1 <!doctype linuxdoc system>
4 <title>cc65 Users Guide
5 <author>Ullrich von Bassewitz, <htmlurl url="mailto:uz@cc65.org" name="uz@cc65.org">
6 <date>2000-09-03, 2001-10-02, 2005-08-01
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
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 --bss-name seg Set the name of the BSS segment
78 --check-stack Generate stack overflow checks
79 --code-name seg Set the name of the CODE segment
80 --codesize x Accept larger code by factor x
81 --cpu type Set cpu type (6502, 65c02)
82 --create-dep name Create a make dependency file
83 --create-full-dep name Create a full make dependency file
84 --data-name seg Set the name of the DATA segment
86 --debug-info Add debug info to object file
87 --debug-opt name Debug optimization steps
88 --disable-opt name Disable an optimization step
89 --enable-opt name Enable an optimization step
90 --forget-inc-paths Forget include search paths
91 --help Help (this text)
92 --include-dir dir Set an include directory search path
93 --list-opt-steps List all optimizer steps and exit
94 --local-strings Emit string literals immediately
95 --memory-model model Set the memory model
96 --register-space b Set space available for register variables
97 --register-vars Enable register variables
98 --rodata-name seg Set the name of the RODATA segment
99 --signed-chars Default characters are signed
100 --standard std Language standard (c89, c99, cc65)
101 --static-locals Make local variables static
102 --target sys Set the target system
103 --verbose Increase verbosity
104 --version Print the compiler version number
105 --writable-strings Make string literals writable
106 ---------------------------------------------------------------------------
110 <sect1>Command line options in detail<p>
112 Here is a description of all the command line options:
116 <label id="option-bss-name">
117 <tag><tt>--bss-name seg</tt></tag>
119 Set the name of the bss segment. See also <tt/<ref id="pragma-bss-name"
120 name="#pragma bss-name">/.
123 <label id="option-check-stack">
124 <tag><tt>--check-stack</tt></tag>
126 Tells the compiler to generate code that checks for stack overflows. See
127 <tt/<ref id="pragma-check-stack" name="#pragma check-stack">/ for an
128 explanation of this feature.
131 <label id="option-code-name">
132 <tag><tt>--code-name seg</tt></tag>
134 Set the name of the code segment. See also <tt/<ref id="pragma-code-name"
135 name="#pragma code-name">/
138 <label id="option-codesize">
139 <tag><tt>--codesize x</tt></tag>
141 This options allows finer control about speed vs. size decisions in the code
142 generation and optimization phases. It gives the allowed size increase
143 factor (in percent). The default is 100 when not using <tt/-Oi/ and 200 when
144 using <tt/-Oi/ (<tt/-Oi/ is the same as <tt/-O --codesize 200/).
147 <label id="option-cpu">
148 <tag><tt>--cpu CPU</tt></tag>
150 A new, still experimental option. You may specify "6502" or "65C02" as the
151 CPU. 6502 is the default, so this will not change anything. Specifying 65C02
152 will use a few 65C02 instructions when generating code. Don't expect too
153 much from this option: It is still new (and may have bugs), and the
154 additional instructions for the 65C02 are not that overwhelming.
157 <label id="option-create-dep">
158 <tag><tt>--create-dep name</tt></tag>
160 Tells the compiler to generate a file containing the dependency list for the
161 compiled module in makefile syntax. The output is written to a file with the
162 given name. The output does not include system include files (in angle
166 <label id="option-create-full-dep">
167 <tag><tt>--create-full-dep name</tt></tag>
169 Tells the compiler to generate a file containing the dependency list for the
170 compiled module in makefile syntax. The output is written to a file with the
171 given name. The output does include system include files (in angle
175 <label id="option-data-name">
176 <tag><tt>--data-name seg</tt></tag>
178 Set the name of the data segment. See also <tt/<ref id="pragma-data-name"
179 name="#pragma data-name">/
182 <tag><tt>-d, --debug</tt></tag>
184 Enables debug mode, something that should not be needed for mere
188 <tag><tt>-D sym[=definition]</tt></tag>
190 Define a macro on the command line. If no definition is given, the macro
191 is defined to the value "1".
194 <tag><tt>--forget-inc-paths</tt></tag>
196 Forget the builtin include paths. This is most useful when building
197 customized C or runtime libraries, in which case the standard header
198 files should be ignored.
201 <tag><tt>-g, --debug-info</tt></tag>
203 This will cause the compiler to insert a <tt/.DEBUGINFO/ command into the
204 generated assembler code. This will cause the assembler to include all
205 symbols in a special section in the object file.
208 <tag><tt>-h, --help</tt></tag>
210 Print the short option summary shown above.
213 <label id="option-local-strings">
214 <tag><tt>--local-strings</tt></tag>
216 Emit string literals to the data segment when they're encountered in the
217 source. The default is to keep string literals until end of assembly, merge
218 read only literals if possible, and then output the literals into the data
219 or rodata segment that is active at that point. Use of this option prevents
220 merging of duplicate strings, but the options that change the name of one of
221 the data segments will work.
