2 <!doctype linuxdoc system>
5 <title>ca65 Users Guide
6 <author>Ullrich von Bassewitz, <htmlurl url="mailto:uz@cc65.org" name="uz@cc65.org">
7 <date>19.07.2000, 29.11.2000, 02.10.2001
10 ca65 is a powerful macro assembler for the 6502, 65C02 and 65816 CPUs. It is
11 used as a companion assembler for the cc65 crosscompiler, but it may also be
12 used as a standalone product.
15 <!-- Table of contents -->
18 <!-- Begin the document -->
22 ca65 is a replacement for the ra65 assembler that was part of the cc65 C
23 compiler, originally developed by John R. Dunning. I had some problems with
24 ra65 and the copyright does not permit some things which I wanted to be
25 possible, so I decided to write a completely new assembler/linker/archiver
26 suite for the cc65 compiler. ca65 is part of this suite.
28 Some parts of the assembler (code generation and some routines for symbol
29 table handling) are taken from an older crossassembler named a816 written
30 by me a long time ago.
33 <sect1>Design criteria<p>
35 Here's a list of the design criteria, that I considered important for the
40 <item> The assembler must support macros. Macros are not essential, but they
41 make some things easier, especially when you use the assembler in the
42 backend of a compiler.
43 <item> The assembler must support the newer 65C02 and 65816 CPUs. I have been
44 thinking about a 65816 backend for the C compiler, and even my old
45 a816 assembler had support for these CPUs, so this wasn't really a
47 <item> The assembler must produce relocatable code. This is necessary for the
48 compiler support, and it is more convenient.
49 <item> Conditional assembly must be supported. This is a must for bigger
50 projects written in assembler (like Elite128).
51 <item> The assembler must support segments, and it must support more than
52 three segments (this is the count, most other assemblers support).
53 Having more than one code segments helps developing code for systems
54 with a divided ROM area (like the C64).
55 <item> The linker must be able to resolve arbitrary expressions. It should
56 be able to get things like
63 <item> True lexical nesting for symbols. This is very convenient for larger
65 <item> "Cheap" local symbols without lexical nesting for those quick, late
67 <item> I liked the idea of "options" as Anre Fachats .o65 format has it, so I
68 introduced the concept into the object file format use by the new cc65
70 <item> The assembler will be a one pass assembler. There was no real need for
71 this decision, but I've written several multipass assemblers, and it
72 started to get boring. A one pass assembler needs much more elaborated
73 data structures, and because of that it's much more fun:-)
74 <item> Non-GPLed code that may be used in any project without restrictions or
75 fear of "GPL infecting" other code.
83 <sect1>Command line option overview<p>
85 The assembler accepts the following options:
88 ---------------------------------------------------------------------------
89 Usage: ca65 [options] file
91 -D name[=value] Define a symbol
92 -I dir Set an include directory search path
93 -U Mark unresolved symbols as import
94 -V Print the assembler version
95 -W n Set warning level n
96 -g Add debug info to object file
98 -i Ignore case of symbols
99 -l Create a listing if assembly was ok
100 -o name Name the output file
102 -t sys Set the target system
103 -v Increase verbosity
106 --auto-import Mark unresolved symbols as import
107 --cpu type Set cpu type
108 --debug-info Add debug info to object file
109 --feature name Set an emulation feature
110 --help Help (this text)
111 --ignore-case Ignore case of symbols
112 --include-dir dir Set an include directory search path
113 --listing Create a listing if assembly was ok
114 --pagelength n Set the page length for the listing
115 --smart Enable smart mode
116 --target sys Set the target system
117 --verbose Increase verbosity
118 --version Print the assembler version
119 ---------------------------------------------------------------------------
123 <sect1>Command line options in detail<p>
125 Here is a description of all the command line options:
129 <tag><tt>--cpu type</tt></tag>
131 Set the default for the CPU type. The option takes a parameter, which
134 6502, 65C02, 65816 and sunplus
136 The latter (sunplus) is not available in the freeware version, because the
137 instruction set of the sunplus CPU is "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 The assembler accepts the standard 6502/65816 assembler syntax. One line may
277 contain a label (which is identified by a colon), and, in addition to the
278 label, an assembler mnemonic, a macro, or a control command (see section <ref
279 id="control-commands" name="Control Commands"> for supported control
280 commands). Alternatively, the line may contain a symbol definition using the
281 '=' token. Everything after a semicolon is handled as a comment (that is, it
284 Here are some examples for valid input lines:
287 Label: ; A label and a comment
288 lda #$20 ; A 6502 instruction plus comment
289 L1: ldx #$20 ; Same with label
290 L2: .byte "Hello world" ; Label plus control command
291 mymac $20 ; Macro expansion
292 MySym = 3*L1 ; Symbol definition
293 MaSym = Label ; Another symbol
296 The assembler accepts all valid 6502 mnemonics when in 6502 mode (the
297 default). The assembler accepts all valid 65SC02 mnemonics when in 65SC02 mode
298 (after a <tt><ref id=".PC02" name=".PC02"></tt> command is found). The
299 assembler accepts all valid 65816 mnemonics with a few exceptions after a
300 .P816 command is found. These exceptions are listed below.
302 In 65816 mode several aliases are accepted in addition to the official
306 BGE is an alias for BCS
307 BLT is an alias for BCC
308 CPA is an alias for CMP
309 DEA is an alias for DEC A
310 INA is an alias for INC A
311 SWA is an alias for XBA
312 TAD is an alias for TCD
313 TAS is an alias for TCS
314 TDA is an alias for TDC
315 TSA is an alias for TSC
318 Evaluation of banked expressions in 65816 mode differs slightly from the
321 Instead of accepting a 24 bit address (something that is difficult for
322 the assembler to determine and would have required one more special
323 .import command), the bank and the absolute address in that bank are
327 jsl 3.$1234 ; Call subroutine at $1234 in bank 3
330 For literal values, the assembler accepts the widely used number formats:
331 A preceeding '$' denotes a hex value, a preceeding '%' denotes a
332 binary value, and a bare number is interpeted as a decimal. There are
333 currently no octal values and no floats.
340 <sect1>Expression evaluation<p>
342 All expressions are evaluated with (at least) 32 bit precision. An
343 expression may contain constant values and any combination of internal and
344 external symbols. Expressions that cannot be evaluated at assembly time
345 are stored inside the object file for evaluation by the linker.
346 Expressions referencing imported symbols must always be evaluated by the
350 <sect1>Size of an expressions result<p>
352 Sometimes, the assembler must know about the size of the value that is the
353 result of an expression. This is usually the case, if a decision has to be
354 made, to generate a zero page or an absolute memory references. In this
355 case, the assembler has to make some assumptions about the result of an
359 <item> If the result of an expression is constant, the actual value is
360 checked to see if it's a byte sized expression or not.
361 <item> If the expression is explicitly casted to a byte sized expression by
362 one of the '>'/'<' operators, it is a byte expression.
363 <item> If this is not the case, and the expression contains a symbol,
364 explicitly declared as zero page symbol (by one of the .importzp or
365 .exportzp instructions), then the whole expression is assumed to be
367 <item> If the expression contains symbols that are not defined, and these
368 symbols are local symbols, the enclosing scopes are searched for a
369 symbol with the same name. If one exists and this symbol is defined,
370 it's attributes are used to determine the result size.
371 <item> In all other cases the expression is assumed to be word sized.
374 Note: If the assembler is not able to evaluate the expression at assembly
375 time, the linker will evaluate it and check for range errors as soon as
379 <sect1>Boolean expressions<p>
381 In the context of a boolean expression, any non zero value is evaluated as
382 true, any other value to false. The result of a boolean expression is 1 if
383 it's true, and zero if it's false. There are boolean operators with extrem
384 low precedence with version 2.x (where x > 0). The <tt/.AND/ and <tt/.OR/
385 operators are shortcut operators. That is, if the result of the expression is
386 already known, after evaluating the left hand side, the right hand side is
390 <sect1>Available operators<p>
392 Available operators sorted by precedence:
395 Op Description Precedence
396 -------------------------------------------------------------------
397 .CONCAT Builtin function 0
398 .LEFT Builtin function 0
399 .MID Builtin function 0
400 .RIGHT Builtin function 0
401 .STRING Builtin function 0
403 * Builtin pseudo variable (r/o) 1
404 .BLANK Builtin function 1
405 .CONST Builtin function 1
406 .CPU Builtin pseudo variable (r/o) 1
407 .DEFINED Builtin function 1
408 .MATCH Builtin function 1
409 .TCOUNT Builtin function 1
410 .TIME Builtin function 1
411 .XMATCH Builtin function 1
412 .PARAMCOUNT Builtin pseudo variable (r/o) 1
413 .REFERENCED Builtin function 1
414 :: Global namespace override 1
417 ~ Unary bitwise not 1
418 .BITNOT Unary bitwise not 1
419 < Low byte operator 1
420 > High byte operator 1
424 .MOD Modulo operation 2
426 .BITAND Bitwise and 2
428 .BITXOR Bitwise xor 2
429 << Shift left operator 2
430 .SHL Shift left operator 2
431 >> Shift right operator
432 .SHR Shift right operator 2
439 = Compare operation (equal) 4
440 <> Compare operation (not equal) 4
441 < Compare operation (less) 4
442 > Compare operation (greater) 4
443 <= Compare operation (less or equal) 4
444 >= Compare operation (greater or equal) 4
446 && Boolean and 5
458 To force a specific order of evaluation, braces may be used as usual.
460 Some of the pseudo variables mentioned above need some more explanation:
463 * This symbol is replaced by the value of the program
464 counter at start of the current instruction. Note, that
465 '*' yields a rvalue, that means, you cannot assign to it.
