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 <tag><tt>--cpu type</tt></tag>
130 Set the default for the CPU type. The option takes a parameter, which
133 6502, 65C02, 65816 and sunplus
135 The latter (sunplus) is not available in the freeware version, because the
136 instruction set of the sunplus CPU is "confidential".
139 <label id="option--feature">
140 <tag><tt>--feature name</tt></tag>
142 Enable an emulation feature. This is identical as using <tt/.FEATURE/
143 in the source with two exceptions: Feature names must be lower case, and
144 each feature must be specified by using an extra <tt/--feature/ option,
145 comma separated lists are not allowed.
147 See the discussion of the <tt><ref id=".FEATURE" name=".FEATURE"></tt>
148 command for a list of emulation features.
151 <label id="option-g">
152 <tag><tt>-g, --debug-info</tt></tag>
154 When this option (or the equivalent control command <tt/.DEBUGINFO/) is
155 used, the assembler will add a section to the object file that contains
156 all symbols (including local ones) together with the symbol values and
157 source file positions. The linker will put these additional symbols into
158 the VICE label file, so even local symbols can be seen in the VICE
162 <tag><tt>-h, --help</tt></tag>
164 Print the short option summary shown above.
167 <tag><tt>-i, --ignore-case</tt></tag>
169 This option makes the assembler case insensitive on identifiers and labels.
170 This option will override the default, but may itself be overriden by the
171 <tt><ref id=".CASE" name=".CASE"></tt> control command.
174 <tag><tt>-l, --listing</tt></tag>
176 Generate an assembler listing. The listing file will always have the
177 name of the main input file with the extension replaced by ".lst". This
178 may change in future versions.
181 <tag><tt>-o name</tt></tag>
183 The default output name is the name of the input file with the extension
184 replaced by ".o". If you don't like that, you may give another name with
185 the -o option. The output file will be placed in the same directory as
186 the source file, or, if -o is given, the full path in this name is used.
189 <tag><tt>--pagelength n</tt></tag>
191 sets the length of a listing page in lines. See the <tt><ref
192 id=".PAGELENGTH" name=".PAGELENGTH"></tt> directive for more information.
195 <tag><tt>-s, --smart-mode</tt></tag>
197 In smart mode (enabled by -s or the <tt><ref id=".SMART" name=".SMART"></tt>
198 pseudo instruction) the assembler will track usage of the <tt/REP/ and
199 <tt/SEP/ instructions in 65816 mode and update the operand sizes
200 accordingly. If the operand of such an instruction cannot be evaluated by
201 the assembler (for example, because the operand is an imported symbol), a
204 Beware: Since the assembler cannot trace the execution flow this may
205 lead to false results in some cases. If in doubt, use the .ixx and .axx
206 instructions to tell the assembler about the current settings. Smart
207 mode is off by default.
210 <label id="option-t">
211 <tag><tt>-t sys, --target sys</tt></tag>
213 Set the target system. This will enable translation of character strings
214 and character constants into the character set of the target platform.
215 The default for the target system is "none", which means that no translation
216 will take place. The assembler supports the same target systems as the
217 compiler, see there for a list.
220 <tag><tt>-v, --verbose</tt></tag>
222 Increase the assembler verbosity. Usually only needed for debugging
223 purposes. You may use this option more than one time for even more
227 <tag><tt>-D</tt></tag>
229 This option allows you to define symbols on the command line. Without a
230 value, the symbol is defined with the value zero. When giving a value,
231 you may use the '$' prefix for hexadecimal symbols. Please note
232 that for some operating systems, '$' has a special meaning, so
233 you may have to quote the expression.
236 <tag><tt>-I dir, --include-dir dir</tt></tag>
238 Name a directory which is searched for include files. The option may be
239 used more than once to specify more than one directory to search. The
240 current directory is always searched first before considering any
241 additional directores.
244 <tag><tt>-U, --auto-import</tt></tag>
246 Mark symbols that are not defined in the sources as imported symbols. This
247 should be used with care since it delays error messages about typos and such
248 until the linker is run. The compiler uses the equivalent of this switch
249 (<tt><ref id=".AUTOIMPORT" name=".AUTOIMPORT"></tt>) to enable auto imported
250 symbols for the runtime library. However, the compiler is supposed to
251 generate code that runs through the assembler without problems, something
252 which is not always true for assembler programmers.
255 <tag><tt>-V, --version</tt></tag>
257 Print the version number of the assembler. If you send any suggestions
258 or bugfixes, please include the version number.
261 <label id="option-W">
262 <tag><tt>-Wn</tt></tag>
264 Set the warning level for the assembler. Using -W2 the assembler will
265 even warn about such things like unused imported symbols. The default
266 warning level is 1, and it would probably be silly to set it to
273 <sect>Input format<p>
275 The assembler accepts the standard 6502/65816 assembler syntax. One line may
276 contain a label (which is identified by a colon), and, in addition to the
277 label, an assembler mnemonic, a macro, or a control command (see section <ref
278 id="control-commands" name="Control Commands"> for supported control
279 commands). Alternatively, the line may contain a symbol definition using the
280 '=' token. Everything after a semicolon is handled as a comment (that is, it
283 Here are some examples for valid input lines:
286 Label: ; A label and a comment
287 lda #$20 ; A 6502 instruction plus comment
288 L1: ldx #$20 ; Same with label
289 L2: .byte "Hello world" ; Label plus control command
290 mymac $20 ; Macro expansion
291 MySym = 3*L1 ; Symbol definition
292 MaSym = Label ; Another symbol
295 The assembler accepts all valid 6502 mnemonics when in 6502 mode (the
296 default). The assembler accepts all valid 65SC02 mnemonics when in 65SC02 mode
297 (after a <tt><ref id=".PC02" name=".PC02"></tt> command is found). The
298 assembler accepts all valid 65816 mnemonics with a few exceptions after a
299 .P816 command is found. These exceptions are listed below.
301 In 65816 mode several aliases are accepted in addition to the official
305 BGE is an alias for BCS
306 BLT is an alias for BCC
307 CPA is an alias for CMP
308 DEA is an alias for DEC A
309 INA is an alias for INC A
310 SWA is an alias for XBA
311 TAD is an alias for TCD
312 TAS is an alias for TCS
313 TDA is an alias for TDC
314 TSA is an alias for TSC
317 Evaluation of banked expressions in 65816 mode differs slightly from the
320 Instead of accepting a 24 bit address (something that is difficult for
321 the assembler to determine and would have required one more special
322 .import command), the bank and the absolute address in that bank are
326 jsl 3.$1234 ; Call subroutine at $1234 in bank 3
329 For literal values, the assembler accepts the widely used number formats:
330 A preceeding '$' denotes a hex value, a preceeding '%' denotes a
331 binary value, and a bare number is interpeted as a decimal. There are
332 currently no octal values and no floats.
339 <sect1>Expression evaluation<p>
341 All expressions are evaluated with (at least) 32 bit precision. An
342 expression may contain constant values and any combination of internal and
343 external symbols. Expressions that cannot be evaluated at assembly time
344 are stored inside the object file for evaluation by the linker.
345 Expressions referencing imported symbols must always be evaluated by the
349 <sect1>Size of an expressions result<p>
351 Sometimes, the assembler must know about the size of the value that is the
352 result of an expression. This is usually the case, if a decision has to be
353 made, to generate a zero page or an absolute memory references. In this
354 case, the assembler has to make some assumptions about the result of an
358 <item> If the result of an expression is constant, the actual value is
359 checked to see if it's a byte sized expression or not.
360 <item> If the expression is explicitly casted to a byte sized expression by
361 one of the '>'/'<' operators, it is a byte expression.
362 <item> If this is not the case, and the expression contains a symbol,
363 explicitly declared as zero page symbol (by one of the .importzp or
364 .exportzp instructions), then the whole expression is assumed to be
366 <item> If the expression contains symbols that are not defined, and these
367 symbols are local symbols, the enclosing scopes are searched for a
368 symbol with the same name. If one exists and this symbol is defined,
369 it's attributes are used to determine the result size.
370 <item> In all other cases the expression is assumed to be word sized.
373 Note: If the assembler is not able to evaluate the expression at assembly
374 time, the linker will evaluate it and check for range errors as soon as
378 <sect1>Boolean expressions<p>
380 In the context of a boolean expression, any non zero value is evaluated as
381 true, any other value to false. The result of a boolean expression is 1 if
382 it's true, and zero if it's false. There are boolean operators with extrem
383 low precedence with version 2.x (where x > 0). The <tt/.AND/ and <tt/.OR/
384 operators are shortcut operators. That is, if the result of the expression is
385 already known, after evaluating the left hand side, the right hand side is
389 <sect1>Available operators<p>
391 Available operators sorted by precedence:
394 Op Description Precedence
395 -------------------------------------------------------------------
396 .CONCAT Builtin function 0
397 .LEFT Builtin function 0
398 .MID Builtin function 0
399 .RIGHT Builtin function 0
400 .STRING Builtin function 0
402 * Builtin pseudo variable (r/o) 1
403 .BLANK Builtin function 1
404 .CONST Builtin function 1
405 .CPU Builtin pseudo variable (r/o) 1
406 .DEFINED Builtin function 1
407 .MATCH Builtin function 1
408 .TCOUNT Builtin function 1
409 .TIME Builtin function 1
410 .XMATCH Builtin function 1
411 .PARAMCOUNT Builtin pseudo variable (r/o) 1
412 .REFERENCED Builtin function 1
413 :: Global namespace override 1
416 ~ Unary bitwise not 1
417 .BITNOT Unary bitwise not 1
418 < Low byte operator 1
419 > High byte operator 1
423 .MOD Modulo operation 2
425 .BITAND Bitwise and 2
427 .BITXOR Bitwise xor 2
428 << Shift left operator 2
429 .SHL Shift left operator 2
430 >> Shift right operator
431 .SHR Shift right operator 2
438 = Compare operation (equal) 4
439 <> Compare operation (not equal) 4
440 < Compare operation (less) 4
441 > Compare operation (greater) 4
442 <= Compare operation (less or equal) 4
443 >= Compare operation (greater or equal) 4
445 && Boolean and 5
457 To force a specific order of evaluation, braces may be used as usual.
459 Some of the pseudo variables mentioned above need some more explanation:
462 * This symbol is replaced by the value of the program
463 counter at start of the current instruction. Note, that
464 '*' yields a rvalue, that means, you cannot assign to it.
