1 <!doctype linuxdoc system>
4 <title>cc65 Users Guide
5 <author><url url="mailto:uz@cc65.org" name="Ullrich von Bassewitz">
9 cc65 is a C compiler for 6502 targets. It supports several 6502 based home
10 computers like the Commodore and Atari machines, but it is easily retargetable.
13 <!-- Table of contents -->
16 <!-- 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)
360 <item>pet (all CBM PET systems except the 2001)
368 <tag><tt>-v, --verbose</tt></tag>
370 Using this option, the compiler will be somewhat more verbose if errors
371 or warnings are encountered.
374 <label id="option-writable-strings">
375 <tag><tt>--writable-strings</tt></tag>
377 Make string literals writable by placing them into the data segment instead
378 of the rodata segment. You can also use <tt><ref id="pragma-writable-strings"
379 name="#pragma writable-strings"></tt> to control this option from within
383 <label id="option-static-locals">
384 <tag><tt>-Cl, --static-locals</tt></tag>
386 Use static storage for local variables instead of storage on the stack.
387 Since the stack is emulated in software, this gives shorter and usually
388 faster code, but the code is no longer reentrant. The difference between
389 <tt/-Cl/ and declaring local variables as static yourself is, that
390 initializer code is executed each time, the function is entered. So when
401 the variable <tt/a/ will always have the value <tt/1/ when entering the
402 function and using <tt/-Cl/, while in
407 static unsigned a = 1;
412 the variable <tt/a/ will have the value <tt/1/ only the first time that the
413 function is entered, and will keep the old value from one call of the
414 function to the next.
416 You may also use <tt><ref id="pragma-static-locals"
417 name="#pragma static-locals"></tt> to change this setting in your
421 <label id="option-include-dir">
422 <tag><tt>-I dir, --include-dir dir</tt></tag>
424 Set a directory where the compiler searches for include files. You may
425 use this option multiple times to add more than one directory to the
429 <label id="option-O">
430 <tag><tt>-O, -Oi, -Or, -Os</tt></tag>
432 Enable an optimizer run over the produced code.
434 Using <tt/-Oi/, the code generator will inline some code where otherwise a
435 runtime functions would have been called, even if the generated code is
436 larger. This will not only remove the overhead for a function call, but will
437 make the code visible for the optimizer. <tt/-Oi/ is an alias for
438 <tt/-O --codesize 200/.
440 <tt/-Or/ will make the compiler honor the <tt/register/ keyword. Local
441 variables may be placed in registers (which are actually zero page
442 locations). See also the <tt/<ref id="option-register-vars"
443 name="--register-vars">/ command line option, and the <ref
444 id="register-vars" name="discussion of register variables"> below.
446 Using <tt/-Os/ will force the compiler to inline some known functions from
447 the C library like strlen. Note: This has two consequences:
450 <item>You may not use names of standard C functions in your own code. If you
451 do that, your program is not standard compliant anyway, but using
452 <tt/-Os/ will actually break things.
454 <item>The inlined string and memory functions will not handle strings or
455 memory areas larger than 255 bytes. Similarly, the inlined <tt/is..()/
456 functions will not work with values outside the char. range (such as
461 It is possible to concatenate the modifiers for <tt/-O/. For example, to
462 enable register variables and inlining of known functions, you may use
466 <tag><tt>-T, --add-source</tt></tag>
468 This include the source code as comments in the generated code. This is
472 <tag><tt>-V, --version</tt></tag>
474 Print the version number of the compiler. When submitting a bug report,
475 please include the operating system you're using, and the compiler
479 <label id="option-W">
480 <tag><tt>-W name[,name]</tt></tag>
482 This option allows to control warnings generated by the compiler. It is
483 followed by a comma separated list of warnings that should be enabled or
484 disabled. To disable a warning, its name is prefixed by a minus sign. If
485 no such prefix exists, or the name is prefixed by a plus sign, the warning
488 The following warning names are currently recognized:
490 <tag><tt/const-comparison/</tag>
491 Warn if the result of a comparison is constant.
492 <tag><tt/error/</tag>
493 Treat all warnings as errors.
494 <tag><tt/no-effect/</tag>
495 Warn about statements that don't have an effect.
496 <tag><tt/struct-param/</tag>
497 Warn when passing structs by value.
498 <tag><tt/unknown-pragma/</tag>
499 Warn about known #pragmas.
500 <tag><tt/unused-label/</tag>
501 Warn about unused labels.
502 <tag><tt/unused-param/</tag>
503 Warn about unused function parameters.
504 <tag><tt/unused-var/</tag>
505 Warn about unused variables.
508 The full list of available warning names may be retrieved by using the
509 option <tt><ref id="option-list-warnings" name="--list-warnings"></tt>.