466 Use <tt/.ORG/ to set the program counter in sections with
473 <sect>Symbols and labels<p>
475 The assembler allows you to use symbols instead of naked values to make
476 the source more readable. There are a lot of different ways to define and
477 use symbols and labels, giving a lot of flexibility.
480 <sect1>Numeric constants<p>
482 Numeric constants are defined using the equal sign. After doing
488 may use the symbol "two" in every place where a number is expected, and it is
489 evaluated to the value 2 in this context. An example would be
496 <sect1>Standard labels<p>
498 A label is defined by writing the name of the label at the start of the line
499 (before any instruction mnemonic, macro or pseudo directive), followed by a
500 colon. This will declare a symbol with the given name and the value of the
501 current program counter.
504 <sect1>Local labels and symbols<p>
506 Using the <tt><ref id=".PROC" name=".PROC"></tt> directive, it is possible to
507 create regions of code where the names of labels and symbols are local to this
508 region. They are not known outside of this region and cannot be accessed from
509 there. Such regions may be nested like PROCEDUREs in Pascal.
511 See the description of the <tt><ref id=".PROC" name=".PROC"></tt>
512 directive for more information.
515 <sect1>Cheap local labels<p>
517 Cheap local labels are defined like standard labels, but the name of the
518 label must begin with a special symbol (usually '@', but this can be
519 changed by the <tt><ref id=".LOCALCHAR" name=".LOCALCHAR"></tt>
522 Cheap local labels are visible only between two non cheap labels. As soon as a
523 standard symbol is encountered (this may also be a local symbol if inside a
524 region defined with the <tt><ref id=".PROC" name=".PROC"></tt> directive), the
525 cheap local symbol goes out of scope.
527 You may use cheap local labels as an easy way to reuse common label
528 names like "Loop". Here is an example:
531 Clear: lda #$00 ; Global label
533 @Loop: sta Mem,y ; Local label
537 Sub: ... ; New global label
538 bne @Loop ; ERROR: Unknown identifier!
541 <sect1>Unnamed labels<p>
543 If you really want to write messy code, there are also unnamed
544 labels. These labels do not have a name (you guessed that already,
545 didn't you?). A colon is used to mark the absence of the name.
547 Unnamed labels may be accessed by using the colon plus several minus
548 or plus characters as a label designator. Using the '-' characters
549 will create a back reference (use the n'th label backwards), using
550 '+' will create a forward reference (use the n'th label in forward
551 direction). An example will help to understand this:
573 As you can see from the example, unnamed labels will make even short
574 sections of code hard to understand, because you have to count labels
575 to find branch targets (this is the reason why I for my part do
576 prefer the "cheap" local labels). Nevertheless, unnamed labels are
577 convenient in some situations, so it's your decision.
580 <sect1>Using macros to define labels and constants<p>
582 While there are drawbacks with this approach, it may be handy in some
583 situations. Using <tt><ref id=".DEFINE" name=".DEFINE"></tt>, it is
584 possible to define symbols or constants that may be used elsewhere. Since
585 the macro facility works on a very low level, there is no scoping. On the
586 other side, you may also define string constants this way (this is not
587 possible with the other symbol types).
593 .DEFINE version "SOS V2.3"
595 four = two * two ; Ok
598 .PROC ; Start local scope
599 two = 3 ; Will give "2 = 3" - invalid!
604 <sect1>Symbols and <tt>.DEBUGINFO</tt><p>
606 If <tt><ref id=".DEBUGINFO" name=".DEBUGINFO"></tt> is enabled (or <ref
607 id="option-g" name="-g"> is given on the command line), global, local and
608 cheap local labels are written to the object file and will be available in the
609 symbol file via the linker. Unnamed labels are not written to the object file,
610 because they don't have a name which would allow to access them.
614 <sect>Control commands<label id="control-commands">
617 Here's a list of all control commands and a description, what they do:
620 <sect1><tt>.A16</tt><label id=".A16"><p>
622 Valid only in 65816 mode. Switch the accumulator to 16 bit.
624 Note: This command will not emit any code, it will tell the assembler to
625 create 16 bit operands for immediate accumulator adressing mode.
627 See also: <tt><ref id=".SMART" name=".SMART"></tt>
630 <sect1><tt>.A8</tt><label id=".A8"><p>
632 Valid only in 65816 mode. Switch the accumulator to 8 bit.
634 Note: This command will not emit any code, it will tell the assembler to
635 create 8 bit operands for immediate accu adressing mode.
637 See also: <tt><ref id=".SMART" name=".SMART"></tt>
640 <sect1><tt>.ADDR</tt><label id=".ADDR"><p>
642 Define word sized data. In 6502 mode, this is an alias for <tt/.WORD/ and
643 may be used for better readability if the data words are address values. In
644 65816 mode, the address is forced to be 16 bit wide to fit into the current
645 segment. See also <tt><ref id=".FARADDR" name=".FARADDR"></tt>. The command
646 must be followed by a sequence of (not necessarily constant) expressions.
651 .addr $0D00, $AF13, _Clear
654 See: <tt><ref id=".FARADDR" name=".FARADDR"></tt>, <tt><ref id=".WORD"
658 <sect1><tt>.ALIGN</tt><label id=".ALIGN"><p>
660 Align data to a given boundary. The command expects a constant integer
661 argument that must be a power of two, plus an optional second argument
662 in byte range. If there is a second argument, it is used as fill value,
663 otherwise the value defined in the linker configuration file is used
664 (the default for this value is zero).
666 Since alignment depends on the base address of the module, you must
667 give the same (or a greater) alignment for the segment when linking.
668 The linker will give you a warning, if you don't do that.
677 <sect1><tt>.ASCIIZ</tt><label id=".ASCIIZ"><p>
679 Define a string with a trailing zero.
684 Msg: .asciiz "Hello world"
687 This will put the string "Hello world" followed by a binary zero into
688 the current segment. There may be more strings separated by commas, but
689 the binary zero is only appended once (after the last one).
692 <sect1><tt>.AUTOIMPORT</tt><label id=".AUTOIMPORT"><p>
694 Is followed by a plus or a minus character. When switched on (using a
695 +), undefined symbols are automatically marked as import instead of
696 giving errors. When switched off (which is the default so this does not
697 make much sense), this does not happen and an error message is
698 displayed. The state of the autoimport flag is evaluated when the
699 complete source was translated, before outputing actual code, so it is
700 <em/not/ possible to switch this feature on or off for separate sections
701 of code. The last setting is used for all symbols.
703 You should probably not use this switch because it delays error
704 messages about undefined symbols until the link stage. The cc65
705 compiler (which is supposed to produce correct assembler code in all
706 circumstances, something which is not true for most assembler
707 programmers) will insert this command to avoid importing each and every
708 routine from the runtime library.
713 .autoimport + ; Switch on auto import
717 <sect1><tt>.BLANK</tt><label id=".BLANK"><p>
719 Builtin function. The function evaluates its argument in braces and
720 yields "false" if the argument is non blank (there is an argument), and
721 "true" if there is no argument. As an example, the <tt/.IFBLANK/ statement
729 <sect1><tt>.BSS</tt><label id=".BSS"><p>
731 Switch to the BSS segment. The name of the BSS segment is always "BSS",
732 so this is a shortcut for
738 See also the <tt><ref id=".SEGMENT" name=".SEGMENT"></tt> command.
741 <sect1><tt>.BYT, .BYTE</tt><label id=".BYTE"><p>
743 Define byte sized data. Must be followed by a sequence of (byte ranged)
744 expressions or strings.
750 .byt "world", $0D, $00
754 <sect1><tt>.CASE</tt><label id=".CASE"><p>
756 Switch on or off case sensitivity on identifiers. The default is off
757 (that is, identifiers are case sensitive), but may be changed by the
758 -i switch on the command line.
759 The command must be followed by a '+' or '-' character to switch the
760 option on or off respectively.
765 .case - ; Identifiers are not case sensitive
769 <sect1><tt>.CHARMAP</tt><label id=".CHARMAP"><p>
771 Apply a custom mapping for characters. The command is followed by two
772 numbers in the range 1..255. The first one is the index of the source
773 character, the second one is the mapping. The mapping applies to all
774 character and string constants when they generate output, and overrides
775 a mapping table specified with the <tt><ref id="option-t" name="-t"></tt>
781 .charmap $41, $61 ; Map 'A' to 'a'
785 <sect1><tt>.CODE</tt><label id=".CODE"><p>
787 Switch to the CODE segment. The name of the CODE segment is always
788 "CODE", so this is a shortcut for
794 See also the <tt><ref id=".SEGMENT" name=".SEGMENT"></tt> command.
797 <sect1><tt>.CONDES</tt><label id=".CONDES"><p>
799 Export a symbol and mark it in a special way. The linker is able to build
800 tables of all such symbols. This may be used to automatically create a list
801 of functions needed to initialize linked library modules.
803 Note: The linker has a feature to build a table of marked routines, but it
804 is your code that must call these routines, so just declaring a symbol with
805 <tt/.CONDES/ does nothing by itself.
807 All symbols are exported as an absolute (16 bit) symbol. You don't need to
808 use an additional <tt><ref id=".EXPORT" name=".EXPORT"></tt> statement, this
809 is implied by <tt/.CONDES/.