465 Use <tt/.ORG/ to set the program counter in sections with
472 <sect>Symbols and labels<p>
474 The assembler allows you to use symbols instead of naked values to make
475 the source more readable. There are a lot of different ways to define and
476 use symbols and labels, giving a lot of flexibility.
479 <sect1>Numeric constants<p>
481 Numeric constants are defined using the equal sign. After doing
487 may use the symbol "two" in every place where a number is expected, and it is
488 evaluated to the value 2 in this context. An example would be
495 <sect1>Standard labels<p>
497 A label is defined by writing the name of the label at the start of the line
498 (before any instruction mnemonic, macro or pseudo directive), followed by a
499 colon. This will declare a symbol with the given name and the value of the
500 current program counter.
503 <sect1>Local labels and symbols<p>
505 Using the <tt><ref id=".PROC" name=".PROC"></tt> directive, it is possible to
506 create regions of code where the names of labels and symbols are local to this
507 region. They are not known outside of this region and cannot be accessed from
508 there. Such regions may be nested like PROCEDUREs in Pascal.
510 See the description of the <tt><ref id=".PROC" name=".PROC"></tt>
511 directive for more information.
514 <sect1>Cheap local labels<p>
516 Cheap local labels are defined like standard labels, but the name of the
517 label must begin with a special symbol (usually '@', but this can be
518 changed by the <tt><ref id=".LOCALCHAR" name=".LOCALCHAR"></tt>
521 Cheap local labels are visible only between two non cheap labels. As soon as a
522 standard symbol is encountered (this may also be a local symbol if inside a
523 region defined with the <tt><ref id=".PROC" name=".PROC"></tt> directive), the
524 cheap local symbol goes out of scope.
526 You may use cheap local labels as an easy way to reuse common label
527 names like "Loop". Here is an example:
530 Clear: lda #$00 ; Global label
532 @Loop: sta Mem,y ; Local label
536 Sub: ... ; New global label
537 bne @Loop ; ERROR: Unknown identifier!
540 <sect1>Unnamed labels<p>
542 If you really want to write messy code, there are also unnamed
543 labels. These labels do not have a name (you guessed that already,
544 didn't you?). A colon is used to mark the absence of the name.
546 Unnamed labels may be accessed by using the colon plus several minus
547 or plus characters as a label designator. Using the '-' characters
548 will create a back reference (use the n'th label backwards), using
549 '+' will create a forward reference (use the n'th label in forward
550 direction). An example will help to understand this:
572 As you can see from the example, unnamed labels will make even short
573 sections of code hard to understand, because you have to count labels
574 to find branch targets (this is the reason why I for my part do
575 prefer the "cheap" local labels). Nevertheless, unnamed labels are
576 convenient in some situations, so it's your decision.
579 <sect1>Using macros to define labels and constants<p>
581 While there are drawbacks with this approach, it may be handy in some
582 situations. Using <tt><ref id=".DEFINE" name=".DEFINE"></tt>, it is
583 possible to define symbols or constants that may be used elsewhere. Since
584 the macro facility works on a very low level, there is no scoping. On the
585 other side, you may also define string constants this way (this is not
586 possible with the other symbol types).
592 .DEFINE version "SOS V2.3"
594 four = two * two ; Ok
597 .PROC ; Start local scope
598 two = 3 ; Will give "2 = 3" - invalid!
603 <sect1>Symbols and <tt>.DEBUGINFO</tt><p>
605 If <tt><ref id=".DEBUGINFO" name=".DEBUGINFO"></tt> is enabled (or <ref
606 id="option-g" name="-g"> is given on the command line), global, local and
607 cheap local labels are written to the object file and will be available in the
608 symbol file via the linker. Unnamed labels are not written to the object file,
609 because they don't have a name which would allow to access them.
613 <sect>Control commands<label id="control-commands">
616 Here's a list of all control commands and a description, what they do:
619 <sect1><tt>.A16</tt><label id=".A16"><p>
621 Valid only in 65816 mode. Switch the accumulator to 16 bit.
623 Note: This command will not emit any code, it will tell the assembler to
624 create 16 bit operands for immediate accumulator adressing mode.
626 See also: <tt><ref id=".SMART" name=".SMART"></tt>
629 <sect1><tt>.A8</tt><label id=".A8"><p>
631 Valid only in 65816 mode. Switch the accumulator to 8 bit.
633 Note: This command will not emit any code, it will tell the assembler to
634 create 8 bit operands for immediate accu adressing mode.
636 See also: <tt><ref id=".SMART" name=".SMART"></tt>
639 <sect1><tt>.ADDR</tt><label id=".ADDR"><p>
641 Define word sized data. In 6502 mode, this is an alias for <tt/.WORD/ and
642 may be used for better readability if the data words are address values. In
643 65816 mode, the address is forced to be 16 bit wide to fit into the current
644 segment. See also <tt><ref id=".FARADDR" name=".FARADDR"></tt>. The command
645 must be followed by a sequence of (not necessarily constant) expressions.
650 .addr $0D00, $AF13, _Clear
653 See: <tt><ref id=".FARADDR" name=".FARADDR"></tt>, <tt><ref id=".WORD"
657 <sect1><tt>.ALIGN</tt><label id=".ALIGN"><p>
659 Align data to a given boundary. The command expects a constant integer
660 argument that must be a power of two, plus an optional second argument
661 in byte range. If there is a second argument, it is used as fill value,
662 otherwise the value defined in the linker configuration file is used
663 (the default for this value is zero).
665 Since alignment depends on the base address of the module, you must
666 give the same (or a greater) alignment for the segment when linking.
667 The linker will give you a warning, if you don't do that.
676 <sect1><tt>.ASCIIZ</tt><label id=".ASCIIZ"><p>
678 Define a string with a trailing zero.
683 Msg: .asciiz "Hello world"
686 This will put the string "Hello world" followed by a binary zero into
687 the current segment. There may be more strings separated by commas, but
688 the binary zero is only appended once (after the last one).
691 <sect1><tt>.ASSERT</tt><label id=".ASSERT"><p>
693 Add an assertion. The command is followed by an expression, an action
694 specifier and a message that is output in case the assertion fails. The
695 action specifier may be one of <tt/warning/ or <tt/error/. The assertion
696 is passed to the linker and will be evaluated when segment placement has
702 .assert * = $8000, error, "Code not at $8000"
705 The example assertion will check that the current location is at $8000,
706 when the output file is written, and abort with an error if this is not
707 the case. More complex expressions are possible. The action specifier
708 <tt/warning/ outputs a warning, while the <tt/error/ specifier outputs
709 an error message. In the latter case, generation if the output file is
713 <sect1><tt>.AUTOIMPORT</tt><label id=".AUTOIMPORT"><p>
715 Is followed by a plus or a minus character. When switched on (using a
716 +), undefined symbols are automatically marked as import instead of
717 giving errors. When switched off (which is the default so this does not
718 make much sense), this does not happen and an error message is
719 displayed. The state of the autoimport flag is evaluated when the
720 complete source was translated, before outputing actual code, so it is
721 <em/not/ possible to switch this feature on or off for separate sections
722 of code. The last setting is used for all symbols.
724 You should probably not use this switch because it delays error
725 messages about undefined symbols until the link stage. The cc65
726 compiler (which is supposed to produce correct assembler code in all
727 circumstances, something which is not true for most assembler
728 programmers) will insert this command to avoid importing each and every
729 routine from the runtime library.
734 .autoimport + ; Switch on auto import
738 <sect1><tt>.BLANK</tt><label id=".BLANK"><p>
740 Builtin function. The function evaluates its argument in braces and
741 yields "false" if the argument is non blank (there is an argument), and
742 "true" if there is no argument. As an example, the <tt/.IFBLANK/ statement
750 <sect1><tt>.BSS</tt><label id=".BSS"><p>
752 Switch to the BSS segment. The name of the BSS segment is always "BSS",
753 so this is a shortcut for
759 See also the <tt><ref id=".SEGMENT" name=".SEGMENT"></tt> command.
762 <sect1><tt>.BYT, .BYTE</tt><label id=".BYTE"><p>
764 Define byte sized data. Must be followed by a sequence of (byte ranged)
765 expressions or strings.
771 .byt "world", $0D, $00
775 <sect1><tt>.CASE</tt><label id=".CASE"><p>
777 Switch on or off case sensitivity on identifiers. The default is off
778 (that is, identifiers are case sensitive), but may be changed by the
779 -i switch on the command line.
780 The command must be followed by a '+' or '-' character to switch the
781 option on or off respectively.