511 You may also use <tt><ref id="pragma-warn" name="#pragma warn"></tt> to
512 control this setting for smaller pieces of code from within your code.
517 <sect>Input and output<p>
519 The compiler will accept one C file per invocation and create a file with
520 the same base name, but with the extension replaced by ".s". The output
521 file contains assembler code suitable for use with the ca65 macro
524 Include files in quotes are searched in the following places:
526 <item>The current file's directory.
527 <item>Any directory added with the <tt/-I/ option on the command line.
528 <item>The value of the environment variable <tt/CC65_INC/ if it is defined.
531 Include files in angle brackets are searched in the following places:
533 <item>Any directory added with the <tt/-I/ option on the command line.
534 <item>The value of the environment variable <tt/CC65_INC/ if it is defined.
535 <item>A subdirectory named <tt/include/ of the directory defined in the
536 environment variable <tt/CC65_HOME/, if it is defined.
537 <item>An optionally compiled-in directory.
542 <sect>Differences to the ISO standard<p>
544 Apart from the things listed below, the compiler does support additional
545 keywords, has several functions in the standard headers with names outside the
546 reserved namespace and a few syntax extensions. All these can be disabled with
547 the <tt><ref id="option--standard" name="--standard"></tt> command line
548 option. Its use for maximum standards compatibility is advised.
550 Here is a list of differences between the language, the compiler accepts,
551 and the one defined by the ISO standard:
555 <item> The datatypes "float" and "double" are not available.
557 <item> C Functions may not return structs (or unions), and structs may not
558 be passed as parameters by value. However, struct assignment *is*
561 <item> Most of the C library is available with only the fastcall calling
562 convention (<ref id="extension-fastcall" name="see below">). It means
563 that you must not mix pointers to those functions with pointers to
564 user-written, cdecl functions (the calling conventions are incompatible).
566 <item> The <tt/volatile/ keyword doesn't have an effect. This is not as bad
567 as it sounds, since the 6502 has so few registers that it isn't
568 possible to keep values in registers anyway.
572 There may be some more minor differences I'm currently not aware of. The
573 biggest problem is the missing float data type. With this limitation in
574 mind, you should be able to write fairly portable code.
580 This cc65 version has some extensions to the ISO C standard.
584 <item> The compiler allows to insert assembler statements into the output
588 asm (<string literal>[, optional parameters]) ;
592 __asm__ (<string literal>[, optional parameters]) ;
595 The first form is in the user namespace and is disabled if the <tt/-A/
598 There is a whole section covering inline assembler statements,
599 <ref id="inline-asm" name="see there">.
602 <label id="extension-fastcall">
603 <item> The normal calling convention -- for non-variadic functions -- is
604 named "fastcall". The syntax for a function declaration that
605 <em/explicitly/ uses fastcall is
608 <return type> fastcall <function name> (<parameter list>)
612 <return type> __fastcall__ <function name> (<parameter list>)
616 void __fastcall__ f (unsigned char c)
618 The first form of the fastcall keyword is in the user namespace and can
619 therefore be disabled with the <tt><ref id="option--standard"
620 name="--standard"></tt> command line option.
622 For functions that are <tt/fastcall/, the rightmost parameter is not
623 pushed on the stack but left in the primary register when the function
624 is called. That significantly reduces the cost of calling those functions.
628 <item> There is another calling convention named "cdecl". Variadic functions
629 (their prototypes have an ellipsis [<tt/.../]) always use that
630 convention. The syntax for a function declaration using cdecl is
633 <return type> cdecl <function name> (<parameter list>)
637 <return type> __cdecl__ <function name> (<parameter list>)
641 int* __cdecl__ f (unsigned char c)
644 The first form of the cdecl keyword is in the user namespace;
645 and therefore, can be disabled with the <tt/<ref id="option--standard"
646 name="--standard">/ command-line option.