811 <tt/.CONDES/ is followed by the type, which may be <tt/constructor/,
812 <tt/destructor/ or a numeric value between 0 and 6 (where 0 is the same as
813 specifiying <tt/constructor/ and 1 is equal to specifying <tt/destructor/).
814 The <tt><ref id=".CONSTRUCTOR" name=".CONSTRUCTOR"></tt> and <tt><ref
815 id=".DESTRUCTOR" name=".DESTRUCTOR"></tt> commands are actually shortcuts
816 for <tt/.CONDES/ with a type of <tt/constructor/ resp. <tt/destructor/.
818 After the type, an optional priority may be specified. If no priority is
819 given, the default priority of 7 is used. Be careful when assigning
820 priorities to your own module constructors so they won't interfere with the
821 ones in the cc65 library.
826 .condes ModuleInit, constructor
827 .condes ModInit, 0, 16
830 See the <tt><ref id=".CONSTRUCTOR" name=".CONSTRUCTOR"></tt> and <tt><ref
831 id=".DESTRUCTOR" name=".DESTRUCTOR"></tt> commands and the separate section
832 <ref id="condes" name="Module constructors/destructors"> explaining the
833 feature in more detail.
836 <sect1><tt>.CONCAT</tt><label id=".CONCAT"><p>
838 Builtin function. The function allows to concatenate a list of string
839 constants separated by commas. The result is a string constant that
840 is the concatentation of all arguments. This function is most useful
841 in macros and when used together with the <tt/.STRING/ builtin function.
842 The function may be used in any case where a string constant is
848 .include .concat ("myheader", ".", "inc")
851 This is the same as the command
854 .include "myheader.inc"
858 <sect1><tt>.CONST</tt><label id=".CONST"><p>
860 Builtin function. The function evaluates its argument in braces and
861 yields "true" if the argument is a constant expression (that is, an
862 expression that yields a constant value at assembly time) and "false"
863 otherwise. As an example, the .IFCONST statement may be replaced by
870 <sect1><tt>.CONSTRUCTOR</tt><label id=".CONSTRUCTOR"><p>
872 Export a symbol and mark it as a module constructor. This may be used
873 together with the linker to build a table of constructor subroutines that
874 are called by the startup code.
876 Note: The linker has a feature to build a table of marked routines, but it
877 is your code that must call these routines, so just declaring a symbol as
878 constructor does nothing by itself.
880 A constructor is always exported as an absolute (16 bit) symbol. You don't
881 need to use an additional <tt/.export/ statement, this is implied by
882 <tt/.constructor/. It may have an optional priority that is separated by a
883 comma. If no priority is given, the default priority of 7 is used. Be
884 careful when assigning priorities to your own module constructors so they
885 won't interfere with the ones in the cc65 library.
890 .constructor ModuleInit
891 .constructor ModInit, 16
894 See the <tt><ref id=".CONDES" name=".CONDES"></tt> and <tt><ref
895 id=".DESTRUCTOR" name=".DESTRUCTOR"></tt> commands and the separate section
896 <ref id="condes" name="Module constructors/destructors"> explaining the
897 feature in more detail.
900 <sect1><tt>.CPU</tt><label id=".CPU"><p>
902 Reading this pseudo variable will give a constant integer value that
903 tells which instruction set is currently enabled. Possible values are:
912 It may be used to replace the .IFPxx pseudo instructions or to construct
913 even more complex expressions.
918 .if (.cpu = 0) .or (.cpu = 1)
930 <sect1><tt>.DATA</tt><label id=".DATA"><p>
932 Switch to the DATA segment. The name of the DATA segment is always
933 "DATA", so this is a shortcut for
939 See also the <tt><ref id=".SEGMENT" name=".SEGMENT"></tt> command.
942 <sect1><tt>.DBYT</tt><label id=".DBYT"><p>
944 Define word sized data with the hi and lo bytes swapped (use <tt/.WORD/ to
945 create word sized data in native 65XX format). Must be followed by a
946 sequence of (word ranged) expressions.
954 This will emit the bytes
960 into the current segment in that order.
963 <sect1><tt>.DEBUGINFO</tt><label id=".DEBUGINFO"><p>
965 Switch on or off debug info generation. The default is off (that is,
966 the object file will not contain debug infos), but may be changed by the
967 -g switch on the command line.
968 The command must be followed by a '+' or '-' character to switch the
969 option on or off respectively.
974 .debuginfo + ; Generate debug info
978 <sect1><tt>.DEFINE</tt><label id=".DEFINE"><p>
980 Start a define style macro definition. The command is followed by an
981 identifier (the macro name) and optionally by a list of formal arguments
983 See section <ref id="macros" name="Macros">.
986 <sect1><tt>.DEF, .DEFINED</tt><label id=".DEFINED"><p>
988 Builtin function. The function expects an identifier as argument in braces.
989 The argument is evaluated, and the function yields "true" if the identifier
990 is a symbol that is already defined somewhere in the source file up to the
991 current position. Otherwise the function yields false. As an example, the
992 <tt><ref id=".IFDEF" name=".IFDEF"></tt> statement may be replaced by
999 <sect1><tt>.DESTRUCTOR</tt><label id=".DESTRUCTOR"><p>
1001 Export a symbol and mark it as a module destructor. This may be used
1002 together with the linker to build a table of destructor subroutines that
1003 are called by the startup code.
1005 Note: The linker has a feature to build a table of marked routines, but it
1006 is your code that must call these routines, so just declaring a symbol as
1007 constructor does nothing by itself.
1009 A destructor is always exported as an absolute (16 bit) symbol. You don't
1010 need to use an additional <tt/.export/ statement, this is implied by
1011 <tt/.destructor/. It may have an optional priority that is separated by a
1012 comma. If no priority is given, the default priority of 7 is used. Be
1013 careful when assigning priorities to your own module destructors so they
1014 won't interfere with the ones in the cc65 library.
1019 .destructor ModuleDone
1020 .destructor ModDone, 16
1023 See the <tt><ref id=".CONDES" name=".CONDES"></tt> and <tt><ref
1024 id=".CONSTRUCTOR" name=".CONSTRUCTOR"></tt> commands and the separate
1025 section <ref id="condes" name="Module constructors/destructors"> explaining
1026 the feature in more detail.
1029 <sect1><tt>.DWORD</tt><label id=".DWORD"><p>
1031 Define dword sized data (4 bytes) Must be followed by a sequence of
1037 .dword $12344512, $12FA489
1041 <sect1><tt>.ELSE</tt><label id=".ELSE"><p>
1043 Conditional assembly: Reverse the current condition.
1046 <sect1><tt>.ELSEIF</tt><label id=".ELSEIF"><p>
1048 Conditional assembly: Reverse current condition and test a new one.
1051 <sect1><tt>.END</tt><label id=".END"><p>
1053 Forced end of assembly. Assembly stops at this point, even if the command
1054 is read from an include file.
1057 <sect1><tt>.ENDIF</tt><label id=".ENDIF"><p>
1059 Conditional assembly: Close a <tt><ref id=".IF" name=".IF..."></tt> or
1060 <tt><ref id=".ELSE" name=".ELSE"></tt> branch.
1063 <sect1><tt>.ENDMAC, .ENDMACRO</tt><label id=".ENDMACRO"><p>
1065 End of macro definition (see section <ref id="macros" name="Macros">).
1068 <sect1><tt>.ENDPROC</tt><label id=".ENDPROC"><p>
1070 End of local lexical level (see <tt><ref id=".PROC" name=".PROC"></tt>).
1073 <sect1><tt>.ENDREP, .ENDREPEAT</tt><label id=".ENDREPEAT"><p>
1075 End a <tt><ref id=".REPEAT" name=".REPEAT"></tt> block.
1078 <sect1><tt>.ERROR</tt><label id=".ERROR"><p>
1080 Force an assembly error. The assembler will output an error message
1081 preceeded by "User error" and will <em/not/ produce an object file.
1083 This command may be used to check for initial conditions that must be
1084 set before assembling a source file.
1094 .error "Must define foo or bar!"
1098 See also the <tt><ref id=".WARNING" name=".WARNING"></tt> and <tt><ref
1099 id=".OUT" name=".OUT"></tt> directives.
1102 <sect1><tt>.EXITMAC, .EXITMACRO</tt><label id=".EXITMACRO"><p>
1104 Abort a macro expansion immidiately. This command is often useful in
1105 recursive macros. See separate section <ref id="macros" name="Macros">.
1108 <sect1><tt>.EXPORT</tt><label id=".EXPORT"><p>
1110 Make symbols accessible from other modules. Must be followed by a comma
1111 separated list of symbols to export.
1119 See: <tt><ref id=".EXPORTZP" name=".EXPORTZP"></tt>
1122 <sect1><tt>.EXPORTZP</tt><label id=".EXPORTZP"><p>
1124 Make symbols accessible from other modules. Must be followed by a comma
1125 separated list of symbols to export. The exported symbols are explicitly
1126 marked as zero page symols.
1134 See: <tt><ref id=".EXPORT" name=".EXPORT"></tt>
1137 <sect1><tt>.FARADDR</tt><label id=".FARADDR"><p>
1139 Define far (24 bit) address data. The command must be followed by a
1140 sequence of (not necessarily constant) expressions.
1145 .faraddr DrawCircle, DrawRectangle, DrawHexagon
1148 See: <tt><ref id=".ADDR" name=".ADDR"></tt>
1151 <sect1><tt>.FEATURE</tt><label id=".FEATURE"><p>
1153 This directive may be used to enable one or more compatibility features
1154 of the assembler. While the use of <tt/.FEATURE/ should be avoided when
1155 possible, it may be useful when porting sources written for other
1156 assemblers. There is no way to switch a feature off, once you have
1157 enabled it, so using
1163 will enable the feature until end of assembly is reached.
