted into the code
1322 segment, the segment that was active when <tt/Code/ was entered. Note that
1323 this value includes the amount of data emitted in child scopes (in this
1324 case <tt/Code::Inner/).
1326 <tag><tt/.sizeof(Code::Inner)/</tag>
1327 will have the value 1 as expected.
1329 <tag><tt/.sizeof(Data)/</tag>
1330 will have the value 0. Data is emitted within the scope <tt/Data/, but since
1331 the segment is switched after entry, this data is emitted into another
1336 <sect1><tt>.STRAT</tt><label id=".STRAT"><p>
1338 Builtin function. The function accepts a string and an index as
1339 arguments and returns the value of the character at the given position
1340 as an integer value. The index is zero based.
1346 ; Check if the argument string starts with '#'
1347 .if (.strat (Arg, 0) = '#')
1354 <sect1><tt>.STRING</tt><label id=".STRING"><p>
1356 Builtin function. The function accepts an argument in braces and converts
1357 this argument into a string constant. The argument may be an identifier, or
1358 a constant numeric value.
1360 Since you can use a string in the first place, the use of the function may
1361 not be obvious. However, it is useful in macros, or more complex setups.
1366 ; Emulate other assemblers:
1368 .segment .string(name)
1373 <sect1><tt>.STRLEN</tt><label id=".STRLEN"><p>
1375 Builtin function. The function accepts a string argument in braces and
1376 eveluates to the length of the string.
1380 The following macro encodes a string as a pascal style string with
1381 a leading length byte.
1385 .byte .strlen(Arg), Arg
1390 <sect1><tt>.TCOUNT</tt><label id=".TCOUNT"><p>
1392 Builtin function. The function accepts a token list in braces. The
1393 function result is the number of tokens given as argument.
1397 The <tt/ldax/ macro accepts the '#' token to denote immidiate addressing (as
1398 with the normal 6502 instructions). To translate it into two separate 8 bit
1399 load instructions, the '#' token has to get stripped from the argument:
1403 .if (.match (.mid (0, 1, arg), #))
1404 ; ldax called with immidiate operand
1405 lda #<(.right (.tcount (arg)-1, arg))
1406 ldx #>(.right (.tcount (arg)-1, arg))
1414 <sect1><tt>.XMATCH</tt><label id=".XMATCH"><p>
1416 Builtin function. Matches two token lists against each other. This is
1417 most useful within macros, since macros are not stored as strings, but
1423 .XMATCH(<token list #1>, <token list #2>)
1426 Both token list may contain arbitrary tokens with the exception of the
1427 terminator token (comma resp. right parenthesis) and
1434 Often a macro parameter is used for any of the token lists.
1436 The function compares tokens <em/and/ token values. If you need a function
1437 that just compares the type of tokens, have a look at the <tt><ref
1438 id=".MATCH" name=".MATCH"></tt> function.
1440 See: <tt><ref id=".MATCH" name=".MATCH"></tt>
1444 <sect>Control commands<label id="control-commands"><p>
1446 Here's a list of all control commands and a description, what they do:
1449 <sect1><tt>.A16</tt><label id=".A16"><p>
1451 Valid only in 65816 mode. Switch the accumulator to 16 bit.
1453 Note: This command will not emit any code, it will tell the assembler to
1454 create 16 bit operands for immediate accumulator adressing mode.
1456 See also: <tt><ref id=".SMART" name=".SMART"></tt>
1459 <sect1><tt>.A8</tt><label id=".A8"><p>
1461 Valid only in 65816 mode. Switch the accumulator to 8 bit.
1463 Note: This command will not emit any code, it will tell the assembler to
1464 create 8 bit operands for immediate accu adressing mode.
1466 See also: <tt><ref id=".SMART" name=".SMART"></tt>
1469 <sect1><tt>.ADDR</tt><label id=".ADDR"><p>
1471 Define word sized data. In 6502 mode, this is an alias for <tt/.WORD/ and
1472 may be used for better readability if the data words are address values. In
1473 65816 mode, the address is forced to be 16 bit wide to fit into the current
1474 segment. See also <tt><ref id=".FARADDR" name=".FARADDR"></tt>. The command
1475 must be followed by a sequence of (not necessarily constant) expressions.
1480 .addr $0D00, $AF13, _Clear
1483 See: <tt><ref id=".FARADDR" name=".FARADDR"></tt>, <tt><ref id=".WORD"
1487 <sect1><tt>.ALIGN</tt><label id=".ALIGN"><p>
1489 Align data to a given boundary. The command expects a constant integer
1490 argument that must be a power of two, plus an optional second argument
1491 in byte range. If there is a second argument, it is used as fill value,
1492 otherwise the value defined in the linker configuration file is used
1493 (the default for this value is zero).
1495 Since alignment depends on the base address of the module, you must
1496 give the same (or a greater) alignment for the segment when linking.
1497 The linker will give you a warning, if you don't do that.
1506 <sect1><tt>.ASCIIZ</tt><label id=".ASCIIZ"><p>
1508 Define a string with a trailing zero.
1513 Msg: .asciiz "Hello world"
1516 This will put the string "Hello world" followed by a binary zero into
1517 the current segment. There may be more strings separated by commas, but
1518 the binary zero is only appended once (after the last one).
1521 <sect1><tt>.ASSERT</tt><label id=".ASSERT"><p>
1523 Add an assertion. The command is followed by an expression, an action
1524 specifier and a message that is output in case the assertion fails. The
1525 action specifier may be one of <tt/warning/ or <tt/error/. The assertion
1526 is passed to the linker and will be evaluated when segment placement has
1532 .assert * = $8000, error, "Code not at $8000"
1535 The example assertion will check that the current location is at $8000,
1536 when the output file is written, and abort with an error if this is not
1537 the case. More complex expressions are possible. The action specifier
1538 <tt/warning/ outputs a warning, while the <tt/error/ specifier outputs
1539 an error message. In the latter case, generation if the output file is
1543 <sect1><tt>.AUTOIMPORT</tt><label id=".AUTOIMPORT"><p>
1545 Is followed by a plus or a minus character. When switched on (using a
1546 +), undefined symbols are automatically marked as import instead of
1547 giving errors. When switched off (which is the default so this does not
1548 make much sense), this does not happen and an error message is
1549 displayed. The state of the autoimport flag is evaluated when the
1550 complete source was translated, before outputing actual code, so it is
1551 <em/not/ possible to switch this feature on or off for separate sections
1552 of code. The last setting is used for all symbols.
1554 You should probably not use this switch because it delays error
1555 messages about undefined symbols until the link stage. The cc65
1556 compiler (which is supposed to produce correct assembler code in all
1557 circumstances, something which is not true for most assembler
1558 programmers) will insert this command to avoid importing each and every
1559 routine from the runtime library.
1564 .autoimport + ; Switch on auto import
1568 <sect1><tt>.BSS</tt><label id=".BSS"><p>
1570 Switch to the BSS segment. The name of the BSS segment is always "BSS",
1571 so this is a shortcut for
1577 See also the <tt><ref id=".SEGMENT" name=".SEGMENT"></tt> command.
1580 <sect1><tt>.BYT, .BYTE</tt><label id=".BYTE"><p>
1582 Define byte sized data. Must be followed by a sequence of (byte ranged)
1583 expressions or strings.
1589 .byt "world", $0D, $00
1593 <sect1><tt>.CASE</tt><label id=".CASE"><p>
1595 Switch on or off case sensitivity on identifiers. The default is off
1596 (that is, identifiers are case sensitive), but may be changed by the
1597 -i switch on the command line.
1598 The command must be followed by a '+' or '-' character to switch the
1599 option on or off respectively.
1604 .case - ; Identifiers are not case sensitive
1608 <sect1><tt>.CHARMAP</tt><label id=".CHARMAP"><p>
1610 Apply a custom mapping for characters. The command is followed by two
1611 numbers in the range 1..255. The first one is the index of the source
1612 character, the second one is the mapping. The mapping applies to all
1613 character and string constants when they generate output, and overrides
1614 a mapping table specified with the <tt><ref id="option-t" name="-t"></tt>
1615 command line switch.
1620 .charmap $41, $61 ; Map 'A' to 'a'
1624 <sect1><tt>.CODE</tt><label id=".CODE"><p>
1626 Switch to the CODE segment. The name of the CODE segment is always
1627 "CODE", so this is a shortcut for
1633 See also the <tt><ref id=".SEGMENT" name=".SEGMENT"></tt> command.
1636 <sect1><tt>.CONDES</tt><label id=".CONDES"><p>
1638 Export a symbol and mark it in a special way. The linker is able to build
1639 tables of all such symbols. This may be used to automatically create a list
1640 of functions needed to initialize linked library modules.
1642 Note: The linker has a feature to build a table of marked routines, but it
1643 is your code that must call these routines, so just declaring a symbol with
1644 <tt/.CONDES/ does nothing by itself.
1646 All symbols are exported as an absolute (16 bit) symbol. You don't need to
1647 use an additional <tt><ref id=".EXPORT" name=".EXPORT"></tt> statement, this
1648 is implied by <tt/.CONDES/.