648 For functions that are <tt/cdecl/, the rightmost parameter is pushed
649 onto the stack before the function is called. That increases the cost
650 of calling those functions, especially when they are called from many
651 places.<newline><newline>
654 <item> There are two pseudo variables named <tt/__AX__/ and <tt/__EAX__/.
655 Both refer to the primary register that is used by the compiler to
656 evaluate expressions or return function results. <tt/__AX__/ is of
657 type <tt/unsigned int/ and <tt/__EAX__/ of type <tt/long unsigned int/
658 respectively. The pseudo variables may be used as lvalue and rvalue as
659 every other variable. They are most useful together with short
660 sequences of assembler code. For example, the macro
670 will give the high byte of any unsigned value.
673 <item> Inside a function, the identifier <tt/__func__/ gives the name of the
674 current function as a string. Outside of functions, <tt/__func__/ is
679 #define PRINT_DEBUG(s) printf ("%s: %s\n", __func__, s);
682 The macro will print the name of the current function plus a given
686 <item> cc65 allows the initialization of <tt/void/ variables. This may be
687 used to create variable structures that are more compatible with
688 interfaces written for assembler languages. Here is an example:
691 void GCmd = { (char)3, (unsigned)0x2000, (unsigned)0x3000 };
694 This will be translated as follows:
703 Since the variable is of type <tt/void/ you may not use it as is.
704 However, taking the address of the variable results in a <tt/void*/
705 which may be passed to any function expecting a pointer.
707 See the <url url="geos.html" name="GEOS library document"> for examples
708 on how to use this feature.
711 <item> cc65 implements flexible array struct members as defined in the C99 ISO
712 standard. As an extension, these fields may be initialized. There are
713 several exceptions, however (which is probably the reason why the
714 standard does not define this feature, because it is highly
715 unorthogonal). Flexible array members cannot be initialized ...
718 <item>... when defining an array of structs with flexible
720 <item>... if such a struct is a member field of another struct
721 which is not the last field.
722 <item>... if the struct which contains a flexible array member is
723 declared as <tt/register/, and the size and compiler settings
724 do allow the compiler actually to place the struct into the
725 register bank in the zero page.
728 Please note that -- as defined in the ISO C standard -- the <tt/sizeof/
729 operator returns the struct size with the flexible array member having
730 size zero, even if it is initialized.
737 <sect>Predefined macros<p>
739 The compiler defines several macros at startup:
742 <tag><tt>__APPLE2__</tt></tag>
744 This macro is defined if the target is the Apple ][ (-t apple2) or the enhanced Apple //e (-t apple2enh).
746 <tag><tt>__APPLE2ENH__</tt></tag>
748 This macro is defined if the target is the enhanced Apple //e (-t apple2enh).
750 <tag><tt>__ATARI5200__</tt></tag>
752 This macro is defined if the target is the Atari 5200 game console.
754 <tag><tt>__ATARI__</tt></tag>
756 This macro is defined if the target is the Atari 400/800 (-t atari) or the Atari 800XL/130XE (-t atarixl).
758 <tag><tt>__ATARIXL__</tt></tag>
760 This macro is defined if the target is the Atari 800XL/130XE (-t atarixl).
762 <tag><tt>__ATMOS__</tt></tag>
764 This macro is defined if the target is the Oric Atmos (-t atmos).
766 <tag><tt>__C128__</tt></tag>
768 This macro is defined if the target is the Commodore 128 (-t c128).
770 <tag><tt>__C16__</tt></tag>
772 This macro is defined if the target is the Commodore 16/116 (-t c16) or the Commodore Plus/4 (-t plus4).
774 <tag><tt>__C64__</tt></tag>
776 This macro is defined if the target is the Commodore 64 (-t c64).
778 <tag><tt>__CBM__</tt></tag>
780 This macro is defined if the target system is one of the CBM targets.
782 <tag><tt>__CBM510__</tt></tag>
784 This macro is defined if the target is the CBM 500 series of computers.
786 <tag><tt>__CBM610__</tt></tag>
788 This macro is defined if the target is one of the CBM 600/700 family of
789 computers (called B series in the US).
791 <tag><tt>__CC65__</tt></tag>
793 This macro is always defined. Its value is the version number of the
794 compiler in hex. For example, version 2.14 of the compiler has this macro
795 defined as <tt/0x02E0/.