1165 The following features are available:
1169 <tag><tt>dollar_is_pc</tt></tag>
1171 The dollar sign may be used as an alias for the star (`*'), which
1172 gives the value of the current PC in expressions.
1173 Note: Assignment to the pseudo variable is not allowed.
1175 <tag><tt>labels_without_colons</tt></tag>
1177 Allow labels without a trailing colon. These labels are only accepted,
1178 if they start at the beginning of a line (no leading white space).
1180 <tag><tt>loose_string_term</tt></tag>
1182 Accept single quotes as well as double quotes as terminators for string
1185 <tag><tt>loose_char_term</tt></tag>
1187 Accept single quotes as well as double quotes as terminators for char
1190 <tag><tt>at_in_identifiers</tt></tag>
1192 Accept the at character (`@') as a valid character in identifiers. The
1193 at character is not allowed to start an identifier, even with this
1196 <tag><tt>dollar_in_identifiers</tt></tag>
1198 Accept the dollar sign (`$') as a valid character in identifiers. The
1199 at character is not allowed to start an identifier, even with this
1202 <tag><tt>leading_dot_in_identifiers</tt></tag>
1204 Accept the dot (`.') as the first character of an identifier. This may be
1205 used for example to create macro names that start with a dot emulating
1206 control directives of other assemblers. Note however, that none of the
1207 reserved keywords built into the assembler, that starts with a dot, may be
1208 overridden. When using this feature, you may also get into trouble if
1209 later versions of the assembler define new keywords starting with a dot.
1211 <tag><tt>pc_assignment</tt></tag>
1213 Allow assignments to the PC symbol (`*' or `$' if <tt/dollar_is_pc/
1214 is enabled). Such an assignment is handled identical to the <tt><ref
1215 id=".ORG" name=".ORG"></tt> command (which is usually not needed, so just
1216 removing the lines with the assignments may also be an option when porting
1217 code written for older assemblers).
1221 It is also possible to specify features on the command line using the
1222 <tt><ref id="option--feature" name="--feature"></tt> command line option.
1223 This is useful when translating sources written for older assemblers, when
1224 you don't want to change the source code.
1226 As an example, to translate sources written for Andre Fachats xa65
1227 assembler, the features
1230 labels_without_colons, pc_assignment, loose_char_term
1233 may be helpful. They do not make ca65 completely compatible, so you may not
1234 be able to translate the sources without changes, even when enabling these
1235 features. However, I have found several sources that translate without
1236 problems when enabling these features on the command line.
1239 <sect1><tt>.FILEOPT, .FOPT</tt><label id=".FOPT"><p>
1241 Insert an option string into the object file. There are two forms of
1242 this command, one specifies the option by a keyword, the second
1243 specifies it as a number. Since usage of the second one needs knowledge
1244 of the internal encoding, its use is not recommended and I will only
1245 describe the first form here.
1247 The command is followed by one of the keywords
1255 a comma and a string. The option is written into the object file
1256 together with the string value. This is currently unidirectional and
1257 there is no way to actually use these options once they are in the
1263 .fileopt comment, "Code stolen from my brother"
1264 .fileopt compiler, "BASIC 2.0"
1265 .fopt author, "J. R. User"
1269 <sect1><tt>.FORCEIMPORT</tt><label id=".FORCEIMPORT"><p>
1271 Import an absolute symbol from another module. The command is followed by a
1272 comma separated list of symbols to import. The command is similar to <tt>
1273 <ref id=".IMPORT" name=".IMPORT"></tt>, but the import reference is always
1274 written to the generated object file, even if the symbol is never referenced
1275 (<tt><ref id=".IMPORT" name=".IMPORT"></tt> will not generate import
1276 references for unused symbols).
1281 .forceimport needthisone, needthistoo
1284 See: <tt><ref id=".IMPORT" name=".IMPORT"></tt>
1287 <sect1><tt>.GLOBAL</tt><label id=".GLOBAL"><p>
1289 Declare symbols as global. Must be followed by a comma separated list of
1290 symbols to declare. Symbols from the list, that are defined somewhere in the
1291 source, are exported, all others are imported. Additional <tt><ref
1292 id=".IMPORT" name=".IMPORT"></tt> or <tt><ref id=".EXPORT"
1293 name=".EXPORT"></tt> commands for the same symbol are allowed.
1302 <sect1><tt>.GLOBALZP</tt><label id=".GLOBALZP"><p>
1304 Declare symbols as global. Must be followed by a comma separated list of
1305 symbols to declare. Symbols from the list, that are defined somewhere in the
1306 source, are exported, all others are imported. Additional <tt><ref
1307 id=".IMPORTZP" name=".IMPORTZP"></tt> or <tt><ref id=".EXPORTZP"
1308 name=".EXPORTZP"></tt> commands for the same symbol are allowed. The symbols
1309 in the list are explicitly marked as zero page symols.
1318 <sect1><tt>.I16</tt><label id=".I16"><p>
1320 Valid only in 65816 mode. Switch the index registers to 16 bit.
1322 Note: This command will not emit any code, it will tell the assembler to
1323 create 16 bit operands for immediate operands.
1325 See also the <tt><ref id=".I8" name=".I8"></tt> and <tt><ref id=".SMART"
1326 name=".SMART"></tt> commands.
1329 <sect1><tt>.I8</tt><label id=".I8"><p>
1331 Valid only in 65816 mode. Switch the index registers to 8 bit.
1333 Note: This command will not emit any code, it will tell the assembler to
1334 create 8 bit operands for immediate operands.
1336 See also the <tt><ref id=".I16" name=".I16"></tt> and <tt><ref id=".SMART"
1337 name=".SMART"></tt> commands.
1340 <sect1><tt>.IF</tt><label id=".IF"><p>
1342 Conditional assembly: Evalute an expression and switch assembler output
1343 on or off depending on the expression. The expression must be a constant
1344 expression, that is, all operands must be defined.
1346 A expression value of zero evaluates to FALSE, any other value evaluates
1350 <sect1><tt>.IFBLANK</tt><label id=".IFBLANK"><p>
1352 Conditional assembly: Check if there are any remaining tokens in this line,
1353 and evaluate to FALSE if this is the case, and to TRUE otherwise. If the
1354 condition is not true, further lines are not assembled until an <tt><ref
1355 id=".ELSE" name=".ESLE"></tt>, <tt><ref id=".ELSEIF" name=".ELSEIF"></tt> or
1356 <tt><ref id=".ENDIF" name=".ENDIF"></tt> directive.
1358 This command is often used to check if a macro parameter was given. Since an
1359 empty macro parameter will evaluate to nothing, the condition will evaluate
1360 to FALSE if an empty parameter was given.
1374 See also: <tt><ref id=".BLANK" name=".BLANK"></tt>
1377 <sect1><tt>.IFCONST</tt><label id=".IFCONST"><p>
1379 Conditional assembly: Evaluate an expression and switch assembler output
1380 on or off depending on the constness of the expression.
1382 A const expression evaluates to to TRUE, a non const expression (one
1383 containing an imported or currently undefined symbol) evaluates to
1386 See also: <tt><ref id=".CONST" name=".CONST"></tt>
1389 <sect1><tt>.IFDEF</tt><label id=".IFDEF"><p>
1391 Conditional assembly: Check if a symbol is defined. Must be followed by
1392 a symbol name. The condition is true if the the given symbol is already
1393 defined, and false otherwise.
1395 See also: <tt><ref id=".DEFINED" name=".DEFINED"></tt>
1398 <sect1><tt>.IFNBLANK</tt><label id=".IFNBLANK"><p>
1400 Conditional assembly: Check if there are any remaining tokens in this line,
1401 and evaluate to TRUE if this is the case, and to FALSE otherwise. If the
1402 condition is not true, further lines are not assembled until an <tt><ref
1403 id=".ELSE" name=".ELSE"></tt>, <tt><ref id=".ELSEIF" name=".ELSEIF"></tt> or
1404 <tt><ref id=".ENDIF" name=".ENDIF"></tt> directive.
1406 This command is often used to check if a macro parameter was given.
1407 Since an empty macro parameter will evaluate to nothing, the condition
1408 will evaluate to FALSE if an empty parameter was given.
1421 See also: <tt><ref id=".BLANK" name=".BLANK"></tt>
1424 <sect1><tt>.IFNDEF</tt><label id=".IFNDEF"><p>
1426 Conditional assembly: Check if a symbol is defined. Must be followed by
1427 a symbol name. The condition is true if the the given symbol is not
1428 defined, and false otherwise.
1430 See also: <tt><ref id=".DEFINED" name=".DEFINED"></tt>
1433 <sect1><tt>.IFNREF</tt><label id=".IFNREF"><p>
1435 Conditional assembly: Check if a symbol is referenced. Must be followed
1436 by a symbol name. The condition is true if if the the given symbol was
1437 not referenced before, and false otherwise.
1439 See also: <tt><ref id=".REFERENCED" name=".REFERENCED"></tt>
1442 <sect1><tt>.IFP02</tt><label id=".IFP02"><p>
1444 Conditional assembly: Check if the assembler is currently in 6502 mode
1445 (see <tt><ref id=".P02" name=".P02"></tt> command).