223 You can also use <tt><ref id="pragma-local-strings"
224 name="#pragma local-strings"></tt> for fine grained control.
227 <tag><tt>-o name</tt></tag>
229 Specify the name of the output file. If you don't specify a name, the
230 name of the C input file is used, with the extension replaced by ".s".
233 <label id="option-register-vars">
234 <tag><tt>-r, --register-vars</tt></tag>
236 <tt/-r/ will make the compiler honor the <tt/register/ keyword. Local
237 variables may be placed in registers (which are actually zero page
238 locations). There is some overhead involved with register variables, since
239 the old contents of the registers must be saved and restored. Since register
240 variables are of limited use without the optimizer, there is also a combined
241 switch: <tt/-Or/ will enable both, the optimizer and register variables.
243 For more information about register variables see <ref id="register-vars"
244 name="register variables">.
246 The compiler setting can also be changed within the source file by using
247 <tt/<ref id="pragma-register-vars" name="#pragma register-vars">/.
250 <label id="option-register-space">
251 <tag><tt>--register-space</tt></tag>
253 This option takes a numeric parameter and is used to specify, how much
254 zero page register space is available. Please note that just giving this
255 option will not increase or decrease by itself, it will just tell the
256 compiler about the available space. You will have to allocate that space
257 yourself using an assembler module with the necessary allocations, and a
258 linker configuration that matches the assembler module. The default value
259 for this option is 6 (bytes).
261 If you don't know what all this means, please don't use this option.
264 <label id="option-rodata-name">
265 <tag><tt>--rodata-name seg</tt></tag>
267 Set the name of the rodata segment (the segment used for readonly data).
268 See also <tt/<ref id="pragma-rodata-name" name="#pragma rodata-name">/
270 <label id="option-signed-chars">
271 <tag><tt>-j, --signed-chars</tt></tag>
273 Using this option, you can make the default characters signed. Since the
274 6502 has no provisions for sign extending characters (which is needed on
275 almost any load operation), this will make the code larger and slower. A
276 better way is to declare characters explicitly as "signed" if needed. You
277 can also use <tt><ref id="pragma-signed-chars"
278 name="#pragma signed-chars"></tt> for better control of this option.
281 <label id="option--standard">
282 <tag><tt>--standard std</tt></tag>
284 This option allows to set the language standard supported. The argument is
288 This disables anything that is illegal in C89/C90. Among those things
289 are <tt>//</tt> comments and the non-standard keywords without
290 underscores. Please note that cc65 is not a fully C89 compliant compiler
291 despite this option. A few more things (like floats) are missing.
294 This enables a few features from the C99 standard. With this option,
295 <tt>//</tt> comments are allowed. It will also cause warnings and even
296 errors in a few situations that are allowed with <tt/--standard c89/.
297 For example, a call to a function without a prototype is an error in
301 This is the default mode. It is like c99 mode, but additional features
302 are enabled. Among these are "void data", non-standard keywords without
303 the underlines, unnamed function parameters and the requirement for
304 main() to return an int.
307 Please note that the compiler does not support the C99 standard and never
308 will. c99 mode is actually c89 mode with a few selected C99 extensions.
311 <label id="option-standard">
312 <tag><tt>-t target, --target target</tt></tag>
314 This option is used to set the target system. The target system
315 determines things like the character set that is used for strings and
316 character constants. The following target systems are supported:
324 <item>c16 (works also for the c116 with memory up to 32K)
327 <item>cbm510 (CBM-II series with 40 column video)
328 <item>cbm610 (all CBM-II II computers with 80 column video)
333 <item>pet (all CBM PET systems except the 2001)
339 <tag><tt>-v, --verbose</tt></tag>
341 Using this option, the compiler will be somewhat more verbose if errors
342 or warnings are encountered.
345 <label id="option-writable-strings">
346 <tag><tt>--writable-strings</tt></tag>
348 Make string literals writable by placing them into the data segment instead
349 of the rodata segment. You can also use <tt><ref id="pragma-writable-strings"
350 name="#pragma writable-strings"></tt> to control this option from within
354 <label id="option-static-locals">
355 <tag><tt>-Cl, --static-locals</tt></tag>
357 Use static storage for local variables instead of storage on the stack.
358 Since the stack is emulated in software, this gives shorter and usually
359 faster code, but the code is no longer reentrant. The difference between
360 <tt/-Cl/ and declaring local variables as static yourself is, that
361 initializer code is executed each time, the function is entered. So when
372 the variable <tt/a/ will always have the value <tt/1/ when entering the
373 function and using <tt/-Cl/, while in
378 static unsigned a = 1;
383 the variable <tt/a/ will have the value <tt/1/ only the first time that the
384 function is entered, and will keep the old value from one call of the
385 function to the next.
