1 <!doctype linuxdoc system>
4 <title>cc65 Users Guide
5 <author><url url="mailto:uz@cc65.org" name="Ullrich von Bassewitz">,<newline>
6 <url url="mailto:gregdk@users.sf.net" name="Greg King">
10 cc65 is a C compiler for 6502 targets. It supports several 6502 based home
11 computers like the Commodore and Atari machines, but it is easily retargetable.
14 <!-- Table of contents -->
17 <!-- Begin the document -->
21 cc65 was originally a C compiler for the Atari 8-bit machines written by
22 John R. Dunning. In prior releases I've described the compiler by listing
23 up the changes made by me. I have made many more changes in the meantime
24 (and rewritten major parts of the compiler), so I will no longer do that,
25 since the list would be too large and of no use to anyone. Instead I will
26 describe the compiler in respect to the ANSI/ISO C standard.
28 There are separate documents named <url url="library.html"> and <url
29 url="funcref.html"> that cover the library that is available for the compiler.
30 If you know C, and are interested in doing actual programming, the library
31 documentation is probably of much more use than this document.
33 If you need some hints for getting the best code out of the compiler, you
34 may have a look at <url url="coding.html"> which covers some code generation
41 The compiler translates C files into files containing assembly code that
42 may be translated by the ca65 macroassembler (for more information about
43 the assembler, have a look at <url url="ca65.html">).
46 <sect1>Command line option overview<p>
48 The compiler may be called as follows:
51 ---------------------------------------------------------------------------
52 Usage: cc65 [options] file
54 -Cl Make local variables static
55 -Dsym[=defn] Define a symbol
56 -E Stop after the preprocessing stage
57 -I dir Set an include directory search path
59 -Oi Optimize code, inline more code
60 -Or Enable register variables
61 -Os Inline some known functions
62 -T Include source as comment
63 -V Print the compiler version number
64 -W warning[,...] Suppress warnings
66 -g Add debug info to object file
68 -j Default characters are signed
69 -mm model Set the memory model
70 -o name Name the output file
71 -r Enable register variables
72 -t sys Set the target system
76 --add-source Include source as comment
77 --all-cdecl Make functions default to __cdecl__
78 --bss-name seg Set the name of the BSS segment
79 --check-stack Generate stack overflow checks
80 --code-name seg Set the name of the CODE segment
81 --codesize x Accept larger code by factor x
82 --cpu type Set cpu type (6502, 65c02)
83 --create-dep name Create a make dependency file
84 --create-full-dep name Create a full make dependency file
85 --data-name seg Set the name of the DATA segment
87 --debug-info Add debug info to object file
88 --debug-opt name Debug optimization steps
89 --dep-target target Use this dependency target
90 --disable-opt name Disable an optimization step
91 --enable-opt name Enable an optimization step
92 --help Help (this text)
93 --include-dir dir Set an include directory search path
94 --list-opt-steps List all optimizer steps and exit
95 --list-warnings List available warning types for -W
96 --local-strings Emit string literals immediately
97 --memory-model model Set the memory model
98 --register-space b Set space available for register variables
99 --register-vars Enable register variables
100 --rodata-name seg Set the name of the RODATA segment
101 --signed-chars Default characters are signed
102 --standard std Language standard (c89, c99, cc65)
103 --static-locals Make local variables static
104 --target sys Set the target system
105 --verbose Increase verbosity
106 --version Print the compiler version number
107 --writable-strings Make string literals writable
108 ---------------------------------------------------------------------------
112 <sect1>Command line options in detail<p>
114 Here is a description of all the command line options:
118 <tag><tt>--all-cdecl</tt></tag>
120 Tells the compiler that functions which aren't declared explicitly with
121 either the <tt/__cdecl__/ or <tt/__fastcall__/ calling conventions should
122 have the cdecl convention. (Normally, functions that aren't variadic are
126 <label id="option-bss-name">
127 <tag><tt>--bss-name seg</tt></tag>
129 Set the name of the bss segment. See also <tt/<ref id="pragma-bss-name"
130 name="#pragma bss-name">/.
133 <label id="option-check-stack">
134 <tag><tt>--check-stack</tt></tag>
136 Tells the compiler to generate code that checks for stack overflows. See
137 <tt/<ref id="pragma-check-stack" name="#pragma check-stack">/ for an
138 explanation of this feature.
141 <label id="option-code-name">
142 <tag><tt>--code-name seg</tt></tag>
144 Set the name of the code segment. See also <tt/<ref id="pragma-code-name"
145 name="#pragma code-name">/
148 <label id="option-codesize">
149 <tag><tt>--codesize x</tt></tag>
151 This options allows finer control about speed vs. size decisions in the code
152 generation and optimization phases. It gives the allowed size increase
153 factor (in percent). The default is 100 when not using <tt/-Oi/ and 200 when
154 using <tt/-Oi/ (<tt/-Oi/ is the same as <tt/-O --codesize 200/).
157 <label id="option--cpu">
158 <tag><tt>--cpu CPU</tt></tag>
160 Set the CPU, the compiler generates code for. You may specify "6502" or
161 "65C02" as the CPU. The default depends on the selected target (see option
162 <tt/<ref id="option-t" name="-t">/). It is the 6502 CPU for most targets or
163 if no target has been set. Specifying 65C02 will use a few 65C02
164 instructions when generating code. Don't expect too much from this option:
165 In most cases the difference in size and speed is just 1-2%.
168 <label id="option-create-dep">
169 <tag><tt>--create-dep name</tt></tag>
171 Tells the compiler to generate a file containing the dependency list for the
172 compiled module in makefile syntax. The output is written to a file with the
173 given name. The output does not include system include files (in angle
177 <label id="option-create-full-dep">
178 <tag><tt>--create-full-dep name</tt></tag>
180 Tells the compiler to generate a file containing the dependency list for the
181 compiled module in makefile syntax. The output is written to a file with the
182 given name. The output does include system include files (in angle
186 <label id="option-data-name">
187 <tag><tt>--data-name seg</tt></tag>
189 Set the name of the data segment. See also <tt/<ref id="pragma-data-name"
190 name="#pragma data-name">/
193 <tag><tt>-d, --debug</tt></tag>
195 Enables debug mode, something that should not be needed for mere
199 <label id="option-dep-target">
200 <tag><tt>--dep-target target</tt></tag>
202 When generating a dependency file, don't use the actual output file as the
203 target of the dependency, but the file specified with this option. The
204 option has no effect if neither <tt/<ref id="option-create-dep"
205 name="--create-dep">/ nor <tt/<ref id="option-create-full-dep"
206 name="--create-full-dep">/ is specified.