1650 <tt/.CONDES/ is followed by the type, which may be <tt/constructor/,
1651 <tt/destructor/ or a numeric value between 0 and 6 (where 0 is the same as
1652 specifiying <tt/constructor/ and 1 is equal to specifying <tt/destructor/).
1653 The <tt><ref id=".CONSTRUCTOR" name=".CONSTRUCTOR"></tt> and <tt><ref
1654 id=".DESTRUCTOR" name=".DESTRUCTOR"></tt> commands are actually shortcuts
1655 for <tt/.CONDES/ with a type of <tt/constructor/ resp. <tt/destructor/.
1657 After the type, an optional priority may be specified. Higher numeric values
1658 mean higher priority. If no priority is given, the default priority of 7 is
1659 used. Be careful when assigning priorities to your own module constructors
1660 so they won't interfere with the ones in the cc65 library.
1665 .condes ModuleInit, constructor
1666 .condes ModInit, 0, 16
1669 See the <tt><ref id=".CONSTRUCTOR" name=".CONSTRUCTOR"></tt> and <tt><ref
1670 id=".DESTRUCTOR" name=".DESTRUCTOR"></tt> commands and the separate section
1671 <ref id="condes" name="Module constructors/destructors"> explaining the
1672 feature in more detail.
1675 <sect1><tt>.CONSTRUCTOR</tt><label id=".CONSTRUCTOR"><p>
1677 Export a symbol and mark it as a module constructor. This may be used
1678 together with the linker to build a table of constructor subroutines that
1679 are called by the startup code.
1681 Note: The linker has a feature to build a table of marked routines, but it
1682 is your code that must call these routines, so just declaring a symbol as
1683 constructor does nothing by itself.
1685 A constructor is always exported as an absolute (16 bit) symbol. You don't
1686 need to use an additional <tt/.export/ statement, this is implied by
1687 <tt/.constructor/. It may have an optional priority that is separated by a
1688 comma. Higher numeric values mean a higher priority. If no priority is
1689 given, the default priority of 7 is used. Be careful when assigning
1690 priorities to your own module constructors so they won't interfere with the
1691 ones in the cc65 library.
1696 .constructor ModuleInit
1697 .constructor ModInit, 16
1700 See the <tt><ref id=".CONDES" name=".CONDES"></tt> and <tt><ref
1701 id=".DESTRUCTOR" name=".DESTRUCTOR"></tt> commands and the separate section
1702 <ref id="condes" name="Module constructors/destructors"> explaining the
1703 feature in more detail.
1706 <sect1><tt>.DATA</tt><label id=".DATA"><p>
1708 Switch to the DATA segment. The name of the DATA segment is always
1709 "DATA", so this is a shortcut for
1715 See also the <tt><ref id=".SEGMENT" name=".SEGMENT"></tt> command.
1718 <sect1><tt>.DBYT</tt><label id=".DBYT"><p>
1720 Define word sized data with the hi and lo bytes swapped (use <tt/.WORD/ to
1721 create word sized data in native 65XX format). Must be followed by a
1722 sequence of (word ranged) expressions.
1730 This will emit the bytes
1736 into the current segment in that order.
1739 <sect1><tt>.DEBUGINFO</tt><label id=".DEBUGINFO"><p>
1741 Switch on or off debug info generation. The default is off (that is,
1742 the object file will not contain debug infos), but may be changed by the
1743 -g switch on the command line.
1744 The command must be followed by a '+' or '-' character to switch the
1745 option on or off respectively.
1750 .debuginfo + ; Generate debug info
1754 <sect1><tt>.DEFINE</tt><label id=".DEFINE"><p>
1756 Start a define style macro definition. The command is followed by an
1757 identifier (the macro name) and optionally by a list of formal arguments
1759 See section <ref id="macros" name="Macros">.
1762 <sect1><tt>.DEF, .DEFINED</tt><label id=".DEFINED"><p>
1764 Builtin function. The function expects an identifier as argument in braces.
1765 The argument is evaluated, and the function yields "true" if the identifier
1766 is a symbol that is already defined somewhere in the source file up to the
1767 current position. Otherwise the function yields false. As an example, the
1768 <tt><ref id=".IFDEF" name=".IFDEF"></tt> statement may be replaced by
1775 <sect1><tt>.DESTRUCTOR</tt><label id=".DESTRUCTOR"><p>
1777 Export a symbol and mark it as a module destructor. This may be used
1778 together with the linker to build a table of destructor subroutines that
1779 are called by the startup code.
1781 Note: The linker has a feature to build a table of marked routines, but it
1782 is your code that must call these routines, so just declaring a symbol as
1783 constructor does nothing by itself.
1785 A destructor is always exported as an absolute (16 bit) symbol. You don't
1786 need to use an additional <tt/.export/ statement, this is implied by
1787 <tt/.destructor/. It may have an optional priority that is separated by a
1788 comma. Higher numerical values mean a higher priority. If no priority is
1789 given, the default priority of 7 is used. Be careful when assigning
1790 priorities to your own module destructors so they won't interfere with the
1791 ones in the cc65 library.
1796 .destructor ModuleDone
1797 .destructor ModDone, 16
1800 See the <tt><ref id=".CONDES" name=".CONDES"></tt> and <tt><ref
1801 id=".CONSTRUCTOR" name=".CONSTRUCTOR"></tt> commands and the separate
1802 section <ref id="condes" name="Module constructors/destructors"> explaining
1803 the feature in more detail.
1806 <sect1><tt>.DWORD</tt><label id=".DWORD"><p>
1808 Define dword sized data (4 bytes) Must be followed by a sequence of
1814 .dword $12344512, $12FA489
1818 <sect1><tt>.ELSE</tt><label id=".ELSE"><p>
1820 Conditional assembly: Reverse the current condition.
1823 <sect1><tt>.ELSEIF</tt><label id=".ELSEIF"><p>
1825 Conditional assembly: Reverse current condition and test a new one.
1828 <sect1><tt>.END</tt><label id=".END"><p>
1830 Forced end of assembly. Assembly stops at this point, even if the command
1831 is read from an include file.
1834 <sect1><tt>.ENDENUM</tt><label id=".ENDENUM"><p>
1836 End a <tt><ref id=".ENUM" name=".ENUM"></tt> declaration.
1839 <sect1><tt>.ENDIF</tt><label id=".ENDIF"><p>
1841 Conditional assembly: Close a <tt><ref id=".IF" name=".IF..."></tt> or
1842 <tt><ref id=".ELSE" name=".ELSE"></tt> branch.
1845 <sect1><tt>.ENDMAC, .ENDMACRO</tt><label id=".ENDMACRO"><p>
1847 End of macro definition (see section <ref id="macros" name="Macros">).
1850 <sect1><tt>.ENDPROC</tt><label id=".ENDPROC"><p>
1852 End of local lexical level (see <tt><ref id=".PROC" name=".PROC"></tt>).
1855 <sect1><tt>.ENDREP, .ENDREPEAT</tt><label id=".ENDREPEAT"><p>
1857 End a <tt><ref id=".REPEAT" name=".REPEAT"></tt> block.
1860 <sect1><tt>.ENDSCOPE</tt><label id=".ENDSCOPE"><p>
1862 End of local lexical level (see <tt/<ref id=".SCOPE" name=".SCOPE">/).
1865 <sect1><tt>.ENDSTRUCT</tt><label id=".ENDSTRUCT"><p>
1867 Ends a struct definition. See the <tt/<ref id=".STRUCT" name=".STRUCT">/
1868 command and the separate section named <ref id="structs" name=""Structs
1872 <sect1><tt>.ENUM</tt><label id=".ENUM"><p>
1874 Start an enumeration. This directive is very similar to the C <tt/enum/
1875 keyword. If a name is given, a new scope is created for the enumeration,
1876 otherwise the enumeration members are placed in the enclosing scope.
1878 In the enumeration body, symbols are declared. The first symbol has a value
1879 of zero, and each following symbol will get the value of the preceeding plus
1880 one. This behaviour may be overriden by an explicit assignment. Two symbols
1881 may have the same value.
1893 Above example will create a new scope named <tt/errorcodes/ with three
1894 symbols in it that get the values 0, 1 and 2 respectively. Another way
1895 to write this would have been:
1905 Please note that explicit scoping must be used to access the identifiers:
1908 .word errorcodes::no_error
1911 A more complex example:
1920 EWOULDBLOCK = EAGAIN
1924 In this example, the enumeration does not have a name, which means that the
1925 members will be visible in the enclosing scope and can be used in this scope
1926 without explicit scoping. The first member (<tt/EUNKNOWN/) has the value -1.
1927 The value for the following members is incremented by one, so <tt/EOK/ would
1928 be zero and so on. <tt/EWOULDBLOCK/ is an alias for <tt/EGAIN/, so it has an
1929 override for the value using an already defined symbol.