387 You may also use <tt><ref id="pragma-static-locals"
388 name="#pragma static-locals"></tt> to change this setting in your
392 <label id="option-include-dir">
393 <tag><tt>-I dir, --include-dir dir</tt></tag>
395 Set a directory where the compiler searches for include files. You may
396 use this option multiple times to add more than one directory to the
400 <label id="option-O">
401 <tag><tt>-O, -Oi, -Or, -Os</tt></tag>
403 Enable an optimizer run over the produced code.
405 Using <tt/-Oi/, the code generator will inline some code where otherwise a
406 runtime functions would have been called, even if the generated code is
407 larger. This will not only remove the overhead for a function call, but will
408 make the code visible for the optimizer. <tt/-Oi/ is an alias for
409 <tt/-O --codesize 200/.
411 <tt/-Or/ will make the compiler honor the <tt/register/ keyword. Local
412 variables may be placed in registers (which are actually zero page
413 locations). See also the <tt/<ref id="option-register-vars"
414 name="--register-vars">/ command line option, and the <ref
415 id="register-vars" name="discussion of register variables"> below.
417 Using <tt/-Os/ will force the compiler to inline some known functions from
418 the C library like strlen. Note: This has two consequences:
421 <item>You may not use names of standard C functions in your own code. If you
422 do that, your program is not standard compliant anyway, but using
423 <tt/-Os/ will actually break things.
425 <item>The inlined string and memory functions will not handle strings or
426 memory areas larger than 255 bytes. Similarly, the inlined <tt/is..()/
427 functions will not work with values outside the char. range (such as
432 It is possible to concatenate the modifiers for <tt/-O/. For example, to
433 enable register variables and inlining of known functions, you may use
437 <tag><tt>-T, --add-source</tt></tag>
439 This include the source code as comments in the generated code. This is
443 <tag><tt>-V, --version</tt></tag>
445 Print the version number of the compiler. When submitting a bug report,
446 please include the operating system you're using, and the compiler
450 <label id="option-W">
451 <tag><tt>-W name[,name]</tt></tag>
453 This option allows to control warnings generated by the compiler. It is
454 followed by a comma separated list of warnings that should be enabled or
455 disabled. To disable a warning, its name is prefixed by a minus sign. If
456 no such prefix exists, or the name is prefixed by a plus sign, the warning
459 The following warning names are currently recognized:
461 <tag><tt/error/</tag>
462 Treat all warnings as errors.
463 <tag><tt/unknown-pragma/</tag>
464 Warn about known #pragmas.
465 <tag><tt/unused-label/</tag>
466 Warn about unused labels.
467 <tag><tt/unused-param/</tag>
468 Warn about unused function parameters.
469 <tag><tt/unused-var/</tag>
470 Warn about unused variables.
473 You may also use <tt><ref id="pragma-warn" name="#pragma warn"></tt> to
474 control this setting for smaller pieces of code from within your code.
479 <sect>Input and output<p>
481 The compiler will accept one C file per invocation and create a file with
482 the same base name, but with the extension replaced by ".s". The output
483 file contains assembler code suitable for the use with the ca65 macro
486 Include files in single quotes are searched in the following places:
488 <item>The current directory.
489 <item>The value of the environment variable <tt/CC65_INC/ if it is defined.
490 <item>Any directory added with the <tt/-I/ option on the command line.
493 Include files in angle brackets are searched in the following places:
495 <item>A compiled in directory which is often <tt>/usr/lib/cc65/include</tt> on
497 <item>The value of the environment variable <tt/CC65_INC/ if it is defined.
498 <item>A subdirectory named <tt/include/ of the directory defined in the
499 environment variable <tt/CC65_HOME/, if it is defined.
500 <item>Any directory added with the <tt/-I/ option on the command line.
505 <sect>Differences to the ISO standard<p>
507 Apart from the things listed below, the compiler does support additional
508 keywords, has several functions in the standard headers with names outside the
509 reserved namespace and a few syntax extensions. All these can be disabled with
510 the <tt><ref id="option--standard" name="--standard"></tt> command line
511 option. Its use for maximum standards compatibility is advised.
513 Here is a list of differences between the language, the compiler accepts,
514 and the one defined by the ISO standard:
518 <item> The datatypes "float" and "double" are not available.
520 <item> C Functions may not return structs (or unions), and structs may not
521 be passed as parameters by value. However, struct assignment *is*
524 <item> Part of the C library is available only with fastcall calling
525 conventions (see below). It means that you must not mix pointers to
526 those functions with pointers to user-written, not-fastcall functions.
528 <item> The <tt/volatile/ keyword doesn't have an effect. This is not as bad
529 as it sounds, since the 6502 has so few registers that it isn't
530 possible to keep values in registers anyway.
534 There may be some more minor differences I'm currently not aware of. The
535 biggest problem is the missing float data type. With this limitation in
536 mind, you should be able to write fairly portable code.
