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>.ASSERT</tt><label id=".ASSERT"><p>
694 Add an assertion. The command is followed by an expression, an action
695 specifier and a message that is output in case the assertion fails. The
696 action specifier may be one of <tt/warning/ or <tt/error/. The assertion
697 is passed to the linker and will be evaluated when segment placement has
703 .assert * = $8000, error, "Code not at $8000"
706 The example assertion will check that the current location is at $8000,
707 when the output file is written, and abort with an error if this is not
708 the case. More complex expressions are possible. The action specifier
709 <tt/warning/ outputs a warning, while the <tt/error/ specifier outputs
710 an error message. In the latter case, generation if the output file is
714 <sect1><tt>.AUTOIMPORT</tt><label id=".AUTOIMPORT"><p>
716 Is followed by a plus or a minus character. When switched on (using a
717 +), undefined symbols are automatically marked as import instead of
718 giving errors. When switched off (which is the default so this does not
719 make much sense), this does not happen and an error message is
720 displayed. The state of the autoimport flag is evaluated when the
721 complete source was translated, before outputing actual code, so it is
722 <em/not/ possible to switch this feature on or off for separate sections
723 of code. The last setting is used for all symbols.
725 You should probably not use this switch because it delays error
726 messages about undefined symbols until the link stage. The cc65
727 compiler (which is supposed to produce correct assembler code in all
728 circumstances, something which is not true for most assembler
729 programmers) will insert this command to avoid importing each and every
730 routine from the runtime library.
735 .autoimport + ; Switch on auto import
739 <sect1><tt>.BLANK</tt><label id=".BLANK"><p>
741 Builtin function. The function evaluates its argument in braces and
742 yields "false" if the argument is non blank (there is an argument), and
743 "true" if there is no argument. As an example, the <tt/.IFBLANK/ statement
751 <sect1><tt>.BSS</tt><label id=".BSS"><p>
753 Switch to the BSS segment. The name of the BSS segment is always "BSS",
754 so this is a shortcut for
760 See also the <tt><ref id=".SEGMENT" name=".SEGMENT"></tt> command.
763 <sect1><tt>.BYT, .BYTE</tt><label id=".BYTE"><p>
765 Define byte sized data. Must be followed by a sequence of (byte ranged)
766 expressions or strings.
772 .byt "world", $0D, $00
776 <sect1><tt>.CASE</tt><label id=".CASE"><p>
778 Switch on or off case sensitivity on identifiers. The default is off
779 (that is, identifiers are case sensitive), but may be changed by the
780 -i switch on the command line.
781 The command must be followed by a '+' or '-' character to switch the
782 option on or off respectively.
787 .case - ; Identifiers are not case sensitive
791 <sect1><tt>.CHARMAP</tt><label id=".CHARMAP"><p>
793 Apply a custom mapping for characters. The command is followed by two
794 numbers in the range 1..255. The first one is the index of the source
795 character, the second one is the mapping. The mapping applies to all
796 character and string constants when they generate output, and overrides
797 a mapping table specified with the <tt><ref id="option-t" name="-t"></tt>
803 .charmap $41, $61 ; Map 'A' to 'a'
807 <sect1><tt>.CODE</tt><label id=".CODE"><p>
809 Switch to the CODE segment. The name of the CODE segment is always
810 "CODE", so this is a shortcut for
816 See also the <tt><ref id=".SEGMENT" name=".SEGMENT"></tt> command.
819 <sect1><tt>.CONDES</tt><label id=".CONDES"><p>
821 Export a symbol and mark it in a special way. The linker is able to build
822 tables of all such symbols. This may be used to automatically create a list
823 of functions needed to initialize linked library modules.
825 Note: The linker has a feature to build a table of marked routines, but it
826 is your code that must call these routines, so just declaring a symbol with
827 <tt/.CONDES/ does nothing by itself.
829 All symbols are exported as an absolute (16 bit) symbol. You don't need to
830 use an additional <tt><ref id=".EXPORT" name=".EXPORT"></tt> statement, this
831 is implied by <tt/.CONDES/.
833 <tt/.CONDES/ is followed by the type, which may be <tt/constructor/,
834 <tt/destructor/ or a numeric value between 0 and 6 (where 0 is the same as
835 specifiying <tt/constructor/ and 1 is equal to specifying <tt/destructor/).
836 The <tt><ref id=".CONSTRUCTOR" name=".CONSTRUCTOR"></tt> and <tt><ref
837 id=".DESTRUCTOR" name=".DESTRUCTOR"></tt> commands are actually shortcuts
838 for <tt/.CONDES/ with a type of <tt/constructor/ resp. <tt/destructor/.
840 After the type, an optional priority may be specified. If no priority is
841 given, the default priority of 7 is used. Be careful when assigning
842 priorities to your own module constructors so they won't interfere with the
843 ones in the cc65 library.
848 .condes ModuleInit, constructor
849 .condes ModInit, 0, 16
852 See the <tt><ref id=".CONSTRUCTOR" name=".CONSTRUCTOR"></tt> and <tt><ref
853 id=".DESTRUCTOR" name=".DESTRUCTOR"></tt> commands and the separate section
854 <ref id="condes" name="Module constructors/destructors"> explaining the
855 feature in more detail.
858 <sect1><tt>.CONCAT</tt><label id=".CONCAT"><p>
860 Builtin function. The function allows to concatenate a list of string
861 constants separated by commas. The result is a string constant that
862 is the concatentation of all arguments. This function is most useful
863 in macros and when used together with the <tt/.STRING/ builtin function.
864 The function may be used in any case where a string constant is
870 .include .concat ("myheader", ".", "inc")
873 This is the same as the command
876 .include "myheader.inc"
880 <sect1><tt>.CONST</tt><label id=".CONST"><p>
882 Builtin function. The function evaluates its argument in braces and
883 yields "true" if the argument is a constant expression (that is, an
884 expression that yields a constant value at assembly time) and "false"
885 otherwise. As an example, the .IFCONST statement may be replaced by
892 <sect1><tt>.CONSTRUCTOR</tt><label id=".CONSTRUCTOR"><p>
894 Export a symbol and mark it as a module constructor. This may be used
895 together with the linker to build a table of constructor subroutines that
896 are called by the startup code.
898 Note: The linker has a feature to build a table of marked routines, but it
899 is your code that must call these routines, so just declaring a symbol as
900 constructor does nothing by itself.
902 A constructor is always exported as an absolute (16 bit) symbol. You don't
903 need to use an additional <tt/.export/ statement, this is implied by
904 <tt/.constructor/. It may have an optional priority that is separated by a
905 comma. If no priority is given, the default priority of 7 is used. Be
906 careful when assigning priorities to your own module constructors so they
907 won't interfere with the ones in the cc65 library.
912 .constructor ModuleInit
913 .constructor ModInit, 16
916 See the <tt><ref id=".CONDES" name=".CONDES"></tt> and <tt><ref
917 id=".DESTRUCTOR" name=".DESTRUCTOR"></tt> commands and the separate section
918 <ref id="condes" name="Module constructors/destructors"> explaining the
919 feature in more detail.
922 <sect1><tt>.CPU</tt><label id=".CPU"><p>
924 Reading this pseudo variable will give a constant integer value that
925 tells which instruction set is currently enabled. Possible values are:
934 It may be used to replace the .IFPxx pseudo instructions or to construct
935 even more complex expressions.
940 .if (.cpu = 0) .or (.cpu = 1)
952 <sect1><tt>.DATA</tt><label id=".DATA"><p>
954 Switch to the DATA segment. The name of the DATA segment is always
955 "DATA", so this is a shortcut for
961 See also the <tt><ref id=".SEGMENT" name=".SEGMENT"></tt> command.
964 <sect1><tt>.DBYT</tt><label id=".DBYT"><p>
966 Define word sized data with the hi and lo bytes swapped (use <tt/.WORD/ to
967 create word sized data in native 65XX format). Must be followed by a
968 sequence of (word ranged) expressions.