786 .case - ; Identifiers are not case sensitive
790 <sect1><tt>.CHARMAP</tt><label id=".CHARMAP"><p>
792 Apply a custom mapping for characters. The command is followed by two
793 numbers in the range 1..255. The first one is the index of the source
794 character, the second one is the mapping. The mapping applies to all
795 character and string constants when they generate output, and overrides
796 a mapping table specified with the <tt><ref id="option-t" name="-t"></tt>
802 .charmap $41, $61 ; Map 'A' to 'a'
806 <sect1><tt>.CODE</tt><label id=".CODE"><p>
808 Switch to the CODE segment. The name of the CODE segment is always
809 "CODE", so this is a shortcut for
815 See also the <tt><ref id=".SEGMENT" name=".SEGMENT"></tt> command.
818 <sect1><tt>.CONDES</tt><label id=".CONDES"><p>
820 Export a symbol and mark it in a special way. The linker is able to build
821 tables of all such symbols. This may be used to automatically create a list
822 of functions needed to initialize linked library modules.
824 Note: The linker has a feature to build a table of marked routines, but it
825 is your code that must call these routines, so just declaring a symbol with
826 <tt/.CONDES/ does nothing by itself.
828 All symbols are exported as an absolute (16 bit) symbol. You don't need to
829 use an additional <tt><ref id=".EXPORT" name=".EXPORT"></tt> statement, this
830 is implied by <tt/.CONDES/.
832 <tt/.CONDES/ is followed by the type, which may be <tt/constructor/,
833 <tt/destructor/ or a numeric value between 0 and 6 (where 0 is the same as
834 specifiying <tt/constructor/ and 1 is equal to specifying <tt/destructor/).
835 The <tt><ref id=".CONSTRUCTOR" name=".CONSTRUCTOR"></tt> and <tt><ref
836 id=".DESTRUCTOR" name=".DESTRUCTOR"></tt> commands are actually shortcuts
837 for <tt/.CONDES/ with a type of <tt/constructor/ resp. <tt/destructor/.
839 After the type, an optional priority may be specified. If no priority is
840 given, the default priority of 7 is used. Be careful when assigning
841 priorities to your own module constructors so they won't interfere with the
842 ones in the cc65 library.
847 .condes ModuleInit, constructor
848 .condes ModInit, 0, 16
851 See the <tt><ref id=".CONSTRUCTOR" name=".CONSTRUCTOR"></tt> and <tt><ref
852 id=".DESTRUCTOR" name=".DESTRUCTOR"></tt> commands and the separate section
853 <ref id="condes" name="Module constructors/destructors"> explaining the
854 feature in more detail.
857 <sect1><tt>.CONCAT</tt><label id=".CONCAT"><p>
859 Builtin function. The function allows to concatenate a list of string
860 constants separated by commas. The result is a string constant that
861 is the concatentation of all arguments. This function is most useful
862 in macros and when used together with the <tt/.STRING/ builtin function.
863 The function may be used in any case where a string constant is
869 .include .concat ("myheader", ".", "inc")
872 This is the same as the command
875 .include "myheader.inc"
879 <sect1><tt>.CONST</tt><label id=".CONST"><p>
881 Builtin function. The function evaluates its argument in braces and
882 yields "true" if the argument is a constant expression (that is, an
883 expression that yields a constant value at assembly time) and "false"
884 otherwise. As an example, the .IFCONST statement may be replaced by
891 <sect1><tt>.CONSTRUCTOR</tt><label id=".CONSTRUCTOR"><p>
893 Export a symbol and mark it as a module constructor. This may be used
894 together with the linker to build a table of constructor subroutines that
895 are called by the startup code.
897 Note: The linker has a feature to build a table of marked routines, but it
898 is your code that must call these routines, so just declaring a symbol as
899 constructor does nothing by itself.
901 A constructor is always exported as an absolute (16 bit) symbol. You don't
902 need to use an additional <tt/.export/ statement, this is implied by
903 <tt/.constructor/. It may have an optional priority that is separated by a
904 comma. If no priority is given, the default priority of 7 is used. Be
905 careful when assigning priorities to your own module constructors so they
906 won't interfere with the ones in the cc65 library.
911 .constructor ModuleInit
912 .constructor ModInit, 16
915 See the <tt><ref id=".CONDES" name=".CONDES"></tt> and <tt><ref
916 id=".DESTRUCTOR" name=".DESTRUCTOR"></tt> commands and the separate section
917 <ref id="condes" name="Module constructors/destructors"> explaining the
918 feature in more detail.
921 <sect1><tt>.CPU</tt><label id=".CPU"><p>
923 Reading this pseudo variable will give a constant integer value that
924 tells which instruction set is currently enabled. Possible values are:
933 It may be used to replace the .IFPxx pseudo instructions or to construct
934 even more complex expressions.
939 .if (.cpu = 0) .or (.cpu = 1)
951 <sect1><tt>.DATA</tt><label id=".DATA"><p>
953 Switch to the DATA segment. The name of the DATA segment is always
954 "DATA", so this is a shortcut for
960 See also the <tt><ref id=".SEGMENT" name=".SEGMENT"></tt> command.
963 <sect1><tt>.DBYT</tt><label id=".DBYT"><p>
965 Define word sized data with the hi and lo bytes swapped (use <tt/.WORD/ to
966 create word sized data in native 65XX format). Must be followed by a
967 sequence of (word ranged) expressions.
975 This will emit the bytes
981 into the current segment in that order.
984 <sect1><tt>.DEBUGINFO</tt><label id=".DEBUGINFO"><p>
986 Switch on or off debug info generation. The default is off (that is,
987 the object file will not contain debug infos), but may be changed by the
988 -g switch on the command line.
989 The command must be followed by a '+' or '-' character to switch the
990 option on or off respectively.
995 .debuginfo + ; Generate debug info
999 <sect1><tt>.DEFINE</tt><label id=".DEFINE"><p>
1001 Start a define style macro definition. The command is followed by an
1002 identifier (the macro name) and optionally by a list of formal arguments
1004 See section <ref id="macros" name="Macros">.
1007 <sect1><tt>.DEF, .DEFINED</tt><label id=".DEFINED"><p>
1009 Builtin function. The function expects an identifier as argument in braces.
1010 The argument is evaluated, and the function yields "true" if the identifier
1011 is a symbol that is already defined somewhere in the source file up to the
1012 current position. Otherwise the function yields false. As an example, the
1013 <tt><ref id=".IFDEF" name=".IFDEF"></tt> statement may be replaced by
1020 <sect1><tt>.DESTRUCTOR</tt><label id=".DESTRUCTOR"><p>
1022 Export a symbol and mark it as a module destructor. This may be used
1023 together with the linker to build a table of destructor subroutines that
1024 are called by the startup code.
1026 Note: The linker has a feature to build a table of marked routines, but it
1027 is your code that must call these routines, so just declaring a symbol as
1028 constructor does nothing by itself.
1030 A destructor is always exported as an absolute (16 bit) symbol. You don't
1031 need to use an additional <tt/.export/ statement, this is implied by
1032 <tt/.destructor/. It may have an optional priority that is separated by a
1033 comma. If no priority is given, the default priority of 7 is used. Be
1034 careful when assigning priorities to your own module destructors so they
1035 won't interfere with the ones in the cc65 library.
1040 .destructor ModuleDone
1041 .destructor ModDone, 16
1044 See the <tt><ref id=".CONDES" name=".CONDES"></tt> and <tt><ref
1045 id=".CONSTRUCTOR" name=".CONSTRUCTOR"></tt> commands and the separate
1046 section <ref id="condes" name="Module constructors/destructors"> explaining
1047 the feature in more detail.
1050 <sect1><tt>.DWORD</tt><label id=".DWORD"><p>
1052 Define dword sized data (4 bytes) Must be followed by a sequence of
1058 .dword $12344512, $12FA489
1062 <sect1><tt>.ELSE</tt><label id=".ELSE"><p>
1064 Conditional assembly: Reverse the current condition.
1067 <sect1><tt>.ELSEIF</tt><label id=".ELSEIF"><p>
1069 Conditional assembly: Reverse current condition and test a new one.
1072 <sect1><tt>.END</tt><label id=".END"><p>
1074 Forced end of assembly. Assembly stops at this point, even if the command
1075 is read from an include file.
1078 <sect1><tt>.ENDIF</tt><label id=".ENDIF"><p>
1080 Conditional assembly: Close a <tt><ref id=".IF" name=".IF..."></tt> or
1081 <tt><ref id=".ELSE" name=".ELSE"></tt> branch.
1084 <sect1><tt>.ENDMAC, .ENDMACRO</tt><label id=".ENDMACRO"><p>
1086 End of macro definition (see section <ref id="macros" name="Macros">).
1089 <sect1><tt>.ENDPROC</tt><label id=".ENDPROC"><p>
1091 End of local lexical level (see <tt><ref id=".PROC" name=".PROC"></tt>).
1094 <sect1><tt>.ENDREP, .ENDREPEAT</tt><label id=".ENDREPEAT"><p>
1096 End a <tt><ref id=".REPEAT" name=".REPEAT"></tt> block.
1099 <sect1><tt>.ERROR</tt><label id=".ERROR"><p>
1101 Force an assembly error. The assembler will output an error message
1102 preceeded by "User error" and will <em/not/ produce an object file.
1104 This command may be used to check for initial conditions that must be
1105 set before assembling a source file.
1115 .error "Must define foo or bar!"
1119 See also the <tt><ref id=".WARNING" name=".WARNING"></tt> and <tt><ref
1120 id=".OUT" name=".OUT"></tt> directives.
1123 <sect1><tt>.EXITMAC, .EXITMACRO</tt><label id=".EXITMACRO"><p>
1125 Abort a macro expansion immidiately. This command is often useful in
1126 recursive macros. See separate section <ref id="macros" name="Macros">.
1129 <sect1><tt>.EXPORT</tt><label id=".EXPORT"><p>
1131 Make symbols accessible from other modules. Must be followed by a comma
1132 separated list of symbols to export.