542 This cc65 version has some extensions to the ISO C standard.
546 <item> The compiler allows to insert assembler statements into the output
550 asm (<string literal>[, optional parameters]) ;
554 __asm__ (<string literal>[, optional parameters]) ;
557 The first form is in the user namespace and is disabled if the <tt/-A/
560 There is a whole section covering inline assembler statements,
561 <ref id="inline-asm" name="see there">.
564 <item> There is a special calling convention named "fastcall".
565 The syntax for a function declaration using fastcall is
568 <return type> fastcall <function name> (<parameter list>)
572 <return type> __fastcall__ <function name> (<parameter list>)
576 void __fastcall__ f (unsigned char c)
578 The first form of the fastcall keyword is in the user namespace and can
579 therefore be disabled with the <tt><ref id="option--standard"
580 name="--standard"></tt> command line option.
582 For functions declared as <tt/fastcall/, the rightmost parameter is not
583 pushed on the stack but left in the primary register when the function
584 is called. This will reduce the cost when calling assembler functions
585 significantly, especially when the function itself is rather small.
588 <item> There are two pseudo variables named <tt/__AX__/ and <tt/__EAX__/.
589 Both refer to the primary register that is used by the compiler to
590 evaluate expressions or return function results. <tt/__AX__/ is of
591 type <tt/unsigned int/ and <tt/__EAX__/ of type <tt/long unsigned int/
592 respectively. The pseudo variables may be used as lvalue and rvalue as
593 every other variable. They are most useful together with short
594 sequences of assembler code. For example, the macro
604 will give the high byte of any unsigned value.
607 <item> Inside a function, the identifier <tt/__func__/ gives the name of the
608 current function as a string. Outside of functions, <tt/__func__/ is
613 #define PRINT_DEBUG(s) printf ("%s: %s\n", __func__, s);
616 The macro will print the name of the current function plus a given
620 <item> cc65 allows the initialization of <tt/void/ variables. This may be
621 used to create variable structures that are more compatible with
622 interfaces written for assembler languages. Here is an example:
625 void GCmd = { (char)3, (unsigned)0x2000, (unsigned)0x3000 };
628 This will be translated as follows:
637 Since the variable is of type <tt/void/ you may not use it as is.
638 However, taking the address of the variable results in a <tt/void*/
639 which may be passed to any function expecting a pointer.
641 See the <url url="geos.html" name="GEOS library document"> for examples
642 on how to use this feature.
645 <item> cc65 implements flexible array struct members as defined in the C99 ISO
646 standard. As an extension, these fields may be initialized. There are
647 several exceptions, however (which is probably the reason why the
648 standard does not define this feature, because it is highly
649 unorthogonal). Flexible array members cannot be initialized ...
652 <item>... when defining an array of structs with flexible
654 <item>... if such a struct is a member field of another struct
655 which is not the last field.
656 <item>... if the struct which contains a flexible array member is
657 declared as <tt/register/, and the size and compiler settings
658 do allow the compiler actually to place the struct into the
659 register bank in the zero page.
662 Please note that -- as defined in the ISO C standard -- the <tt/sizeof/
663 operator returns the struct size with the flexible array member having
664 size zero, even if it is initialized.
671 <sect>Predefined macros<p>
673 The compiler defines several macros at startup:
677 <tag><tt>__CC65__</tt></tag>
679 This macro is always defined. Its value is the version number of the
680 compiler in hex. For example, version 2.10.1 of the compiler has this macro
681 defined as <tt/0x02A1/.
683 <tag><tt>__APPLE2__</tt></tag>
685 This macro is defined if the target is the Apple ][ (-t apple2).
687 <tag><tt>__APPLE2ENH__</tt></tag>
689 This macro is defined if the target is the enhanced Apple //e (-t apple2enh).
691 <tag><tt>__ATARI__</tt></tag>
693 This macro is defined if the target is one of the Atari computers
694 (400/800/130XL/800XL).
696 <tag><tt>__ATMOS__</tt></tag>
698 This macro is defined if the target is the Oric Atmos (-t atmos).
700 <tag><tt>__CBM__</tt></tag>
702 This macro is defined if the target system is one of the CBM targets.
704 <tag><tt>__C16__</tt></tag>
706 This macro is defined if the target is the c16 (-t c16).
708 <tag><tt>__C64__</tt></tag>
710 This macro is defined if the target is the c64 (-t c64).
712 <tag><tt>__C128__</tt></tag>
714 This macro is defined if the target is the c128 (-t c128).
716 <tag><tt>__CBM510__</tt></tag>
718 This macro is defined if the target is the CBM 500 series of computers.
720 <tag><tt>__CBM610__</tt></tag>
722 This macro is defined if the target is one of the CBM 600/700 family of
723 computers (called B series in the US).