1932 <sect1><tt>.ERROR</tt><label id=".ERROR"><p>
1934 Force an assembly error. The assembler will output an error message
1935 preceeded by "User error" and will <em/not/ produce an object file.
1937 This command may be used to check for initial conditions that must be
1938 set before assembling a source file.
1948 .error "Must define foo or bar!"
1952 See also the <tt><ref id=".WARNING" name=".WARNING"></tt> and <tt><ref
1953 id=".OUT" name=".OUT"></tt> directives.
1956 <sect1><tt>.EXITMAC, .EXITMACRO</tt><label id=".EXITMACRO"><p>
1958 Abort a macro expansion immidiately. This command is often useful in
1959 recursive macros. See separate section <ref id="macros" name="Macros">.
1962 <sect1><tt>.EXPORT</tt><label id=".EXPORT"><p>
1964 Make symbols accessible from other modules. Must be followed by a comma
1965 separated list of symbols to export.
1973 See: <tt><ref id=".EXPORTZP" name=".EXPORTZP"></tt>
1976 <sect1><tt>.EXPORTZP</tt><label id=".EXPORTZP"><p>
1978 Make symbols accessible from other modules. Must be followed by a comma
1979 separated list of symbols to export. The exported symbols are explicitly
1980 marked as zero page symols.
1988 See: <tt><ref id=".EXPORT" name=".EXPORT"></tt>
1991 <sect1><tt>.FARADDR</tt><label id=".FARADDR"><p>
1993 Define far (24 bit) address data. The command must be followed by a
1994 sequence of (not necessarily constant) expressions.
1999 .faraddr DrawCircle, DrawRectangle, DrawHexagon
2002 See: <tt><ref id=".ADDR" name=".ADDR"></tt>
2005 <sect1><tt>.FEATURE</tt><label id=".FEATURE"><p>
2007 This directive may be used to enable one or more compatibility features
2008 of the assembler. While the use of <tt/.FEATURE/ should be avoided when
2009 possible, it may be useful when porting sources written for other
2010 assemblers. There is no way to switch a feature off, once you have
2011 enabled it, so using
2017 will enable the feature until end of assembly is reached.
2019 The following features are available:
2023 <tag><tt>dollar_is_pc</tt></tag>
2025 The dollar sign may be used as an alias for the star (`*'), which
2026 gives the value of the current PC in expressions.
2027 Note: Assignment to the pseudo variable is not allowed.
2029 <tag><tt>labels_without_colons</tt></tag>
2031 Allow labels without a trailing colon. These labels are only accepted,
2032 if they start at the beginning of a line (no leading white space).
2034 <tag><tt>loose_string_term</tt></tag>
2036 Accept single quotes as well as double quotes as terminators for string
2039 <tag><tt>loose_char_term</tt></tag>
2041 Accept single quotes as well as double quotes as terminators for char
2044 <tag><tt>at_in_identifiers</tt></tag>
2046 Accept the at character (`@') as a valid character in identifiers. The
2047 at character is not allowed to start an identifier, even with this
2050 <tag><tt>dollar_in_identifiers</tt></tag>
2052 Accept the dollar sign (`$') as a valid character in identifiers. The
2053 at character is not allowed to start an identifier, even with this
2056 <tag><tt>leading_dot_in_identifiers</tt></tag>
2058 Accept the dot (`.') as the first character of an identifier. This may be
2059 used for example to create macro names that start with a dot emulating
2060 control directives of other assemblers. Note however, that none of the
2061 reserved keywords built into the assembler, that starts with a dot, may be
2062 overridden. When using this feature, you may also get into trouble if
2063 later versions of the assembler define new keywords starting with a dot.
2065 <tag><tt>pc_assignment</tt></tag>
2067 Allow assignments to the PC symbol (`*' or `$' if <tt/dollar_is_pc/
2068 is enabled). Such an assignment is handled identical to the <tt><ref
2069 id=".ORG" name=".ORG"></tt> command (which is usually not needed, so just
2070 removing the lines with the assignments may also be an option when porting
2071 code written for older assemblers).
2075 It is also possible to specify features on the command line using the
2076 <tt><ref id="option--feature" name="--feature"></tt> command line option.
2077 This is useful when translating sources written for older assemblers, when
2078 you don't want to change the source code.
2080 As an example, to translate sources written for Andre Fachats xa65
2081 assembler, the features
2084 labels_without_colons, pc_assignment, loose_char_term
2087 may be helpful. They do not make ca65 completely compatible, so you may not
2088 be able to translate the sources without changes, even when enabling these
2089 features. However, I have found several sources that translate without
2090 problems when enabling these features on the command line.
2093 <sect1><tt>.FILEOPT, .FOPT</tt><label id=".FOPT"><p>
2095 Insert an option string into the object file. There are two forms of
2096 this command, one specifies the option by a keyword, the second
2097 specifies it as a number. Since usage of the second one needs knowledge
2098 of the internal encoding, its use is not recommended and I will only
2099 describe the first form here.
2101 The command is followed by one of the keywords
2109 a comma and a string. The option is written into the object file
2110 together with the string value. This is currently unidirectional and
2111 there is no way to actually use these options once they are in the
2117 .fileopt comment, "Code stolen from my brother"
2118 .fileopt compiler, "BASIC 2.0"
2119 .fopt author, "J. R. User"
2123 <sect1><tt>.FORCEIMPORT</tt><label id=".FORCEIMPORT"><p>
2125 Import an absolute symbol from another module. The command is followed by a
2126 comma separated list of symbols to import. The command is similar to <tt>
2127 <ref id=".IMPORT" name=".IMPORT"></tt>, but the import reference is always
2128 written to the generated object file, even if the symbol is never referenced
2129 (<tt><ref id=".IMPORT" name=".IMPORT"></tt> will not generate import
2130 references for unused symbols).
2135 .forceimport needthisone, needthistoo
2138 See: <tt><ref id=".IMPORT" name=".IMPORT"></tt>
2141 <sect1><tt>.GLOBAL</tt><label id=".GLOBAL"><p>
2143 Declare symbols as global. Must be followed by a comma separated list of
2144 symbols to declare. Symbols from the list, that are defined somewhere in the
2145 source, are exported, all others are imported. Additional <tt><ref
2146 id=".IMPORT" name=".IMPORT"></tt> or <tt><ref id=".EXPORT"
2147 name=".EXPORT"></tt> commands for the same symbol are allowed.
2156 <sect1><tt>.GLOBALZP</tt><label id=".GLOBALZP"><p>
2158 Declare symbols as global. Must be followed by a comma separated list of
2159 symbols to declare. Symbols from the list, that are defined somewhere in the
2160 source, are exported, all others are imported. Additional <tt><ref
2161 id=".IMPORTZP" name=".IMPORTZP"></tt> or <tt><ref id=".EXPORTZP"
2162 name=".EXPORTZP"></tt> commands for the same symbol are allowed. The symbols
2163 in the list are explicitly marked as zero page symols.
2172 <sect1><tt>.I16</tt><label id=".I16"><p>
2174 Valid only in 65816 mode. Switch the index registers to 16 bit.
2176 Note: This command will not emit any code, it will tell the assembler to
2177 create 16 bit operands for immediate operands.
2179 See also the <tt><ref id=".I8" name=".I8"></tt> and <tt><ref id=".SMART"
2180 name=".SMART"></tt> commands.
2183 <sect1><tt>.I8</tt><label id=".I8"><p>
2185 Valid only in 65816 mode. Switch the index registers to 8 bit.
2187 Note: This command will not emit any code, it will tell the assembler to
2188 create 8 bit operands for immediate operands.
2190 See also the <tt><ref id=".I16" name=".I16"></tt> and <tt><ref id=".SMART"
2191 name=".SMART"></tt> commands.
2194 <sect1><tt>.IF</tt><label id=".IF"><p>
2196 Conditional assembly: Evalute an expression and switch assembler output
2197 on or off depending on the expression. The expression must be a constant
2198 expression, that is, all operands must be defined.
2200 A expression value of zero evaluates to FALSE, any other value evaluates
2204 <sect1><tt>.IFBLANK</tt><label id=".IFBLANK"><p>
2206 Conditional assembly: Check if there are any remaining tokens in this line,
2207 and evaluate to FALSE if this is the case, and to TRUE otherwise. If the
2208 condition is not true, further lines are not assembled until an <tt><ref
2209 id=".ELSE" name=".ESLE"></tt>, <tt><ref id=".ELSEIF" name=".ELSEIF"></tt> or
2210 <tt><ref id=".ENDIF" name=".ENDIF"></tt> directive.
2212 This command is often used to check if a macro parameter was given. Since an
2213 empty macro parameter will evaluate to nothing, the condition will evaluate
2214 to FALSE if an empty parameter was given.
2228 See also: <tt><ref id=".BLANK" name=".BLANK"></tt>
2231 <sect1><tt>.IFCONST</tt><label id=".IFCONST"><p>
2233 Conditional assembly: Evaluate an expression and switch assembler output
2234 on or off depending on the constness of the expression.