209 <tag><tt>-D sym[=definition]</tt></tag>
211 Define a macro on the command line. If no definition is given, the macro
212 is defined to the value "1".
215 <tag><tt>-g, --debug-info</tt></tag>
217 This will cause the compiler to insert a <tt/.DEBUGINFO/ command into the
218 generated assembler code. This will cause the assembler to include all
219 symbols in a special section in the object file.
222 <tag><tt>-h, --help</tt></tag>
224 Print the short option summary shown above.
227 <label id="option-list-warnings">
228 <tag><tt>--list-warnings</tt></tag>
230 List the names of warning types available for use with <tt><ref
231 id="option-W" name="-W"></tt>.
234 <label id="option-local-strings">
235 <tag><tt>--local-strings</tt></tag>
237 Emit string literals into the rodata segment as soon as they're encountered
238 in the source (even if you do nothing but get the sizeof those strings). The
239 default is to keep string literals until end of assembly, merge read only
240 literals if possible, and then output the literals into the data or rodata
241 segment that is active at that point. Use of this option prevents merging of
242 duplicate strings, but the options that change the name of one of the data
245 You can also use <tt><ref id="pragma-local-strings"
246 name="#pragma local-strings"></tt> for fine grained control.
249 <tag><tt>-o name</tt></tag>
251 Specify the name of the output file. If you don't specify a name, the
252 name of the C input file is used, with the extension replaced by ".s".
255 <label id="option-register-vars">
256 <tag><tt>-r, --register-vars</tt></tag>
258 <tt/-r/ will make the compiler honor the <tt/register/ keyword. Local
259 variables may be placed in registers (which are actually zero page
260 locations). There is some overhead involved with register variables, since
261 the old contents of the registers must be saved and restored. Since register
262 variables are of limited use without the optimizer, there is also a combined
263 switch: <tt/-Or/ will enable both, the optimizer and register variables.
265 For more information about register variables see <ref id="register-vars"
266 name="register variables">.
268 The compiler setting can also be changed within the source file by using
269 <tt/<ref id="pragma-register-vars" name="#pragma register-vars">/.
272 <label id="option-register-space">
273 <tag><tt>--register-space</tt></tag>
275 This option takes a numeric parameter and is used to specify, how much
276 zero page register space is available. Please note that just giving this
277 option will not increase or decrease by itself, it will just tell the
278 compiler about the available space. You will have to allocate that space
279 yourself using an assembler module with the necessary allocations, and a
280 linker configuration that matches the assembler module. The default value
281 for this option is 6 (bytes).
283 If you don't know what all this means, please don't use this option.
286 <label id="option-rodata-name">
287 <tag><tt>--rodata-name seg</tt></tag>
289 Set the name of the rodata segment (the segment used for readonly data).
290 See also <tt/<ref id="pragma-rodata-name" name="#pragma rodata-name">/
292 <label id="option-signed-chars">
293 <tag><tt>-j, --signed-chars</tt></tag>
295 Using this option, you can make the default characters signed. Since the
296 6502 has no provisions for sign extending characters (which is needed on
297 almost any load operation), this will make the code larger and slower. A
298 better way is to declare characters explicitly as "signed" if needed. You
299 can also use <tt><ref id="pragma-signed-chars"
300 name="#pragma signed-chars"></tt> for better control of this option.
303 <label id="option--standard">
304 <tag><tt>--standard std</tt></tag>
306 This option allows to set the language standard supported. The argument is
310 This disables anything that is illegal in C89/C90. Among those things
311 are <tt>//</tt> comments and the non-standard keywords without
312 underscores. Please note that cc65 is not a fully C89 compliant compiler
313 despite this option. A few more things (like floats) are missing.
316 This enables a few features from the C99 standard. With this option,
317 <tt>//</tt> comments are allowed. It will also cause warnings and even
318 errors in a few situations that are allowed with <tt/--standard c89/.
319 For example, a call to a function without a prototype is an error in
323 This is the default mode. It is like c99 mode, but additional features
324 are enabled. Among these are "void data", non-standard keywords without
325 the underlines, unnamed function parameters and the requirement for
326 main() to return an int.
329 Please note that the compiler does not support the C99 standard and never
330 will. c99 mode is actually c89 mode with a few selected C99 extensions.
333 <label id="option-t">
334 <tag><tt>-t target, --target target</tt></tag>
336 This option is used to set the target system. The target system determines
337 the character set that is used for strings and character constants and the
338 default CPU. The CPU setting can be overriden by use of the <tt/<ref
339 id="option--cpu" name="--cpu">/ option.
341 The following target systems are supported:
350 <item>c16 (works also for the c116 with memory up to 32K)
353 <item>cbm510 (CBM-II series with 40 column video)
354 <item>cbm610 (all CBM-II II computers with 80 column video)
361 <item>pet (all CBM PET systems except the 2001)
369 <tag><tt>-v, --verbose</tt></tag>
371 Using this option, the compiler will be somewhat more verbose if errors
372 or warnings are encountered.