725 <tag><tt>__GEOS__</tt></tag>
727 This macro is defined if you are compiling for the GEOS system (-t geos).
729 <tag><tt>__LUNIX__</tt></tag>
731 This macro is defined if you are compiling for the LUnix system (-t lunix).
733 <tag><tt>__LYNX__</tt></tag>
735 This macro is defined if the target is the Atari Lynx (-t lynx).
737 <tag><tt>__NES__</tt></tag>
739 This macro is defined if the target is the NES (-t nes).
741 <tag><tt>__PET__</tt></tag>
743 This macro is defined if the target is the PET family of computers (-t pet).
745 <tag><tt>__PLUS4__</tt></tag>
747 This macro is defined if the target is the plus/4 (-t plus4).
749 <tag><tt>__SUPERVISION__</tt></tag>
751 This macro is defined if the target is the supervision (-t supervision).
753 <tag><tt>__VIC20__</tt></tag>
755 This macro is defined if the target is the vic20 (-t vic20).
757 <tag><tt>__FILE__</tt></tag>
759 This macro expands to a string containing the name of the C source file.
761 <tag><tt>__LINE__</tt></tag>
763 This macro expands to the current line number.
765 <tag><tt>__CC65_STD__</tt></tag>
767 This macro is defined to one of the following depending on the <tt><ref
768 id="option--standard" name="--standard"></tt> command line option:
770 <item><tt/__CC65_STD_C89__/
771 <item><tt/__CC65_STD_C99__/
772 <item><tt/__CC65_STD_CC65__/
775 <tag><tt>__OPT__</tt></tag>
777 Is defined if the compiler was called with the <tt/-O/ command line option.
779 <tag><tt>__OPT_i__</tt></tag>
781 Is defined if the compiler was called with the <tt/-Oi/ command line option.
783 <tag><tt>__OPT_r__</tt></tag>
785 Is defined if the compiler was called with the <tt/-Or/ command line option.
787 <tag><tt>__OPT_s__</tt></tag>
789 Is defined if the compiler was called with the <tt/-Os/ command line option.
794 <sect>#pragmas<label id="pragmas"><p>
796 The compiler understands some pragmas that may be used to change code
797 generation and other stuff. Some of these pragmas understand a special form:
798 If the first parameter is <tt/push/, the old value is saved onto a stack
799 before changing it. The value may later be restored by using the <tt/pop/
800 parameter with the <tt/#pragma/.
802 <sect1><tt>#pragma bss-name ([push,] <name>)</tt><label id="pragma-bss-name"><p>
804 This pragma changes the name used for the BSS segment (the BSS segment
805 is used to store uninitialized data). The argument is a string enclosed
808 Note: The default linker configuration file does only map the standard
809 segments. If you use other segments, you have to create a new linker
812 Beware: The startup code will zero only the default BSS segment. If you
813 use another BSS segment, you have to do that yourself, otherwise
814 uninitialized variables do not have the value zero.
816 The <tt/#pragma/ understands the push and pop parameters as explained above.
820 #pragma bss-name ("MyBSS")
824 <sect1><tt>#pragma charmap (<index>, <code>)</tt><label id="pragma-charmap"><p>
826 Each literal string and each literal character in the source is translated
827 by use of a translation table. This translation table is preset when the
828 compiler is started depending on the target system, for example to map
829 ISO-8859-1 characters into PETSCII if the target is a commodore machine.
831 This pragma allows to change entries in the translation table, so the
832 translation for individual characters, or even the complete table may be
835 Both arguments are assumed to be unsigned characters with a valid range of
838 Beware of two pitfalls:
841 <item>The character index is actually the code of the character in the
842 C source, so character mappings do always depend on the source
843 character set. This means that <tt/#pragma charmap/ is not
844 portable -- it depends on the build environment.
845 <item>While it is possible to use character literals as indices, the
846 result may be somewhat unexpected, since character literals are
847 itself translated. For this reason I would suggest to avoid
848 character literals and use numeric character codes instead.
853 /* Use a space wherever an 'a' occurs in ISO-8859-1 source */
854 #pragma charmap (0x61, 0x20);
858 <sect1><tt>#pragma check-stack ([push,] on|off)</tt><label id="pragma-check-stack"><p>
860 Tells the compiler to insert calls to a stack checking subroutine to detect
861 stack overflows. The stack checking code will lead to somewhat larger and
862 slower programs, so you may want to use this pragma when debugging your
863 program and switch it off for the release version. If a stack overflow is
864 detected, the program is aborted.