1140 See: <tt><ref id=".EXPORTZP" name=".EXPORTZP"></tt>
1143 <sect1><tt>.EXPORTZP</tt><label id=".EXPORTZP"><p>
1145 Make symbols accessible from other modules. Must be followed by a comma
1146 separated list of symbols to export. The exported symbols are explicitly
1147 marked as zero page symols.
1155 See: <tt><ref id=".EXPORT" name=".EXPORT"></tt>
1158 <sect1><tt>.FARADDR</tt><label id=".FARADDR"><p>
1160 Define far (24 bit) address data. The command must be followed by a
1161 sequence of (not necessarily constant) expressions.
1166 .faraddr DrawCircle, DrawRectangle, DrawHexagon
1169 See: <tt><ref id=".ADDR" name=".ADDR"></tt>
1172 <sect1><tt>.FEATURE</tt><label id=".FEATURE"><p>
1174 This directive may be used to enable one or more compatibility features
1175 of the assembler. While the use of <tt/.FEATURE/ should be avoided when
1176 possible, it may be useful when porting sources written for other
1177 assemblers. There is no way to switch a feature off, once you have
1178 enabled it, so using
1184 will enable the feature until end of assembly is reached.
1186 The following features are available:
1190 <tag><tt>dollar_is_pc</tt></tag>
1192 The dollar sign may be used as an alias for the star (`*'), which
1193 gives the value of the current PC in expressions.
1194 Note: Assignment to the pseudo variable is not allowed.
1196 <tag><tt>labels_without_colons</tt></tag>
1198 Allow labels without a trailing colon. These labels are only accepted,
1199 if they start at the beginning of a line (no leading white space).
1201 <tag><tt>loose_string_term</tt></tag>
1203 Accept single quotes as well as double quotes as terminators for string
1206 <tag><tt>loose_char_term</tt></tag>
1208 Accept single quotes as well as double quotes as terminators for char
1211 <tag><tt>at_in_identifiers</tt></tag>
1213 Accept the at character (`@') as a valid character in identifiers. The
1214 at character is not allowed to start an identifier, even with this
1217 <tag><tt>dollar_in_identifiers</tt></tag>
1219 Accept the dollar sign (`$') as a valid character in identifiers. The
1220 at character is not allowed to start an identifier, even with this
1223 <tag><tt>leading_dot_in_identifiers</tt></tag>
1225 Accept the dot (`.') as the first character of an identifier. This may be
1226 used for example to create macro names that start with a dot emulating
1227 control directives of other assemblers. Note however, that none of the
1228 reserved keywords built into the assembler, that starts with a dot, may be
1229 overridden. When using this feature, you may also get into trouble if
1230 later versions of the assembler define new keywords starting with a dot.
1232 <tag><tt>pc_assignment</tt></tag>
1234 Allow assignments to the PC symbol (`*' or `$' if <tt/dollar_is_pc/
1235 is enabled). Such an assignment is handled identical to the <tt><ref
1236 id=".ORG" name=".ORG"></tt> command (which is usually not needed, so just
1237 removing the lines with the assignments may also be an option when porting
1238 code written for older assemblers).
1242 It is also possible to specify features on the command line using the
1243 <tt><ref id="option--feature" name="--feature"></tt> command line option.
1244 This is useful when translating sources written for older assemblers, when
1245 you don't want to change the source code.
1247 As an example, to translate sources written for Andre Fachats xa65
1248 assembler, the features
1251 labels_without_colons, pc_assignment, loose_char_term
1254 may be helpful. They do not make ca65 completely compatible, so you may not
1255 be able to translate the sources without changes, even when enabling these
1256 features. However, I have found several sources that translate without
1257 problems when enabling these features on the command line.
1260 <sect1><tt>.FILEOPT, .FOPT</tt><label id=".FOPT"><p>
1262 Insert an option string into the object file. There are two forms of
1263 this command, one specifies the option by a keyword, the second
1264 specifies it as a number. Since usage of the second one needs knowledge
1265 of the internal encoding, its use is not recommended and I will only
1266 describe the first form here.
1268 The command is followed by one of the keywords
1276 a comma and a string. The option is written into the object file
1277 together with the string value. This is currently unidirectional and
1278 there is no way to actually use these options once they are in the
1284 .fileopt comment, "Code stolen from my brother"
1285 .fileopt compiler, "BASIC 2.0"
1286 .fopt author, "J. R. User"
1290 <sect1><tt>.FORCEIMPORT</tt><label id=".FORCEIMPORT"><p>
1292 Import an absolute symbol from another module. The command is followed by a
1293 comma separated list of symbols to import. The command is similar to <tt>
1294 <ref id=".IMPORT" name=".IMPORT"></tt>, but the import reference is always
1295 written to the generated object file, even if the symbol is never referenced
1296 (<tt><ref id=".IMPORT" name=".IMPORT"></tt> will not generate import
1297 references for unused symbols).
1302 .forceimport needthisone, needthistoo
1305 See: <tt><ref id=".IMPORT" name=".IMPORT"></tt>
1308 <sect1><tt>.GLOBAL</tt><label id=".GLOBAL"><p>
1310 Declare symbols as global. Must be followed by a comma separated list of
1311 symbols to declare. Symbols from the list, that are defined somewhere in the
1312 source, are exported, all others are imported. Additional <tt><ref
1313 id=".IMPORT" name=".IMPORT"></tt> or <tt><ref id=".EXPORT"
1314 name=".EXPORT"></tt> commands for the same symbol are allowed.
1323 <sect1><tt>.GLOBALZP</tt><label id=".GLOBALZP"><p>
1325 Declare symbols as global. Must be followed by a comma separated list of
1326 symbols to declare. Symbols from the list, that are defined somewhere in the
1327 source, are exported, all others are imported. Additional <tt><ref
1328 id=".IMPORTZP" name=".IMPORTZP"></tt> or <tt><ref id=".EXPORTZP"
1329 name=".EXPORTZP"></tt> commands for the same symbol are allowed. The symbols
1330 in the list are explicitly marked as zero page symols.
1339 <sect1><tt>.I16</tt><label id=".I16"><p>
1341 Valid only in 65816 mode. Switch the index registers to 16 bit.
1343 Note: This command will not emit any code, it will tell the assembler to
1344 create 16 bit operands for immediate operands.
1346 See also the <tt><ref id=".I8" name=".I8"></tt> and <tt><ref id=".SMART"
1347 name=".SMART"></tt> commands.
1350 <sect1><tt>.I8</tt><label id=".I8"><p>
1352 Valid only in 65816 mode. Switch the index registers to 8 bit.
1354 Note: This command will not emit any code, it will tell the assembler to
1355 create 8 bit operands for immediate operands.
1357 See also the <tt><ref id=".I16" name=".I16"></tt> and <tt><ref id=".SMART"
1358 name=".SMART"></tt> commands.
1361 <sect1><tt>.IF</tt><label id=".IF"><p>
1363 Conditional assembly: Evalute an expression and switch assembler output
1364 on or off depending on the expression. The expression must be a constant
1365 expression, that is, all operands must be defined.
1367 A expression value of zero evaluates to FALSE, any other value evaluates
1371 <sect1><tt>.IFBLANK</tt><label id=".IFBLANK"><p>
1373 Conditional assembly: Check if there are any remaining tokens in this line,
1374 and evaluate to FALSE if this is the case, and to TRUE otherwise. If the
1375 condition is not true, further lines are not assembled until an <tt><ref
1376 id=".ELSE" name=".ESLE"></tt>, <tt><ref id=".ELSEIF" name=".ELSEIF"></tt> or
1377 <tt><ref id=".ENDIF" name=".ENDIF"></tt> directive.
1379 This command is often used to check if a macro parameter was given. Since an
1380 empty macro parameter will evaluate to nothing, the condition will evaluate
1381 to FALSE if an empty parameter was given.
1395 See also: <tt><ref id=".BLANK" name=".BLANK"></tt>
1398 <sect1><tt>.IFCONST</tt><label id=".IFCONST"><p>
1400 Conditional assembly: Evaluate an expression and switch assembler output
1401 on or off depending on the constness of the expression.
1403 A const expression evaluates to to TRUE, a non const expression (one
1404 containing an imported or currently undefined symbol) evaluates to
1407 See also: <tt><ref id=".CONST" name=".CONST"></tt>
1410 <sect1><tt>.IFDEF</tt><label id=".IFDEF"><p>
1412 Conditional assembly: Check if a symbol is defined. Must be followed by
1413 a symbol name. The condition is true if the the given symbol is already
1414 defined, and false otherwise.
1416 See also: <tt><ref id=".DEFINED" name=".DEFINED"></tt>
1419 <sect1><tt>.IFNBLANK</tt><label id=".IFNBLANK"><p>
1421 Conditional assembly: Check if there are any remaining tokens in this line,
1422 and evaluate to TRUE if this is the case, and to FALSE otherwise. If the
1423 condition is not true, further lines are not assembled until an <tt><ref
1424 id=".ELSE" name=".ELSE"></tt>, <tt><ref id=".ELSEIF" name=".ELSEIF"></tt> or
1425 <tt><ref id=".ENDIF" name=".ENDIF"></tt> directive.
1427 This command is often used to check if a macro parameter was given.
1428 Since an empty macro parameter will evaluate to nothing, the condition
1429 will evaluate to FALSE if an empty parameter was given.
1442 See also: <tt><ref id=".BLANK" name=".BLANK"></tt>
1445 <sect1><tt>.IFNDEF</tt><label id=".IFNDEF"><p>
1447 Conditional assembly: Check if a symbol is defined. Must be followed by
1448 a symbol name. The condition is true if the the given symbol is not
1449 defined, and false otherwise.