797 <tag><tt>__CC65_STD__</tt></tag>
799 This macro is defined to one of the following depending on the <tt><ref
800 id="option--standard" name="--standard"></tt> command line option:
802 <item><tt/__CC65_STD_C89__/
803 <item><tt/__CC65_STD_C99__/
804 <item><tt/__CC65_STD_CC65__/
807 <tag><tt>__DATE__</tt></tag>
809 This macro expands to the date of translation of the preprocessing
810 translation unit in the form "Mmm dd yyyy".
812 <tag><tt>__FILE__</tt></tag>
814 This macro expands to a string containing the name of the C source file.
816 <tag><tt>__GEOS__</tt></tag>
818 This macro is defined if you are compiling for one of the GEOS systems.
820 <tag><tt>__GEOS_APPLE__</tt></tag>
822 This macro is defined if you are compiling for the Apple GEOS system (-t geos-apple).
824 <tag><tt>__GEOS_CBM__</tt></tag>
826 This macro is defined if you are compiling for the GEOS 64/128 system (-t geos-cbm).
828 <tag><tt>__LINE__</tt></tag>
830 This macro expands to the current line number.
832 <tag><tt>__LUNIX__</tt></tag>
834 This macro is defined if you are compiling for the LUnix system (-t lunix).
836 <tag><tt>__LYNX__</tt></tag>
838 This macro is defined if the target is the Atari Lynx (-t lynx).
840 <tag><tt>__NES__</tt></tag>
842 This macro is defined if the target is the Nintendo Entertainment System (-t nes).
844 <tag><tt>__OPT__</tt></tag>
846 Is defined if the compiler was called with the <tt/-O/ command line option.
848 <tag><tt>__OPT_i__</tt></tag>
850 Is defined if the compiler was called with the <tt/-Oi/ command line option.
852 <tag><tt>__OPT_r__</tt></tag>
854 Is defined if the compiler was called with the <tt/-Or/ command line option.
856 <tag><tt>__OPT_s__</tt></tag>
858 Is defined if the compiler was called with the <tt/-Os/ command line option.
860 <tag><tt>__PET__</tt></tag>
862 This macro is defined if the target is the PET family of computers (-t pet).
864 <tag><tt>__PLUS4__</tt></tag>
866 This macro is defined if the target is the Commodore Plus/4 (-t plus4).
868 <tag><tt>__STDC_HOSTED__</tt></tag>
870 This macro is expands to the integer constant 1.
872 <tag><tt>__SIM6502__</tt></tag>
874 This macro is defined if the target is sim65 in 6502 mode (-t sim6502).
876 <tag><tt>__SIM65C02__</tt></tag>
877 This macro is defined if the target is sim65 in 65C02 mode (-t sim65c02).
879 <tag><tt>__SUPERVISION__</tt></tag>
881 This macro is defined if the target is the Supervision (-t supervision).
883 <tag><tt>__TIME__</tt></tag>
885 This macro expands to the time of translation of the preprocessing
886 translation unit in the form "hh:mm:ss".
888 <tag><tt>__VIC20__</tt></tag>
890 This macro is defined if the target is the Commodore VIC20 (-t vic20).
894 <sect>#pragmas<label id="pragmas"><p>
896 The compiler understands some pragmas that may be used to change code
897 generation and other stuff. Some of these pragmas understand a special form:
898 If the first parameter is <tt/push/, the old value is saved onto a stack
899 before changing it. The value may later be restored by using the <tt/pop/
900 parameter with the <tt/#pragma/.
902 <sect1><tt>#pragma bss-name ([push,] <name>)</tt><label id="pragma-bss-name"><p>
904 This pragma changes the name used for the BSS segment (the BSS segment
905 is used to store uninitialized data). The argument is a string enclosed
908 Note: The default linker configuration file does only map the standard
909 segments. If you use other segments, you have to create a new linker
912 Beware: The startup code will zero only the default BSS segment. If you
913 use another BSS segment, you have to do that yourself, otherwise
914 uninitialized variables do not have the value zero.