866 If the argument is "off", stack checks are disabled (the default), otherwise
869 The <tt/#pragma/ understands the push and pop parameters as explained above.
871 <sect1><tt>#pragma code-name ([push,] <name>)</tt><label id="pragma-code-name"><p>
873 This pragma changes the name used for the CODE segment (the CODE segment
874 is used to store executable code). The argument is a string enclosed in
877 Note: The default linker configuration file does only map the standard
878 segments. If you use other segments, you have to create a new linker
881 The <tt/#pragma/ understands the push and pop parameters as explained above.
885 #pragma code-name ("MyCODE")
889 <sect1><tt>#pragma codesize ([push,] <int>)</tt><label id="pragma-codesize"><p>
891 This pragma allows finer control about speed vs. size decisions in the code
892 generation and optimization phase. It gives the allowed size increase factor
893 (in percent). The default is can be changed by use of the <tt/<ref
894 id="option-codesize" name="--codesize">/ compiler option.
896 The <tt/#pragma/ understands the push and pop parameters as explained above.
899 <sect1><tt>#pragma data-name ([push,] <name>)</tt><label id="pragma-data-name"><p>
901 This pragma changes the name used for the DATA segment (the DATA segment
902 is used to store initialized data). The argument is a string enclosed in
905 Note: The default linker configuration file does only map the standard
906 segments. If you use other segments, you have to create a new linker
909 The <tt/#pragma/ understands the push and pop parameters as explained above.
913 #pragma data-name ("MyDATA")
917 <sect1><tt>#pragma local-strings ([push,] on|off)</tt><label id="pragma-local-strings"><p>
919 When "on", emit string literals to the data segment when they're encountered
920 in the source. The default ("off") is to keep string literals until end of
921 assembly, merge read only literals if possible, and then output the literals
922 into the data or rodata segment that is active at that point.
924 Using this <tt/#pragma/ it is possible to control the behaviour from within
925 the source. When <tt/#pragma local-strings/ is active, string literals are
926 output immediately, which means that they go into the currently active data
927 or rodata segment, but cannot be merged. When inactive, string literals are
928 remembered and output as a whole when translation is finished.
931 <sect1><tt>#pragma optimize ([push,] on|off)</tt><label id="pragma-optimize"><p>
933 Switch optimization on or off. If the argument is "off", optimization is
934 disabled, otherwise it is enabled. Please note that this pragma only effects
935 whole functions. The setting in effect when the function is encountered will
936 determine if the generated code is optimized or not.
938 Optimization and code generation is also controlled by the <ref
939 id="pragma-codesize" name="codesize pragma">.
941 The default is "off", but may be changed with the <tt/<ref name="-O"
942 id="option-O">/ compiler option.
944 The <tt/#pragma/ understands the push and pop parameters as explained above.
947 <sect1><tt>#pragma rodata-name ([push,] <name>)</tt><label id="pragma-rodata-name"><p>
949 This pragma changes the name used for the RODATA segment (the RODATA
950 segment is used to store readonly data). The argument is a string
951 enclosed in double quotes.
953 Note: The default linker configuration file does only map the standard
954 segments. If you use other segments, you have to create a new linker
957 The <tt/#pragma/ understands the push and pop parameters as explained above.
961 #pragma rodata-name ("MyRODATA")
965 <sect1><tt>#pragma regvaraddr ([push,] on|off)</tt><label id="pragma-regvaraddr"><p>
967 The compiler does not allow to take the address of register variables.
968 The regvaraddr pragma changes this. Taking the address of a register
969 variable is allowed after using this pragma with "on" as argument.
970 Using "off" as an argument switches back to the default behaviour.
972 Beware: The C standard does not allow taking the address of a variable
973 declared as register. So your programs become non-portable if you use
974 this pragma. In addition, your program may not work. This is usually the
975 case if a subroutine is called with the address of a register variable,
976 and this subroutine (or a subroutine called from there) uses
977 register variables. So be careful with this #pragma.
979 The <tt/#pragma/ understands the push and pop parameters as explained above.
983 #pragma regvaraddr(on) /* Allow taking the address
984 * of register variables
989 <sect1><tt>#pragma register-vars ([push,] on|off)</tt><label id="pragma-register-vars"><p>
991 Enables or disables use of register variables. If register variables are
992 disabled (the default), the <tt/register/ keyword is ignored. Register
993 variables are explained in more detail in <ref id="register-vars" name="a separate
996 The <tt/#pragma/ understands the push and pop parameters as explained above.
999 <sect1><tt>#pragma signed-chars ([push,] on|off)</tt><label id="pragma-signed-chars"><p>
1001 Changes the signedness of the default character type. If the argument is
1002 "on", default characters are signed, otherwise characters are unsigned. The
1003 compiler default is to make characters unsigned since this creates a lot
1004 better code. This default may be overridden by the <tt/<ref
1005 name="--signed-chars" id="option-signed-chars">/ command line option.
1007 The <tt/#pragma/ understands the push and pop parameters as explained above.
1010 <sect1><tt>#pragma static-locals ([push,] on|off)</tt><label id="pragma-static-locals"<p>
1012 Use variables in the bss segment instead of variables on the stack. This
1013 pragma changes the default set by the compiler option <tt/<ref
1014 name="--static-locals" id="option-static-locals">/. If the argument is "on",
1015 local variables are allocated in the BSS segment, leading to shorter and in
1016 most cases faster, but non-reentrant code.