1448 <sect1><tt>.IFP816</tt><label id=".IFP816"><p>
1450 Conditional assembly: Check if the assembler is currently in 65816 mode
1451 (see <tt><ref id=".P816" name=".P816"></tt> command).
1454 <sect1><tt>.IFPC02</tt><label id=".IFPC02"><p>
1456 Conditional assembly: Check if the assembler is currently in 65C02 mode
1457 (see <tt><ref id=".PC02" name=".PC02"></tt> command).
1460 <sect1><tt>.IFREF</tt><label id=".IFREF"><p>
1462 Conditional assembly: Check if a symbol is referenced. Must be followed
1463 by a symbol name. The condition is true if if the the given symbol was
1464 referenced before, and false otherwise.
1466 This command may be used to build subroutine libraries in include files
1467 (you may use separate object modules for this purpose too).
1472 .ifref ToHex ; If someone used this subroutine
1473 ToHex: tay ; Define subroutine
1479 See also: <tt><ref id=".REFERENCED" name=".REFERENCED"></tt>
1482 <sect1><tt>.IMPORT</tt><label id=".IMPORT"><p>
1484 Import a symbol from another module. The command is followed by a comma
1485 separated list of symbols to import.
1493 See: <tt><ref id=".IMPORTZP" name=".IMPORTZP"></tt>
1496 <sect1><tt>.IMPORTZP</tt><label id=".IMPORTZP"><p>
1498 Import a symbol from another module. The command is followed by a comma
1499 separated list of symbols to import. The symbols are explicitly imported
1500 as zero page symbols (that is, symbols with values in byte range).
1508 See: <tt><ref id=".IMPORT" name=".IMPORT"></tt>
1511 <sect1><tt>.INCBIN</tt><label id=".INCBIN"><p>
1513 Include a file as binary data. The command expects a string argument
1514 that is the name of a file to include literally in the current segment.
1515 In addition to that, a start offset and a size value may be specified,
1516 separated by commas. If no size is specified, all of the file from the
1517 start offset to end-of-file is used. If no start position is specified
1518 either, zero is assume (which means that the whole file is inserted).
1523 ; Include whole file
1524 .incbin "sprites.dat"
1526 ; Include file starting at offset 256
1527 .incbin "music.dat", $100
1529 ; Read 100 bytes starting at offset 200
1530 .incbin "graphics.dat", 200, 100
1534 <sect1><tt>.INCLUDE</tt><label id=".INCLUDE"><p>
1536 Include another file. Include files may be nested up to a depth of 16.
1545 <sect1><tt>.LEFT</tt><label id=".LEFT"><p>
1547 Builtin function. Extracts the left part of a given token list.
1552 .LEFT (<int expr>, <token list>)
1555 The first integer expression gives the number of tokens to extract from
1556 the token list. The second argument is the token list itself.
1560 To check in a macro if the given argument has a '#' as first token
1561 (immidiate addressing mode), use something like this:
1566 .if (.match (.left (1, arg), #))
1568 ; ldax called with immidiate operand
1576 See also the <tt><ref id=".MID" name=".MID"></tt> and <tt><ref id=".RIGHT"
1577 name=".RIGHT"></tt> builtin functions.
1580 <sect1><tt>.LINECONT</tt><label id=".LINECONT"><p>
1582 Switch on or off line continuations using the backslash character
1583 before a newline. The option is off by default.
1584 Note: Line continuations do not work in a comment. A backslash at the
1585 end of a comment is treated as part of the comment and does not trigger
1587 The command must be followed by a '+' or '-' character to switch the
1588 option on or off respectively.
1593 .linecont + ; Allow line continuations
1596 #$20 ; This is legal now
1600 <sect1><tt>.LIST</tt><label id=".LIST"><p>
1602 Enable output to the listing. The command must be followed by a boolean
1603 switch ("on", "off", "+" or "-") and will enable or disable listing
1605 The option has no effect if the listing is not enabled by the command line
1606 switch -l. If -l is used, an internal counter is set to 1. Lines are output
1607 to the listing file, if the counter is greater than zero, and suppressed if
1608 the counter is zero. Each use of <tt/.LIST/ will increment or decrement the
1614 .list on ; Enable listing output
1618 <sect1><tt>.LISTBYTES</tt><label id=".LISTBYTES"><p>
1620 Set, how many bytes are shown in the listing for one source line. The
1621 default is 12, so the listing will show only the first 12 bytes for any
1622 source line that generates more than 12 bytes of code or data.
1623 The directive needs an argument, which is either "unlimited", or an
1624 integer constant in the range 4..255.
1629 .listbytes unlimited ; List all bytes
1630 .listbytes 12 ; List the first 12 bytes
1631 .incbin "data.bin" ; Include large binary file
1635 <sect1><tt>.LOCAL</tt><label id=".LOCAL"><p>
1637 This command may only be used inside a macro definition. It declares a
1638 list of identifiers as local to the macro expansion.
1640 A problem when using macros are labels: Since they don't change their name,
1641 you get a "duplicate symbol" error if the macro is expanded the second time.
1642 Labels declared with <tt><ref id=".LOCAL" name=".LOCAL"></tt> have their
1643 name mapped to an internal unique name (<tt/___ABCD__/) with each macro
1646 Some other assemblers start a new lexical block inside a macro expansion.
1647 This has some drawbacks however, since that will not allow <em/any/ symbol
1648 to be visible outside a macro, a feature that is sometimes useful. The
1649 <tt><ref id=".LOCAL" name=".LOCAL"></tt> command is in my eyes a better way
1650 to address the problem.
1652 You get an error when using <tt><ref id=".LOCAL" name=".LOCAL"></tt> outside
1656 <sect1><tt>.LOCALCHAR</tt><label id=".LOCALCHAR"><p>
1658 Defines the character that start "cheap" local labels. You may use one
1659 of '@' and '?' as start character. The default is '@'.
1661 Cheap local labels are labels that are visible only between two non
1662 cheap labels. This way you can reuse identifiers like "<tt/loop/" without
1663 using explicit lexical nesting.
1670 Clear: lda #$00 ; Global label
1671 ?Loop: sta Mem,y ; Local label
1675 Sub: ... ; New global label
1676 bne ?Loop ; ERROR: Unknown identifier!
1680 <sect1><tt>.MACPACK</tt><label id=".MACPACK"><p>
1682 Insert a predefined macro package. The command is followed by an
1683 identifier specifying the macro package to insert. Available macro
1687 generic Defines generic macros like add and sub.
1688 longbranch Defines conditional long jump macros.
1691 Including a macro package twice, or including a macro package that
1692 redefines already existing macros will lead to an error.
1697 .macpack longbranch ; Include macro package
1699 cmp #$20 ; Set condition codes
1700 jne Label ; Jump long on condition
1703 Macro packages are explained in more detail in section <ref
1704 id="macropackages" name="Macro packages">.
1707 <sect1><tt>.MAC, .MACRO</tt><label id=".MAC"><p>
1709 Start a classic macro definition. The command is followed by an identifier
1710 (the macro name) and optionally by a comma separated list of identifiers
1711 that are macro parameters.
1713 See section <ref id="macros" name="Macros">.
1716 <sect1><tt>.MATCH</tt><label id=".MATCH"><p>
1718 Builtin function. Matches two token lists against each other. This is
1719 most useful within macros, since macros are not stored as strings, but
1725 .MATCH(<token list #1>, <token list #2>)
1728 Both token list may contain arbitrary tokens with the exception of the
1729 terminator token (comma resp. right parenthesis) and
1736 Often a macro parameter is used for any of the token lists.
1738 Please note that the function does only compare tokens, not token
1739 attributes. So any number is equal to any other number, regardless of the
1740 actual value. The same is true for strings. If you need to compare tokens
1741 <em/and/ token attributes, use the <tt><ref id=".XMATCH"
1742 name=".XMATCH"></tt> function.
1746 Assume the macro <tt/ASR/, that will shift right the accumulator by one,
1747 while honoring the sign bit. The builtin processor instructions will allow
1748 an optional "A" for accu addressing for instructions like <tt/ROL/ and
1749 <tt/ROR/. We will use the <tt><ref id=".MATCH" name=".MATCH"></tt> function
1750 to check for this and print and error for invalid calls.
1755 .if (.not .blank(arg)) .and (.not .match (arg, a))
1756 .error "Syntax error"
1759 cmp #$80 ; Bit 7 into carry
1760 lsr a ; Shift carry into bit 7
1765 The macro will only accept no arguments, or one argument that must be the
1766 reserved keyword "A".
1768 See: <tt><ref id=".XMATCH" name=".XMATCH"></tt>
1771 <sect1><tt>.MID</tt><label id=".MID"><p>
1773 Builtin function. Takes a starting index, a count and a token list as
1774 arguments. Will return part of the token list.
1779 .MID (<int expr>, <int expr>, <token list>)
1782 The first integer expression gives the starting token in the list (the
1783 first token has index 0). The second integer expression gives the number
1784 of tokens to extract from the token list. The third argument is the
1789 To check in a macro if the given argument has a '<tt/#/' as first token
1790 (immidiate addressing mode), use something like this:
1795 .if (.match (.mid (0, 1, arg), #))
1797 ; ldax called with immidiate operand
1805 See also the <tt><ref id=".LEFT" name=".LEFT"></tt> and <tt><ref id=".RIGHT"
1806 name=".RIGHT"></tt> builtin functions.