916 The <tt/#pragma/ understands the push and pop parameters as explained above.
920 #pragma bss-name ("MyBSS")
924 <sect1><tt>#pragma charmap (<index>, <code>)</tt><label id="pragma-charmap"><p>
926 Each literal string and each literal character in the source is translated
927 by use of a translation table. This translation table is preset when the
928 compiler is started depending on the target system, for example to map
929 ISO-8859-1 characters into PETSCII if the target is a commodore machine.
931 This pragma allows to change entries in the translation table, so the
932 translation for individual characters, or even the complete table may be
935 Both arguments are assumed to be unsigned characters with a valid range of
938 Beware of two pitfalls:
941 <item>The character index is actually the code of the character in the
942 C source, so character mappings do always depend on the source
943 character set. This means that <tt/#pragma charmap/ is not
944 portable -- it depends on the build environment.
945 <item>While it is possible to use character literals as indices, the
946 result may be somewhat unexpected, since character literals are
947 itself translated. For this reason I would suggest to avoid
948 character literals and use numeric character codes instead.
953 /* Use a space wherever an 'a' occurs in ISO-8859-1 source */
954 #pragma charmap (0x61, 0x20);
958 <sect1><tt>#pragma check-stack ([push,] on|off)</tt><label id="pragma-check-stack"><p>
960 Tells the compiler to insert calls to a stack checking subroutine to detect
961 stack overflows. The stack checking code will lead to somewhat larger and
962 slower programs, so you may want to use this pragma when debugging your
963 program and switch it off for the release version. If a stack overflow is
964 detected, the program is aborted.
966 If the argument is "off", stack checks are disabled (the default), otherwise
969 The <tt/#pragma/ understands the push and pop parameters as explained above.
971 <sect1><tt>#pragma code-name ([push,] <name>)</tt><label id="pragma-code-name"><p>
973 This pragma changes the name used for the CODE segment (the CODE segment
974 is used to store executable code). The argument is a string enclosed in
977 Note: The default linker configuration file does only map the standard
978 segments. If you use other segments, you have to create a new linker
981 The <tt/#pragma/ understands the push and pop parameters as explained above.
985 #pragma code-name ("MyCODE")
989 <sect1><tt>#pragma codesize ([push,] <int>)</tt><label id="pragma-codesize"><p>
991 This pragma allows finer control about speed vs. size decisions in the code
992 generation and optimization phase. It gives the allowed size increase factor
993 (in percent). The default is can be changed by use of the <tt/<ref
994 id="option-codesize" name="--codesize">/ compiler option.
996 The <tt/#pragma/ understands the push and pop parameters as explained above.
999 <sect1><tt>#pragma data-name ([push,] <name>)</tt><label id="pragma-data-name"><p>
1001 This pragma changes the name used for the DATA segment (the DATA segment
1002 is used to store initialized data). The argument is a string enclosed in
1005 Note: The default linker configuration file does only map the standard
1006 segments. If you use other segments, you have to create a new linker
1009 The <tt/#pragma/ understands the push and pop parameters as explained above.
1013 #pragma data-name ("MyDATA")
1017 <sect1><tt>#pragma local-strings ([push,] on|off)</tt><label id="pragma-local-strings"><p>
1019 When "on", emit string literals to the data segment when they're encountered
1020 in the source. The default ("off") is to keep string literals until end of
1021 assembly, merge read only literals if possible, and then output the literals
1022 into the data or rodata segment that is active at that point.
1024 Using this <tt/#pragma/ it is possible to control the behaviour from within
1025 the source. When <tt/#pragma local-strings/ is active, string literals are
1026 output immediately, which means that they go into the currently active data
1027 or rodata segment, but cannot be merged. When inactive, string literals are
1028 remembered and output as a whole when translation is finished.
1031 <sect1><tt>#pragma optimize ([push,] on|off)</tt><label id="pragma-optimize"><p>
1033 Switch optimization on or off. If the argument is "off", optimization is
1034 disabled, otherwise it is enabled. Please note that this pragma only effects
1035 whole functions. The setting in effect when the function is encountered will
1036 determine if the generated code is optimized or not.
1038 Optimization and code generation is also controlled by the <ref
1039 id="pragma-codesize" name="codesize pragma">.
1041 The default is "off", but may be changed with the <tt/<ref name="-O"
1042 id="option-O">/ compiler option.
1044 The <tt/#pragma/ understands the push and pop parameters as explained above.
1047 <sect1><tt>#pragma rodata-name ([push,] <name>)</tt><label id="pragma-rodata-name"><p>
1049 This pragma changes the name used for the RODATA segment (the RODATA
1050 segment is used to store readonly data). The argument is a string
1051 enclosed in double quotes.