1451 See also: <tt><ref id=".DEFINED" name=".DEFINED"></tt>
1454 <sect1><tt>.IFNREF</tt><label id=".IFNREF"><p>
1456 Conditional assembly: Check if a symbol is referenced. Must be followed
1457 by a symbol name. The condition is true if if the the given symbol was
1458 not referenced before, and false otherwise.
1460 See also: <tt><ref id=".REFERENCED" name=".REFERENCED"></tt>
1463 <sect1><tt>.IFP02</tt><label id=".IFP02"><p>
1465 Conditional assembly: Check if the assembler is currently in 6502 mode
1466 (see <tt><ref id=".P02" name=".P02"></tt> command).
1469 <sect1><tt>.IFP816</tt><label id=".IFP816"><p>
1471 Conditional assembly: Check if the assembler is currently in 65816 mode
1472 (see <tt><ref id=".P816" name=".P816"></tt> command).
1475 <sect1><tt>.IFPC02</tt><label id=".IFPC02"><p>
1477 Conditional assembly: Check if the assembler is currently in 65C02 mode
1478 (see <tt><ref id=".PC02" name=".PC02"></tt> command).
1481 <sect1><tt>.IFREF</tt><label id=".IFREF"><p>
1483 Conditional assembly: Check if a symbol is referenced. Must be followed
1484 by a symbol name. The condition is true if if the the given symbol was
1485 referenced before, and false otherwise.
1487 This command may be used to build subroutine libraries in include files
1488 (you may use separate object modules for this purpose too).
1493 .ifref ToHex ; If someone used this subroutine
1494 ToHex: tay ; Define subroutine
1500 See also: <tt><ref id=".REFERENCED" name=".REFERENCED"></tt>
1503 <sect1><tt>.IMPORT</tt><label id=".IMPORT"><p>
1505 Import a symbol from another module. The command is followed by a comma
1506 separated list of symbols to import.
1514 See: <tt><ref id=".IMPORTZP" name=".IMPORTZP"></tt>
1517 <sect1><tt>.IMPORTZP</tt><label id=".IMPORTZP"><p>
1519 Import a symbol from another module. The command is followed by a comma
1520 separated list of symbols to import. The symbols are explicitly imported
1521 as zero page symbols (that is, symbols with values in byte range).
1529 See: <tt><ref id=".IMPORT" name=".IMPORT"></tt>
1532 <sect1><tt>.INCBIN</tt><label id=".INCBIN"><p>
1534 Include a file as binary data. The command expects a string argument
1535 that is the name of a file to include literally in the current segment.
1536 In addition to that, a start offset and a size value may be specified,
1537 separated by commas. If no size is specified, all of the file from the
1538 start offset to end-of-file is used. If no start position is specified
1539 either, zero is assume (which means that the whole file is inserted).
1544 ; Include whole file
1545 .incbin "sprites.dat"
1547 ; Include file starting at offset 256
1548 .incbin "music.dat", $100
1550 ; Read 100 bytes starting at offset 200
1551 .incbin "graphics.dat", 200, 100
1555 <sect1><tt>.INCLUDE</tt><label id=".INCLUDE"><p>
1557 Include another file. Include files may be nested up to a depth of 16.
1566 <sect1><tt>.LEFT</tt><label id=".LEFT"><p>
1568 Builtin function. Extracts the left part of a given token list.
1573 .LEFT (<int expr>, <token list>)
1576 The first integer expression gives the number of tokens to extract from
1577 the token list. The second argument is the token list itself.
1581 To check in a macro if the given argument has a '#' as first token
1582 (immidiate addressing mode), use something like this:
1587 .if (.match (.left (1, arg), #))
1589 ; ldax called with immidiate operand
1597 See also the <tt><ref id=".MID" name=".MID"></tt> and <tt><ref id=".RIGHT"
1598 name=".RIGHT"></tt> builtin functions.
1601 <sect1><tt>.LINECONT</tt><label id=".LINECONT"><p>
1603 Switch on or off line continuations using the backslash character
1604 before a newline. The option is off by default.
1605 Note: Line continuations do not work in a comment. A backslash at the
1606 end of a comment is treated as part of the comment and does not trigger
1608 The command must be followed by a '+' or '-' character to switch the
1609 option on or off respectively.
1614 .linecont + ; Allow line continuations
1617 #$20 ; This is legal now
1621 <sect1><tt>.LIST</tt><label id=".LIST"><p>
1623 Enable output to the listing. The command must be followed by a boolean
1624 switch ("on", "off", "+" or "-") and will enable or disable listing
1626 The option has no effect if the listing is not enabled by the command line
1627 switch -l. If -l is used, an internal counter is set to 1. Lines are output
1628 to the listing file, if the counter is greater than zero, and suppressed if
1629 the counter is zero. Each use of <tt/.LIST/ will increment or decrement the
1635 .list on ; Enable listing output
1639 <sect1><tt>.LISTBYTES</tt><label id=".LISTBYTES"><p>
1641 Set, how many bytes are shown in the listing for one source line. The
1642 default is 12, so the listing will show only the first 12 bytes for any
1643 source line that generates more than 12 bytes of code or data.
1644 The directive needs an argument, which is either "unlimited", or an
1645 integer constant in the range 4..255.
1650 .listbytes unlimited ; List all bytes
1651 .listbytes 12 ; List the first 12 bytes
1652 .incbin "data.bin" ; Include large binary file
1656 <sect1><tt>.LOCAL</tt><label id=".LOCAL"><p>
1658 This command may only be used inside a macro definition. It declares a
1659 list of identifiers as local to the macro expansion.
1661 A problem when using macros are labels: Since they don't change their name,
1662 you get a "duplicate symbol" error if the macro is expanded the second time.
1663 Labels declared with <tt><ref id=".LOCAL" name=".LOCAL"></tt> have their
1664 name mapped to an internal unique name (<tt/___ABCD__/) with each macro
1667 Some other assemblers start a new lexical block inside a macro expansion.
1668 This has some drawbacks however, since that will not allow <em/any/ symbol
1669 to be visible outside a macro, a feature that is sometimes useful. The
1670 <tt><ref id=".LOCAL" name=".LOCAL"></tt> command is in my eyes a better way
1671 to address the problem.
1673 You get an error when using <tt><ref id=".LOCAL" name=".LOCAL"></tt> outside
1677 <sect1><tt>.LOCALCHAR</tt><label id=".LOCALCHAR"><p>
1679 Defines the character that start "cheap" local labels. You may use one
1680 of '@' and '?' as start character. The default is '@'.
1682 Cheap local labels are labels that are visible only between two non
1683 cheap labels. This way you can reuse identifiers like "<tt/loop/" without
1684 using explicit lexical nesting.
1691 Clear: lda #$00 ; Global label
1692 ?Loop: sta Mem,y ; Local label
1696 Sub: ... ; New global label
1697 bne ?Loop ; ERROR: Unknown identifier!
1701 <sect1><tt>.MACPACK</tt><label id=".MACPACK"><p>
1703 Insert a predefined macro package. The command is followed by an
1704 identifier specifying the macro package to insert. Available macro
1708 generic Defines generic macros like add and sub.
1709 longbranch Defines conditional long jump macros.
1712 Including a macro package twice, or including a macro package that
1713 redefines already existing macros will lead to an error.
1718 .macpack longbranch ; Include macro package
1720 cmp #$20 ; Set condition codes
1721 jne Label ; Jump long on condition
1724 Macro packages are explained in more detail in section <ref
1725 id="macropackages" name="Macro packages">.
1728 <sect1><tt>.MAC, .MACRO</tt><label id=".MAC"><p>
1730 Start a classic macro definition. The command is followed by an identifier
1731 (the macro name) and optionally by a comma separated list of identifiers
1732 that are macro parameters.
1734 See section <ref id="macros" name="Macros">.
1737 <sect1><tt>.MATCH</tt><label id=".MATCH"><p>
1739 Builtin function. Matches two token lists against each other. This is
1740 most useful within macros, since macros are not stored as strings, but
1746 .MATCH(<token list #1>, <token list #2>)
1749 Both token list may contain arbitrary tokens with the exception of the
1750 terminator token (comma resp. right parenthesis) and
1757 Often a macro parameter is used for any of the token lists.
1759 Please note that the function does only compare tokens, not token
1760 attributes. So any number is equal to any other number, regardless of the
1761 actual value. The same is true for strings. If you need to compare tokens
1762 <em/and/ token attributes, use the <tt><ref id=".XMATCH"
1763 name=".XMATCH"></tt> function.
1767 Assume the macro <tt/ASR/, that will shift right the accumulator by one,
1768 while honoring the sign bit. The builtin processor instructions will allow
1769 an optional "A" for accu addressing for instructions like <tt/ROL/ and
1770 <tt/ROR/. We will use the <tt><ref id=".MATCH" name=".MATCH"></tt> function
1771 to check for this and print and error for invalid calls.
1776 .if (.not .blank(arg)) .and (.not .match (arg, a))
1777 .error "Syntax error"
1780 cmp #$80 ; Bit 7 into carry
1781 lsr a ; Shift carry into bit 7
1786 The macro will only accept no arguments, or one argument that must be the
1787 reserved keyword "A".
1789 See: <tt><ref id=".XMATCH" name=".XMATCH"></tt>
1792 <sect1><tt>.MID</tt><label id=".MID"><p>
1794 Builtin function. Takes a starting index, a count and a token list as
1795 arguments. Will return part of the token list.