976 This will emit the bytes
982 into the current segment in that order.
985 <sect1><tt>.DEBUGINFO</tt><label id=".DEBUGINFO"><p>
987 Switch on or off debug info generation. The default is off (that is,
988 the object file will not contain debug infos), but may be changed by the
989 -g switch on the command line.
990 The command must be followed by a '+' or '-' character to switch the
991 option on or off respectively.
996 .debuginfo + ; Generate debug info
1000 <sect1><tt>.DEFINE</tt><label id=".DEFINE"><p>
1002 Start a define style macro definition. The command is followed by an
1003 identifier (the macro name) and optionally by a list of formal arguments
1005 See section <ref id="macros" name="Macros">.
1008 <sect1><tt>.DEF, .DEFINED</tt><label id=".DEFINED"><p>
1010 Builtin function. The function expects an identifier as argument in braces.
1011 The argument is evaluated, and the function yields "true" if the identifier
1012 is a symbol that is already defined somewhere in the source file up to the
1013 current position. Otherwise the function yields false. As an example, the
1014 <tt><ref id=".IFDEF" name=".IFDEF"></tt> statement may be replaced by
1021 <sect1><tt>.DESTRUCTOR</tt><label id=".DESTRUCTOR"><p>
1023 Export a symbol and mark it as a module destructor. This may be used
1024 together with the linker to build a table of destructor subroutines that
1025 are called by the startup code.
1027 Note: The linker has a feature to build a table of marked routines, but it
1028 is your code that must call these routines, so just declaring a symbol as
1029 constructor does nothing by itself.
1031 A destructor is always exported as an absolute (16 bit) symbol. You don't
1032 need to use an additional <tt/.export/ statement, this is implied by
1033 <tt/.destructor/. It may have an optional priority that is separated by a
1034 comma. If no priority is given, the default priority of 7 is used. Be
1035 careful when assigning priorities to your own module destructors so they
1036 won't interfere with the ones in the cc65 library.
1041 .destructor ModuleDone
1042 .destructor ModDone, 16
1045 See the <tt><ref id=".CONDES" name=".CONDES"></tt> and <tt><ref
1046 id=".CONSTRUCTOR" name=".CONSTRUCTOR"></tt> commands and the separate
1047 section <ref id="condes" name="Module constructors/destructors"> explaining
1048 the feature in more detail.
1051 <sect1><tt>.DWORD</tt><label id=".DWORD"><p>
1053 Define dword sized data (4 bytes) Must be followed by a sequence of
1059 .dword $12344512, $12FA489
1063 <sect1><tt>.ELSE</tt><label id=".ELSE"><p>
1065 Conditional assembly: Reverse the current condition.
1068 <sect1><tt>.ELSEIF</tt><label id=".ELSEIF"><p>
1070 Conditional assembly: Reverse current condition and test a new one.
1073 <sect1><tt>.END</tt><label id=".END"><p>
1075 Forced end of assembly. Assembly stops at this point, even if the command
1076 is read from an include file.
1079 <sect1><tt>.ENDIF</tt><label id=".ENDIF"><p>
1081 Conditional assembly: Close a <tt><ref id=".IF" name=".IF..."></tt> or
1082 <tt><ref id=".ELSE" name=".ELSE"></tt> branch.
1085 <sect1><tt>.ENDMAC, .ENDMACRO</tt><label id=".ENDMACRO"><p>
1087 End of macro definition (see section <ref id="macros" name="Macros">).
1090 <sect1><tt>.ENDPROC</tt><label id=".ENDPROC"><p>
1092 End of local lexical level (see <tt><ref id=".PROC" name=".PROC"></tt>).
1095 <sect1><tt>.ENDREP, .ENDREPEAT</tt><label id=".ENDREPEAT"><p>
1097 End a <tt><ref id=".REPEAT" name=".REPEAT"></tt> block.
1100 <sect1><tt>.ERROR</tt><label id=".ERROR"><p>
1102 Force an assembly error. The assembler will output an error message
1103 preceeded by "User error" and will <em/not/ produce an object file.
1105 This command may be used to check for initial conditions that must be
1106 set before assembling a source file.
1116 .error "Must define foo or bar!"
1120 See also the <tt><ref id=".WARNING" name=".WARNING"></tt> and <tt><ref
1121 id=".OUT" name=".OUT"></tt> directives.
1124 <sect1><tt>.EXITMAC, .EXITMACRO</tt><label id=".EXITMACRO"><p>
1126 Abort a macro expansion immidiately. This command is often useful in
1127 recursive macros. See separate section <ref id="macros" name="Macros">.
1130 <sect1><tt>.EXPORT</tt><label id=".EXPORT"><p>
1132 Make symbols accessible from other modules. Must be followed by a comma
1133 separated list of symbols to export.
1141 See: <tt><ref id=".EXPORTZP" name=".EXPORTZP"></tt>
1144 <sect1><tt>.EXPORTZP</tt><label id=".EXPORTZP"><p>
1146 Make symbols accessible from other modules. Must be followed by a comma
1147 separated list of symbols to export. The exported symbols are explicitly
1148 marked as zero page symols.
1156 See: <tt><ref id=".EXPORT" name=".EXPORT"></tt>
1159 <sect1><tt>.FARADDR</tt><label id=".FARADDR"><p>
1161 Define far (24 bit) address data. The command must be followed by a
1162 sequence of (not necessarily constant) expressions.
1167 .faraddr DrawCircle, DrawRectangle, DrawHexagon
1170 See: <tt><ref id=".ADDR" name=".ADDR"></tt>
1173 <sect1><tt>.FEATURE</tt><label id=".FEATURE"><p>
1175 This directive may be used to enable one or more compatibility features
1176 of the assembler. While the use of <tt/.FEATURE/ should be avoided when
1177 possible, it may be useful when porting sources written for other
1178 assemblers. There is no way to switch a feature off, once you have
1179 enabled it, so using
1185 will enable the feature until end of assembly is reached.
1187 The following features are available:
1191 <tag><tt>dollar_is_pc</tt></tag>
1193 The dollar sign may be used as an alias for the star (`*'), which
1194 gives the value of the current PC in expressions.
1195 Note: Assignment to the pseudo variable is not allowed.
1197 <tag><tt>labels_without_colons</tt></tag>
1199 Allow labels without a trailing colon. These labels are only accepted,
1200 if they start at the beginning of a line (no leading white space).
1202 <tag><tt>loose_string_term</tt></tag>
1204 Accept single quotes as well as double quotes as terminators for string
1207 <tag><tt>loose_char_term</tt></tag>
1209 Accept single quotes as well as double quotes as terminators for char
1212 <tag><tt>at_in_identifiers</tt></tag>
1214 Accept the at character (`@') as a valid character in identifiers. The
1215 at character is not allowed to start an identifier, even with this
1218 <tag><tt>dollar_in_identifiers</tt></tag>
1220 Accept the dollar sign (`$') as a valid character in identifiers. The
1221 at character is not allowed to start an identifier, even with this
1224 <tag><tt>leading_dot_in_identifiers</tt></tag>
1226 Accept the dot (`.') as the first character of an identifier. This may be
1227 used for example to create macro names that start with a dot emulating
1228 control directives of other assemblers. Note however, that none of the
1229 reserved keywords built into the assembler, that starts with a dot, may be
1230 overridden. When using this feature, you may also get into trouble if
1231 later versions of the assembler define new keywords starting with a dot.