2236 A const expression evaluates to to TRUE, a non const expression (one
2237 containing an imported or currently undefined symbol) evaluates to
2240 See also: <tt><ref id=".CONST" name=".CONST"></tt>
2243 <sect1><tt>.IFDEF</tt><label id=".IFDEF"><p>
2245 Conditional assembly: Check if a symbol is defined. Must be followed by
2246 a symbol name. The condition is true if the the given symbol is already
2247 defined, and false otherwise.
2249 See also: <tt><ref id=".DEFINED" name=".DEFINED"></tt>
2252 <sect1><tt>.IFNBLANK</tt><label id=".IFNBLANK"><p>
2254 Conditional assembly: Check if there are any remaining tokens in this line,
2255 and evaluate to TRUE if this is the case, and to FALSE otherwise. If the
2256 condition is not true, further lines are not assembled until an <tt><ref
2257 id=".ELSE" name=".ELSE"></tt>, <tt><ref id=".ELSEIF" name=".ELSEIF"></tt> or
2258 <tt><ref id=".ENDIF" name=".ENDIF"></tt> directive.
2260 This command is often used to check if a macro parameter was given.
2261 Since an empty macro parameter will evaluate to nothing, the condition
2262 will evaluate to FALSE if an empty parameter was given.
2275 See also: <tt><ref id=".BLANK" name=".BLANK"></tt>
2278 <sect1><tt>.IFNDEF</tt><label id=".IFNDEF"><p>
2280 Conditional assembly: Check if a symbol is defined. Must be followed by
2281 a symbol name. The condition is true if the the given symbol is not
2282 defined, and false otherwise.
2284 See also: <tt><ref id=".DEFINED" name=".DEFINED"></tt>
2287 <sect1><tt>.IFNREF</tt><label id=".IFNREF"><p>
2289 Conditional assembly: Check if a symbol is referenced. Must be followed
2290 by a symbol name. The condition is true if if the the given symbol was
2291 not referenced before, and false otherwise.
2293 See also: <tt><ref id=".REFERENCED" name=".REFERENCED"></tt>
2296 <sect1><tt>.IFP02</tt><label id=".IFP02"><p>
2298 Conditional assembly: Check if the assembler is currently in 6502 mode
2299 (see <tt><ref id=".P02" name=".P02"></tt> command).
2302 <sect1><tt>.IFP816</tt><label id=".IFP816"><p>
2304 Conditional assembly: Check if the assembler is currently in 65816 mode
2305 (see <tt><ref id=".P816" name=".P816"></tt> command).
2308 <sect1><tt>.IFPC02</tt><label id=".IFPC02"><p>
2310 Conditional assembly: Check if the assembler is currently in 65C02 mode
2311 (see <tt><ref id=".PC02" name=".PC02"></tt> command).
2314 <sect1><tt>.IFPSC02</tt><label id=".IFPSC02"><p>
2316 Conditional assembly: Check if the assembler is currently in 65SC02 mode
2317 (see <tt><ref id=".PSC02" name=".PSC02"></tt> command).
2320 <sect1><tt>.IFREF</tt><label id=".IFREF"><p>
2322 Conditional assembly: Check if a symbol is referenced. Must be followed
2323 by a symbol name. The condition is true if if the the given symbol was
2324 referenced before, and false otherwise.
2326 This command may be used to build subroutine libraries in include files
2327 (you may use separate object modules for this purpose too).
2332 .ifref ToHex ; If someone used this subroutine
2333 ToHex: tay ; Define subroutine
2339 See also: <tt><ref id=".REFERENCED" name=".REFERENCED"></tt>
2342 <sect1><tt>.IMPORT</tt><label id=".IMPORT"><p>
2344 Import a symbol from another module. The command is followed by a comma
2345 separated list of symbols to import.
2353 See: <tt><ref id=".IMPORTZP" name=".IMPORTZP"></tt>
2356 <sect1><tt>.IMPORTZP</tt><label id=".IMPORTZP"><p>
2358 Import a symbol from another module. The command is followed by a comma
2359 separated list of symbols to import. The symbols are explicitly imported
2360 as zero page symbols (that is, symbols with values in byte range).
2368 See: <tt><ref id=".IMPORT" name=".IMPORT"></tt>
2371 <sect1><tt>.INCBIN</tt><label id=".INCBIN"><p>
2373 Include a file as binary data. The command expects a string argument
2374 that is the name of a file to include literally in the current segment.
2375 In addition to that, a start offset and a size value may be specified,
2376 separated by commas. If no size is specified, all of the file from the
2377 start offset to end-of-file is used. If no start position is specified
2378 either, zero is assume (which means that the whole file is inserted).
2383 ; Include whole file
2384 .incbin "sprites.dat"
2386 ; Include file starting at offset 256
2387 .incbin "music.dat", $100
2389 ; Read 100 bytes starting at offset 200
2390 .incbin "graphics.dat", 200, 100
2394 <sect1><tt>.INCLUDE</tt><label id=".INCLUDE"><p>
2396 Include another file. Include files may be nested up to a depth of 16.
2405 <sect1><tt>.LINECONT</tt><label id=".LINECONT"><p>
2407 Switch on or off line continuations using the backslash character
2408 before a newline. The option is off by default.
2409 Note: Line continuations do not work in a comment. A backslash at the
2410 end of a comment is treated as part of the comment and does not trigger
2412 The command must be followed by a '+' or '-' character to switch the
2413 option on or off respectively.
2418 .linecont + ; Allow line continuations
2421 #$20 ; This is legal now
2425 <sect1><tt>.LIST</tt><label id=".LIST"><p>
2427 Enable output to the listing. The command must be followed by a boolean
2428 switch ("on", "off", "+" or "-") and will enable or disable listing
2430 The option has no effect if the listing is not enabled by the command line
2431 switch -l. If -l is used, an internal counter is set to 1. Lines are output
2432 to the listing file, if the counter is greater than zero, and suppressed if
2433 the counter is zero. Each use of <tt/.LIST/ will increment or decrement the
2439 .list on ; Enable listing output
2443 <sect1><tt>.LISTBYTES</tt><label id=".LISTBYTES"><p>
2445 Set, how many bytes are shown in the listing for one source line. The
2446 default is 12, so the listing will show only the first 12 bytes for any
2447 source line that generates more than 12 bytes of code or data.
2448 The directive needs an argument, which is either "unlimited", or an
2449 integer constant in the range 4..255.
2454 .listbytes unlimited ; List all bytes
2455 .listbytes 12 ; List the first 12 bytes
2456 .incbin "data.bin" ; Include large binary file
2460 <sect1><tt>.LOCAL</tt><label id=".LOCAL"><p>
2462 This command may only be used inside a macro definition. It declares a
2463 list of identifiers as local to the macro expansion.
2465 A problem when using macros are labels: Since they don't change their name,
2466 you get a "duplicate symbol" error if the macro is expanded the second time.
2467 Labels declared with <tt><ref id=".LOCAL" name=".LOCAL"></tt> have their
2468 name mapped to an internal unique name (<tt/___ABCD__/) with each macro
2471 Some other assemblers start a new lexical block inside a macro expansion.
2472 This has some drawbacks however, since that will not allow <em/any/ symbol
2473 to be visible outside a macro, a feature that is sometimes useful. The
2474 <tt><ref id=".LOCAL" name=".LOCAL"></tt> command is in my eyes a better way
2475 to address the problem.
2477 You get an error when using <tt><ref id=".LOCAL" name=".LOCAL"></tt> outside
2481 <sect1><tt>.LOCALCHAR</tt><label id=".LOCALCHAR"><p>
2483 Defines the character that start "cheap" local labels. You may use one
2484 of '@' and '?' as start character. The default is '@'.
2486 Cheap local labels are labels that are visible only between two non
2487 cheap labels. This way you can reuse identifiers like "<tt/loop/" without
2488 using explicit lexical nesting.
2495 Clear: lda #$00 ; Global label
2496 ?Loop: sta Mem,y ; Local label
2500 Sub: ... ; New global label
2501 bne ?Loop ; ERROR: Unknown identifier!
2505 <sect1><tt>.MACPACK</tt><label id=".MACPACK"><p>
2507 Insert a predefined macro package. The command is followed by an
2508 identifier specifying the macro package to insert. Available macro
2512 generic Defines generic macros like add and sub.
2513 longbranch Defines conditional long jump macros.
2514 cbm Defines the scrcode macro
2515 cpu Defines constants for the .CPU variable
2518 Including a macro package twice, or including a macro package that
2519 redefines already existing macros will lead to an error.
2524 .macpack longbranch ; Include macro package
2526 cmp #$20 ; Set condition codes
2527 jne Label ; Jump long on condition
2530 Macro packages are explained in more detail in section <ref
2531 id="macropackages" name="Macro packages">.
2534 <sect1><tt>.MAC, .MACRO</tt><label id=".MAC"><p>
2536 Start a classic macro definition. The command is followed by an identifier
2537 (the macro name) and optionally by a comma separated list of identifiers
2538 that are macro parameters.