1809 <sect1><tt>.ORG</tt><label id=".ORG"><p>
1811 Start a section of absolute code. The command is followed by a constant
1812 expression that gives the new PC counter location for which the code is
1813 assembled. Use <tt><ref id=".RELOC" name=".RELOC"></tt> to switch back to
1816 Please note that you <em/do not need/ this command in most cases. Placing
1817 code at a specific address is the job of the linker, not the assembler, so
1818 there is usually no reason to assemble code to a specific address.
1820 You may not switch segments while inside a section of absolute code.
1825 .org $7FF ; Emit code starting at $7FF
1829 <sect1><tt>.OUT</tt><label id=".OUT"><p>
1831 Output a string to the console without producing an error. This command
1832 is similiar to <tt/.ERROR/, however, it does not force an assembler error
1833 that prevents the creation of an object file.
1838 .out "This code was written by the codebuster(tm)"
1841 See also the <tt><ref id=".WARNING" name=".WARNING"></tt> and <tt><ref
1842 id=".ERROR" name=".ERROR"></tt> directives.
1845 <sect1><tt>.P02</tt><label id=".P02"><p>
1847 Enable the 6502 instruction set, disable 65C02 and 65816 instructions.
1848 This is the default if not overridden by the <tt/--cpu/ command line
1851 See: <tt><ref id=".PC02" name=".PC02"></tt> and <tt><ref id=".P816"
1855 <sect1><tt>.P816</tt><label id=".P816"><p>
1857 Enable the 65816 instruction set. This is a superset of the 65C02 and
1858 6502 instruction sets.
1860 See: <tt><ref id=".P02" name=".P02"></tt> and <tt><ref id=".PC02"
1864 <sect1><tt>.PAGELEN, .PAGELENGTH</tt><label id=".PAGELENGTH"><p>
1866 Set the page length for the listing. Must be followed by an integer
1867 constant. The value may be "unlimited", or in the range 32 to 127. The
1868 statement has no effect if no listing is generated. The default value is -1
1869 (unlimited) but may be overridden by the <tt/--pagelength/ command line
1870 option. Beware: Since ca65 is a one pass assembler, the listing is generated
1871 after assembly is complete, you cannot use multiple line lengths with one
1872 source. Instead, the value set with the last <tt/.PAGELENGTH/ is used.
1877 .pagelength 66 ; Use 66 lines per listing page
1879 .pagelength unlimited ; Unlimited page length
1883 <sect1><tt>.PARAMCOUNT</tt><label id=".PARAMCOUNT"><p>
1885 This builtin pseudo variable is only available in macros. It is replaced by
1886 the actual number of parameters that were given in the macro invocation.
1891 .macro foo arg1, arg2, arg3
1892 .if .paramcount <> 3
1893 .error "Too few parameters for macro foo"
1899 See section <ref id="macros" name="Macros">.
1902 <sect1><tt>.PC02</tt><label id=".PC02"><p>
1904 Enable the 65C02 instructions set. This instruction set includes all
1907 See: <tt><ref id=".P02" name=".P02"></tt> and <tt><ref id=".P816"
1911 <sect1><tt>.POPSEG</tt><label id=".POPSEG"><p>
1913 Pop the last pushed segment from the stack, and set it.
1915 This command will switch back to the segment that was last pushed onto the
1916 segment stack using the <tt><ref id=".PUSHSEG" name=".PUSHSEG"></tt>
1917 command, and remove this entry from the stack.
1919 The assembler will print an error message if the segment stack is empty
1920 when this command is issued.
1922 See: <tt><ref id=".PUSHSEG" name=".PUSHSEG"></tt>
1925 <sect1><tt>.PROC</tt><label id=".PROC"><p>
1927 Start a nested lexical level. All new symbols from now on are in the local
1928 lexical level and are not accessible from outside. Symbols defined outside
1929 this local level may be accessed as long as their names are not used for new
1930 symbols inside the level. Symbols names in other lexical levels do not
1931 clash, so you may use the same names for identifiers. The lexical level ends
1932 when the <tt><ref id=".ENDPROC" name=".ENDPROC"></tt> command is read.
1933 Lexical levels may be nested up to a depth of 16.
1935 The command may be followed by an identifier, in this case the
1936 identifier is declared in the outer level as a label having the value of
1937 the program counter at the start of the lexical level.
1939 Note: Macro names are always in the global level and in a separate name
1940 space. There is no special reason for this, it's just that I've never
1941 had any need for local macro definitions.
1946 .proc Clear ; Define Clear subroutine, start new level
1948 L1: sta Mem,y ; L1 is local and does not cause a
1949 ; duplicate symbol error if used in other
1952 bne L1 ; Reference local symbol
1954 .endproc ; Leave lexical level
1957 See: <tt><ref id=".ENDPROC" name=".ENDPROC"></tt>
1960 <sect1><tt>.PUSHSEG</tt><label id=".PUSHSEG"><p>
1962 Push the currently active segment onto a stack. The entries on the stack
1963 include the name of the segment and the segment type. The stack has a size
1966 <tt/.PUSHSEG/ allows together with <tt><ref id=".POPSEG" name=".POPSEG"></tt>
1967 to switch to another segment and to restore the old segment later, without
1968 even knowing the name and type of the current segment.
1970 The assembler will print an error message if the segment stack is already
1971 full, when this command is issued.
1973 See: <tt><ref id=".POPSEG" name=".POPSEG"></tt>
1976 <sect1><tt>.REF, .REFERENCED</tt><label id=".REFERENCED"><p>
1978 Builtin function. The function expects an identifier as argument in braces.
1979 The argument is evaluated, and the function yields "true" if the identifier
1980 is a symbol that has already been referenced somewhere in the source file up
1981 to the current position. Otherwise the function yields false. As an example,
1982 the <tt><ref id=".IFREF" name=".IFREF"></tt> statement may be replaced by
1988 See: <tt><ref id=".DEFINED" name=".DEFINED"></tt>
1991 <sect1><tt>.REPEAT</tt><label id=".REPEAT"><p>
1993 Repeat all commands between <tt/.REPEAT/ and <tt><ref id=".ENDREPEAT"
1994 name=".ENDREPEAT"></tt> constant number of times. The command is followed by
1995 a constant expression that tells how many times the commands in the body
1996 should get repeated. Optionally, a comma and an identifier may be specified.
1997 If this identifier is found in the body of the repeat statement, it is
1998 replaced by the current repeat count (starting with zero for the first time
1999 the body is repeated).
2001 <tt/.REPEAT/ statements may be nested. If you use the same repeat count
2002 identifier for a nested <tt/.REPEAT/ statement, the one from the inner
2003 level will be used, not the one from the outer level.
2007 The following macro will emit a string that is "encrypted" in that all
2008 characters of the string are XORed by the value $55.
2012 .repeat .strlen(Arg), I
2013 .byte .strat(Arg, I) .xor $55
2018 See: <tt><ref id=".ENDREPEAT" name=".ENDREPEAT"></tt>
2021 <sect1><tt>.RELOC</tt><label id=".RELOC"><p>
2023 Switch back to relocatable mode. See the <tt><ref id=".ORG"
2024 name=".ORG"></tt> command.
2027 <sect1><tt>.RES</tt><label id=".RES"><p>
2029 Reserve storage. The command is followed by one or two constant
2030 expressions. The first one is mandatory and defines, how many bytes of
2031 storage should be defined. The second, optional expression must by a
2032 constant byte value that will be used as value of the data. If there
2033 is no fill value given, the linker will use the value defined in the
2034 linker configuration file (default: zero).
2039 ; Reserve 12 bytes of memory with value $AA
2044 <sect1><tt>.RIGHT</tt><label id=".RIGHT"><p>
2046 Builtin function. Extracts the right part of a given token list.
2051 .RIGHT (<int expr>, <token list>)
2054 The first integer expression gives the number of tokens to extract from
2055 the token list. The second argument is the token list itself.
2057 See also the <tt><ref id=".LEFT" name=".LEFT"></tt> and <tt><ref id=".MID"
2058 name=".MID"></tt> builtin functions.
2061 <sect1><tt>.RODATA</tt><label id=".RODATA"><p>
2063 Switch to the RODATA segment. The name of the RODATA segment is always
2064 "RODATA", so this is a shortcut for
2070 The RODATA segment is a segment that is used by the compiler for
2071 readonly data like string constants.
2073 See also the <tt><ref id=".SEGMENT" name=".SEGMENT"></tt> command.
2076 <sect1><tt>.SEGMENT</tt><label id=".SEGMENT"><p>
2078 Switch to another segment. Code and data is always emitted into a
2079 segment, that is, a named section of data. The default segment is
2080 "CODE". There may be up to 254 different segments per object file
2081 (and up to 65534 per executable). There are shortcut commands for
2082 the most common segments ("CODE", "DATA" and "BSS").
2084 The command is followed by a string containing the segment name (there
2085 are some constraints for the name - as a rule of thumb use only those
2086 segment names that would also be valid identifiers). There may also be
2087 an optional attribute separated by a comma. Valid attributes are
2088 "<tt/zeropage/" and "<tt/absolute/".
2090 When specifying a segment for the first time, "absolute" is the
2091 default. For all other uses, the attribute specified the first time
2094 "absolute" means that this is a segment with absolute addressing. That
2095 is, the segment will reside somewhere in core memory outside the zero
2096 page. "zeropage" means the opposite: The segment will be placed in the
2097 zero page and direct (short) addressing is possible for data in this
2100 Beware: Only labels in a segment with the zeropage attribute are marked
2101 as reachable by short addressing. The `*' (PC counter) operator will
2102 work as in other segments and will create absolute variable values.