375 <label id="option-writable-strings">
376 <tag><tt>--writable-strings</tt></tag>
378 Make string literals writable by placing them into the data segment instead
379 of the rodata segment. You can also use <tt><ref id="pragma-writable-strings"
380 name="#pragma writable-strings"></tt> to control this option from within
384 <label id="option-static-locals">
385 <tag><tt>-Cl, --static-locals</tt></tag>
387 Use static storage for local variables instead of storage on the stack.
388 Since the stack is emulated in software, this gives shorter and usually
389 faster code, but the code is no longer reentrant. The difference between
390 <tt/-Cl/ and declaring local variables as static yourself is, that
391 initializer code is executed each time, the function is entered. So when
402 the variable <tt/a/ will always have the value <tt/1/ when entering the
403 function and using <tt/-Cl/, while in
408 static unsigned a = 1;
413 the variable <tt/a/ will have the value <tt/1/ only the first time that the
414 function is entered, and will keep the old value from one call of the
415 function to the next.
417 You may also use <tt><ref id="pragma-static-locals"
418 name="#pragma static-locals"></tt> to change this setting in your
422 <label id="option-include-dir">
423 <tag><tt>-I dir, --include-dir dir</tt></tag>
425 Set a directory where the compiler searches for include files. You may
426 use this option multiple times to add more than one directory to the
430 <label id="option-O">
431 <tag><tt>-O, -Oi, -Or, -Os</tt></tag>
433 Enable an optimizer run over the produced code.
435 Using <tt/-Oi/, the code generator will inline some code where otherwise a
436 runtime functions would have been called, even if the generated code is
437 larger. This will not only remove the overhead for a function call, but will
438 make the code visible for the optimizer. <tt/-Oi/ is an alias for
439 <tt/-O --codesize 200/.
441 <tt/-Or/ will make the compiler honor the <tt/register/ keyword. Local
442 variables may be placed in registers (which are actually zero page
443 locations). See also the <tt/<ref id="option-register-vars"
444 name="--register-vars">/ command line option, and the <ref
445 id="register-vars" name="discussion of register variables"> below.
447 Using <tt/-Os/ will force the compiler to inline some known functions from
448 the C library like strlen. Note: This has two consequences:
451 <item>You may not use names of standard C functions in your own code. If you
452 do that, your program is not standard compliant anyway, but using
453 <tt/-Os/ will actually break things.
455 <item>The inlined string and memory functions will not handle strings or
456 memory areas larger than 255 bytes. Similarly, the inlined <tt/is..()/
457 functions will not work with values outside the char. range (such as
462 It is possible to concatenate the modifiers for <tt/-O/. For example, to
463 enable register variables and inlining of known functions, you may use
467 <tag><tt>-T, --add-source</tt></tag>
469 This include the source code as comments in the generated code. This is
473 <tag><tt>-V, --version</tt></tag>
475 Print the version number of the compiler. When submitting a bug report,
476 please include the operating system you're using, and the compiler
480 <label id="option-W">
481 <tag><tt>-W name[,name,...]</tt></tag>
483 This option allows to control warnings generated by the compiler. It is
484 followed by a comma-separated list of warnings that should be enabled or
485 disabled. To disable a warning, its name is prefixed by a minus sign. If
486 no such prefix exists, or the name is prefixed by a plus sign, the warning
489 The following warning names currently are recognized:
491 <tag><tt/const-comparison/</tag>
492 Warn if the result of a comparison is constant.
493 <tag><tt/error/</tag>
494 Treat all warnings as errors.
495 <tag><tt/no-effect/</tag>
496 Warn about statements that don't have an effect.
497 <tag><tt/remap-zero/</tag>
498 Warn about a <tt/<ref id="pragma-charmap" name="#pragma charmap()">/
499 that changes a character's code number from/to 0x00.
500 <tag><tt/struct-param/</tag>
501 Warn when passing structs by value.
502 <tag><tt/unknown-pragma/</tag>
503 Warn about #pragmas that aren't recognized by cc65.
504 <tag><tt/unused-label/</tag>
505 Warn about unused labels.
506 <tag><tt/unused-param/</tag>
507 Warn about unused function parameters.
508 <tag><tt/unused-var/</tag>
509 Warn about unused variables.
512 The full list of available warning names can be retrieved by using the
513 option <tt><ref id="option-list-warnings" name="--list-warnings"></tt>.
515 You may use also <tt><ref id="pragma-warn" name="#pragma warn"></tt> to
516 control this setting, for smaller pieces of code, from within your sources.
521 <sect>Input and output<p>
523 The compiler will accept one C file per invocation and create a file with
524 the same base name, but with the extension replaced by ".s". The output
525 file contains assembler code suitable for use with the ca65 macro
528 Include files in quotes are searched in the following places:
530 <item>The current file's directory.
531 <item>Any directory added with the <tt/-I/ option on the command line.
532 <item>The value of the environment variable <tt/CC65_INC/ if it is defined.
535 Include files in angle brackets are searched in the following places:
537 <item>Any directory added with the <tt/-I/ option on the command line.
538 <item>The value of the environment variable <tt/CC65_INC/ if it is defined.
539 <item>A subdirectory named <tt/include/ of the directory defined in the
540 environment variable <tt/CC65_HOME/, if it is defined.
541 <item>An optionally compiled-in directory.
546 <sect>Differences to the ISO standard<p>
548 Apart from the things listed below, the compiler does support additional
549 keywords, has several functions in the standard headers with names outside the
550 reserved namespace and a few syntax extensions. All these can be disabled with
551 the <tt><ref id="option--standard" name="--standard"></tt> command line
552 option. Its use for maximum standards compatibility is advised.
554 Here is a list of differences between the language, the compiler accepts,
555 and the one defined by the ISO standard:
559 <item> The datatypes "float" and "double" are not available.
561 <item> C Functions may not return structs (or unions), and structs may not
562 be passed as parameters by value. However, struct assignment *is*
565 <item> Most of the C library is available with only the fastcall calling
566 convention (<ref id="extension-fastcall" name="see below">). It means
567 that you must not mix pointers to those functions with pointers to
568 user-written, cdecl functions (the calling conventions are incompatible).