1053 Note: The default linker configuration file does only map the standard
1054 segments. If you use other segments, you have to create a new linker
1057 The <tt/#pragma/ understands the push and pop parameters as explained above.
1061 #pragma rodata-name ("MyRODATA")
1065 <sect1><tt>#pragma regvaraddr ([push,] on|off)</tt><label id="pragma-regvaraddr"><p>
1067 The compiler does not allow to take the address of register variables.
1068 The regvaraddr pragma changes this. Taking the address of a register
1069 variable is allowed after using this pragma with "on" as argument.
1070 Using "off" as an argument switches back to the default behaviour.
1072 Beware: The C standard does not allow taking the address of a variable
1073 declared as register. So your programs become non-portable if you use
1074 this pragma. In addition, your program may not work. This is usually the
1075 case if a subroutine is called with the address of a register variable,
1076 and this subroutine (or a subroutine called from there) uses
1077 register variables. So be careful with this #pragma.
1079 The <tt/#pragma/ understands the push and pop parameters as explained above.
1083 #pragma regvaraddr(on) /* Allow taking the address
1084 * of register variables
1089 <sect1><tt>#pragma register-vars ([push,] on|off)</tt><label id="pragma-register-vars"><p>
1091 Enables or disables use of register variables. If register variables are
1092 disabled (the default), the <tt/register/ keyword is ignored. Register
1093 variables are explained in more detail in <ref id="register-vars" name="a separate
1096 The <tt/#pragma/ understands the push and pop parameters as explained above.
1099 <sect1><tt>#pragma signed-chars ([push,] on|off)</tt><label id="pragma-signed-chars"><p>
1101 Changes the signedness of the default character type. If the argument is
1102 "on", default characters are signed, otherwise characters are unsigned. The
1103 compiler default is to make characters unsigned since this creates a lot
1104 better code. This default may be overridden by the <tt/<ref
1105 name="--signed-chars" id="option-signed-chars">/ command line option.
1107 The <tt/#pragma/ understands the push and pop parameters as explained above.
1110 <sect1><tt>#pragma static-locals ([push,] on|off)</tt><label id="pragma-static-locals"<p>
1112 Use variables in the bss segment instead of variables on the stack. This
1113 pragma changes the default set by the compiler option <tt/<ref
1114 name="--static-locals" id="option-static-locals">/. If the argument is "on",
1115 local variables are allocated in the BSS segment, leading to shorter and in
1116 most cases faster, but non-reentrant code.
1118 The <tt/#pragma/ understands the push and pop parameters as explained above.
1121 <sect1><tt>#pragma warn (name, [push,] on|off)</tt><label id="pragma-warn"><p>
1123 Switch compiler warnings on or off. "name" is the name of a warning (see the
1124 <tt/<ref name="-W" id="option-W">/ compiler option for a list). The name is
1125 either followed by "pop", which restores the last pushed state, or by "on" or
1126 "off", optionally preceeded by "push" to push the current state before
1131 /* Don't warn about the unused parameter in function func */
1132 #pragma warn (unused-param, push, off)
1133 static int func (int unused)
1137 #pragma warn (unused-param, pop)
1140 <sect1><tt>#pragma writable-strings ([push,] on|off)</tt><label id="pragma-writable-strings"><p>
1142 Changes the storage location of string literals. For historical reasons,
1143 the C standard defines that string literals are of type "char[]", but
1144 writing to such a literal causes undefined behaviour. Most compilers
1145 (including cc65) place string literals in the read-only data segment, which
1146 may cause problems with old C code that writes to string literals.
1148 Using this pragma (or the corresponding command line option <tt/<ref
1149 name="--writable-strings" id="option-writable-strings">/) causes the
1150 literals to be placed in the data segment so they can be written to without
1153 The <tt/#pragma/ understands the push and pop parameters as explained above.
1156 <sect1><tt>#pragma zpsym (<name>)</tt><p>
1158 Tell the compiler that the -- previously as external declared -- symbol with
1159 the given name is a zero page symbol (usually from an assembler file).