2540 See section <ref id="macros" name="Macros">.
2543 <sect1><tt>.ORG</tt><label id=".ORG"><p>
2545 Start a section of absolute code. The command is followed by a constant
2546 expression that gives the new PC counter location for which the code is
2547 assembled. Use <tt><ref id=".RELOC" name=".RELOC"></tt> to switch back to
2550 Please note that you <em/do not need/ this command in most cases. Placing
2551 code at a specific address is the job of the linker, not the assembler, so
2552 there is usually no reason to assemble code to a specific address.
2554 You may not switch segments while inside a section of absolute code.
2559 .org $7FF ; Emit code starting at $7FF
2563 <sect1><tt>.OUT</tt><label id=".OUT"><p>
2565 Output a string to the console without producing an error. This command
2566 is similiar to <tt/.ERROR/, however, it does not force an assembler error
2567 that prevents the creation of an object file.
2572 .out "This code was written by the codebuster(tm)"
2575 See also the <tt><ref id=".WARNING" name=".WARNING"></tt> and <tt><ref
2576 id=".ERROR" name=".ERROR"></tt> directives.
2579 <sect1><tt>.P02</tt><label id=".P02"><p>
2581 Enable the 6502 instruction set, disable 65SC02, 65C02 and 65816
2582 instructions. This is the default if not overridden by the
2583 <tt><ref id="option--cpu" name="--cpu"></tt> command line option.
2585 See: <tt><ref id=".PC02" name=".PC02"></tt>, <tt><ref id=".PSC02"
2586 name=".PSC02"></tt> and <tt><ref id=".P816" name=".P816"></tt>
2589 <sect1><tt>.P816</tt><label id=".P816"><p>
2591 Enable the 65816 instruction set. This is a superset of the 65SC02 and
2592 6502 instruction sets.
2594 See: <tt><ref id=".P02" name=".P02"></tt>, <tt><ref id=".PSC02"
2595 name=".PSC02"></tt> and <tt><ref id=".PC02" name=".PC02"></tt>
2598 <sect1><tt>.PAGELEN, .PAGELENGTH</tt><label id=".PAGELENGTH"><p>
2600 Set the page length for the listing. Must be followed by an integer
2601 constant. The value may be "unlimited", or in the range 32 to 127. The
2602 statement has no effect if no listing is generated. The default value is -1
2603 (unlimited) but may be overridden by the <tt/--pagelength/ command line
2604 option. Beware: Since ca65 is a one pass assembler, the listing is generated
2605 after assembly is complete, you cannot use multiple line lengths with one
2606 source. Instead, the value set with the last <tt/.PAGELENGTH/ is used.
2611 .pagelength 66 ; Use 66 lines per listing page
2613 .pagelength unlimited ; Unlimited page length
2617 <sect1><tt>.PC02</tt><label id=".PC02"><p>
2619 Enable the 65C02 instructions set. This instruction set includes all
2620 6502 and 65SC02 instructions.
2622 See: <tt><ref id=".P02" name=".P02"></tt>, <tt><ref id=".PSC02"
2623 name=".PSC02"></tt> and <tt><ref id=".P816" name=".P816"></tt>
2626 <sect1><tt>.POPSEG</tt><label id=".POPSEG"><p>
2628 Pop the last pushed segment from the stack, and set it.
2630 This command will switch back to the segment that was last pushed onto the
2631 segment stack using the <tt><ref id=".PUSHSEG" name=".PUSHSEG"></tt>
2632 command, and remove this entry from the stack.
2634 The assembler will print an error message if the segment stack is empty
2635 when this command is issued.
2637 See: <tt><ref id=".PUSHSEG" name=".PUSHSEG"></tt>
2640 <sect1><tt>.PROC</tt><label id=".PROC"><p>
2642 Start a nested lexical level with the given name and adds a symbol with this
2643 name to the enclosing scope. All new symbols from now on are in the local
2644 lexical level and are accessible from outside only via <ref id="scopesyntax"
2645 name="explicit scope specification">. Symbols defined outside this local
2646 level may be accessed as long as their names are not used for new symbols
2647 inside the level. Symbols names in other lexical levels do not clash, so you
2648 may use the same names for identifiers. The lexical level ends when the
2649 <tt><ref id=".ENDPROC" name=".ENDPROC"></tt> command is read. Lexical levels
2650 may be nested up to a depth of 16 (this is an artificial limit to protect
2651 against errors in the source).
2653 Note: Macro names are always in the global level and in a separate name
2654 space. There is no special reason for this, it's just that I've never
2655 had any need for local macro definitions.
2660 .proc Clear ; Define Clear subroutine, start new level
2662 L1: sta Mem,y ; L1 is local and does not cause a
2663 ; duplicate symbol error if used in other
2666 bne L1 ; Reference local symbol
2668 .endproc ; Leave lexical level
2671 See: <tt/<ref id=".ENDPROC" name=".ENDPROC">/ and <tt/<ref id=".SCOPE"
2675 <sect1><tt>.PSC02</tt><label id=".PSC02"><p>
2677 Enable the 65SC02 instructions set. This instruction set includes all
2680 See: <tt><ref id=".P02" name=".P02"></tt>, <tt><ref id=".PC02"
2681 name=".PC02"></tt> and <tt><ref id=".P816" name=".P816"></tt>
2684 <sect1><tt>.PUSHSEG</tt><label id=".PUSHSEG"><p>
2686 Push the currently active segment onto a stack. The entries on the stack
2687 include the name of the segment and the segment type. The stack has a size
2690 <tt/.PUSHSEG/ allows together with <tt><ref id=".POPSEG" name=".POPSEG"></tt>
2691 to switch to another segment and to restore the old segment later, without
2692 even knowing the name and type of the current segment.
2694 The assembler will print an error message if the segment stack is already
2695 full, when this command is issued.
2697 See: <tt><ref id=".POPSEG" name=".POPSEG"></tt>
2700 <sect1><tt>.REPEAT</tt><label id=".REPEAT"><p>
2702 Repeat all commands between <tt/.REPEAT/ and <tt><ref id=".ENDREPEAT"
2703 name=".ENDREPEAT"></tt> constant number of times. The command is followed by
2704 a constant expression that tells how many times the commands in the body
2705 should get repeated. Optionally, a comma and an identifier may be specified.
2706 If this identifier is found in the body of the repeat statement, it is
2707 replaced by the current repeat count (starting with zero for the first time
2708 the body is repeated).
2710 <tt/.REPEAT/ statements may be nested. If you use the same repeat count
2711 identifier for a nested <tt/.REPEAT/ statement, the one from the inner
2712 level will be used, not the one from the outer level.
2716 The following macro will emit a string that is "encrypted" in that all
2717 characters of the string are XORed by the value $55.
2721 .repeat .strlen(Arg), I
2722 .byte .strat(Arg, I) .xor $55
2727 See: <tt><ref id=".ENDREPEAT" name=".ENDREPEAT"></tt>
2730 <sect1><tt>.RELOC</tt><label id=".RELOC"><p>
2732 Switch back to relocatable mode. See the <tt><ref id=".ORG"
2733 name=".ORG"></tt> command.
2736 <sect1><tt>.RES</tt><label id=".RES"><p>
2738 Reserve storage. The command is followed by one or two constant
2739 expressions. The first one is mandatory and defines, how many bytes of
2740 storage should be defined. The second, optional expression must by a
2741 constant byte value that will be used as value of the data. If there
2742 is no fill value given, the linker will use the value defined in the
2743 linker configuration file (default: zero).
2748 ; Reserve 12 bytes of memory with value $AA
2753 <sect1><tt>.RODATA</tt><label id=".RODATA"><p>
2755 Switch to the RODATA segment. The name of the RODATA segment is always
2756 "RODATA", so this is a shortcut for
2762 The RODATA segment is a segment that is used by the compiler for
2763 readonly data like string constants.
2765 See also the <tt><ref id=".SEGMENT" name=".SEGMENT"></tt> command.
2768 <sect1><tt>.SCOPE</tt><label id=".SCOPE"><p>
2770 Start a nested lexical level with the given name. All new symbols from now
2771 on are in the local lexical level and are accessible from outside only via
2772 <ref id="scopesyntax" name="explicit scope specification">. Symbols defined
2773 outside this local level may be accessed as long as their names are not used
2774 for new symbols inside the level. Symbols names in other lexical levels do
2775 not clash, so you may use the same names for identifiers. The lexical level
2776 ends when the <tt><ref id=".ENDSCOPE" name=".ENDSCOPE"></tt> command is
2777 read. Lexical levels may be nested up to a depth of 16 (this is an
2778 artificial limit to protect against errors in the source).
2780 Note: Macro names are always in the global level and in a separate name
2781 space. There is no special reason for this, it's just that I've never
2782 had any need for local macro definitions.