570 <item> The <tt/volatile/ keyword has almost no effect. That is not as bad
571 as it sounds, since the 6502 has so few registers that it isn't
572 possible to keep values in registers anyway.
576 There may be some more minor differences I'm currently not aware of. The
577 biggest problem is the missing float data type. With this limitation in
578 mind, you should be able to write fairly portable code.
584 This cc65 version has some extensions to the ISO C standard.
588 <item> The compiler allows to insert assembler statements into the output
592 asm [optional volatile] (<string literal>[, optional parameters]) ;
596 __asm__ [optional volatile] (<string literal>[, optional parameters]) ;
599 The first form is in the user namespace; and, is disabled if the <tt/-A/
602 There is a whole section covering inline assembler statements,
603 <ref id="inline-asm" name="see there">.
606 <label id="extension-fastcall">
607 <item> The normal calling convention -- for non-variadic functions -- is
608 named "fastcall". The syntax for a function declaration that
609 <em/explicitly/ uses fastcall is
612 <return type> fastcall <function name> (<parameter list>)
616 <return type> __fastcall__ <function name> (<parameter list>)
620 void __fastcall__ f (unsigned char c)
622 The first form of the fastcall keyword is in the user namespace and can
623 therefore be disabled with the <tt><ref id="option--standard"
624 name="--standard"></tt> command line option.
626 For functions that are <tt/fastcall/, the rightmost parameter is not
627 pushed on the stack but left in the primary register when the function
628 is called. That significantly reduces the cost of calling those functions.
632 <item> There is another calling convention named "cdecl". Variadic functions
633 (their prototypes have an ellipsis [<tt/.../]) always use that
634 convention. The syntax for a function declaration using cdecl is
637 <return type> cdecl <function name> (<parameter list>)
641 <return type> __cdecl__ <function name> (<parameter list>)
645 int* __cdecl__ f (unsigned char c)
648 The first form of the cdecl keyword is in the user namespace;
649 and therefore, can be disabled with the <tt/<ref id="option--standard"
650 name="--standard">/ command-line option.
652 For functions that are <tt/cdecl/, the rightmost parameter is pushed
653 onto the stack before the function is called. That increases the cost
654 of calling those functions, especially when they are called from many
655 places.<newline><newline>
658 <item> There are two pseudo variables named <tt/__AX__/ and <tt/__EAX__/.
659 Both refer to the primary register that is used by the compiler to
660 evaluate expressions or return function results. <tt/__AX__/ is of
661 type <tt/unsigned int/ and <tt/__EAX__/ of type <tt/long unsigned int/
662 respectively. The pseudo variables may be used as lvalue and rvalue as
663 every other variable. They are most useful together with short
664 sequences of assembler code. For example, the macro
674 will give the high byte of any unsigned value.
677 <item> Inside a function, the identifier <tt/__func__/ gives the name of the
678 current function as a string. Outside of functions, <tt/__func__/ is
683 #define PRINT_DEBUG(s) printf ("%s: %s\n", __func__, s);
686 The macro will print the name of the current function plus a given
690 <item> cc65 allows the initialization of <tt/void/ variables. This may be
691 used to create arbitrary structures that are more compatible with
692 interfaces written for assembler languages. Here is an example:
695 void GCmd = { (char)3, (unsigned)0x2000, (unsigned)0x3000 };
698 That will be translated as follows:
707 Since the variable is of type <tt/void/, you may not use it as-is.
708 However, taking the address of the variable results in a <tt/void*/
709 which may be passed to any function expecting a pointer. Also, the
710 <tt/sizeof/ operator will give the length of the initializer:
716 will assign the value 5 to <tt/GLen/.
718 See the <url url="geos.html" name="GEOS library document"> for examples
719 on how to use that feature.
722 <item> cc65 implements flexible array struct members as defined in the C99 ISO
723 standard. As an extension, these fields may be initialized. There are
724 several exceptions, however (which is probably the reason why the
725 standard does not define this feature, because it is highly
726 unorthogonal). Flexible array members cannot be initialized ...
729 <item>... when defining an array of structs with flexible
731 <item>... if such a struct is a member field of another struct
732 which is not the last field.
733 <item>... if the struct which contains a flexible array member is
734 declared as <tt/register/, and the size and compiler settings
735 do allow the compiler actually to place the struct into the
736 register bank in the zero page.
739 Please note that -- as defined in the ISO C standard -- the <tt/sizeof/
740 operator returns the struct size with the flexible array member having
741 size zero, even if it is initialized.
749 <sect>Predefined macros<p>
751 The compiler defines several macros at startup:
754 <tag><tt>__APPLE2__</tt></tag>
756 This macro is defined if the target is the Apple ][ (-t apple2) or the enhanced Apple //e (-t apple2enh).
758 <tag><tt>__APPLE2ENH__</tt></tag>
760 This macro is defined if the target is the enhanced Apple //e (-t apple2enh).
762 <tag><tt>__ATARI2600__</tt></tag>
764 This macro is defined if the target is the Atari 2600 game console.
766 <tag><tt>__ATARI5200__</tt></tag>
768 This macro is defined if the target is the Atari 5200 game console.
770 <tag><tt>__ATARI__</tt></tag>
772 This macro is defined if the target is the Atari 400/800 (-t atari) or the Atari 800XL/130XE (-t atarixl).
774 <tag><tt>__ATARIXL__</tt></tag>
776 This macro is defined if the target is the Atari 800XL/130XE (-t atarixl).
778 <tag><tt>__ATMOS__</tt></tag>
780 This macro is defined if the target is the Oric Atmos (-t atmos).
782 <tag><tt>__C128__</tt></tag>
784 This macro is defined if the target is the Commodore 128 (-t c128).
786 <tag><tt>__C16__</tt></tag>
788 This macro is defined if the target is the Commodore 16/116 (-t c16) or the Commodore Plus/4 (-t plus4).
790 <tag><tt>__C64__</tt></tag>
792 This macro is defined if the target is the Commodore 64 (-t c64).
794 <tag><tt>__CBM__</tt></tag>
796 This macro is defined if the target system is one of the CBM targets.
798 <tag><tt>__CBM510__</tt></tag>
800 This macro is defined if the target is the CBM 500 series of computers.
802 <tag><tt>__CBM610__</tt></tag>
804 This macro is defined if the target is one of the CBM 600/700 family of
805 computers (called B series in the US).