2107 .segment "ROM2" ; Switch to ROM2 segment
2108 .segment "ZP2", zeropage ; New direct segment
2109 .segment "ZP2" ; Ok, will use last attribute
2110 .segment "ZP2", absolute ; Error, redecl mismatch
2113 See: <tt><ref id=".BSS" name=".BSS"></tt>, <tt><ref id=".CODE"
2114 name=".CODE"></tt>, <tt><ref id=".DATA" name=".DATA"></tt> and <tt><ref
2115 id=".RODATA" name=".RODATA"></tt>
2118 <sect1><tt>.SMART</tt><label id=".SMART"><p>
2120 Switch on or off smart mode. The command must be followed by a '+' or
2121 '-' character to switch the option on or off respectively. The default
2122 is off (that is, the assembler doesn't try to be smart), but this
2123 default may be changed by the -s switch on the command line.
2125 In smart mode the assembler will track usage of the <tt/REP/ and <tt/SEP/
2126 instructions in 65816 mode and update the operand sizes accordingly. If
2127 the operand of such an instruction cannot be evaluated by the assembler
2128 (for example, because the operand is an imported symbol), a warning is
2129 issued. Beware: Since the assembler cannot trace the execution flow this
2130 may lead to false results in some cases. If in doubt, use the <tt/.Inn/ and
2131 <tt/.Ann/ instructions to tell the assembler about the current settings.
2137 .smart - ; Stop being smart
2141 <sect1><tt>.STRAT</tt><label id=".STRAT"><p>
2143 Builtin function. The function accepts a string and an index as
2144 arguments and returns the value of the character at the given position
2145 as an integer value. The index is zero based.
2151 ; Check if the argument string starts with '#'
2152 .if (.strat (Arg, 0) = '#')
2159 <sect1><tt>.STRING</tt><label id=".STRING"><p>
2161 Builtin function. The function accepts an argument in braces and converts
2162 this argument into a string constant. The argument may be an identifier, or
2163 a constant numeric value.
2165 Since you can use a string in the first place, the use of the function may
2166 not be obvious. However, it is useful in macros, or more complex setups.
2171 ; Emulate other assemblers:
2173 .segment .string(name)
2178 <sect1><tt>.STRLEN</tt><label id=".STRLEN"><p>
2180 Builtin function. The function accepts a string argument in braces and
2181 eveluates to the length of the string.
2185 The following macro encodes a string as a pascal style string with
2186 a leading length byte.
2190 .byte .strlen(Arg), Arg
2195 <sect1><tt>.TCOUNT</tt><label id=".TCOUNT"><p>
2197 Builtin function. The function accepts a token list in braces. The
2198 function result is the number of tokens given as argument.
2202 The <tt/ldax/ macro accepts the '#' token to denote immidiate addressing (as
2203 with the normal 6502 instructions). To translate it into two separate 8 bit
2204 load instructions, the '#' token has to get stripped from the argument:
2208 .if (.match (.mid (0, 1, arg), #))
2209 ; ldax called with immidiate operand
2210 lda #<(.right (.tcount (arg)-1, arg))
2211 ldx #>(.right (.tcount (arg)-1, arg))
2219 <sect1><tt>.TIME</tt><label id=".TIME"><p>
2221 Reading this pseudo variable will give a constant integer value that
2222 represents the current time in POSIX standard (as seconds since the
2225 It may be used to encode the time of translation somewhere in the created
2231 .dword .time ; Place time here
2235 <sect1><tt>.WARNING</tt><label id=".WARNING"><p>
2237 Force an assembly warning. The assembler will output a warning message
2238 preceeded by "User warning". This warning will always be output, even if
2239 other warnings are disabled with the <tt><ref id="option-W" name="-W0"></tt>
2240 command line option.
2242 This command may be used to output possible problems when assembling
2251 .warning "Forward jump in jne, cannot optimize!"
2261 See also the <tt><ref id=".ERROR" name=".ERROR"></tt> and <tt><ref id=".OUT"
2262 name=".OUT"></tt> directives.
2265 <sect1><tt>.WORD</tt><label id=".WORD"><p>
2267 Define word sized data. Must be followed by a sequence of (word ranged,
2268 but not necessarily constant) expressions.
2273 .word $0D00, $AF13, _Clear
2277 <sect1><tt>.XMATCH</tt><label id=".XMATCH"><p>
2279 Builtin function. Matches two token lists against each other. This is
2280 most useful within macros, since macros are not stored as strings, but
2286 .XMATCH(<token list #1>, <token list #2>)
2289 Both token list may contain arbitrary tokens with the exception of the
2290 terminator token (comma resp. right parenthesis) and
2297 Often a macro parameter is used for any of the token lists.
2299 The function compares tokens <em/and/ token values. If you need a function
2300 that just compares the type of tokens, have a look at the <tt><ref
2301 id=".MATCH" name=".MATCH"></tt> function.
2303 See: <tt><ref id=".MATCH" name=".MATCH"></tt>
2306 <sect1><tt>.ZEROPAGE</tt><label id=".ZEROPAGE"><p>
2308 Switch to the ZEROPAGE segment and mark it as direct (zeropage) segment.
2309 The name of the ZEROPAGE segment is always "ZEROPAGE", so this is a
2313 .segment "ZEROPAGE", zeropage
2316 Because of the "zeropage" attribute, labels declared in this segment are
2317 addressed using direct addressing mode if possible. You <em/must/ instruct
2318 the linker to place this segment somewhere in the address range 0..$FF
2319 otherwise you will get errors.
2321 See: <tt><ref id=".SEGMENT" name=".SEGMENT"></tt>
2325 <sect>Macros<label id="macros"><p>
2328 <sect1>Introduction<p>
2330 Macros may be thought of as "parametrized super instructions". Macros are
2331 sequences of tokens that have a name. If that name is used in the source
2332 file, the macro is "expanded", that is, it is replaced by the tokens that
2333 were specified when the macro was defined.
2336 <sect1>Macros without parameters<p>
2338 In it's simplest form, a macro does not have parameters. Here's an
2342 .macro asr ; Arithmetic shift right
2343 cmp #$80 ; Put bit 7 into carry
2344 ror ; Rotate right with carry
2348 The macro above consists of two real instructions, that are inserted into
2349 the code, whenever the macro is expanded. Macro expansion is simply done
2350 by using the name, like this:
2359 <sect1>Parametrized macros<p>
2361 When using macro parameters, macros can be even more useful:
2375 When calling the macro, you may give a parameter, and each occurence of
2376 the name "addr" in the macro definition will be replaced by the given
2395 A macro may have more than one parameter, in this case, the parameters
2396 are separated by commas. You are free to give less parameters than the
2397 macro actually takes in the definition. You may also leave intermediate
2398 parameters empty. Empty parameters are replaced by empty space (that is,
2399 they are removed when the macro is exanded). If you have a look at our
2400 macro definition above, you will see, that replacing the "addr" parameter
2401 by nothing will lead to wrong code in most lines. To help you, writing
2402 macros with a variable parameter list, there are some control commands:
2404 <tt><ref id=".IFBLANK" name=".IFBLANK"></tt> tests the rest of the line and
2405 returns true, if there are any tokens on the remainder of the line. Since
2406 empty parameters are replaced by nothing, this may be used to test if a given
2407 parameter is empty. <tt><ref id=".IFNBLANK" name=".IFNBLANK"></tt> tests the
2410 Look at this example:
2413 .macro ldaxy a, x, y
2426 This macro may be called as follows:
2429 ldaxy 1, 2, 3 ; Load all three registers
2431 ldaxy 1, , 3 ; Load only a and y
2433 ldaxy , , 3 ; Load y only
2436 There's another helper command for determining, which macro parameters are
2437 valid: <tt><ref id=".PARAMCOUNT" name=".PARAMCOUNT"></tt> This command is
2438 replaced by the parameter count given, <em/including/ intermediate empty macro
2442 ldaxy 1 ; .PARAMCOUNT = 1
2443 ldaxy 1,,3 ; .PARAMCOUNT = 3
2444 ldaxy 1,2 ; .PARAMCOUNT = 2
2445 ldaxy 1, ; .PARAMCOUNT = 2
2446 ldaxy 1,2,3 ; .PARAMCOUNT = 3
2450 <sect1>Recursive macros<p>
2452 Macros may be used recursively:
2455 .macro push r1, r2, r3
2464 There's also a special macro to help writing recursive macros: <tt><ref
2465 id=".EXITMACRO" name=".EXITMACRO"></tt> This command will stop macro expansion
2469 .macro push r1, r2, r3, r4, r5, r6, r7
2471 ; First parameter is empty
2477 push r2, r3, r4, r5, r6, r7
2481 When expanding this macro, the expansion will push all given parameters
2482 until an empty one is encountered. The macro may be called like this:
2485 push $20, $21, $32 ; Push 3 ZP locations
2486 push $21 ; Push one ZP location
2490 <sect1>Local symbols inside macros<p>
2492 Now, with recursive macros, <tt><ref id=".IFBLANK" name=".IFBLANK"></tt> and
2493 <tt><ref id=".PARAMCOUNT" name=".PARAMCOUNT"></tt>, what else do you need?
2494 Have a look at the inc16 macro above. Here is it again:
2508 If you have a closer look at the code, you will notice, that it could be
2509 written more efficiently, like this:
2520 But imagine what happens, if you use this macro twice? Since the label
2521 "Skip" has the same name both times, you get a "duplicate symbol" error.