2787 .scope Error ; Start new scope named Error
2789 File = 1 ; File error
2790 Parse = 2 ; Parse error
2791 .endproc ; Close lexical level
2794 lda #Error::File ; Use symbol from scope Error
2797 See: <tt/<ref id=".ENDSCOPE" name=".ENDSCOPE">/ and <tt/<ref id=".PROC"
2801 <sect1><tt>.SEGMENT</tt><label id=".SEGMENT"><p>
2803 Switch to another segment. Code and data is always emitted into a
2804 segment, that is, a named section of data. The default segment is
2805 "CODE". There may be up to 254 different segments per object file
2806 (and up to 65534 per executable). There are shortcut commands for
2807 the most common segments ("CODE", "DATA" and "BSS").
2809 The command is followed by a string containing the segment name (there
2810 are some constraints for the name - as a rule of thumb use only those
2811 segment names that would also be valid identifiers). There may also be
2812 an optional attribute separated by a comma. Valid attributes are
2813 "<tt/zeropage/" and "<tt/absolute/".
2815 When specifying a segment for the first time, "absolute" is the
2816 default. For all other uses, the attribute specified the first time
2819 "absolute" means that this is a segment with absolute addressing. That
2820 is, the segment will reside somewhere in core memory outside the zero
2821 page. "zeropage" means the opposite: The segment will be placed in the
2822 zero page and direct (short) addressing is possible for data in this
2825 Beware: Only labels in a segment with the zeropage attribute are marked
2826 as reachable by short addressing. The `*' (PC counter) operator will
2827 work as in other segments and will create absolute variable values.
2832 .segment "ROM2" ; Switch to ROM2 segment
2833 .segment "ZP2", zeropage ; New direct segment
2834 .segment "ZP2" ; Ok, will use last attribute
2835 .segment "ZP2", absolute ; Error, redecl mismatch
2838 See: <tt><ref id=".BSS" name=".BSS"></tt>, <tt><ref id=".CODE"
2839 name=".CODE"></tt>, <tt><ref id=".DATA" name=".DATA"></tt> and <tt><ref
2840 id=".RODATA" name=".RODATA"></tt>
2843 <sect1><tt>.SETCPU</tt><label id=".SETCPU"><p>
2845 Switch the CPU instruction set. The command is followed by a string that
2846 specifies the CPU. Possible values are those that can also be supplied to
2847 the <tt><ref id="option--cpu" name="--cpu"></tt> command line option,
2848 namely: 6502, 65SC02, 65C02, 65816 and sunplus. Please note that support
2849 for the sunplus CPU is not available in the freeware version, because the
2850 instruction set of the sunplus CPU is "proprietary and confidential".
2852 See: <tt><ref id=".CPU" name=".CPU"></tt>,
2853 <tt><ref id=".IFP02" name=".IFP02"></tt>,
2854 <tt><ref id=".IFP816" name=".IFP816"></tt>,
2855 <tt><ref id=".IFPC02" name=".IFPC02"></tt>,
2856 <tt><ref id=".IFPSC02" name=".IFPSC02"></tt>,
2857 <tt><ref id=".P02" name=".P02"></tt>,
2858 <tt><ref id=".P816" name=".P816"></tt>,
2859 <tt><ref id=".PC02" name=".PC02"></tt>,
2860 <tt><ref id=".PSC02" name=".PSC02"></tt>
2863 <sect1><tt>.SMART</tt><label id=".SMART"><p>
2865 Switch on or off smart mode. The command must be followed by a '+' or
2866 '-' character to switch the option on or off respectively. The default
2867 is off (that is, the assembler doesn't try to be smart), but this
2868 default may be changed by the -s switch on the command line.
2870 In smart mode the assembler will do the following:
2873 <item>Track usage of the <tt/REP/ and <tt/SEP/ instructions in 65816 mode
2874 and update the operand sizes accordingly. If the operand of such an
2875 instruction cannot be evaluated by the assembler (for example, because
2876 the operand is an imported symbol), a warning is issued. Beware: Since
2877 the assembler cannot trace the execution flow this may lead to false
2878 results in some cases. If in doubt, use the <tt/.Inn/ and <tt/.Ann/
2879 instructions to tell the assembler about the current settings.
2880 <item>In 65816 mode, replace a <tt/RTS/ instruction by <tt/RTL/ if it is
2881 used within a procedure declared as <tt/far/, or if the procedure has
2882 no explicit address specification, but it is <tt/far/ because of the
2890 .smart - ; Stop being smart
2893 See: <tt><ref id=".A16" name=".A16"></tt>,
2894 <tt><ref id=".A8" name=".A8"></tt>,
2895 <tt><ref id=".I16" name=".I16"></tt>,
2896 <tt><ref id=".I8" name=".I8"></tt>
2899 <sect1><tt>.STRUCT</tt><label id=".STRUCT"><p>
2901 Starts a struct definition. Structs are covered in a separate section named
2902 <ref id="structs" name=""Structs and unions"">.
2904 See: <tt><ref id=".ENDSTRUCT" name=".ENDSTRUCT"></tt>
2907 <sect1><tt>.SUNPLUS</tt><label id=".SUNPLUS"><p>
2909 Enable the SunPlus instructions set. This command will not work in the
2910 freeware version of the assembler, because the instruction set is
2911 "proprietary and confidential".
2913 See: <tt><ref id=".P02" name=".P02"></tt>, <tt><ref id=".PSC02"
2914 name=".PSC02"></tt>, <tt><ref id=".PC02" name=".PC02"></tt>, and
2915 <tt><ref id=".P816" name=".P816"></tt>
2918 <sect1><tt>.TAG</tt><label id=".TAG"><p>
2920 Allocate space for a struct or union.
2931 .tag Point ; Allocate 4 bytes
2935 <sect1><tt>.WARNING</tt><label id=".WARNING"><p>
2937 Force an assembly warning. The assembler will output a warning message
2938 preceeded by "User warning". This warning will always be output, even if
2939 other warnings are disabled with the <tt><ref id="option-W" name="-W0"></tt>
2940 command line option.
2942 This command may be used to output possible problems when assembling
2951 .warning "Forward jump in jne, cannot optimize!"
2961 See also the <tt><ref id=".ERROR" name=".ERROR"></tt> and <tt><ref id=".OUT"
2962 name=".OUT"></tt> directives.
2965 <sect1><tt>.WORD</tt><label id=".WORD"><p>
2967 Define word sized data. Must be followed by a sequence of (word ranged,
2968 but not necessarily constant) expressions.
2973 .word $0D00, $AF13, _Clear
2977 <sect1><tt>.ZEROPAGE</tt><label id=".ZEROPAGE"><p>
2979 Switch to the ZEROPAGE segment and mark it as direct (zeropage) segment.
2980 The name of the ZEROPAGE segment is always "ZEROPAGE", so this is a
2984 .segment "ZEROPAGE", zeropage
2987 Because of the "zeropage" attribute, labels declared in this segment are
2988 addressed using direct addressing mode if possible. You <em/must/ instruct
2989 the linker to place this segment somewhere in the address range 0..$FF
2990 otherwise you will get errors.
2992 See: <tt><ref id=".SEGMENT" name=".SEGMENT"></tt>
2996 <sect>Macros<label id="macros"><p>
2999 <sect1>Introduction<p>
3001 Macros may be thought of as "parametrized super instructions". Macros are
3002 sequences of tokens that have a name. If that name is used in the source
3003 file, the macro is "expanded", that is, it is replaced by the tokens that
3004 were specified when the macro was defined.