1018 The <tt/#pragma/ understands the push and pop parameters as explained above.
1021 <sect1><tt>#pragma warn (name, [push,] on|off)</tt><label id="pragma-warn"><p>
1023 Switch compiler warnings on or off. "name" is the name of a warning (see the
1024 <tt/<ref name="-W" id="option-W">/ compiler option for a list). The name is
1025 either followed by "pop", which restores the last pushed state, or by "on" or
1026 "off", optionally preceeded by "push" to push the current state before
1031 /* Don't warn about the unused parameter in function func */
1032 #pragma warn (unused-param, push, off)
1033 static int func (int unused)
1037 #pragma warn (unused-param, pop)
1040 <sect1><tt>#pragma writable-strings ([push,] on|off)</tt><label id="pragma-writable-strings"><p>
1042 Changes the storage location of string literals. For historical reasons,
1043 the C standard defines that string literals are of type "char[]", but
1044 writing to such a literal causes undefined behaviour. Most compilers
1045 (including cc65) place string literals in the read-only data segment, which
1046 may cause problems with old C code that writes to string literals.
1048 Using this pragma (or the corresponding command line option <tt/<ref
1049 name="--writable-strings" id="option-writable-strings">/) causes the
1050 literals to be placed in the data segment so they can be written to without
1053 The <tt/#pragma/ understands the push and pop parameters as explained above.
1056 <sect1><tt>#pragma zpsym (<name>)</tt><p>
1058 Tell the compiler that the -- previously as external declared -- symbol with
1059 the given name is a zero page symbol (usually from an assembler file).
1060 The compiler will create a matching import declaration for the assembler.
1065 #pragma zpsym ("foo"); /* foo is in the zeropage */
1071 <sect>Register variables<label id="register-vars"><p>
1073 The runtime for all supported platforms has 6 bytes of zero page space
1074 available for register variables (this could be increased, but I think it's a
1075 good value). So you can declare register variables up to a total size of 6 per
1076 function. The compiler will allocate register space on a "first come, first
1077 served" base and convert any <tt/register/ declarations that exceed the
1078 available register space silently to <tt/auto/. Parameters can also be
1079 declared as <tt/register/, this will in fact give slightly shorter code than
1080 using a register variable.
1082 Since a function must save the current values of the registers on entry and
1083 restore them on exit, there is an overhead associated with register variables,
1084 and this overhead is quite high (about 20 bytes per variable). This means that
1085 just declaring anything as <tt/register/ is not a good idea.
1087 The best use for register variables are pointers, especially those that point
1088 to structures. The magic number here is about 3 uses of a struct field: If the
1089 function contains this number or even more, the generated code will be usually
1090 shorter and faster when using a register variable for the struct pointer. The
1091 reason for this is that the register variable can in many cases be used as a
1092 pointer directly. Having a pointer in an auto variable means that this pointer
1093 must first be copied into a zero page location, before it can be dereferenced.
1095 Second best use for register variables are counters. However, there is not
1096 much difference in the code generated for counters, so you will need at least
1097 100 operations on this variable (for example in a loop) to make it worth the
1098 trouble. The only savings you get here are by the use of a zero page variable
1099 instead of one on the stack or in the data segment.
1101 Register variables must be explicitly enabled, either by using <tt/<ref
1102 name="-Or" id="option-O">/ or <tt/<ref name="--register-vars"
1103 id="option-register-vars">/ on the command line or by use of <tt/<ref
1104 name="#pragma register-vars" id="pragma-register-vars">/. Register variables
1105 are only accepted on function top level, register variables declared in
1106 interior blocks are silently converted to <tt/auto/. With register variables
1107 disabled, all variables declared as <tt/register/ are actually auto variables.
1109 Please take care when using register variables: While they are helpful and can
1110 lead to a tremendous speedup when used correctly, improper usage will cause
1111 bloated code and a slowdown.
1115 <sect>Inline assembler<label id="inline-asm"><p>
1117 The compiler allows to insert assembler statements into the output file. The
1121 asm (<string literal>[, optional parameters]) ;
1125 __asm__ (<string literal>[, optional parameters]) ;
1129 The first form is in the user namespace and is disabled by <tt><ref
1130 id="option--standard" name="--standard"></tt> if the argument is not <tt/cc65/.
1132 The asm statement may be used inside a function and on global file level. An
1133 inline assembler statement is a primary expression, so it may also be used as
1134 part of an expression. Please note however that the result of an expression
1135 containing just an inline assembler statement is always of type <tt/void/.