1233 <tag><tt>pc_assignment</tt></tag>
1235 Allow assignments to the PC symbol (`*' or `$' if <tt/dollar_is_pc/
1236 is enabled). Such an assignment is handled identical to the <tt><ref
1237 id=".ORG" name=".ORG"></tt> command (which is usually not needed, so just
1238 removing the lines with the assignments may also be an option when porting
1239 code written for older assemblers).
1243 It is also possible to specify features on the command line using the
1244 <tt><ref id="option--feature" name="--feature"></tt> command line option.
1245 This is useful when translating sources written for older assemblers, when
1246 you don't want to change the source code.
1248 As an example, to translate sources written for Andre Fachats xa65
1249 assembler, the features
1252 labels_without_colons, pc_assignment, loose_char_term
1255 may be helpful. They do not make ca65 completely compatible, so you may not
1256 be able to translate the sources without changes, even when enabling these
1257 features. However, I have found several sources that translate without
1258 problems when enabling these features on the command line.
1261 <sect1><tt>.FILEOPT, .FOPT</tt><label id=".FOPT"><p>
1263 Insert an option string into the object file. There are two forms of
1264 this command, one specifies the option by a keyword, the second
1265 specifies it as a number. Since usage of the second one needs knowledge
1266 of the internal encoding, its use is not recommended and I will only
1267 describe the first form here.
1269 The command is followed by one of the keywords
1277 a comma and a string. The option is written into the object file
1278 together with the string value. This is currently unidirectional and
1279 there is no way to actually use these options once they are in the
1285 .fileopt comment, "Code stolen from my brother"
1286 .fileopt compiler, "BASIC 2.0"
1287 .fopt author, "J. R. User"
1291 <sect1><tt>.FORCEIMPORT</tt><label id=".FORCEIMPORT"><p>
1293 Import an absolute symbol from another module. The command is followed by a
1294 comma separated list of symbols to import. The command is similar to <tt>
1295 <ref id=".IMPORT" name=".IMPORT"></tt>, but the import reference is always
1296 written to the generated object file, even if the symbol is never referenced
1297 (<tt><ref id=".IMPORT" name=".IMPORT"></tt> will not generate import
1298 references for unused symbols).
1303 .forceimport needthisone, needthistoo
1306 See: <tt><ref id=".IMPORT" name=".IMPORT"></tt>
1309 <sect1><tt>.GLOBAL</tt><label id=".GLOBAL"><p>
1311 Declare symbols as global. Must be followed by a comma separated list of
1312 symbols to declare. Symbols from the list, that are defined somewhere in the
1313 source, are exported, all others are imported. Additional <tt><ref
1314 id=".IMPORT" name=".IMPORT"></tt> or <tt><ref id=".EXPORT"
1315 name=".EXPORT"></tt> commands for the same symbol are allowed.
1324 <sect1><tt>.GLOBALZP</tt><label id=".GLOBALZP"><p>
1326 Declare symbols as global. Must be followed by a comma separated list of
1327 symbols to declare. Symbols from the list, that are defined somewhere in the
1328 source, are exported, all others are imported. Additional <tt><ref
1329 id=".IMPORTZP" name=".IMPORTZP"></tt> or <tt><ref id=".EXPORTZP"
1330 name=".EXPORTZP"></tt> commands for the same symbol are allowed. The symbols
1331 in the list are explicitly marked as zero page symols.
1340 <sect1><tt>.I16</tt><label id=".I16"><p>
1342 Valid only in 65816 mode. Switch the index registers to 16 bit.
1344 Note: This command will not emit any code, it will tell the assembler to
1345 create 16 bit operands for immediate operands.
1347 See also the <tt><ref id=".I8" name=".I8"></tt> and <tt><ref id=".SMART"
1348 name=".SMART"></tt> commands.
1351 <sect1><tt>.I8</tt><label id=".I8"><p>
1353 Valid only in 65816 mode. Switch the index registers to 8 bit.
1355 Note: This command will not emit any code, it will tell the assembler to
1356 create 8 bit operands for immediate operands.
1358 See also the <tt><ref id=".I16" name=".I16"></tt> and <tt><ref id=".SMART"
1359 name=".SMART"></tt> commands.
1362 <sect1><tt>.IF</tt><label id=".IF"><p>
1364 Conditional assembly: Evalute an expression and switch assembler output
1365 on or off depending on the expression. The expression must be a constant
1366 expression, that is, all operands must be defined.
1368 A expression value of zero evaluates to FALSE, any other value evaluates
1372 <sect1><tt>.IFBLANK</tt><label id=".IFBLANK"><p>
1374 Conditional assembly: Check if there are any remaining tokens in this line,
1375 and evaluate to FALSE if this is the case, and to TRUE otherwise. If the
1376 condition is not true, further lines are not assembled until an <tt><ref
1377 id=".ELSE" name=".ESLE"></tt>, <tt><ref id=".ELSEIF" name=".ELSEIF"></tt> or
1378 <tt><ref id=".ENDIF" name=".ENDIF"></tt> directive.
1380 This command is often used to check if a macro parameter was given. Since an
1381 empty macro parameter will evaluate to nothing, the condition will evaluate
1382 to FALSE if an empty parameter was given.
1396 See also: <tt><ref id=".BLANK" name=".BLANK"></tt>
1399 <sect1><tt>.IFCONST</tt><label id=".IFCONST"><p>
1401 Conditional assembly: Evaluate an expression and switch assembler output
1402 on or off depending on the constness of the expression.
1404 A const expression evaluates to to TRUE, a non const expression (one
1405 containing an imported or currently undefined symbol) evaluates to
1408 See also: <tt><ref id=".CONST" name=".CONST"></tt>
1411 <sect1><tt>.IFDEF</tt><label id=".IFDEF"><p>
1413 Conditional assembly: Check if a symbol is defined. Must be followed by
1414 a symbol name. The condition is true if the the given symbol is already
1415 defined, and false otherwise.
1417 See also: <tt><ref id=".DEFINED" name=".DEFINED"></tt>
1420 <sect1><tt>.IFNBLANK</tt><label id=".IFNBLANK"><p>
1422 Conditional assembly: Check if there are any remaining tokens in this line,
1423 and evaluate to TRUE if this is the case, and to FALSE otherwise. If the
1424 condition is not true, further lines are not assembled until an <tt><ref
1425 id=".ELSE" name=".ELSE"></tt>, <tt><ref id=".ELSEIF" name=".ELSEIF"></tt> or
1426 <tt><ref id=".ENDIF" name=".ENDIF"></tt> directive.
1428 This command is often used to check if a macro parameter was given.
1429 Since an empty macro parameter will evaluate to nothing, the condition
1430 will evaluate to FALSE if an empty parameter was given.
1443 See also: <tt><ref id=".BLANK" name=".BLANK"></tt>
1446 <sect1><tt>.IFNDEF</tt><label id=".IFNDEF"><p>
1448 Conditional assembly: Check if a symbol is defined. Must be followed by
1449 a symbol name. The condition is true if the the given symbol is not
1450 defined, and false otherwise.
1452 See also: <tt><ref id=".DEFINED" name=".DEFINED"></tt>
1455 <sect1><tt>.IFNREF</tt><label id=".IFNREF"><p>
1457 Conditional assembly: Check if a symbol is referenced. Must be followed
1458 by a symbol name. The condition is true if if the the given symbol was
1459 not referenced before, and false otherwise.
1461 See also: <tt><ref id=".REFERENCED" name=".REFERENCED"></tt>
1464 <sect1><tt>.IFP02</tt><label id=".IFP02"><p>
1466 Conditional assembly: Check if the assembler is currently in 6502 mode
1467 (see <tt><ref id=".P02" name=".P02"></tt> command).