1160 The compiler will create a matching import declaration for the assembler.
1165 #pragma zpsym ("foo"); /* foo is in the zeropage */
1171 <sect>Register variables<label id="register-vars"><p>
1173 The runtime for all supported platforms has 6 bytes of zero page space
1174 available for register variables (this could be increased, but I think it's a
1175 good value). So you can declare register variables up to a total size of 6 per
1176 function. The compiler will allocate register space on a "first come, first
1177 served" base and convert any <tt/register/ declarations that exceed the
1178 available register space silently to <tt/auto/. Parameters can also be
1179 declared as <tt/register/, this will in fact give slightly shorter code than
1180 using a register variable.
1182 Since a function must save the current values of the registers on entry and
1183 restore them on exit, there is an overhead associated with register variables,
1184 and this overhead is quite high (about 20 bytes per variable). This means that
1185 just declaring anything as <tt/register/ is not a good idea.
1187 The best use for register variables are pointers, especially those that point
1188 to structures. The magic number here is about 3 uses of a struct field: If the
1189 function contains this number or even more, the generated code will be usually
1190 shorter and faster when using a register variable for the struct pointer. The
1191 reason for this is that the register variable can in many cases be used as a
1192 pointer directly. Having a pointer in an auto variable means that this pointer
1193 must first be copied into a zero page location, before it can be dereferenced.
1195 Second best use for register variables are counters. However, there is not
1196 much difference in the code generated for counters, so you will need at least
1197 100 operations on this variable (for example in a loop) to make it worth the
1198 trouble. The only savings you get here are by the use of a zero page variable
1199 instead of one on the stack or in the data segment.
1201 Register variables must be explicitly enabled, either by using <tt/<ref
1202 name="-Or" id="option-O">/ or <tt/<ref name="--register-vars"
1203 id="option-register-vars">/ on the command line or by use of <tt/<ref
1204 name="#pragma register-vars" id="pragma-register-vars">/. Register variables
1205 are only accepted on function top level, register variables declared in
1206 interior blocks are silently converted to <tt/auto/. With register variables
1207 disabled, all variables declared as <tt/register/ are actually auto variables.
1209 Please take care when using register variables: While they are helpful and can
1210 lead to a tremendous speedup when used correctly, improper usage will cause
1211 bloated code and a slowdown.
1215 <sect>Inline assembler<label id="inline-asm"><p>
1217 The compiler allows to insert assembler statements into the output file. The
1221 asm (<string literal>[, optional parameters]) ;
1225 __asm__ (<string literal>[, optional parameters]) ;
1229 The first form is in the user namespace and is disabled by <tt><ref
1230 id="option--standard" name="--standard"></tt> if the argument is not <tt/cc65/.
1232 The asm statement may be used inside a function and on global file level. An
1233 inline assembler statement is a primary expression, so it may also be used as
1234 part of an expression. Please note however that the result of an expression
1235 containing just an inline assembler statement is always of type <tt/void/.
1237 The contents of the string literal are preparsed by the compiler and inserted
1238 into the generated assembly output, so that the can be further processed by
1239 the backend and especially the optimizer. For this reason, the compiler does
1240 only allow regular 6502 opcodes to be used with the inline assembler. Pseudo
1241 instructions (like <tt/.import/, <tt/.byte/ and so on) are <em/not/ allowed,
1242 even if the ca65 assembler (which is used to translate the generated assembler
1243 code) would accept them. The builtin inline assembler is not a replacement for
1244 the full blown macro assembler which comes with the compiler.
1246 Note: Inline assembler statements are subject to all optimizations done by the
1247 compiler. There is currently no way to protect an inline assembler statement
1248 from being moved or removed completely by the optimizer. If in doubt, check
1249 the generated assembler output, or disable optimizations.
1251 The string literal may contain format specifiers from the following list. For
1252 each format specifier, an argument is expected which is inserted instead of
1253 the format specifier before passing the assembly code line to the backend.