2522 Without a way to circumvent this problem, macros are not as useful, as
2523 they could be. One solution is, to start a new lexical block inside the
2537 Now the label is local to the block and not visible outside. However,
2538 sometimes you want a label inside the macro to be visible outside. To make
2539 that possible, there's a new command that's only usable inside a macro
2540 definition: <tt><ref id=".LOCAL" name=".LOCAL"></tt>. <tt/.LOCAL/ declares one
2541 or more symbols as local to the macro expansion. The names of local variables
2542 are replaced by a unique name in each separate macro expansion. So we could
2543 also solve the problem above by using <tt/.LOCAL/:
2547 .local Skip ; Make Skip a local symbol
2554 Skip: ; Not visible outside
2559 <sect1>C style macros<p>
2561 Starting with version 2.5 of the assembler, there is a second macro type
2562 available: C style macros using the <tt/.DEFINE/ directive. These macros are
2563 similar to the classic macro type described above, but behaviour is sometimes
2568 <item> Macros defined with <tt><ref id=".DEFINE" name=".DEFINE"></tt> may not
2569 span more than a line. You may use line continuation (see <tt><ref
2570 id=".LINECONT" name=".LINECONT"></tt>) to spread the definition over
2571 more than one line for increased readability, but the macro itself
2572 may not contain an end-of-line token.
2574 <item> Macros defined with <tt><ref id=".DEFINE" name=".DEFINE"></tt> share
2575 the name space with classic macros, but they are detected and replaced
2576 at the scanner level. While classic macros may be used in every place,
2577 where a mnemonic or other directive is allowed, <tt><ref id=".DEFINE"
2578 name=".DEFINE"></tt> style macros are allowed anywhere in a line. So
2579 they are more versatile in some situations.
2581 <item> <tt><ref id=".DEFINE" name=".DEFINE"></tt> style macros may take
2582 parameters. While classic macros may have empty parameters, this is
2583 not true for <tt><ref id=".DEFINE" name=".DEFINE"></tt> style macros.
2584 For this macro type, the number of actual parameters must match
2585 exactly the number of formal parameters.
2587 To make this possible, formal parameters are enclosed in braces when
2588 defining the macro. If there are no parameters, the empty braces may
2591 <item> Since <tt><ref id=".DEFINE" name=".DEFINE"></tt> style macros may not
2592 contain end-of-line tokens, there are things that cannot be done. They
2593 may not contain several processor instructions for example. So, while
2594 some things may be done with both macro types, each type has special
2595 usages. The types complement each other.
2599 Let's look at a few examples to make the advantages and disadvantages
2602 To emulate assemblers that use "<tt/EQU/" instead of "<tt/=/" you may use the
2603 following <tt/.DEFINE/:
2608 foo EQU $1234 ; This is accepted now
2611 You may use the directive to define string constants used elsewhere:
2614 ; Define the version number
2615 .define VERSION "12.3a"
2621 Macros with parameters may also be useful:
2624 .define DEBUG(message) .out message
2626 DEBUG "Assembling include file #3"
2629 Note that, while formal parameters have to be placed in braces, this is
2630 not true for the actual parameters. Beware: Since the assembler cannot
2631 detect the end of one parameter, only the first token is used. If you
2632 don't like that, use classic macros instead:
2640 (This is an example where a problem can be solved with both macro types).
2643 <sect1>Characters in macros<p>
2645 When using the <ref id="option-t" name="-t"> option, characters are translated
2646 into the target character set of the specific machine. However, this happens
2647 as late as possible. This means that strings are translated if they are part
2648 of a <tt><ref id=".BYTE" name=".BYTE"></tt> or <tt><ref id=".ASCIIZ"
2649 name=".ASCIIZ"></tt> command. Characters are translated as soon as they are
2650 used as part of an expression.
2652 This behaviour is very intuitive outside of macros but may be confusing when
2653 doing more complex macros. If you compare characters against numeric values,
2654 be sure to take the translation into account.
2659 <sect>Macro packages<label id="macropackages"><p>
2661 Using the <tt><ref id=".MACPACK" name=".MACPACK"></tt> directive, predefined
2662 macro packages may be included with just one command. Available macro packages
2666 <sect1><tt>.MACPACK generic</tt><p>
2668 This macro package defines macros that are useful in almost any program.
2669 Currently, two macros are defined:
2684 <sect1><tt>.MACPACK longbranch</tt><p>
2686 This macro package defines long conditional jumps. They are named like the
2687 short counterpart but with the 'b' replaced by a 'j'. Here is a sample
2688 definition for the "<tt/jeq/" macro, the other macros are built using the same
2693 .if .def(Target) .and ((*+2)-(Target) <= 127)
2702 All macros expand to a short branch, if the label is already defined (back
2703 jump) and is reachable with a short jump. Otherwise the macro expands to a
2704 conditional branch with the branch condition inverted, followed by an absolute
2705 jump to the actual branch target.
2707 The package defines the following macros:
2710 jeq, jne, jmi, jpl, jcs, jcc, jvs, jvc
2715 <sect>Module constructors/destructors<label id="condes"><p>
2717 <em>Note:</em> This section applies mostly to C programs, so the explanation
2718 below uses examples from the C libraries. However, the feature may also be
2719 useful for assembler programs.
2722 <sect1>Module overview<p>
2724 Using the <tt><ref id=".CONSTRUCTOR" name=".CONSTRUCTOR"></tt> and <tt><ref
2725 id=".DESTRUCTOR" name=".DESTRUCTOR"></tt> keywords it it possible to export
2726 functions in a special way. The linker is able to generate tables with all
2727 functions of a specific type. Such a table will <em>only</em> include symbols
2728 from object files that are linked into a specific executable. This may be used
2729 to add initialization and cleanup code for library modules.
2731 The C heap functions are an example where module initialization code is used.
2732 All heap functions (<tt>malloc</tt>, <tt>free</tt>, ...) work with a few
2733 variables that contain the start and the end of the heap, pointers to the free
2734 list and so on. Since the end of the heap depends on the size and start of the
2735 stack, it must be initialized at runtime. However, initializing these
2736 variables for programs that do not use the heap are a waste of time and
2739 So the central module defines a function that contains initialization code and
2740 exports this function using the <tt/.CONSTRUCTOR/ statement. If (and only if)
2741 this module is added to an executable by the linker, the initialization
2742 function will be placed into the table of constructors by the linker. The C
2743 startup code will call all constructors before <tt/main/ and all destructors
2744 after <tt/main/, so without any further work, the heap initialization code is
2745 called once the module is linked in.
2747 While it would be possible to add explicit calls to initialization functions
2748 in the startup code, the new approach has several advantages:
2752 If a module is not included, the initialization code is not linked in and not
2753 called. So you don't pay for things you don't need.
2756 Adding another library that needs initialization does not mean that the
2757 startup code has to be changed. Before we had module constructors and
2758 destructors, the startup code for all systems had to be adjusted to call the
2759 new initialization code.
2762 The feature saves memory: Each additional initialization function needs just
2763 two bytes in the table (a pointer to the function).
2770 When creating and using module constructors and destructors, please take care
2776 The linker will only generate function tables, it will not generate code to
2777 call these functions. If you're using the feature in some other than the
2778 existing C environments, you have to write code to call all functions in a
2779 linker generated table yourself. See the <tt>condes</tt> module in the C
2780 runtime for an example on how to do this.
2783 The linker will only add addresses of functions that are in modules linked to
2784 the executable. This means that you have to be careful where to place the
2785 condes functions. If initialization is needed for a group of functions, be
2786 sure to place the initialization function into a module that is linked in
2787 regardless of which function is called by the user.
2790 The linker will generate the tables only when requested to do so by the
2791 <tt/FEATURE CONDES/ statement in the linker config file. Each table has to
2792 be requested separately.
2795 Constructors and destructors may have priorities. These priorities determine
2796 the order of the functions in the table. If your intialization or cleanup code
2797 does depend on other initialization or cleanup code, you have to choose the
2798 priority for the functions accordingly.
2801 Besides the <tt><ref id=".CONSTRUCTOR" name=".CONSTRUCTOR"></tt> and <tt><ref
2802 id=".DESTRUCTOR" name=".DESTRUCTOR"></tt> statements, there is also a more
2803 generic command: <tt><ref id=".CONDES" name=".CONDES"></tt>. This allows to
2804 specify an additional type. Predefined types are 0 (constructor) and 1
2805 (destructor). The linker generates a separate table for each type on request.
2813 <sect>Bugs/Feedback<p>
2815 If you have problems using the assembler, if you find any bugs, or if
2816 you're doing something interesting with the assembler, I would be glad to
2817 hear from you. Feel free to contact me by email
2818 (<htmlurl url="mailto:uz@cc65.org" name="uz@cc65.org">).
2824 ca65 (and all cc65 binutils) are (C) Copyright 1998-2001 Ullrich von
2825 Bassewitz. For usage of the binaries and/or sources the following
2826 conditions do apply:
2828 This software is provided 'as-is', without any expressed or implied
2829 warranty. In no event will the authors be held liable for any damages
2830 arising from the use of this software.
2832 Permission is granted to anyone to use this software for any purpose,
2833 including commercial applications, and to alter it and redistribute it
2834 freely, subject to the following restrictions:
2837 <item> The origin of this software must not be misrepresented; you must not
2838 claim that you wrote the original software. If you use this software
2839 in a product, an acknowledgment in the product documentation would be
2840 appreciated but is not required.
2841 <item> Altered source versions must be plainly marked as such, and must not
2842 be misrepresented as being the original software.
2843 <item> This notice may not be removed or altered from any source
projects / cc65 / blob