1470 <sect1><tt>.IFP816</tt><label id=".IFP816"><p>
1472 Conditional assembly: Check if the assembler is currently in 65816 mode
1473 (see <tt><ref id=".P816" name=".P816"></tt> command).
1476 <sect1><tt>.IFPC02</tt><label id=".IFPC02"><p>
1478 Conditional assembly: Check if the assembler is currently in 65C02 mode
1479 (see <tt><ref id=".PC02" name=".PC02"></tt> command).
1482 <sect1><tt>.IFREF</tt><label id=".IFREF"><p>
1484 Conditional assembly: Check if a symbol is referenced. Must be followed
1485 by a symbol name. The condition is true if if the the given symbol was
1486 referenced before, and false otherwise.
1488 This command may be used to build subroutine libraries in include files
1489 (you may use separate object modules for this purpose too).
1494 .ifref ToHex ; If someone used this subroutine
1495 ToHex: tay ; Define subroutine
1501 See also: <tt><ref id=".REFERENCED" name=".REFERENCED"></tt>
1504 <sect1><tt>.IMPORT</tt><label id=".IMPORT"><p>
1506 Import a symbol from another module. The command is followed by a comma
1507 separated list of symbols to import.
1515 See: <tt><ref id=".IMPORTZP" name=".IMPORTZP"></tt>
1518 <sect1><tt>.IMPORTZP</tt><label id=".IMPORTZP"><p>
1520 Import a symbol from another module. The command is followed by a comma
1521 separated list of symbols to import. The symbols are explicitly imported
1522 as zero page symbols (that is, symbols with values in byte range).
1530 See: <tt><ref id=".IMPORT" name=".IMPORT"></tt>
1533 <sect1><tt>.INCBIN</tt><label id=".INCBIN"><p>
1535 Include a file as binary data. The command expects a string argument
1536 that is the name of a file to include literally in the current segment.
1537 In addition to that, a start offset and a size value may be specified,
1538 separated by commas. If no size is specified, all of the file from the
1539 start offset to end-of-file is used. If no start position is specified
1540 either, zero is assume (which means that the whole file is inserted).
1545 ; Include whole file
1546 .incbin "sprites.dat"
1548 ; Include file starting at offset 256
1549 .incbin "music.dat", $100
1551 ; Read 100 bytes starting at offset 200
1552 .incbin "graphics.dat", 200, 100
1556 <sect1><tt>.INCLUDE</tt><label id=".INCLUDE"><p>
1558 Include another file. Include files may be nested up to a depth of 16.
1567 <sect1><tt>.LEFT</tt><label id=".LEFT"><p>
1569 Builtin function. Extracts the left part of a given token list.
1574 .LEFT (<int expr>, <token list>)
1577 The first integer expression gives the number of tokens to extract from
1578 the token list. The second argument is the token list itself.
1582 To check in a macro if the given argument has a '#' as first token
1583 (immidiate addressing mode), use something like this:
1588 .if (.match (.left (1, arg), #))
1590 ; ldax called with immidiate operand
1598 See also the <tt><ref id=".MID" name=".MID"></tt> and <tt><ref id=".RIGHT"
1599 name=".RIGHT"></tt> builtin functions.
1602 <sect1><tt>.LINECONT</tt><label id=".LINECONT"><p>
1604 Switch on or off line continuations using the backslash character
1605 before a newline. The option is off by default.
1606 Note: Line continuations do not work in a comment. A backslash at the
1607 end of a comment is treated as part of the comment and does not trigger
1609 The command must be followed by a '+' or '-' character to switch the
1610 option on or off respectively.
1615 .linecont + ; Allow line continuations
1618 #$20 ; This is legal now
1622 <sect1><tt>.LIST</tt><label id=".LIST"><p>
1624 Enable output to the listing. The command must be followed by a boolean
1625 switch ("on", "off", "+" or "-") and will enable or disable listing
1627 The option has no effect if the listing is not enabled by the command line
1628 switch -l. If -l is used, an internal counter is set to 1. Lines are output
1629 to the listing file, if the counter is greater than zero, and suppressed if
1630 the counter is zero. Each use of <tt/.LIST/ will increment or decrement the
1636 .list on ; Enable listing output
1640 <sect1><tt>.LISTBYTES</tt><label id=".LISTBYTES"><p>
1642 Set, how many bytes are shown in the listing for one source line. The
1643 default is 12, so the listing will show only the first 12 bytes for any
1644 source line that generates more than 12 bytes of code or data.
1645 The directive needs an argument, which is either "unlimited", or an
1646 integer constant in the range 4..255.
1651 .listbytes unlimited ; List all bytes
1652 .listbytes 12 ; List the first 12 bytes
1653 .incbin "data.bin" ; Include large binary file
1657 <sect1><tt>.LOCAL</tt><label id=".LOCAL"><p>
1659 This command may only be used inside a macro definition. It declares a
1660 list of identifiers as local to the macro expansion.
1662 A problem when using macros are labels: Since they don't change their name,
1663 you get a "duplicate symbol" error if the macro is expanded the second time.
1664 Labels declared with <tt><ref id=".LOCAL" name=".LOCAL"></tt> have their
1665 name mapped to an internal unique name (<tt/___ABCD__/) with each macro
1668 Some other assemblers start a new lexical block inside a macro expansion.
1669 This has some drawbacks however, since that will not allow <em/any/ symbol
1670 to be visible outside a macro, a feature that is sometimes useful. The
1671 <tt><ref id=".LOCAL" name=".LOCAL"></tt> command is in my eyes a better way
1672 to address the problem.
1674 You get an error when using <tt><ref id=".LOCAL" name=".LOCAL"></tt> outside
1678 <sect1><tt>.LOCALCHAR</tt><label id=".LOCALCHAR"><p>
1680 Defines the character that start "cheap" local labels. You may use one
1681 of '@' and '?' as start character. The default is '@'.
1683 Cheap local labels are labels that are visible only between two non
1684 cheap labels. This way you can reuse identifiers like "<tt/loop/" without
1685 using explicit lexical nesting.
1692 Clear: lda #$00 ; Global label
1693 ?Loop: sta Mem,y ; Local label
1697 Sub: ... ; New global label
1698 bne ?Loop ; ERROR: Unknown identifier!
1702 <sect1><tt>.MACPACK</tt><label id=".MACPACK"><p>
1704 Insert a predefined macro package. The command is followed by an
1705 identifier specifying the macro package to insert. Available macro
1709 generic Defines generic macros like add and sub.
1710 longbranch Defines conditional long jump macros.
1713 Including a macro package twice, or including a macro package that
1714 redefines already existing macros will lead to an error.
1719 .macpack longbranch ; Include macro package
1721 cmp #$20 ; Set condition codes
1722 jne Label ; Jump long on condition
1725 Macro packages are explained in more detail in section <ref
1726 id="macropackages" name="Macro packages">.
1729 <sect1><tt>.MAC, .MACRO</tt><label id=".MAC"><p>
1731 Start a classic macro definition. The command is followed by an identifier
1732 (the macro name) and optionally by a comma separated list of identifiers
1733 that are macro parameters.
1735 See section <ref id="macros" name="Macros">.
1738 <sect1><tt>.MATCH</tt><label id=".MATCH"><p>
1740 Builtin function. Matches two token lists against each other. This is
1741 most useful within macros, since macros are not stored as strings, but
1747 .MATCH(<token list #1>, <token list #2>)
1750 Both token list may contain arbitrary tokens with the exception of the
1751 terminator token (comma resp. right parenthesis) and
1758 Often a macro parameter is used for any of the token lists.
1760 Please note that the function does only compare tokens, not token
1761 attributes. So any number is equal to any other number, regardless of the
1762 actual value. The same is true for strings. If you need to compare tokens
1763 <em/and/ token attributes, use the <tt><ref id=".XMATCH"
1764 name=".XMATCH"></tt> function.