3007 <sect1>Macros without parameters<p>
3009 In it's simplest form, a macro does not have parameters. Here's an
3013 .macro asr ; Arithmetic shift right
3014 cmp #$80 ; Put bit 7 into carry
3015 ror ; Rotate right with carry
3019 The macro above consists of two real instructions, that are inserted into
3020 the code, whenever the macro is expanded. Macro expansion is simply done
3021 by using the name, like this:
3030 <sect1>Parametrized macros<p>
3032 When using macro parameters, macros can be even more useful:
3046 When calling the macro, you may give a parameter, and each occurence of
3047 the name "addr" in the macro definition will be replaced by the given
3066 A macro may have more than one parameter, in this case, the parameters
3067 are separated by commas. You are free to give less parameters than the
3068 macro actually takes in the definition. You may also leave intermediate
3069 parameters empty. Empty parameters are replaced by empty space (that is,
3070 they are removed when the macro is exanded). If you have a look at our
3071 macro definition above, you will see, that replacing the "addr" parameter
3072 by nothing will lead to wrong code in most lines. To help you, writing
3073 macros with a variable parameter list, there are some control commands:
3075 <tt><ref id=".IFBLANK" name=".IFBLANK"></tt> tests the rest of the line and
3076 returns true, if there are any tokens on the remainder of the line. Since
3077 empty parameters are replaced by nothing, this may be used to test if a given
3078 parameter is empty. <tt><ref id=".IFNBLANK" name=".IFNBLANK"></tt> tests the
3081 Look at this example:
3084 .macro ldaxy a, x, y
3097 This macro may be called as follows:
3100 ldaxy 1, 2, 3 ; Load all three registers
3102 ldaxy 1, , 3 ; Load only a and y
3104 ldaxy , , 3 ; Load y only
3107 There's another helper command for determining, which macro parameters are
3108 valid: <tt><ref id=".PARAMCOUNT" name=".PARAMCOUNT"></tt> This command is
3109 replaced by the parameter count given, <em/including/ intermediate empty macro
3113 ldaxy 1 ; .PARAMCOUNT = 1
3114 ldaxy 1,,3 ; .PARAMCOUNT = 3
3115 ldaxy 1,2 ; .PARAMCOUNT = 2
3116 ldaxy 1, ; .PARAMCOUNT = 2
3117 ldaxy 1,2,3 ; .PARAMCOUNT = 3
3121 <sect1>Detecting parameter types<p>
3123 Sometimes it is nice to write a macro that acts differently depending on the
3124 type of the argument supplied. An example would be a macro that loads a 16 bit
3125 value from either an immediate operand, or from memory. The <tt/<ref
3126 id=".MATCH" name=".MATCH">/ and <tt/<ref id=".XMATCH" name=".XMATCH">/
3127 functions will allow you to do exactly this:
3131 .if (.match (.left (1, arg), #))
3133 lda #<(.right (.tcount (arg)-1, arg))
3134 ldx #>(.right (.tcount (arg)-1, arg))
3136 ; assume absolute or zero page
3143 Using the <tt/<ref id=".MATCH" name=".MATCH">/ function, the macro is able to
3144 check if its argument begins with a hash mark. If so, two immediate loads are
3145 emitted, Otherwise a load from an absolute zero page memory location is
3146 assumed. So this macro can be used as
3151 ldax #$1234 ; X=$12, A=$34
3153 ldax foo ; X=$56, A=$78
3157 <sect1>Recursive macros<p>
3159 Macros may be used recursively:
3162 .macro push r1, r2, r3
3171 There's also a special macro to help writing recursive macros: <tt><ref
3172 id=".EXITMACRO" name=".EXITMACRO"></tt> This command will stop macro expansion
3176 .macro push r1, r2, r3, r4, r5, r6, r7
3178 ; First parameter is empty
3184 push r2, r3, r4, r5, r6, r7
3188 When expanding this macro, the expansion will push all given parameters
3189 until an empty one is encountered. The macro may be called like this:
3192 push $20, $21, $32 ; Push 3 ZP locations
3193 push $21 ; Push one ZP location
3197 <sect1>Local symbols inside macros<p>
3199 Now, with recursive macros, <tt><ref id=".IFBLANK" name=".IFBLANK"></tt> and
3200 <tt><ref id=".PARAMCOUNT" name=".PARAMCOUNT"></tt>, what else do you need?
3201 Have a look at the inc16 macro above. Here is it again:
3215 If you have a closer look at the code, you will notice, that it could be
3216 written more efficiently, like this:
3227 But imagine what happens, if you use this macro twice? Since the label
3228 "Skip" has the same name both times, you get a "duplicate symbol" error.
3229 Without a way to circumvent this problem, macros are not as useful, as
3230 they could be. One solution is, to start a new lexical block inside the
3244 Now the label is local to the block and not visible outside. However,
3245 sometimes you want a label inside the macro to be visible outside. To make
3246 that possible, there's a new command that's only usable inside a macro
3247 definition: <tt><ref id=".LOCAL" name=".LOCAL"></tt>. <tt/.LOCAL/ declares one
3248 or more symbols as local to the macro expansion. The names of local variables
3249 are replaced by a unique name in each separate macro expansion. So we could
3250 also solve the problem above by using <tt/.LOCAL/:
3254 .local Skip ; Make Skip a local symbol
3261 Skip: ; Not visible outside
3266 <sect1>C style macros<p>
3268 Starting with version 2.5 of the assembler, there is a second macro type
3269 available: C style macros using the <tt/.DEFINE/ directive. These macros are
3270 similar to the classic macro type described above, but behaviour is sometimes
3275 <item> Macros defined with <tt><ref id=".DEFINE" name=".DEFINE"></tt> may not
3276 span more than a line. You may use line continuation (see <tt><ref
3277 id=".LINECONT" name=".LINECONT"></tt>) to spread the definition over
3278 more than one line for increased readability, but the macro itself
3279 may not contain an end-of-line token.
3281 <item> Macros defined with <tt><ref id=".DEFINE" name=".DEFINE"></tt> share
3282 the name space with classic macros, but they are detected and replaced
3283 at the scanner level. While classic macros may be used in every place,
3284 where a mnemonic or other directive is allowed, <tt><ref id=".DEFINE"
3285 name=".DEFINE"></tt> style macros are allowed anywhere in a line. So
3286 they are more versatile in some situations.
3288 <item> <tt><ref id=".DEFINE" name=".DEFINE"></tt> style macros may take
3289 parameters. While classic macros may have empty parameters, this is
3290 not true for <tt><ref id=".DEFINE" name=".DEFINE"></tt> style macros.
3291 For this macro type, the number of actual parameters must match
3292 exactly the number of formal parameters.
3294 To make this possible, formal parameters are enclosed in braces when
3295 defining the macro. If there are no parameters, the empty braces may
3298 <item> Since <tt><ref id=".DEFINE" name=".DEFINE"></tt> style macros may not
3299 contain end-of-line tokens, there are things that cannot be done. They
3300 may not contain several processor instructions for example. So, while
3301 some things may be done with both macro types, each type has special
3302 usages. The types complement each other.
3306 Let's look at a few examples to make the advantages and disadvantages
3309 To emulate assemblers that use "<tt/EQU/" instead of "<tt/=/" you may use the
3310 following <tt/.DEFINE/:
3315 foo EQU $1234 ; This is accepted now
3318 You may use the directive to define string constants used elsewhere:
3321 ; Define the version number
3322 .define VERSION "12.3a"
3328 Macros with parameters may also be useful:
3331 .define DEBUG(message) .out message
3333 DEBUG "Assembling include file #3"
3336 Note that, while formal parameters have to be placed in braces, this is
3337 not true for the actual parameters. Beware: Since the assembler cannot
3338 detect the end of one parameter, only the first token is used. If you
3339 don't like that, use classic macros instead:
3347 (This is an example where a problem can be solved with both macro types).
3350 <sect1>Characters in macros<p>
3352 When using the <ref id="option-t" name="-t"> option, characters are translated
3353 into the target character set of the specific machine. However, this happens
3354 as late as possible. This means that strings are translated if they are part
3355 of a <tt><ref id=".BYTE" name=".BYTE"></tt> or <tt><ref id=".ASCIIZ"
3356 name=".ASCIIZ"></tt> command. Characters are translated as soon as they are
3357 used as part of an expression.
3359 This behaviour is very intuitive outside of macros but may be confusing when
3360 doing more complex macros. If you compare characters against numeric values,
3361 be sure to take the translation into account.
3366 <sect>Macro packages<label id="macropackages"><p>
3368 Using the <tt><ref id=".MACPACK" name=".MACPACK"></tt> directive, predefined
3369 macro packages may be included with just one command. Available macro packages
3373 <sect1><tt>.MACPACK generic</tt><p>
3375 This macro package defines macros that are useful in almost any program.
3376 Currently, two macros are defined:
3391 <sect1><tt>.MACPACK longbranch</tt><p>
3393 This macro package defines long conditional jumps. They are named like the
3394 short counterpart but with the 'b' replaced by a 'j'. Here is a sample
3395 definition for the "<tt/jeq/" macro, the other macros are built using the same
3400 .if .def(Target) .and ((*+2)-(Target) <= 127)
3409 All macros expand to a short branch, if the label is already defined (back
3410 jump) and is reachable with a short jump. Otherwise the macro expands to a
3411 conditional branch with the branch condition inverted, followed by an absolute
3412 jump to the actual branch target.
3414 The package defines the following macros:
3417 jeq, jne, jmi, jpl, jcs, jcc, jvs, jvc
3422 <sect1><tt>.MACPACK cbm</tt><p>
3424 The cbm macro package will define a macro named <tt/scrcode/. It takes a
3425 string as argument and places this string into memory translated into screen
3429 <sect1><tt>.MACPACK cpu</tt><p>
3431 This macro package does not define any macros but constants used to examine
3432 the value read from the <tt/<ref id=".CPU" name=".CPU">/ pseudo variable. For
3433 each supported CPU a constant similar to
3443 is defined. These constants may be used to determine the exact type of the
3444 currently enabled CPU. In addition to that, for each CPU instruction set,
3445 another constant is defined:
3455 The value read from the <tt/<ref id=".CPU" name=".CPU">/ pseudo variable may
3456 be checked with <tt/<ref id="operators" name=".BITAND">/ to determine if the
3457 currently enabled CPU supports a specific instruction set. For example the
3458 65C02 supports all instructions of the 65SC02 CPU, so it has the
3459 <tt/CPU_ISET_65SC02/ bit set in addition to its native <tt/CPU_ISET_65C02/
3463 .if (.cpu .bitand CPU_ISET_65SC02)
3471 it is possible to determine if the
3477 instruction is supported, which is the case for the 65SC02, 65C02 and 65816
3478 CPUs (the latter two are upwards compatible to the 65SC02).
3482 <sect>Structs and unions<label id="structs"><p>
3484 Structs and unions are special forms of <ref id="scopes" name="scopes">. They
3485 are to some degree comparable to their C counterparts. Both have a list of
3486 members. Each member allocates storage and may optionally have a name, which,
3487 in case of a struct, is the offset from the beginning and, in case of a union,
3490 Here is an example for a very simple struct with two members and a total size
3500 A union shares the total space between all its members, its size is the same
3501 as that of the largest member.