807 <tag><tt>__CC65__</tt></tag>
809 This macro is always defined. Its value is the version number of the
810 compiler in hex. For example, version 2.14 of the compiler has this macro
811 defined as <tt/0x02E0/.
813 <tag><tt>__CC65_STD__</tt></tag>
815 This macro is defined to one of the following depending on the <tt><ref
816 id="option--standard" name="--standard"></tt> command line option:
818 <item><tt/__CC65_STD_C89__/
819 <item><tt/__CC65_STD_C99__/
820 <item><tt/__CC65_STD_CC65__/
823 <tag><tt>__DATE__</tt></tag>
825 This macro expands to the date of translation of the preprocessing
826 translation unit in the form "Mmm dd yyyy".
828 <tag><tt>__FILE__</tt></tag>
830 This macro expands to a string containing the name of the C source file.
832 <tag><tt>__GEOS__</tt></tag>
834 This macro is defined if you are compiling for one of the GEOS systems.
836 <tag><tt>__GEOS_APPLE__</tt></tag>
838 This macro is defined if you are compiling for the Apple GEOS system (-t geos-apple).
840 <tag><tt>__GEOS_CBM__</tt></tag>
842 This macro is defined if you are compiling for the GEOS 64/128 system (-t geos-cbm).
844 <tag><tt>__LINE__</tt></tag>
846 This macro expands to the current line number.
848 <tag><tt>__LUNIX__</tt></tag>
850 This macro is defined if you are compiling for the LUnix system (-t lunix).
852 <tag><tt>__LYNX__</tt></tag>
854 This macro is defined if the target is the Atari Lynx (-t lynx).
856 <tag><tt>__NES__</tt></tag>
858 This macro is defined if the target is the Nintendo Entertainment System (-t nes).
860 <tag><tt>__OPT__</tt></tag>
862 Is defined if the compiler was called with the <tt/-O/ command line option.
864 <tag><tt>__OPT_i__</tt></tag>
866 Is defined if the compiler was called with the <tt/-Oi/ command line option.
868 <tag><tt>__OPT_r__</tt></tag>
870 Is defined if the compiler was called with the <tt/-Or/ command line option.
872 <tag><tt>__OPT_s__</tt></tag>
874 Is defined if the compiler was called with the <tt/-Os/ command line option.
876 <tag><tt>__OSIC1P__</tt></tag>
878 This macro is defined if the target is the Ohio Scientific Challenger 1P
881 <tag><tt>__PET__</tt></tag>
883 This macro is defined if the target is the PET family of computers (-t pet).
885 <tag><tt>__PLUS4__</tt></tag>
887 This macro is defined if the target is the Commodore Plus/4 (-t plus4).
889 <tag><tt>__STDC_HOSTED__</tt></tag>
891 This macro is expands to the integer constant 1.
893 <tag><tt>__SIM6502__</tt></tag>
895 This macro is defined if the target is sim65 in 6502 mode (-t sim6502).
897 <tag><tt>__SIM65C02__</tt></tag>
898 This macro is defined if the target is sim65 in 65C02 mode (-t sim65c02).
900 <tag><tt>__SUPERVISION__</tt></tag>
902 This macro is defined if the target is the Supervision (-t supervision).
904 <tag><tt>__TIME__</tt></tag>
906 This macro expands to the time of translation of the preprocessing
907 translation unit in the form "hh:mm:ss".
909 <tag><tt>__VIC20__</tt></tag>
911 This macro is defined if the target is the Commodore VIC20 (-t vic20).
915 <sect>#pragmas<label id="pragmas"><p>
917 The compiler understands some pragmas that may be used to change code
918 generation and other stuff. Some of these pragmas understand a special form:
919 If the first parameter is <tt/push/, the old value is saved onto a stack
920 before changing it. The value may later be restored by using the <tt/pop/
921 parameter with the <tt/#pragma/.
923 <sect1><tt>#pragma bss-name ([push,] <name>)</tt><label id="pragma-bss-name"><p>
925 This pragma changes the name used for the BSS segment (the BSS segment
926 is used to store uninitialized data). The argument is a string enclosed
929 Note: The default linker configuration file does only map the standard
930 segments. If you use other segments, you have to create a new linker
933 Beware: The startup code will zero only the default BSS segment. If you
934 use another BSS segment, you have to do that yourself, otherwise
935 uninitialized variables do not have the value zero.
937 The <tt/#pragma/ understands the push and pop parameters as explained above.
941 #pragma bss-name ("MyBSS")
945 <sect1><tt>#pragma charmap (<index>, <code>)</tt><label id="pragma-charmap"><p>
947 Each literal string and each literal character in the source is translated
948 by use of a translation table. That translation table is preset when the
949 compiler is started, depending on the target system; for example, to map
950 ISO-8859-1 characters into PETSCII if the target is a Commodore machine.
952 This pragma allows to change entries in the translation table, so the
953 translation for individual characters, or even the complete table may be
954 adjusted. Both arguments are assumed to be unsigned characters with a valid
957 Beware of some pitfalls:
959 <item>The character index is actually the code of the character in the
960 C source; so, character mappings do always depend on the source
961 character set. That means that <tt/#pragma charmap()/ is not
962 portable -- it depends on the build environment.