1768 Assume the macro <tt/ASR/, that will shift right the accumulator by one,
1769 while honoring the sign bit. The builtin processor instructions will allow
1770 an optional "A" for accu addressing for instructions like <tt/ROL/ and
1771 <tt/ROR/. We will use the <tt><ref id=".MATCH" name=".MATCH"></tt> function
1772 to check for this and print and error for invalid calls.
1777 .if (.not .blank(arg)) .and (.not .match (arg, a))
1778 .error "Syntax error"
1781 cmp #$80 ; Bit 7 into carry
1782 lsr a ; Shift carry into bit 7
1787 The macro will only accept no arguments, or one argument that must be the
1788 reserved keyword "A".
1790 See: <tt><ref id=".XMATCH" name=".XMATCH"></tt>
1793 <sect1><tt>.MID</tt><label id=".MID"><p>
1795 Builtin function. Takes a starting index, a count and a token list as
1796 arguments. Will return part of the token list.
1801 .MID (<int expr>, <int expr>, <token list>)
1804 The first integer expression gives the starting token in the list (the
1805 first token has index 0). The second integer expression gives the number
1806 of tokens to extract from the token list. The third argument is the
1811 To check in a macro if the given argument has a '<tt/#/' as first token
1812 (immidiate addressing mode), use something like this:
1817 .if (.match (.mid (0, 1, arg), #))
1819 ; ldax called with immidiate operand
1827 See also the <tt><ref id=".LEFT" name=".LEFT"></tt> and <tt><ref id=".RIGHT"
1828 name=".RIGHT"></tt> builtin functions.
1831 <sect1><tt>.ORG</tt><label id=".ORG"><p>
1833 Start a section of absolute code. The command is followed by a constant
1834 expression that gives the new PC counter location for which the code is
1835 assembled. Use <tt><ref id=".RELOC" name=".RELOC"></tt> to switch back to
1838 Please note that you <em/do not need/ this command in most cases. Placing
1839 code at a specific address is the job of the linker, not the assembler, so
1840 there is usually no reason to assemble code to a specific address.
1842 You may not switch segments while inside a section of absolute code.
1847 .org $7FF ; Emit code starting at $7FF
1851 <sect1><tt>.OUT</tt><label id=".OUT"><p>
1853 Output a string to the console without producing an error. This command
1854 is similiar to <tt/.ERROR/, however, it does not force an assembler error
1855 that prevents the creation of an object file.
1860 .out "This code was written by the codebuster(tm)"
1863 See also the <tt><ref id=".WARNING" name=".WARNING"></tt> and <tt><ref
1864 id=".ERROR" name=".ERROR"></tt> directives.
1867 <sect1><tt>.P02</tt><label id=".P02"><p>
1869 Enable the 6502 instruction set, disable 65C02 and 65816 instructions.
1870 This is the default if not overridden by the <tt/--cpu/ command line
1873 See: <tt><ref id=".PC02" name=".PC02"></tt> and <tt><ref id=".P816"
1877 <sect1><tt>.P816</tt><label id=".P816"><p>
1879 Enable the 65816 instruction set. This is a superset of the 65C02 and
1880 6502 instruction sets.
1882 See: <tt><ref id=".P02" name=".P02"></tt> and <tt><ref id=".PC02"
1886 <sect1><tt>.PAGELEN, .PAGELENGTH</tt><label id=".PAGELENGTH"><p>
1888 Set the page length for the listing. Must be followed by an integer
1889 constant. The value may be "unlimited", or in the range 32 to 127. The
1890 statement has no effect if no listing is generated. The default value is -1
1891 (unlimited) but may be overridden by the <tt/--pagelength/ command line
1892 option. Beware: Since ca65 is a one pass assembler, the listing is generated
1893 after assembly is complete, you cannot use multiple line lengths with one
1894 source. Instead, the value set with the last <tt/.PAGELENGTH/ is used.
1899 .pagelength 66 ; Use 66 lines per listing page
1901 .pagelength unlimited ; Unlimited page length
1905 <sect1><tt>.PARAMCOUNT</tt><label id=".PARAMCOUNT"><p>
1907 This builtin pseudo variable is only available in macros. It is replaced by
1908 the actual number of parameters that were given in the macro invocation.
1913 .macro foo arg1, arg2, arg3
1914 .if .paramcount <> 3
1915 .error "Too few parameters for macro foo"
1921 See section <ref id="macros" name="Macros">.
1924 <sect1><tt>.PC02</tt><label id=".PC02"><p>
1926 Enable the 65C02 instructions set. This instruction set includes all
1929 See: <tt><ref id=".P02" name=".P02"></tt> and <tt><ref id=".P816"
1933 <sect1><tt>.POPSEG</tt><label id=".POPSEG"><p>
1935 Pop the last pushed segment from the stack, and set it.
1937 This command will switch back to the segment that was last pushed onto the
1938 segment stack using the <tt><ref id=".PUSHSEG" name=".PUSHSEG"></tt>
1939 command, and remove this entry from the stack.
1941 The assembler will print an error message if the segment stack is empty
1942 when this command is issued.
1944 See: <tt><ref id=".PUSHSEG" name=".PUSHSEG"></tt>
1947 <sect1><tt>.PROC</tt><label id=".PROC"><p>
1949 Start a nested lexical level. All new symbols from now on are in the local
1950 lexical level and are not accessible from outside. Symbols defined outside
1951 this local level may be accessed as long as their names are not used for new
1952 symbols inside the level. Symbols names in other lexical levels do not
1953 clash, so you may use the same names for identifiers. The lexical level ends
1954 when the <tt><ref id=".ENDPROC" name=".ENDPROC"></tt> command is read.
1955 Lexical levels may be nested up to a depth of 16.
1957 The command may be followed by an identifier, in this case the
1958 identifier is declared in the outer level as a label having the value of
1959 the program counter at the start of the lexical level.
1961 Note: Macro names are always in the global level and in a separate name
1962 space. There is no special reason for this, it's just that I've never
1963 had any need for local macro definitions.
1968 .proc Clear ; Define Clear subroutine, start new level
1970 L1: sta Mem,y ; L1 is local and does not cause a
1971 ; duplicate symbol error if used in other
1974 bne L1 ; Reference local symbol
1976 .endproc ; Leave lexical level
1979 See: <tt><ref id=".ENDPROC" name=".ENDPROC"></tt>
1982 <sect1><tt>.PUSHSEG</tt><label id=".PUSHSEG"><p>
1984 Push the currently active segment onto a stack. The entries on the stack
1985 include the name of the segment and the segment type. The stack has a size
1988 <tt/.PUSHSEG/ allows together with <tt><ref id=".POPSEG" name=".POPSEG"></tt>
1989 to switch to another segment and to restore the old segment later, without
1990 even knowing the name and type of the current segment.
1992 The assembler will print an error message if the segment stack is already
1993 full, when this command is issued.
1995 See: <tt><ref id=".POPSEG" name=".POPSEG"></tt>
1998 <sect1><tt>.REF, .REFERENCED</tt><label id=".REFERENCED"><p>
2000 Builtin function. The function expects an identifier as argument in braces.
2001 The argument is evaluated, and the function yields "true" if the identifier
2002 is a symbol that has already been referenced somewhere in the source file up
2003 to the current position. Otherwise the function yields false. As an example,
2004 the <tt><ref id=".IFREF" name=".IFREF"></tt> statement may be replaced by
2010 See: <tt><ref id=".DEFINED" name=".DEFINED"></tt>
2013 <sect1><tt>.REPEAT</tt><label id=".REPEAT"><p>
2015 Repeat all commands between <tt/.REPEAT/ and <tt><ref id=".ENDREPEAT"
2016 name=".ENDREPEAT"></tt> constant number of times. The command is followed by
2017 a constant expression that tells how many times the commands in the body
2018 should get repeated. Optionally, a comma and an identifier may be specified.