1137 The contents of the string literal are preparsed by the compiler and inserted
1138 into the generated assembly output, so that the can be further processed by
1139 the backend and especially the optimizer. For this reason, the compiler does
1140 only allow regular 6502 opcodes to be used with the inline assembler. Pseudo
1141 instructions (like <tt/.import/, <tt/.byte/ and so on) are <em/not/ allowed,
1142 even if the ca65 assembler (which is used to translate the generated assembler
1143 code) would accept them. The builtin inline assembler is not a replacement for
1144 the full blown macro assembler which comes with the compiler.
1146 Note: Inline assembler statements are subject to all optimizations done by the
1147 compiler. There is currently no way to protect an inline assembler statement
1148 from being moved or removed completely by the optimizer. If in doubt, check
1149 the generated assembler output, or disable optimizations.
1151 The string literal may contain format specifiers from the following list. For
1152 each format specifier, an argument is expected which is inserted instead of
1153 the format specifier before passing the assembly code line to the backend.
1156 <item><tt/%b/ - Numerical 8-bit value
1157 <item><tt/%w/ - Numerical 16-bit value
1158 <item><tt/%l/ - Numerical 32-bit value
1159 <item><tt/%v/ - Assembler name of a (global) variable or function
1160 <item><tt/%o/ - Stack offset of a (local) variable
1161 <item><tt/%g/ - Assembler name of a C label
1162 <item><tt/%s/ - The argument is converted to a string
1163 <item><tt/%%/ - The % sign itself
1166 Using these format specifiers, you can access C <tt/#defines/, variables or
1167 similar stuff from the inline assembler. For example, to load the value of
1168 a C <tt/#define/ into the Y register, one would use
1172 __asm__ ("ldy #%b", OFFS);
1175 Or, to access a struct member of a static variable:
1181 unsigned char color;
1183 static pixel_t pixel;
1184 __asm__ ("ldy #%b", offsetof(pixel_t, color));
1185 __asm__ ("lda %v,y", pixel);
1189 Note: Do not embed the assembler labels that are used as names of global
1190 variables or functions into your asm statements. Code like this
1194 int bar () { return 1; }
1195 __asm__ ("lda _foo"); /* DON'T DO THAT! */
1197 __asm__ ("jsr _bar"); /* DON'T DO THAT EITHER! */
1201 may stop working if the way, the compiler generates these names is changed in
1202 a future version. Instead use the format specifiers from the table above:
1205 __asm__ ("lda %v", foo); /* OK */
1207 __asm__ ("jsr %v", bar); /* OK */
1212 <sect>Implementation-defined behavior<p>
1214 This section describes the behavior of cc65 when the standard describes the
1215 behavior as implementation-defined.
1219 <sect>Bugs/Feedback<p>
1221 If you have problems using the compiler, if you find any bugs, or if you're
1222 doing something interesting with it, I would be glad to hear from you. Feel
1223 free to contact me by email (<htmlurl url="mailto:uz@cc65.org"
1224 name="uz@cc65.org">).
1230 This is the original compiler copyright:
1233 --------------------------------------------------------------------------
1236 This is the copyright notice for RA65, LINK65, LIBR65, and other
1237 Atari 8-bit programs. Said programs are Copyright 1989, by John R.
1238 Dunning. All rights reserved, with the following exceptions:
1240 Anyone may copy or redistribute these programs, provided that:
1242 1: You don't charge anything for the copy. It is permissable to
1243 charge a nominal fee for media, etc.
1245 2: All source code and documentation for the programs is made
1246 available as part of the distribution.
1248 3: This copyright notice is preserved verbatim, and included in
1251 You are allowed to modify these programs, and redistribute the
1252 modified versions, provided that the modifications are clearly noted.
1254 There is NO WARRANTY with this software, it comes as is, and is
1255 distributed in the hope that it may be useful.
1257 This copyright notice applies to any program which contains
1258 this text, or the refers to this file.
1260 This copyright notice is based on the one published by the Free
1261 Software Foundation, sometimes known as the GNU project. The idea
1262 is the same as theirs, ie the software is free, and is intended to
1263 stay that way. Everybody has the right to copy, modify, and re-
1264 distribute this software. Nobody has the right to prevent anyone
1265 else from copying, modifying or redistributing it.
1267 --------------------------------------------------------------------------
1270 Small parts of the compiler (parts of the preprocessor and main parser) are
1271 still covered by this copyright. The main portion is covered by the usual
1272 cc65 license, which reads:
1274 This software is provided 'as-is', without any expressed or implied
1275 warranty. In no event will the authors be held liable for any damages
1276 arising from the use of this software.
1278 Permission is granted to anyone to use this software for any purpose,
1279 including commercial applications, and to alter it and redistribute it
1280 freely, subject to the following restrictions:
1283 <item> The origin of this software must not be misrepresented; you must not
1284 claim that you wrote the original software. If you use this software
1285 in a product, an acknowledgment in the product documentation would be
1286 appreciated but is not required.
1287 <item> Altered source versions must be plainly marked as such, and must not
1288 be misrepresented as being the original software.
1289 <item> This notice may not be removed or altered from any source