1800 .MID (<int expr>, <int expr>, <token list>)
1803 The first integer expression gives the starting token in the list (the
1804 first token has index 0). The second integer expression gives the number
1805 of tokens to extract from the token list. The third argument is the
1810 To check in a macro if the given argument has a '<tt/#/' as first token
1811 (immidiate addressing mode), use something like this:
1816 .if (.match (.mid (0, 1, arg), #))
1818 ; ldax called with immidiate operand
1826 See also the <tt><ref id=".LEFT" name=".LEFT"></tt> and <tt><ref id=".RIGHT"
1827 name=".RIGHT"></tt> builtin functions.
1830 <sect1><tt>.ORG</tt><label id=".ORG"><p>
1832 Start a section of absolute code. The command is followed by a constant
1833 expression that gives the new PC counter location for which the code is
1834 assembled. Use <tt><ref id=".RELOC" name=".RELOC"></tt> to switch back to
1837 Please note that you <em/do not need/ this command in most cases. Placing
1838 code at a specific address is the job of the linker, not the assembler, so
1839 there is usually no reason to assemble code to a specific address.
1841 You may not switch segments while inside a section of absolute code.
1846 .org $7FF ; Emit code starting at $7FF
1850 <sect1><tt>.OUT</tt><label id=".OUT"><p>
1852 Output a string to the console without producing an error. This command
1853 is similiar to <tt/.ERROR/, however, it does not force an assembler error
1854 that prevents the creation of an object file.
1859 .out "This code was written by the codebuster(tm)"
1862 See also the <tt><ref id=".WARNING" name=".WARNING"></tt> and <tt><ref
1863 id=".ERROR" name=".ERROR"></tt> directives.
1866 <sect1><tt>.P02</tt><label id=".P02"><p>
1868 Enable the 6502 instruction set, disable 65C02 and 65816 instructions.
1869 This is the default if not overridden by the <tt/--cpu/ command line
1872 See: <tt><ref id=".PC02" name=".PC02"></tt> and <tt><ref id=".P816"
1876 <sect1><tt>.P816</tt><label id=".P816"><p>
1878 Enable the 65816 instruction set. This is a superset of the 65C02 and
1879 6502 instruction sets.
1881 See: <tt><ref id=".P02" name=".P02"></tt> and <tt><ref id=".PC02"
1885 <sect1><tt>.PAGELEN, .PAGELENGTH</tt><label id=".PAGELENGTH"><p>
1887 Set the page length for the listing. Must be followed by an integer
1888 constant. The value may be "unlimited", or in the range 32 to 127. The
1889 statement has no effect if no listing is generated. The default value is -1
1890 (unlimited) but may be overridden by the <tt/--pagelength/ command line
1891 option. Beware: Since ca65 is a one pass assembler, the listing is generated
1892 after assembly is complete, you cannot use multiple line lengths with one
1893 source. Instead, the value set with the last <tt/.PAGELENGTH/ is used.
1898 .pagelength 66 ; Use 66 lines per listing page
1900 .pagelength unlimited ; Unlimited page length
1904 <sect1><tt>.PARAMCOUNT</tt><label id=".PARAMCOUNT"><p>
1906 This builtin pseudo variable is only available in macros. It is replaced by
1907 the actual number of parameters that were given in the macro invocation.
1912 .macro foo arg1, arg2, arg3
1913 .if .paramcount <> 3
1914 .error "Too few parameters for macro foo"
1920 See section <ref id="macros" name="Macros">.
1923 <sect1><tt>.PC02</tt><label id=".PC02"><p>
1925 Enable the 65C02 instructions set. This instruction set includes all
1928 See: <tt><ref id=".P02" name=".P02"></tt> and <tt><ref id=".P816"
1932 <sect1><tt>.POPSEG</tt><label id=".POPSEG"><p>
1934 Pop the last pushed segment from the stack, and set it.
1936 This command will switch back to the segment that was last pushed onto the
1937 segment stack using the <tt><ref id=".PUSHSEG" name=".PUSHSEG"></tt>
1938 command, and remove this entry from the stack.
1940 The assembler will print an error message if the segment stack is empty
1941 when this command is issued.
1943 See: <tt><ref id=".PUSHSEG" name=".PUSHSEG"></tt>
1946 <sect1><tt>.PROC</tt><label id=".PROC"><p>
1948 Start a nested lexical level. All new symbols from now on are in the local
1949 lexical level and are not accessible from outside. Symbols defined outside
1950 this local level may be accessed as long as their names are not used for new
1951 symbols inside the level. Symbols names in other lexical levels do not
1952 clash, so you may use the same names for identifiers. The lexical level ends
1953 when the <tt><ref id=".ENDPROC" name=".ENDPROC"></tt> command is read.
1954 Lexical levels may be nested up to a depth of 16.
1956 The command may be followed by an identifier, in this case the
1957 identifier is declared in the outer level as a label having the value of
1958 the program counter at the start of the lexical level.
1960 Note: Macro names are always in the global level and in a separate name
1961 space. There is no special reason for this, it's just that I've never
1962 had any need for local macro definitions.
1967 .proc Clear ; Define Clear subroutine, start new level
1969 L1: sta Mem,y ; L1 is local and does not cause a
1970 ; duplicate symbol error if used in other
1973 bne L1 ; Reference local symbol
1975 .endproc ; Leave lexical level
1978 See: <tt><ref id=".ENDPROC" name=".ENDPROC"></tt>
1981 <sect1><tt>.PUSHSEG</tt><label id=".PUSHSEG"><p>
1983 Push the currently active segment onto a stack. The entries on the stack
1984 include the name of the segment and the segment type. The stack has a size
1987 <tt/.PUSHSEG/ allows together with <tt><ref id=".POPSEG" name=".POPSEG"></tt>
1988 to switch to another segment and to restore the old segment later, without
1989 even knowing the name and type of the current segment.
1991 The assembler will print an error message if the segment stack is already
1992 full, when this command is issued.
1994 See: <tt><ref id=".POPSEG" name=".POPSEG"></tt>
1997 <sect1><tt>.REF, .REFERENCED</tt><label id=".REFERENCED"><p>
1999 Builtin function. The function expects an identifier as argument in braces.
2000 The argument is evaluated, and the function yields "true" if the identifier
2001 is a symbol that has already been referenced somewhere in the source file up
2002 to the current position. Otherwise the function yields false. As an example,
2003 the <tt><ref id=".IFREF" name=".IFREF"></tt> statement may be replaced by
2009 See: <tt><ref id=".DEFINED" name=".DEFINED"></tt>
2012 <sect1><tt>.REPEAT</tt><label id=".REPEAT"><p>
2014 Repeat all commands between <tt/.REPEAT/ and <tt><ref id=".ENDREPEAT"
2015 name=".ENDREPEAT"></tt> constant number of times. The command is followed by
2016 a constant expression that tells how many times the commands in the body
2017 should get repeated. Optionally, a comma and an identifier may be specified.
2018 If this identifier is found in the body of the repeat statement, it is
2019 replaced by the current repeat count (starting with zero for the first time
2020 the body is repeated).
2022 <tt/.REPEAT/ statements may be nested. If you use the same repeat count
2023 identifier for a nested <tt/.REPEAT/ statement, the one from the inner
2024 level will be used, not the one from the outer level.
2028 The following macro will emit a string that is "encrypted" in that all
2029 characters of the string are XORed by the value $55.
2033 .repeat .strlen(Arg), I
2034 .byte .strat(Arg, I) .xor $55
2039 See: <tt><ref id=".ENDREPEAT" name=".ENDREPEAT"></tt>
2042 <sect1><tt>.RELOC</tt><label id=".RELOC"><p>
2044 Switch back to relocatable mode. See the <tt><ref id=".ORG"
2045 name=".ORG"></tt> command.
2048 <sect1><tt>.RES</tt><label id=".RES"><p>
2050 Reserve storage. The command is followed by one or two constant
2051 expressions. The first one is mandatory and defines, how many bytes of
2052 storage should be defined. The second, optional expression must by a
2053 constant byte value that will be used as value of the data. If there
2054 is no fill value given, the linker will use the value defined in the
2055 linker configuration file (default: zero).
2060 ; Reserve 12 bytes of memory with value $AA
2065 <sect1><tt>.RIGHT</tt><label id=".RIGHT"><p>
2067 Builtin function. Extracts the right part of a given token list.
2072 .RIGHT (<int expr>, <token list>)
2075 The first integer expression gives the number of tokens to extract from
2076 the token list. The second argument is the token list itself.
2078 See also the <tt><ref id=".LEFT" name=".LEFT"></tt> and <tt><ref id=".MID"
2079 name=".MID"></tt> builtin functions.
2082 <sect1><tt>.RODATA</tt><label id=".RODATA"><p>
2084 Switch to the RODATA segment. The name of the RODATA segment is always
2085 "RODATA", so this is a shortcut for
2091 The RODATA segment is a segment that is used by the compiler for
2092 readonly data like string constants.
2094 See also the <tt><ref id=".SEGMENT" name=".SEGMENT"></tt> command.
2097 <sect1><tt>.SEGMENT</tt><label id=".SEGMENT"><p>
2099 Switch to another segment. Code and data is always emitted into a
2100 segment, that is, a named section of data. The default segment is
2101 "CODE". There may be up to 254 different segments per object file
2102 (and up to 65534 per executable). There are shortcut commands for
2103 the most common segments ("CODE", "DATA" and "BSS").
2105 The command is followed by a string containing the segment name (there
2106 are some constraints for the name - as a rule of thumb use only those
2107 segment names that would also be valid identifiers). There may also be
2108 an optional attribute separated by a comma. Valid attributes are
2109 "<tt/zeropage/" and "<tt/absolute/".