2019 If this identifier is found in the body of the repeat statement, it is
2020 replaced by the current repeat count (starting with zero for the first time
2021 the body is repeated).
2023 <tt/.REPEAT/ statements may be nested. If you use the same repeat count
2024 identifier for a nested <tt/.REPEAT/ statement, the one from the inner
2025 level will be used, not the one from the outer level.
2029 The following macro will emit a string that is "encrypted" in that all
2030 characters of the string are XORed by the value $55.
2034 .repeat .strlen(Arg), I
2035 .byte .strat(Arg, I) .xor $55
2040 See: <tt><ref id=".ENDREPEAT" name=".ENDREPEAT"></tt>
2043 <sect1><tt>.RELOC</tt><label id=".RELOC"><p>
2045 Switch back to relocatable mode. See the <tt><ref id=".ORG"
2046 name=".ORG"></tt> command.
2049 <sect1><tt>.RES</tt><label id=".RES"><p>
2051 Reserve storage. The command is followed by one or two constant
2052 expressions. The first one is mandatory and defines, how many bytes of
2053 storage should be defined. The second, optional expression must by a
2054 constant byte value that will be used as value of the data. If there
2055 is no fill value given, the linker will use the value defined in the
2056 linker configuration file (default: zero).
2061 ; Reserve 12 bytes of memory with value $AA
2066 <sect1><tt>.RIGHT</tt><label id=".RIGHT"><p>
2068 Builtin function. Extracts the right part of a given token list.
2073 .RIGHT (<int expr>, <token list>)
2076 The first integer expression gives the number of tokens to extract from
2077 the token list. The second argument is the token list itself.
2079 See also the <tt><ref id=".LEFT" name=".LEFT"></tt> and <tt><ref id=".MID"
2080 name=".MID"></tt> builtin functions.
2083 <sect1><tt>.RODATA</tt><label id=".RODATA"><p>
2085 Switch to the RODATA segment. The name of the RODATA segment is always
2086 "RODATA", so this is a shortcut for
2092 The RODATA segment is a segment that is used by the compiler for
2093 readonly data like string constants.
2095 See also the <tt><ref id=".SEGMENT" name=".SEGMENT"></tt> command.
2098 <sect1><tt>.SEGMENT</tt><label id=".SEGMENT"><p>
2100 Switch to another segment. Code and data is always emitted into a
2101 segment, that is, a named section of data. The default segment is
2102 "CODE". There may be up to 254 different segments per object file
2103 (and up to 65534 per executable). There are shortcut commands for
2104 the most common segments ("CODE", "DATA" and "BSS").
2106 The command is followed by a string containing the segment name (there
2107 are some constraints for the name - as a rule of thumb use only those
2108 segment names that would also be valid identifiers). There may also be
2109 an optional attribute separated by a comma. Valid attributes are
2110 "<tt/zeropage/" and "<tt/absolute/".
2112 When specifying a segment for the first time, "absolute" is the
2113 default. For all other uses, the attribute specified the first time
2116 "absolute" means that this is a segment with absolute addressing. That
2117 is, the segment will reside somewhere in core memory outside the zero
2118 page. "zeropage" means the opposite: The segment will be placed in the
2119 zero page and direct (short) addressing is possible for data in this
2122 Beware: Only labels in a segment with the zeropage attribute are marked
2123 as reachable by short addressing. The `*' (PC counter) operator will
2124 work as in other segments and will create absolute variable values.
2129 .segment "ROM2" ; Switch to ROM2 segment
2130 .segment "ZP2", zeropage ; New direct segment
2131 .segment "ZP2" ; Ok, will use last attribute
2132 .segment "ZP2", absolute ; Error, redecl mismatch
2135 See: <tt><ref id=".BSS" name=".BSS"></tt>, <tt><ref id=".CODE"
2136 name=".CODE"></tt>, <tt><ref id=".DATA" name=".DATA"></tt> and <tt><ref
2137 id=".RODATA" name=".RODATA"></tt>
2140 <sect1><tt>.SMART</tt><label id=".SMART"><p>
2142 Switch on or off smart mode. The command must be followed by a '+' or
2143 '-' character to switch the option on or off respectively. The default
2144 is off (that is, the assembler doesn't try to be smart), but this
2145 default may be changed by the -s switch on the command line.
2147 In smart mode the assembler will track usage of the <tt/REP/ and <tt/SEP/
2148 instructions in 65816 mode and update the operand sizes accordingly. If
2149 the operand of such an instruction cannot be evaluated by the assembler
2150 (for example, because the operand is an imported symbol), a warning is
2151 issued. Beware: Since the assembler cannot trace the execution flow this
2152 may lead to false results in some cases. If in doubt, use the <tt/.Inn/ and
2153 <tt/.Ann/ instructions to tell the assembler about the current settings.
2159 .smart - ; Stop being smart
2163 <sect1><tt>.STRAT</tt><label id=".STRAT"><p>
2165 Builtin function. The function accepts a string and an index as
2166 arguments and returns the value of the character at the given position
2167 as an integer value. The index is zero based.
2173 ; Check if the argument string starts with '#'
2174 .if (.strat (Arg, 0) = '#')
2181 <sect1><tt>.STRING</tt><label id=".STRING"><p>
2183 Builtin function. The function accepts an argument in braces and converts
2184 this argument into a string constant. The argument may be an identifier, or
2185 a constant numeric value.
2187 Since you can use a string in the first place, the use of the function may
2188 not be obvious. However, it is useful in macros, or more complex setups.
2193 ; Emulate other assemblers:
2195 .segment .string(name)
2200 <sect1><tt>.STRLEN</tt><label id=".STRLEN"><p>
2202 Builtin function. The function accepts a string argument in braces and
2203 eveluates to the length of the string.
2207 The following macro encodes a string as a pascal style string with
2208 a leading length byte.
2212 .byte .strlen(Arg), Arg
2217 <sect1><tt>.TCOUNT</tt><label id=".TCOUNT"><p>
2219 Builtin function. The function accepts a token list in braces. The
2220 function result is the number of tokens given as argument.
2224 The <tt/ldax/ macro accepts the '#' token to denote immidiate addressing (as
2225 with the normal 6502 instructions). To translate it into two separate 8 bit
2226 load instructions, the '#' token has to get stripped from the argument:
2230 .if (.match (.mid (0, 1, arg), #))
2231 ; ldax called with immidiate operand
2232 lda #<(.right (.tcount (arg)-1, arg))
2233 ldx #>(.right (.tcount (arg)-1, arg))
2241 <sect1><tt>.TIME</tt><label id=".TIME"><p>
2243 Reading this pseudo variable will give a constant integer value that
2244 represents the current time in POSIX standard (as seconds since the
2247 It may be used to encode the time of translation somewhere in the created
2253 .dword .time ; Place time here
2257 <sect1><tt>.WARNING</tt><label id=".WARNING"><p>
2259 Force an assembly warning. The assembler will output a warning message
2260 preceeded by "User warning". This warning will always be output, even if
2261 other warnings are disabled with the <tt><ref id="option-W" name="-W0"></tt>
2262 command line option.
2264 This command may be used to output possible problems when assembling
2273 .warning "Forward jump in jne, cannot optimize!"