963 <item>While it is possible to use character literals as indices, the
964 result may be somewhat unexpected, since character literals are
965 themselves translated. For that reason, I would suggest to avoid
966 character literals, and use numeric character codes instead.
967 <item>It is risky to change index <tt/0x00/, because string functions depend
968 on it. If it is changed, then the <tt/'\0'/ at the end of string
969 literals will become non-zero. Functions that are used on those
970 literals won't stop at the end of them. cc65 will warn you if you do
971 change that code number. You can turn off that <tt/remap-zero/ warning
972 if you are certain that you know what you are doing (see <tt/<ref
973 id="pragma-warn" name="#pragma warn()">/).
978 /* Use a space wherever an 'a' occurs in ISO-8859-1 source */
979 #pragma charmap (0x61, 0x20);
983 <sect1><tt>#pragma check-stack ([push,] on|off)</tt><label id="pragma-check-stack"><p>
985 Tells the compiler to insert calls to a stack checking subroutine to detect
986 stack overflows. The stack checking code will lead to somewhat larger and
987 slower programs, so you may want to use this pragma when debugging your
988 program and switch it off for the release version. If a stack overflow is
989 detected, the program is aborted.
991 If the argument is "off", stack checks are disabled (the default), otherwise
994 The <tt/#pragma/ understands the push and pop parameters as explained above.
996 <sect1><tt>#pragma code-name ([push,] <name>)</tt><label id="pragma-code-name"><p>
998 This pragma changes the name used for the CODE segment (the CODE segment
999 is used to store executable code). The argument is a string enclosed in
1002 Note: The default linker configuration file does only map the standard
1003 segments. If you use other segments, you have to create a new linker
1006 The <tt/#pragma/ understands the push and pop parameters as explained above.
1010 #pragma code-name ("MyCODE")
1014 <sect1><tt>#pragma codesize ([push,] <int>)</tt><label id="pragma-codesize"><p>
1016 This pragma allows finer control about speed vs. size decisions in the code
1017 generation and optimization phase. It gives the allowed size increase factor
1018 (in percent). The default is can be changed by use of the <tt/<ref
1019 id="option-codesize" name="--codesize">/ compiler option.
1021 The <tt/#pragma/ understands the push and pop parameters as explained above.
1024 <sect1><tt>#pragma data-name ([push,] <name>)</tt><label id="pragma-data-name"><p>
1026 This pragma changes the name used for the DATA segment (the DATA segment
1027 is used to store initialized data). The argument is a string enclosed in
1030 Note: The default linker configuration file does only map the standard
1031 segments. If you use other segments, you have to create a new linker
1034 The <tt/#pragma/ understands the push and pop parameters as explained above.
1038 #pragma data-name ("MyDATA")
1042 <sect1><tt>#pragma local-strings ([push,] on|off)</tt><label id="pragma-local-strings"><p>
1044 When "on", emit string literals to the data segment when they're encountered
1045 in the source. The default ("off") is to keep string literals until end of
1046 assembly, merge read only literals if possible, and then output the literals
1047 into the data or rodata segment that is active at that point.
1049 Using this <tt/#pragma/ it is possible to control the behaviour from within
1050 the source. When <tt/#pragma local-strings/ is active, string literals are
1051 output immediately, which means that they go into the currently active data
1052 or rodata segment, but cannot be merged. When inactive, string literals are
1053 remembered and output as a whole when translation is finished.
1056 <sect1><tt>#pragma optimize ([push,] on|off)</tt><label id="pragma-optimize"><p>
1058 Switch optimization on or off. If the argument is "off", optimization is
1059 disabled, otherwise it is enabled. Please note that this pragma only effects
1060 whole functions. The setting in effect when the function is encountered will
1061 determine if the generated code is optimized or not.
1063 Optimization and code generation is also controlled by the <ref
1064 id="pragma-codesize" name="codesize pragma">.
1066 The default is "off", but may be changed with the <tt/<ref name="-O"
1067 id="option-O">/ compiler option.
1069 The <tt/#pragma/ understands the push and pop parameters as explained above.
1072 <sect1><tt>#pragma rodata-name ([push,] <name>)</tt><label id="pragma-rodata-name"><p>
1074 This pragma changes the name used for the RODATA segment (the RODATA
1075 segment is used to store readonly data). The argument is a string
1076 enclosed in double quotes.
1078 Note: The default linker configuration file does only map the standard
1079 segments. If you use other segments, you have to create a new linker
1082 The <tt/#pragma/ understands the push and pop parameters as explained above.
1086 #pragma rodata-name ("MyRODATA")
1090 <sect1><tt>#pragma regvaraddr ([push,] on|off)</tt><label id="pragma-regvaraddr"><p>
1092 The compiler does not allow to take the address of register variables.
1093 The regvaraddr pragma changes this. Taking the address of a register
1094 variable is allowed after using this pragma with "on" as argument.
1095 Using "off" as an argument switches back to the default behaviour.
1097 Beware: The C standard does not allow taking the address of a variable
1098 declared as register. So your programs become non-portable if you use
1099 this pragma. In addition, your program may not work. This is usually the
1100 case if a subroutine is called with the address of a register variable,
1101 and this subroutine (or a subroutine called from there) uses
1102 register variables. So be careful with this #pragma.
1104 The <tt/#pragma/ understands the push and pop parameters as explained above.
1108 #pragma regvaraddr(on) /* Allow taking the address
1109 * of register variables
1114 <sect1><tt>#pragma register-vars ([push,] on|off)</tt><label id="pragma-register-vars"><p>
1116 Enables or disables use of register variables. If register variables are
1117 disabled (the default), the <tt/register/ keyword is ignored. Register
1118 variables are explained in more detail in <ref id="register-vars" name="a separate
1121 The <tt/#pragma/ understands the push and pop parameters as explained above.
1124 <sect1><tt>#pragma signed-chars ([push,] on|off)</tt><label id="pragma-signed-chars"><p>
1126 Changes the signedness of the default character type. If the argument is
1127 "on", default characters are signed, otherwise characters are unsigned. The
1128 compiler default is to make characters unsigned since this creates a lot
1129 better code. This default may be overridden by the <tt/<ref
1130 name="--signed-chars" id="option-signed-chars">/ command line option.