2111 When specifying a segment for the first time, "absolute" is the
2112 default. For all other uses, the attribute specified the first time
2115 "absolute" means that this is a segment with absolute addressing. That
2116 is, the segment will reside somewhere in core memory outside the zero
2117 page. "zeropage" means the opposite: The segment will be placed in the
2118 zero page and direct (short) addressing is possible for data in this
2121 Beware: Only labels in a segment with the zeropage attribute are marked
2122 as reachable by short addressing. The `*' (PC counter) operator will
2123 work as in other segments and will create absolute variable values.
2128 .segment "ROM2" ; Switch to ROM2 segment
2129 .segment "ZP2", zeropage ; New direct segment
2130 .segment "ZP2" ; Ok, will use last attribute
2131 .segment "ZP2", absolute ; Error, redecl mismatch
2134 See: <tt><ref id=".BSS" name=".BSS"></tt>, <tt><ref id=".CODE"
2135 name=".CODE"></tt>, <tt><ref id=".DATA" name=".DATA"></tt> and <tt><ref
2136 id=".RODATA" name=".RODATA"></tt>
2139 <sect1><tt>.SMART</tt><label id=".SMART"><p>
2141 Switch on or off smart mode. The command must be followed by a '+' or
2142 '-' character to switch the option on or off respectively. The default
2143 is off (that is, the assembler doesn't try to be smart), but this
2144 default may be changed by the -s switch on the command line.
2146 In smart mode the assembler will track usage of the <tt/REP/ and <tt/SEP/
2147 instructions in 65816 mode and update the operand sizes accordingly. If
2148 the operand of such an instruction cannot be evaluated by the assembler
2149 (for example, because the operand is an imported symbol), a warning is
2150 issued. Beware: Since the assembler cannot trace the execution flow this
2151 may lead to false results in some cases. If in doubt, use the <tt/.Inn/ and
2152 <tt/.Ann/ instructions to tell the assembler about the current settings.
2158 .smart - ; Stop being smart
2162 <sect1><tt>.STRAT</tt><label id=".STRAT"><p>
2164 Builtin function. The function accepts a string and an index as
2165 arguments and returns the value of the character at the given position
2166 as an integer value. The index is zero based.
2172 ; Check if the argument string starts with '#'
2173 .if (.strat (Arg, 0) = '#')
2180 <sect1><tt>.STRING</tt><label id=".STRING"><p>
2182 Builtin function. The function accepts an argument in braces and converts
2183 this argument into a string constant. The argument may be an identifier, or
2184 a constant numeric value.
2186 Since you can use a string in the first place, the use of the function may
2187 not be obvious. However, it is useful in macros, or more complex setups.
2192 ; Emulate other assemblers:
2194 .segment .string(name)
2199 <sect1><tt>.STRLEN</tt><label id=".STRLEN"><p>
2201 Builtin function. The function accepts a string argument in braces and
2202 eveluates to the length of the string.
2206 The following macro encodes a string as a pascal style string with
2207 a leading length byte.
2211 .byte .strlen(Arg), Arg
2216 <sect1><tt>.TCOUNT</tt><label id=".TCOUNT"><p>
2218 Builtin function. The function accepts a token list in braces. The
2219 function result is the number of tokens given as argument.
2223 The <tt/ldax/ macro accepts the '#' token to denote immidiate addressing (as
2224 with the normal 6502 instructions). To translate it into two separate 8 bit
2225 load instructions, the '#' token has to get stripped from the argument:
2229 .if (.match (.mid (0, 1, arg), #))
2230 ; ldax called with immidiate operand
2231 lda #<(.right (.tcount (arg)-1, arg))
2232 ldx #>(.right (.tcount (arg)-1, arg))
2240 <sect1><tt>.TIME</tt><label id=".TIME"><p>
2242 Reading this pseudo variable will give a constant integer value that
2243 represents the current time in POSIX standard (as seconds since the
2246 It may be used to encode the time of translation somewhere in the created
2252 .dword .time ; Place time here
2256 <sect1><tt>.WARNING</tt><label id=".WARNING"><p>
2258 Force an assembly warning. The assembler will output a warning message
2259 preceeded by "User warning". This warning will always be output, even if
2260 other warnings are disabled with the <tt><ref id="option-W" name="-W0"></tt>
2261 command line option.
2263 This command may be used to output possible problems when assembling
2272 .warning "Forward jump in jne, cannot optimize!"
2282 See also the <tt><ref id=".ERROR" name=".ERROR"></tt> and <tt><ref id=".OUT"
2283 name=".OUT"></tt> directives.
2286 <sect1><tt>.WORD</tt><label id=".WORD"><p>
2288 Define word sized data. Must be followed by a sequence of (word ranged,
2289 but not necessarily constant) expressions.
2294 .word $0D00, $AF13, _Clear
2298 <sect1><tt>.XMATCH</tt><label id=".XMATCH"><p>
2300 Builtin function. Matches two token lists against each other. This is
2301 most useful within macros, since macros are not stored as strings, but
2307 .XMATCH(<token list #1>, <token list #2>)
2310 Both token list may contain arbitrary tokens with the exception of the
2311 terminator token (comma resp. right parenthesis) and
2318 Often a macro parameter is used for any of the token lists.
2320 The function compares tokens <em/and/ token values. If you need a function
2321 that just compares the type of tokens, have a look at the <tt><ref
2322 id=".MATCH" name=".MATCH"></tt> function.
2324 See: <tt><ref id=".MATCH" name=".MATCH"></tt>
2327 <sect1><tt>.ZEROPAGE</tt><label id=".ZEROPAGE"><p>
2329 Switch to the ZEROPAGE segment and mark it as direct (zeropage) segment.
2330 The name of the ZEROPAGE segment is always "ZEROPAGE", so this is a
2334 .segment "ZEROPAGE", zeropage
2337 Because of the "zeropage" attribute, labels declared in this segment are
2338 addressed using direct addressing mode if possible. You <em/must/ instruct
2339 the linker to place this segment somewhere in the address range 0..$FF
2340 otherwise you will get errors.
2342 See: <tt><ref id=".SEGMENT" name=".SEGMENT"></tt>
2346 <sect>Macros<label id="macros"><p>
2349 <sect1>Introduction<p>
2351 Macros may be thought of as "parametrized super instructions". Macros are
2352 sequences of tokens that have a name. If that name is used in the source
2353 file, the macro is "expanded", that is, it is replaced by the tokens that
2354 were specified when the macro was defined.
2357 <sect1>Macros without parameters<p>
2359 In it's simplest form, a macro does not have parameters. Here's an
2363 .macro asr ; Arithmetic shift right
2364 cmp #$80 ; Put bit 7 into carry
2365 ror ; Rotate right with carry
2369 The macro above consists of two real instructions, that are inserted into
2370 the code, whenever the macro is expanded. Macro expansion is simply done
2371 by using the name, like this:
2380 <sect1>Parametrized macros<p>
2382 When using macro parameters, macros can be even more useful:
2396 When calling the macro, you may give a parameter, and each occurence of
2397 the name "addr" in the macro definition will be replaced by the given
2416 A macro may have more than one parameter, in this case, the parameters
2417 are separated by commas. You are free to give less parameters than the
2418 macro actually takes in the definition. You may also leave intermediate
2419 parameters empty. Empty parameters are replaced by empty space (that is,
2420 they are removed when the macro is exanded). If you have a look at our
2421 macro definition above, you will see, that replacing the "addr" parameter
2422 by nothing will lead to wrong code in most lines. To help you, writing
2423 macros with a variable parameter list, there are some control commands:
2425 <tt><ref id=".IFBLANK" name=".IFBLANK"></tt> tests the rest of the line and
2426 returns true, if there are any tokens on the remainder of the line. Since
2427 empty parameters are replaced by nothing, this may be used to test if a given
2428 parameter is empty. <tt><ref id=".IFNBLANK" name=".IFNBLANK"></tt> tests the
2431 Look at this example:
2434 .macro ldaxy a, x, y
2447 This macro may be called as follows:
2450 ldaxy 1, 2, 3 ; Load all three registers
2452 ldaxy 1, , 3 ; Load only a and y
2454 ldaxy , , 3 ; Load y only
2457 There's another helper command for determining, which macro parameters are
2458 valid: <tt><ref id=".PARAMCOUNT" name=".PARAMCOUNT"></tt> This command is
2459 replaced by the parameter count given, <em/including/ intermediate empty macro
2463 ldaxy 1 ; .PARAMCOUNT = 1
2464 ldaxy 1,,3 ; .PARAMCOUNT = 3
2465 ldaxy 1,2 ; .PARAMCOUNT = 2
2466 ldaxy 1, ; .PARAMCOUNT = 2
2467 ldaxy 1,2,3 ; .PARAMCOUNT = 3
2471 <sect1>Recursive macros<p>
2473 Macros may be used recursively:
2476 .macro push r1, r2, r3
2485 There's also a special macro to help writing recursive macros: <tt><ref
2486 id=".EXITMACRO" name=".EXITMACRO"></tt> This command will stop macro expansion
2490 .macro push r1, r2, r3, r4, r5, r6, r7
2492 ; First parameter is empty
2498 push r2, r3, r4, r5, r6, r7
2502 When expanding this macro, the expansion will push all given parameters
2503 until an empty one is encountered. The macro may be called like this:
2506 push $20, $21, $32 ; Push 3 ZP locations
2507 push $21 ; Push one ZP location
2511 <sect1>Local symbols inside macros<p>
2513 Now, with recursive macros, <tt><ref id=".IFBLANK" name=".IFBLANK"></tt> and
2514 <tt><ref id=".PARAMCOUNT" name=".PARAMCOUNT"></tt>, what else do you need?
2515 Have a look at the inc16 macro above. Here is it again:
2529 If you have a closer look at the code, you will notice, that it could be
2530 written more efficiently, like this:
2541 But imagine what happens, if you use this macro twice? Since the label
2542 "Skip" has the same name both times, you get a "duplicate symbol" error.