2283 See also the <tt><ref id=".ERROR" name=".ERROR"></tt> and <tt><ref id=".OUT"
2284 name=".OUT"></tt> directives.
2287 <sect1><tt>.WORD</tt><label id=".WORD"><p>
2289 Define word sized data. Must be followed by a sequence of (word ranged,
2290 but not necessarily constant) expressions.
2295 .word $0D00, $AF13, _Clear
2299 <sect1><tt>.XMATCH</tt><label id=".XMATCH"><p>
2301 Builtin function. Matches two token lists against each other. This is
2302 most useful within macros, since macros are not stored as strings, but
2308 .XMATCH(<token list #1>, <token list #2>)
2311 Both token list may contain arbitrary tokens with the exception of the
2312 terminator token (comma resp. right parenthesis) and
2319 Often a macro parameter is used for any of the token lists.
2321 The function compares tokens <em/and/ token values. If you need a function
2322 that just compares the type of tokens, have a look at the <tt><ref
2323 id=".MATCH" name=".MATCH"></tt> function.
2325 See: <tt><ref id=".MATCH" name=".MATCH"></tt>
2328 <sect1><tt>.ZEROPAGE</tt><label id=".ZEROPAGE"><p>
2330 Switch to the ZEROPAGE segment and mark it as direct (zeropage) segment.
2331 The name of the ZEROPAGE segment is always "ZEROPAGE", so this is a
2335 .segment "ZEROPAGE", zeropage
2338 Because of the "zeropage" attribute, labels declared in this segment are
2339 addressed using direct addressing mode if possible. You <em/must/ instruct
2340 the linker to place this segment somewhere in the address range 0..$FF
2341 otherwise you will get errors.
2343 See: <tt><ref id=".SEGMENT" name=".SEGMENT"></tt>
2347 <sect>Macros<label id="macros"><p>
2350 <sect1>Introduction<p>
2352 Macros may be thought of as "parametrized super instructions". Macros are
2353 sequences of tokens that have a name. If that name is used in the source
2354 file, the macro is "expanded", that is, it is replaced by the tokens that
2355 were specified when the macro was defined.
2358 <sect1>Macros without parameters<p>
2360 In it's simplest form, a macro does not have parameters. Here's an
2364 .macro asr ; Arithmetic shift right
2365 cmp #$80 ; Put bit 7 into carry
2366 ror ; Rotate right with carry
2370 The macro above consists of two real instructions, that are inserted into
2371 the code, whenever the macro is expanded. Macro expansion is simply done
2372 by using the name, like this:
2381 <sect1>Parametrized macros<p>
2383 When using macro parameters, macros can be even more useful:
2397 When calling the macro, you may give a parameter, and each occurence of
2398 the name "addr" in the macro definition will be replaced by the given
2417 A macro may have more than one parameter, in this case, the parameters
2418 are separated by commas. You are free to give less parameters than the
2419 macro actually takes in the definition. You may also leave intermediate
2420 parameters empty. Empty parameters are replaced by empty space (that is,
2421 they are removed when the macro is exanded). If you have a look at our
2422 macro definition above, you will see, that replacing the "addr" parameter
2423 by nothing will lead to wrong code in most lines. To help you, writing
2424 macros with a variable parameter list, there are some control commands:
2426 <tt><ref id=".IFBLANK" name=".IFBLANK"></tt> tests the rest of the line and
2427 returns true, if there are any tokens on the remainder of the line. Since
2428 empty parameters are replaced by nothing, this may be used to test if a given
2429 parameter is empty. <tt><ref id=".IFNBLANK" name=".IFNBLANK"></tt> tests the
2432 Look at this example:
2435 .macro ldaxy a, x, y
2448 This macro may be called as follows:
2451 ldaxy 1, 2, 3 ; Load all three registers
2453 ldaxy 1, , 3 ; Load only a and y
2455 ldaxy , , 3 ; Load y only
2458 There's another helper command for determining, which macro parameters are
2459 valid: <tt><ref id=".PARAMCOUNT" name=".PARAMCOUNT"></tt> This command is
2460 replaced by the parameter count given, <em/including/ intermediate empty macro
2464 ldaxy 1 ; .PARAMCOUNT = 1
2465 ldaxy 1,,3 ; .PARAMCOUNT = 3
2466 ldaxy 1,2 ; .PARAMCOUNT = 2
2467 ldaxy 1, ; .PARAMCOUNT = 2
2468 ldaxy 1,2,3 ; .PARAMCOUNT = 3
2472 <sect1>Recursive macros<p>
2474 Macros may be used recursively:
2477 .macro push r1, r2, r3
2486 There's also a special macro to help writing recursive macros: <tt><ref
2487 id=".EXITMACRO" name=".EXITMACRO"></tt> This command will stop macro expansion
2491 .macro push r1, r2, r3, r4, r5, r6, r7
2493 ; First parameter is empty
2499 push r2, r3, r4, r5, r6, r7
2503 When expanding this macro, the expansion will push all given parameters
2504 until an empty one is encountered. The macro may be called like this:
2507 push $20, $21, $32 ; Push 3 ZP locations
2508 push $21 ; Push one ZP location
2512 <sect1>Local symbols inside macros<p>
2514 Now, with recursive macros, <tt><ref id=".IFBLANK" name=".IFBLANK"></tt> and
2515 <tt><ref id=".PARAMCOUNT" name=".PARAMCOUNT"></tt>, what else do you need?
2516 Have a look at the inc16 macro above. Here is it again:
2530 If you have a closer look at the code, you will notice, that it could be
2531 written more efficiently, like this:
2542 But imagine what happens, if you use this macro twice? Since the label
2543 "Skip" has the same name both times, you get a "duplicate symbol" error.
2544 Without a way to circumvent this problem, macros are not as useful, as
2545 they could be. One solution is, to start a new lexical block inside the
2559 Now the label is local to the block and not visible outside. However,
2560 sometimes you want a label inside the macro to be visible outside. To make
2561 that possible, there's a new command that's only usable inside a macro
2562 definition: <tt><ref id=".LOCAL" name=".LOCAL"></tt>. <tt/.LOCAL/ declares one
2563 or more symbols as local to the macro expansion. The names of local variables
2564 are replaced by a unique name in each separate macro expansion. So we could
2565 also solve the problem above by using <tt/.LOCAL/:
2569 .local Skip ; Make Skip a local symbol
2576 Skip: ; Not visible outside
2581 <sect1>C style macros<p>
2583 Starting with version 2.5 of the assembler, there is a second macro type
2584 available: C style macros using the <tt/.DEFINE/ directive. These macros are
2585 similar to the classic macro type described above, but behaviour is sometimes
2590 <item> Macros defined with <tt><ref id=".DEFINE" name=".DEFINE"></tt> may not
2591 span more than a line. You may use line continuation (see <tt><ref
2592 id=".LINECONT" name=".LINECONT"></tt>) to spread the definition over
2593 more than one line for increased readability, but the macro itself
2594 may not contain an end-of-line token.
2596 <item> Macros defined with <tt><ref id=".DEFINE" name=".DEFINE"></tt> share
2597 the name space with classic macros, but they are detected and replaced
2598 at the scanner level. While classic macros may be used in every place,
2599 where a mnemonic or other directive is allowed, <tt><ref id=".DEFINE"
2600 name=".DEFINE"></tt> style macros are allowed anywhere in a line. So
2601 they are more versatile in some situations.
2603 <item> <tt><ref id=".DEFINE" name=".DEFINE"></tt> style macros may take
2604 parameters. While classic macros may have empty parameters, this is
2605 not true for <tt><ref id=".DEFINE" name=".DEFINE"></tt> style macros.