1132 The <tt/#pragma/ understands the push and pop parameters as explained above.
1135 <sect1><tt>#pragma static-locals ([push,] on|off)</tt><label id="pragma-static-locals"<p>
1137 Use variables in the bss segment instead of variables on the stack. This
1138 pragma changes the default set by the compiler option <tt/<ref
1139 name="--static-locals" id="option-static-locals">/. If the argument is "on",
1140 local variables are allocated in the BSS segment, leading to shorter and in
1141 most cases faster, but non-reentrant code.
1143 The <tt/#pragma/ understands the push and pop parameters as explained above.
1146 <sect1><tt>#pragma warn (name, [push,] on|off)</tt><label id="pragma-warn"><p>
1148 Switch compiler warnings on or off. "name" is the name of a warning (see the
1149 <tt/<ref name="-W" id="option-W">/ compiler option for a list). The name is
1150 followed either by "pop", which restores the last pushed state, or by "on" or
1151 "off", optionally preceeded by "push" to push the current state before
1156 /* Don't warn about the unused parameter in function func */
1157 #pragma warn (unused-param, push, off)
1158 static int func (int unused)
1162 #pragma warn (unused-param, pop)
1166 <sect1><tt>#pragma writable-strings ([push,] on|off)</tt><label id="pragma-writable-strings"><p>
1168 Changes the storage location of string literals. For historical reasons,
1169 the C standard defines that string literals are of type "char[]", but
1170 writing to such a literal causes undefined behaviour. Most compilers
1171 (including cc65) place string literals in the read-only data segment, which
1172 may cause problems with old C code that writes to string literals.
1174 Using this pragma (or the corresponding command line option <tt/<ref
1175 name="--writable-strings" id="option-writable-strings">/) causes the
1176 literals to be placed in the data segment so they can be written to without
1179 The <tt/#pragma/ understands the push and pop parameters as explained above.
1182 <sect1><tt>#pragma zpsym (<name>)</tt><p>
1184 Tell the compiler that the -- previously as external declared -- symbol with
1185 the given name is a zero page symbol (usually from an assembler file).
1186 The compiler will create a matching import declaration for the assembler.
1191 #pragma zpsym ("foo"); /* foo is in the zeropage */
1197 <sect>Register variables<label id="register-vars"><p>
1199 The runtime for all supported platforms has 6 bytes of zero page space
1200 available for register variables (this could be increased, but I think it's a
1201 good value). So you can declare register variables up to a total size of 6 per
1202 function. The compiler will allocate register space on a "first come, first
1203 served" base and convert any <tt/register/ declarations that exceed the
1204 available register space silently to <tt/auto/. Parameters can also be
1205 declared as <tt/register/, this will in fact give slightly shorter code than
1206 using a register variable.
1208 Since a function must save the current values of the registers on entry and
1209 restore them on exit, there is an overhead associated with register variables,
1210 and this overhead is quite high (about 20 bytes per variable). This means that
1211 just declaring anything as <tt/register/ is not a good idea.
1213 The best use for register variables are pointers, especially those that point
1214 to structures. The magic number here is about 3 uses of a struct field: If the
1215 function contains this number or even more, the generated code will be usually
1216 shorter and faster when using a register variable for the struct pointer. The
1217 reason for this is that the register variable can in many cases be used as a
1218 pointer directly. Having a pointer in an auto variable means that this pointer
1219 must first be copied into a zero page location, before it can be dereferenced.
1221 Second best use for register variables are counters. However, there is not
1222 much difference in the code generated for counters, so you will need at least
1223 100 operations on this variable (for example in a loop) to make it worth the
1224 trouble. The only savings you get here are by the use of a zero page variable
1225 instead of one on the stack or in the data segment.
1227 Register variables must be explicitly enabled, either by using <tt/<ref
1228 name="-Or" id="option-O">/ or <tt/<ref name="--register-vars"
1229 id="option-register-vars">/ on the command line or by use of <tt/<ref
1230 name="#pragma register-vars" id="pragma-register-vars">/. Register variables
1231 are only accepted on function top level, register variables declared in
1232 interior blocks are silently converted to <tt/auto/. With register variables
1233 disabled, all variables declared as <tt/register/ are actually auto variables.
1235 Please take care when using register variables: While they are helpful and can
1236 lead to a tremendous speedup when used correctly, improper usage will cause
1237 bloated code and a slowdown.
1241 <sect>Inline assembler<label id="inline-asm"><p>
1243 The compiler allows to insert assembler statements into the output file. The
1247 asm [optional volatile] (<string literal>[, optional parameters]) ;
1251 __asm__ [optional volatile] (<string literal>[, optional parameters]) ;
1255 The first form is in the user namespace; and, is disabled by <tt><ref
1256 id="option--standard" name="--standard"></tt> if the argument is not <tt/cc65/.
1258 The <tt/asm/ statement can be used only inside a function. Please note that
1259 the result of an inline assembler expression is always of type <tt/void/.
1261 The contents of the string literal are preparsed by the compiler; and, inserted
1262 into the generated assembly output, so that it can be processed further by
1263 the backend -- and, especially the optimizer. For that reason, the compiler does
1264 allow only regular 6502 opcodes to be used with the inline assembler. Pseudo
1265 instructions (like <tt/.import/, <tt/.byte/, and so on) are <em/not/ allowed,
1266 even if the ca65 assembler (which is used to translate the generated assembler
1267 code) would accept them. The built-in inline assembler is not a replacement for
1268 the full-blown macro assembler which comes with the compiler.