2543 Without a way to circumvent this problem, macros are not as useful, as
2544 they could be. One solution is, to start a new lexical block inside the
2558 Now the label is local to the block and not visible outside. However,
2559 sometimes you want a label inside the macro to be visible outside. To make
2560 that possible, there's a new command that's only usable inside a macro
2561 definition: <tt><ref id=".LOCAL" name=".LOCAL"></tt>. <tt/.LOCAL/ declares one
2562 or more symbols as local to the macro expansion. The names of local variables
2563 are replaced by a unique name in each separate macro expansion. So we could
2564 also solve the problem above by using <tt/.LOCAL/:
2568 .local Skip ; Make Skip a local symbol
2575 Skip: ; Not visible outside
2580 <sect1>C style macros<p>
2582 Starting with version 2.5 of the assembler, there is a second macro type
2583 available: C style macros using the <tt/.DEFINE/ directive. These macros are
2584 similar to the classic macro type described above, but behaviour is sometimes
2589 <item> Macros defined with <tt><ref id=".DEFINE" name=".DEFINE"></tt> may not
2590 span more than a line. You may use line continuation (see <tt><ref
2591 id=".LINECONT" name=".LINECONT"></tt>) to spread the definition over
2592 more than one line for increased readability, but the macro itself
2593 may not contain an end-of-line token.
2595 <item> Macros defined with <tt><ref id=".DEFINE" name=".DEFINE"></tt> share
2596 the name space with classic macros, but they are detected and replaced
2597 at the scanner level. While classic macros may be used in every place,
2598 where a mnemonic or other directive is allowed, <tt><ref id=".DEFINE"
2599 name=".DEFINE"></tt> style macros are allowed anywhere in a line. So
2600 they are more versatile in some situations.
2602 <item> <tt><ref id=".DEFINE" name=".DEFINE"></tt> style macros may take
2603 parameters. While classic macros may have empty parameters, this is
2604 not true for <tt><ref id=".DEFINE" name=".DEFINE"></tt> style macros.
2605 For this macro type, the number of actual parameters must match
2606 exactly the number of formal parameters.
2608 To make this possible, formal parameters are enclosed in braces when
2609 defining the macro. If there are no parameters, the empty braces may
2612 <item> Since <tt><ref id=".DEFINE" name=".DEFINE"></tt> style macros may not
2613 contain end-of-line tokens, there are things that cannot be done. They
2614 may not contain several processor instructions for example. So, while
2615 some things may be done with both macro types, each type has special
2616 usages. The types complement each other.
2620 Let's look at a few examples to make the advantages and disadvantages
2623 To emulate assemblers that use "<tt/EQU/" instead of "<tt/=/" you may use the
2624 following <tt/.DEFINE/:
2629 foo EQU $1234 ; This is accepted now
2632 You may use the directive to define string constants used elsewhere:
2635 ; Define the version number
2636 .define VERSION "12.3a"
2642 Macros with parameters may also be useful:
2645 .define DEBUG(message) .out message
2647 DEBUG "Assembling include file #3"
2650 Note that, while formal parameters have to be placed in braces, this is
2651 not true for the actual parameters. Beware: Since the assembler cannot
2652 detect the end of one parameter, only the first token is used. If you
2653 don't like that, use classic macros instead:
2661 (This is an example where a problem can be solved with both macro types).
2664 <sect1>Characters in macros<p>
2666 When using the <ref id="option-t" name="-t"> option, characters are translated
2667 into the target character set of the specific machine. However, this happens
2668 as late as possible. This means that strings are translated if they are part
2669 of a <tt><ref id=".BYTE" name=".BYTE"></tt> or <tt><ref id=".ASCIIZ"
2670 name=".ASCIIZ"></tt> command. Characters are translated as soon as they are
2671 used as part of an expression.
2673 This behaviour is very intuitive outside of macros but may be confusing when
2674 doing more complex macros. If you compare characters against numeric values,
2675 be sure to take the translation into account.
2680 <sect>Macro packages<label id="macropackages"><p>
2682 Using the <tt><ref id=".MACPACK" name=".MACPACK"></tt> directive, predefined
2683 macro packages may be included with just one command. Available macro packages
2687 <sect1><tt>.MACPACK generic</tt><p>
2689 This macro package defines macros that are useful in almost any program.
2690 Currently, two macros are defined:
2705 <sect1><tt>.MACPACK longbranch</tt><p>
2707 This macro package defines long conditional jumps. They are named like the
2708 short counterpart but with the 'b' replaced by a 'j'. Here is a sample
2709 definition for the "<tt/jeq/" macro, the other macros are built using the same
2714 .if .def(Target) .and ((*+2)-(Target) <= 127)
2723 All macros expand to a short branch, if the label is already defined (back
2724 jump) and is reachable with a short jump. Otherwise the macro expands to a
2725 conditional branch with the branch condition inverted, followed by an absolute
2726 jump to the actual branch target.
2728 The package defines the following macros:
2731 jeq, jne, jmi, jpl, jcs, jcc, jvs, jvc
2736 <sect>Module constructors/destructors<label id="condes"><p>
2738 <em>Note:</em> This section applies mostly to C programs, so the explanation
2739 below uses examples from the C libraries. However, the feature may also be
2740 useful for assembler programs.
2743 <sect1>Module overview<p>
2745 Using the <tt><ref id=".CONSTRUCTOR" name=".CONSTRUCTOR"></tt> and <tt><ref
2746 id=".DESTRUCTOR" name=".DESTRUCTOR"></tt> keywords it it possible to export
2747 functions in a special way. The linker is able to generate tables with all
2748 functions of a specific type. Such a table will <em>only</em> include symbols
2749 from object files that are linked into a specific executable. This may be used
2750 to add initialization and cleanup code for library modules.
2752 The C heap functions are an example where module initialization code is used.
2753 All heap functions (<tt>malloc</tt>, <tt>free</tt>, ...) work with a few
2754 variables that contain the start and the end of the heap, pointers to the free
2755 list and so on. Since the end of the heap depends on the size and start of the
2756 stack, it must be initialized at runtime. However, initializing these
2757 variables for programs that do not use the heap are a waste of time and
2760 So the central module defines a function that contains initialization code and
2761 exports this function using the <tt/.CONSTRUCTOR/ statement. If (and only if)
2762 this module is added to an executable by the linker, the initialization
2763 function will be placed into the table of constructors by the linker. The C
2764 startup code will call all constructors before <tt/main/ and all destructors
2765 after <tt/main/, so without any further work, the heap initialization code is
2766 called once the module is linked in.
2768 While it would be possible to add explicit calls to initialization functions
2769 in the startup code, the new approach has several advantages:
2773 If a module is not included, the initialization code is not linked in and not
2774 called. So you don't pay for things you don't need.
2777 Adding another library that needs initialization does not mean that the
2778 startup code has to be changed. Before we had module constructors and
2779 destructors, the startup code for all systems had to be adjusted to call the
2780 new initialization code.
2783 The feature saves memory: Each additional initialization function needs just
2784 two bytes in the table (a pointer to the function).
2791 When creating and using module constructors and destructors, please take care
2797 The linker will only generate function tables, it will not generate code to
2798 call these functions. If you're using the feature in some other than the
2799 existing C environments, you have to write code to call all functions in a
2800 linker generated table yourself. See the <tt>condes</tt> module in the C
2801 runtime for an example on how to do this.
2804 The linker will only add addresses of functions that are in modules linked to
2805 the executable. This means that you have to be careful where to place the
2806 condes functions. If initialization is needed for a group of functions, be
2807 sure to place the initialization function into a module that is linked in
2808 regardless of which function is called by the user.
2811 The linker will generate the tables only when requested to do so by the
2812 <tt/FEATURE CONDES/ statement in the linker config file. Each table has to
2813 be requested separately.
2816 Constructors and destructors may have priorities. These priorities determine
2817 the order of the functions in the table. If your intialization or cleanup code
2818 does depend on other initialization or cleanup code, you have to choose the
2819 priority for the functions accordingly.
2822 Besides the <tt><ref id=".CONSTRUCTOR" name=".CONSTRUCTOR"></tt> and <tt><ref
2823 id=".DESTRUCTOR" name=".DESTRUCTOR"></tt> statements, there is also a more
2824 generic command: <tt><ref id=".CONDES" name=".CONDES"></tt>. This allows to
2825 specify an additional type. Predefined types are 0 (constructor) and 1
2826 (destructor). The linker generates a separate table for each type on request.
2834 <sect>Bugs/Feedback<p>
2836 If you have problems using the assembler, if you find any bugs, or if
2837 you're doing something interesting with the assembler, I would be glad to
2838 hear from you. Feel free to contact me by email
2839 (<htmlurl url="mailto:uz@cc65.org" name="uz@cc65.org">).
2845 ca65 (and all cc65 binutils) are (C) Copyright 1998-2001 Ullrich von
2846 Bassewitz. For usage of the binaries and/or sources the following
2847 conditions do apply:
2849 This software is provided 'as-is', without any expressed or implied
2850 warranty. In no event will the authors be held liable for any damages
2851 arising from the use of this software.
2853 Permission is granted to anyone to use this software for any purpose,
2854 including commercial applications, and to alter it and redistribute it
2855 freely, subject to the following restrictions:
2858 <item> The origin of this software must not be misrepresented; you must not
2859 claim that you wrote the original software. If you use this software
2860 in a product, an acknowledgment in the product documentation would be
2861 appreciated but is not required.
2862 <item> Altered source versions must be plainly marked as such, and must not
2863 be misrepresented as being the original software.
2864 <item> This notice may not be removed or altered from any source
projects / cc65 / blob