2606 For this macro type, the number of actual parameters must match
2607 exactly the number of formal parameters.
2609 To make this possible, formal parameters are enclosed in braces when
2610 defining the macro. If there are no parameters, the empty braces may
2613 <item> Since <tt><ref id=".DEFINE" name=".DEFINE"></tt> style macros may not
2614 contain end-of-line tokens, there are things that cannot be done. They
2615 may not contain several processor instructions for example. So, while
2616 some things may be done with both macro types, each type has special
2617 usages. The types complement each other.
2621 Let's look at a few examples to make the advantages and disadvantages
2624 To emulate assemblers that use "<tt/EQU/" instead of "<tt/=/" you may use the
2625 following <tt/.DEFINE/:
2630 foo EQU $1234 ; This is accepted now
2633 You may use the directive to define string constants used elsewhere:
2636 ; Define the version number
2637 .define VERSION "12.3a"
2643 Macros with parameters may also be useful:
2646 .define DEBUG(message) .out message
2648 DEBUG "Assembling include file #3"
2651 Note that, while formal parameters have to be placed in braces, this is
2652 not true for the actual parameters. Beware: Since the assembler cannot
2653 detect the end of one parameter, only the first token is used. If you
2654 don't like that, use classic macros instead:
2662 (This is an example where a problem can be solved with both macro types).
2665 <sect1>Characters in macros<p>
2667 When using the <ref id="option-t" name="-t"> option, characters are translated
2668 into the target character set of the specific machine. However, this happens
2669 as late as possible. This means that strings are translated if they are part
2670 of a <tt><ref id=".BYTE" name=".BYTE"></tt> or <tt><ref id=".ASCIIZ"
2671 name=".ASCIIZ"></tt> command. Characters are translated as soon as they are
2672 used as part of an expression.
2674 This behaviour is very intuitive outside of macros but may be confusing when
2675 doing more complex macros. If you compare characters against numeric values,
2676 be sure to take the translation into account.
2681 <sect>Macro packages<label id="macropackages"><p>
2683 Using the <tt><ref id=".MACPACK" name=".MACPACK"></tt> directive, predefined
2684 macro packages may be included with just one command. Available macro packages
2688 <sect1><tt>.MACPACK generic</tt><p>
2690 This macro package defines macros that are useful in almost any program.
2691 Currently, two macros are defined:
2706 <sect1><tt>.MACPACK longbranch</tt><p>
2708 This macro package defines long conditional jumps. They are named like the
2709 short counterpart but with the 'b' replaced by a 'j'. Here is a sample
2710 definition for the "<tt/jeq/" macro, the other macros are built using the same
2715 .if .def(Target) .and ((*+2)-(Target) <= 127)
2724 All macros expand to a short branch, if the label is already defined (back
2725 jump) and is reachable with a short jump. Otherwise the macro expands to a
2726 conditional branch with the branch condition inverted, followed by an absolute
2727 jump to the actual branch target.
2729 The package defines the following macros:
2732 jeq, jne, jmi, jpl, jcs, jcc, jvs, jvc
2737 <sect>Module constructors/destructors<label id="condes"><p>
2739 <em>Note:</em> This section applies mostly to C programs, so the explanation
2740 below uses examples from the C libraries. However, the feature may also be
2741 useful for assembler programs.
2744 <sect1>Module overview<p>
2746 Using the <tt><ref id=".CONSTRUCTOR" name=".CONSTRUCTOR"></tt> and <tt><ref
2747 id=".DESTRUCTOR" name=".DESTRUCTOR"></tt> keywords it it possible to export
2748 functions in a special way. The linker is able to generate tables with all
2749 functions of a specific type. Such a table will <em>only</em> include symbols
2750 from object files that are linked into a specific executable. This may be used
2751 to add initialization and cleanup code for library modules.
2753 The C heap functions are an example where module initialization code is used.
2754 All heap functions (<tt>malloc</tt>, <tt>free</tt>, ...) work with a few
2755 variables that contain the start and the end of the heap, pointers to the free
2756 list and so on. Since the end of the heap depends on the size and start of the
2757 stack, it must be initialized at runtime. However, initializing these
2758 variables for programs that do not use the heap are a waste of time and
2761 So the central module defines a function that contains initialization code and
2762 exports this function using the <tt/.CONSTRUCTOR/ statement. If (and only if)
2763 this module is added to an executable by the linker, the initialization
2764 function will be placed into the table of constructors by the linker. The C
2765 startup code will call all constructors before <tt/main/ and all destructors
2766 after <tt/main/, so without any further work, the heap initialization code is
2767 called once the module is linked in.
2769 While it would be possible to add explicit calls to initialization functions
2770 in the startup code, the new approach has several advantages:
2774 If a module is not included, the initialization code is not linked in and not
2775 called. So you don't pay for things you don't need.
2778 Adding another library that needs initialization does not mean that the
2779 startup code has to be changed. Before we had module constructors and
2780 destructors, the startup code for all systems had to be adjusted to call the
2781 new initialization code.
2784 The feature saves memory: Each additional initialization function needs just
2785 two bytes in the table (a pointer to the function).
2792 When creating and using module constructors and destructors, please take care
2798 The linker will only generate function tables, it will not generate code to
2799 call these functions. If you're using the feature in some other than the
2800 existing C environments, you have to write code to call all functions in a
2801 linker generated table yourself. See the <tt>condes</tt> module in the C
2802 runtime for an example on how to do this.
2805 The linker will only add addresses of functions that are in modules linked to
2806 the executable. This means that you have to be careful where to place the
2807 condes functions. If initialization is needed for a group of functions, be
2808 sure to place the initialization function into a module that is linked in
2809 regardless of which function is called by the user.
2812 The linker will generate the tables only when requested to do so by the
2813 <tt/FEATURE CONDES/ statement in the linker config file. Each table has to
2814 be requested separately.
2817 Constructors and destructors may have priorities. These priorities determine
2818 the order of the functions in the table. If your intialization or cleanup code
2819 does depend on other initialization or cleanup code, you have to choose the
2820 priority for the functions accordingly.
2823 Besides the <tt><ref id=".CONSTRUCTOR" name=".CONSTRUCTOR"></tt> and <tt><ref
2824 id=".DESTRUCTOR" name=".DESTRUCTOR"></tt> statements, there is also a more
2825 generic command: <tt><ref id=".CONDES" name=".CONDES"></tt>. This allows to
2826 specify an additional type. Predefined types are 0 (constructor) and 1
2827 (destructor). The linker generates a separate table for each type on request.
2835 <sect>Bugs/Feedback<p>
2837 If you have problems using the assembler, if you find any bugs, or if
2838 you're doing something interesting with the assembler, I would be glad to
2839 hear from you. Feel free to contact me by email
2840 (<htmlurl url="mailto:uz@cc65.org" name="uz@cc65.org">).
2846 ca65 (and all cc65 binutils) are (C) Copyright 1998-2001 Ullrich von
2847 Bassewitz. For usage of the binaries and/or sources the following
2848 conditions do apply:
2850 This software is provided 'as-is', without any expressed or implied
2851 warranty. In no event will the authors be held liable for any damages
2852 arising from the use of this software.
2854 Permission is granted to anyone to use this software for any purpose,
2855 including commercial applications, and to alter it and redistribute it
2856 freely, subject to the following restrictions:
2859 <item> The origin of this software must not be misrepresented; you must not
2860 claim that you wrote the original software. If you use this software
2861 in a product, an acknowledgment in the product documentation would be
2862 appreciated but is not required.
2863 <item> Altered source versions must be plainly marked as such, and must not
2864 be misrepresented as being the original software.
2865 <item> This notice may not be removed or altered from any source
projects / cc65 / blob