3503 A struct or union must not necessarily have a name. If it is anonymous, no
3504 local scope is opened, the identifiers used to name the members are placed
3505 into the current scope instead.
3507 A struct may contain unnamed members and definitions of local structs. The
3508 storage allocators may contain a multiplier, as in the example below:
3513 .word 2 ; Allocate two words
3519 Using the <ref id=".TAG" name=".TAG"> keyword, it is possible to embedd
3520 already defined structs or unions in structs:
3534 Space for a struct or union may be allocated using the <ref id=".TAG"
3535 name=".TAG"> directive.
3541 Currently, members are just offsets from the start of the struct or union. To
3542 access a field of a struct, the member offset has to be added to the address
3543 of the struct itself:
3546 lda C+Circle::Radius ; Load circle radius into A
3549 This may change in a future version of the assembler.
3552 <sect>Module constructors/destructors<label id="condes"><p>
3554 <em>Note:</em> This section applies mostly to C programs, so the explanation
3555 below uses examples from the C libraries. However, the feature may also be
3556 useful for assembler programs.
3559 <sect1>Module overview<p>
3561 Using the <tt><ref id=".CONSTRUCTOR" name=".CONSTRUCTOR"></tt> and <tt><ref
3562 id=".DESTRUCTOR" name=".DESTRUCTOR"></tt> keywords it it possible to export
3563 functions in a special way. The linker is able to generate tables with all
3564 functions of a specific type. Such a table will <em>only</em> include symbols
3565 from object files that are linked into a specific executable. This may be used
3566 to add initialization and cleanup code for library modules.
3568 The C heap functions are an example where module initialization code is used.
3569 All heap functions (<tt>malloc</tt>, <tt>free</tt>, ...) work with a few
3570 variables that contain the start and the end of the heap, pointers to the free
3571 list and so on. Since the end of the heap depends on the size and start of the
3572 stack, it must be initialized at runtime. However, initializing these
3573 variables for programs that do not use the heap are a waste of time and
3576 So the central module defines a function that contains initialization code and
3577 exports this function using the <tt/.CONSTRUCTOR/ statement. If (and only if)
3578 this module is added to an executable by the linker, the initialization
3579 function will be placed into the table of constructors by the linker. The C
3580 startup code will call all constructors before <tt/main/ and all destructors
3581 after <tt/main/, so without any further work, the heap initialization code is
3582 called once the module is linked in.
3584 While it would be possible to add explicit calls to initialization functions
3585 in the startup code, the new approach has several advantages:
3589 If a module is not included, the initialization code is not linked in and not
3590 called. So you don't pay for things you don't need.
3593 Adding another library that needs initialization does not mean that the
3594 startup code has to be changed. Before we had module constructors and
3595 destructors, the startup code for all systems had to be adjusted to call the
3596 new initialization code.
3599 The feature saves memory: Each additional initialization function needs just
3600 two bytes in the table (a pointer to the function).
3605 <sect1>Calling order<p>
3607 Both, constructors and destructors are sorted in increasing priority order by
3608 the linker when using one of the builtin linker configurations, so the
3609 functions with lower priorities come first and are followed by those with
3610 higher priorities. The C library runtime subroutine that walks over the
3611 constructor and destructor tables calls the functions starting from the top of
3612 the table - which means that functions with a high priority are called first.
3614 So when using the C runtime, both constructors and destructors are called with
3615 high priority functions first, followed by low priority functions.
3620 When creating and using module constructors and destructors, please take care
3626 The linker will only generate function tables, it will not generate code to
3627 call these functions. If you're using the feature in some other than the
3628 existing C environments, you have to write code to call all functions in a
3629 linker generated table yourself. See the <tt>condes</tt> module in the C
3630 runtime for an example on how to do this.
3633 The linker will only add addresses of functions that are in modules linked to
3634 the executable. This means that you have to be careful where to place the
3635 condes functions. If initialization is needed for a group of functions, be
3636 sure to place the initialization function into a module that is linked in
3637 regardless of which function is called by the user.
3640 The linker will generate the tables only when requested to do so by the
3641 <tt/FEATURE CONDES/ statement in the linker config file. Each table has to
3642 be requested separately.
3645 Constructors and destructors may have priorities. These priorities determine
3646 the order of the functions in the table. If your intialization or cleanup code
3647 does depend on other initialization or cleanup code, you have to choose the
3648 priority for the functions accordingly.
3651 Besides the <tt><ref id=".CONSTRUCTOR" name=".CONSTRUCTOR"></tt> and <tt><ref
3652 id=".DESTRUCTOR" name=".DESTRUCTOR"></tt> statements, there is also a more
3653 generic command: <tt><ref id=".CONDES" name=".CONDES"></tt>. This allows to
3654 specify an additional type. Predefined types are 0 (constructor) and 1
3655 (destructor). The linker generates a separate table for each type on request.
3660 <sect>Porting sources from other assemblers<p>
3662 Sometimes it is necessary to port code written for older assemblers to ca65.
3663 In some cases, this can be done without any changes to the source code by
3664 using the emulation features of ca65 (see <tt><ref id=".FEATURE"
3665 name=".FEATURE"></tt>). In other cases, it is necessary to make changes to the
3668 Probably the biggest difference is the handling of the <tt><ref id=".ORG"
3669 name=".ORG"></tt> directive. ca65 generates relocatable code, and placement is
3670 done by the linker. Most other assemblers generate absolute code, placement is
3671 done within the assembler and there is no external linker.
3673 In general it is not a good idea to write new code using the emulation
3674 features of the assembler, but there may be situations where even this rule is
3679 You need to use some of the ca65 emulation features to simulate the behaviour
3680 of such simple assemblers.
3683 <item>Prepare your sourcecode like this:
3686 ; if you want TASS style labels without colons
3687 .feature labels_without_colons
3689 ; if you want TASS style character constants
3690 ; ("a" instead of the default 'a')
3691 .feature loose_char_term
3693 .word *+2 ; the cbm load address
3698 notice that the two emulation features are mostly useful for porting
3699 sources originally written in/for TASS, they are not needed for the
3700 actual "simple assembler operation" and are not recommended if you are
3701 writing new code from scratch.
3703 <item>Replace all program counter assignments (which are not possible in ca65
3704 by default, and the respective emulation feature works different from what
3705 you'd expect) by another way to skip to another memory location, for example
3706 the <tt><ref id=".RES" name=".RES"></tt>directive.
3710 .res $2000-* ; reserve memory up to $2000
3713 notice that other than the original TASS, ca65 can never move the
3714 programmcounter backwards - think of it as if you are assembling to disc with
3717 <item>Conditional assembly (<tt/.ifeq//<tt/.endif//<tt/.goto/ etc.) must be
3718 rewritten to match ca65 syntax. Most importantly notice that due to the lack
3719 of <tt/.goto/, everything involving loops must be replaced by
3720 <tt><ref id=".REPEAT" name=".REPEAT"></tt>.
3722 <item>To assemble code to a different address than it is executed at, use the
3723 <tt><ref id=".ORG" name=".ORG"></tt> directive instead of
3724 <tt/.offs/-constructs.
3731 .reloc ; back to normal
3734 <item>Then assemble like this:
3737 cl65 --start-addr 0x0ffe -t none myprog.s -o myprog.prg
3740 notice that you need to use the actual start address minus two, since two
3741 bytes are used for the cbm load address.
3746 <sect>Bugs/Feedback<p>
3748 If you have problems using the assembler, if you find any bugs, or if
3749 you're doing something interesting with the assembler, I would be glad to
3750 hear from you. Feel free to contact me by email
3751 (<htmlurl url="mailto:uz@cc65.org" name="uz@cc65.org">).
3757 ca65 (and all cc65 binutils) are (C) Copyright 1998-2003 Ullrich von
3758 Bassewitz. For usage of the binaries and/or sources the following
3759 conditions do apply:
3761 This software is provided 'as-is', without any expressed or implied
3762 warranty. In no event will the authors be held liable for any damages
3763 arising from the use of this software.
3765 Permission is granted to anyone to use this software for any purpose,
3766 including commercial applications, and to alter it and redistribute it
3767 freely, subject to the following restrictions:
3770 <item> The origin of this software must not be misrepresented; you must not
3771 claim that you wrote the original software. If you use this software
3772 in a product, an acknowledgment in the product documentation would be
3773 appreciated but is not required.
3774 <item> Altered source versions must be plainly marked as such, and must not
3775 be misrepresented as being the original software.
3776 <item> This notice may not be removed or altered from any source
projects / cc65 / blob