1270 Note: Inline assembler statements are subject to all optimizations done by the
1271 compiler. There currently is no way to protect an inline assembler statement
1272 -- alone -- from being moved or removed completely by the optimizer. If in
1273 doubt, check the generated assembler output; or, disable optimizations (for
1276 As a shortcut, you can put the <tt/volatile/ qualifier in your <tt/asm/
1277 statements. It will disable optimization for the functions in which those
1278 <tt/asm volatile/ statements sit. The effect is the same as though you put
1279 </#pragma optimize(push, off)/ above those functions, and </#pragma
1280 optimize(pop)/ below those functions.
1282 The string literal may contain format specifiers from the following list. For
1283 each format specifier, an argument is expected which is inserted instead of
1284 the format specifier, before passing the assembly code line to the backend.
1287 <item><tt/%b/ - Numerical 8-bit value
1288 <item><tt/%w/ - Numerical 16-bit value
1289 <item><tt/%l/ - Numerical 32-bit value
1290 <item><tt/%v/ - Assembler name of a global variable or function
1291 <item><tt/%o/ - Stack offset of a local variable
1292 <item><tt/%g/ - Assembler name of a C label
1293 <item><tt/%s/ - The argument is converted to a string
1294 <item><tt/%%/ - The % sign itself
1297 Using those format specifiers, you can access C <tt/#defines/, variables, or
1298 similar stuff from the inline assembler. For example, to load the value of
1299 a C <tt/#define/ into the Y index register, one would use
1303 __asm__ ("ldy #%b", OFFS);
1306 Or, to access a struct member of a static variable:
1312 unsigned char color;
1314 static pixel_t pixel;
1315 __asm__ ("ldy #%b", offsetof(pixel_t, color));
1316 __asm__ ("lda %v,y", pixel);
1319 The next example shows how to use global variables to exchange data between C
1320 and assembler; and, how to handle assembler jumps:
1323 static unsigned char globalSubA, globalSubB, globalSubResult;
1325 /* return a-b, return 255 if b>a */
1326 unsigned char sub (unsigned char a, unsigned char b)
1331 __asm__ ("lda %v", globalSubA);
1332 __asm__ ("sbc %v", globalSubB);
1333 __asm__ ("bcs %g", jumpSubNoError);
1334 __asm__ ("lda #$FF");
1336 __asm__ ("sta %v", globalSubResult);
1337 return globalSubResult;
1342 Arrays also can be accessed:
1345 static const unsigned char globalSquareTable[] = {
1346 0, 1, 4, 9, 16, 25, 36, 49, 64, 81,
1347 100, 121, 144, 169, 196, 225
1349 static unsigned char globalSquareA, globalSquareResult;
1351 /* return a*a for a<16, else 255 */
1352 unsigned char square (unsigned char a)
1358 __asm__ ("ldx %v", globalSquareA);
1359 __asm__ ("lda %v,x", globalSquareTable);
1360 __asm__ ("sta %v", globalSquareResult);
1361 return globalSquareResult;
1366 Note: Do not embed the assembler labels that are used as names of global
1367 variables or functions into your <tt/asm/ statements. Code such as this:
1371 int bar (void) { return 1; }
1373 __asm__ ("lda _foo"); /* DON'T DO THAT! */
1375 __asm__ ("jsr _bar"); /* DON'T DO THAT EITHER! */
1379 might stop working if the way that the compiler generates those names is changed in
1380 a future version. Instead, use the format specifiers from the table above:
1383 __asm__ ("lda %v", foo); /* OK */
1385 __asm__ ("jsr %v", bar); /* OK */
1391 <sect>Implementation-defined behavior<p>
1393 This section describes the behavior of cc65 when the standard describes the
1394 behavior as implementation-defined.
1400 This is the original compiler copyright:
1403 --------------------------------------------------------------------------
1406 This is the copyright notice for RA65, LINK65, LIBR65, and other
1407 Atari 8-bit programs. Said programs are Copyright 1989, by John R.
1408 Dunning. All rights reserved, with the following exceptions:
1410 Anyone may copy or redistribute these programs, provided that:
1412 1: You don't charge anything for the copy. It is permissable to
1413 charge a nominal fee for media, etc.
1415 2: All source code and documentation for the programs is made
1416 available as part of the distribution.
1418 3: This copyright notice is preserved verbatim, and included in
1421 You are allowed to modify these programs, and redistribute the
1422 modified versions, provided that the modifications are clearly noted.
1424 There is NO WARRANTY with this software, it comes as is, and is
1425 distributed in the hope that it may be useful.
1427 This copyright notice applies to any program which contains
1428 this text, or the refers to this file.
1430 This copyright notice is based on the one published by the Free
1431 Software Foundation, sometimes known as the GNU project. The idea
1432 is the same as theirs, ie the software is free, and is intended to
1433 stay that way. Everybody has the right to copy, modify, and re-
1434 distribute this software. Nobody has the right to prevent anyone
1435 else from copying, modifying or redistributing it.
1437 --------------------------------------------------------------------------
1440 Small parts of the compiler (parts of the preprocessor and main parser) are
1441 still covered by this copyright. The main portion is covered by the usual
1442 cc65 license, which reads:
1444 This software is provided 'as-is', without any expressed or implied
1445 warranty. In no event will the authors be held liable for any damages
1446 arising from the use of this software.
1448 Permission is granted to anyone to use this software for any purpose,
1449 including commercial applications, and to alter it and redistribute it
1450 freely, subject to the following restrictions:
1453 <item> The origin of this software must not be misrepresented; you must not
1454 claim that you wrote the original software. If you use this software
1455 in a product, an acknowledgment in the product documentation would be
1456 appreciated but is not required.
1457 <item> Altered source versions must be plainly marked as such, and must not
1458 be misrepresented as being the original software.
1459 <item> This notice may not be removed or altered from any source