1256 <item><tt/%b/ - Numerical 8-bit value
1257 <item><tt/%w/ - Numerical 16-bit value
1258 <item><tt/%l/ - Numerical 32-bit value
1259 <item><tt/%v/ - Assembler name of a global variable or function
1260 <item><tt/%o/ - Stack offset of a local variable
1261 <item><tt/%g/ - Assembler name of a C label
1262 <item><tt/%s/ - The argument is converted to a string
1263 <item><tt/%%/ - The % sign itself
1266 Using these format specifiers, you can access C <tt/#defines/, variables or
1267 similar stuff from the inline assembler. For example, to load the value of
1268 a C <tt/#define/ into the Y register, one would use
1272 __asm__ ("ldy #%b", OFFS);
1275 Or, to access a struct member of a static variable:
1281 unsigned char color;
1283 static pixel_t pixel;
1284 __asm__ ("ldy #%b", offsetof(pixel_t, color));
1285 __asm__ ("lda %v,y", pixel);
1288 The next example shows how to use global variables to exchange data between C
1289 an assembler and how to handle assembler jumps:
1292 unsigned char globalSubA, globalSubB, globalSubResult;
1294 /* return a-b, return 255 if b>a */
1295 unsigned char sub (unsigned char a, unsigned char b)
1300 __asm__ ("lda %v", globalSubA);
1301 __asm__ ("sbc %v", globalSubB);
1302 __asm__ ("bcs %g", jumpSubNoError);
1303 __asm__ ("lda #$FF");
1305 __asm__ ("sta %v", globalSubResult);
1306 return globalSubResult;
1311 Arrays can also be accessed:
1314 unsigned char globalSquareTable[] = {
1315 0, 1, 4, 9, 16, 25, 36, 49, 64, 81,
1316 100, 121, 144, 169, 196, 225
1318 unsigned char globalSquareA, globalSquareResult;
1320 /* return a*a for a<16, else 255 */
1321 unsigned char square (unsigned char a)
1327 __asm__ ("ldx %v", globalSquareA);
1328 __asm__ ("lda %v,x", globalSquareTable);
1329 __asm__ ("sta %v", globalSquareResult);
1330 return globalSquareResult;
1335 Note: Do not embed the assembler labels that are used as names of global
1336 variables or functions into your asm statements. Code like this
1340 int bar () { return 1; }
1341 __asm__ ("lda _foo"); /* DON'T DO THAT! */
1343 __asm__ ("jsr _bar"); /* DON'T DO THAT EITHER! */
1347 may stop working if the way, the compiler generates these names is changed in
1348 a future version. Instead use the format specifiers from the table above:
1351 __asm__ ("lda %v", foo); /* OK */
1353 __asm__ ("jsr %v", bar); /* OK */
1358 <sect>Implementation-defined behavior<p>
1360 This section describes the behavior of cc65 when the standard describes the
1361 behavior as implementation-defined.
1367 This is the original compiler copyright:
1370 --------------------------------------------------------------------------
1373 This is the copyright notice for RA65, LINK65, LIBR65, and other
1374 Atari 8-bit programs. Said programs are Copyright 1989, by John R.
1375 Dunning. All rights reserved, with the following exceptions:
1377 Anyone may copy or redistribute these programs, provided that:
1379 1: You don't charge anything for the copy. It is permissable to
1380 charge a nominal fee for media, etc.
1382 2: All source code and documentation for the programs is made
1383 available as part of the distribution.
1385 3: This copyright notice is preserved verbatim, and included in
1388 You are allowed to modify these programs, and redistribute the
1389 modified versions, provided that the modifications are clearly noted.
1391 There is NO WARRANTY with this software, it comes as is, and is
1392 distributed in the hope that it may be useful.
1394 This copyright notice applies to any program which contains
1395 this text, or the refers to this file.
1397 This copyright notice is based on the one published by the Free
1398 Software Foundation, sometimes known as the GNU project. The idea
1399 is the same as theirs, ie the software is free, and is intended to
1400 stay that way. Everybody has the right to copy, modify, and re-
1401 distribute this software. Nobody has the right to prevent anyone
1402 else from copying, modifying or redistributing it.
1404 --------------------------------------------------------------------------
1407 Small parts of the compiler (parts of the preprocessor and main parser) are
1408 still covered by this copyright. The main portion is covered by the usual
1409 cc65 license, which reads:
1411 This software is provided 'as-is', without any expressed or implied
1412 warranty. In no event will the authors be held liable for any damages
1413 arising from the use of this software.
1415 Permission is granted to anyone to use this software for any purpose,
1416 including commercial applications, and to alter it and redistribute it
1417 freely, subject to the following restrictions:
1420 <item> The origin of this software must not be misrepresented; you must not
1421 claim that you wrote the original software. If you use this software
1422 in a product, an acknowledgment in the product documentation would be
1423 appreciated but is not required.
1424 <item> Altered source versions must be plainly marked as such, and must not
1425 be misrepresented as being the original software.
1426 <item> This notice may not be removed or altered from any source