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>03.09.2000, 02.10.2001
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. In fact, I'm
27 planning a complete rewrite (that is, a complete new compiler) for the
28 next release, since there are too many limitations in the current code,
29 and removing these limitations would mean a rewrite of many more parts of
32 There is a separate document named "library.txt" that covers the library
33 available for the compiler. If you know C and are interested in doing
34 actual programming, the library documentation is probably of much more use
37 If you need some hints for getting the best code out of the compiler, you
38 may have a look at "coding.txt" which covers some code generation issues.
44 The compiler translates C files into files containing assembler code that
45 may be translated by the ca65 macroassembler (for more information about
46 the assembler, have a look at ca65.txt).
49 <sect1>Command line option overview<p>
51 The compiler may be called as follows:
54 ---------------------------------------------------------------------------
55 Usage: cc65 [options] file
58 -Cl Make local variables static
59 -Dsym[=defn] Define a symbol
60 -I dir Set an include directory search path
62 -Oi Optimize code, inline more code
63 -Or Enable register variables
64 -Os Inline some known functions
65 -T Include source as comment
66 -V Print the compiler version number
69 -g Add debug info to object file
71 -j Default characters are signed
72 -o name Name the output file
73 -t sys Set the target system
77 --add-source Include source as comment
78 --ansi Strict ANSI mode
79 --bss-name seg Set the name of the BSS segment
80 --check-stack Generate stack overflow checks
81 --code-name seg Set the name of the CODE segment
82 --codesize x Accept larger code by factor x
83 --cpu type Set cpu type
84 --create-dep Create a make dependency file
85 --data-name seg Set the name of the DATA segment
87 --debug-info Add debug info to object file
88 --help Help (this text)
89 --include-dir dir Set an include directory search path
90 --rodata-name seg Set the name of the RODATA segment
91 --signed-chars Default characters are signed
92 --static-locals Make local variables static
93 --target sys Set the target system
94 --verbose Increase verbosity
95 --version Print the compiler version number
96 ---------------------------------------------------------------------------
100 <sect1>Command line options in detail<p>
102 Here is a description of all the command line options:
106 <label id="option-A">
107 <tag><tt>-A, --ansi</tt></tag>
109 This option disables any compiler exensions. Have a look at section 5
110 for a discussion of compiler extensions. In addition, the macro
111 <tt/__STRICT_ANSI__/ is defined, when using one of these options.
114 <tag><tt>--bss-name seg</tt></tag>
116 Set the name of the bss segment.
119 <tag><tt>--check-stack</tt></tag>
121 Tells the compiler to generate code that checks for stack overflows. See
122 <tt><ref id="pragma-checkstack" name="#pragma checkstack"></tt> for an
123 explanation of this feature.
126 <tag><tt>--code-name seg</tt></tag>
128 Set the name of the code segment.
131 <tag><tt>--codesize x</tt></tag>
133 This options allows finer control about speed vs. size decisions in the
134 code generation phase. It gives the allowed size increase factor (in
135 percent). The default is 100 when not using <tt/-Oi/ and 200 when using
136 <tt/-Oi/ (<tt/-Oi/ is the same as <tt/--codesize 200/).
139 <tag><tt>--cpu CPU</tt></tag>
141 A new, still experimental option. You may specify "6502" or "65C02" as
142 the CPU. 6502 is the default, so this will not change anything.
143 Specifying 65C02 will use a few 65C02 instructions when generating code.
144 Don't expect too much from this option: It is still new (and may have
145 bugs), and the additional instructions for the 65C02 are not that
149 <tag><tt>--create-dep</tt></tag>
151 Tells the compiler to generate a file containing the dependency list for
152 the compiled module in makefile syntax. The file is named as the C input
153 file with the extension replaced by <tt/.u/.
156 <tag><tt>-d, --debug</tt></tag>
158 Enables debug mode, something that should not be needed for mere
162 <tag><tt>-D sym[=definition]</tt></tag>
164 Define a macro on the command line. If no definition is given, the macro
165 is defined to the value "1".
168 <tag><tt>-g, --debug-info</tt></tag>
170 This will cause the compiler to insert a <tt/.DEBUGINFO/ command into the
171 generated assembler code. This will cause the assembler to include all
172 symbols in a special section in the object file.
175 <tag><tt>-h, --help</tt></tag>
177 Print the short option summary shown above.
180 <tag><tt>--rodata-name seg</tt></tag>
182 Set the name of the rodata segment (the segment used for readonly data).
185 <tag><tt>-j, --signed-chars</tt></tag>
187 Using this option, you can make the default characters signed. Since the
188 6502 has no provisions for sign extending characters (which is needed on
189 almost any load operation), this will make the code larger and slower. A
190 better way is to declare characters explicitly as "signed" if needed. You
191 can also use <tt><ref id="pragma-signedchars" name="#pragma
192 signedchars"></tt> for better control of this option.
195 <tag><tt>-t target, --target target</tt></tag>
197 This option is used to set the target system. The target system
198 determines things like the character set that is used for strings and
199 character constants. The following target systems are supported:
207 <item>cbm510 (CBM-II series with 40 column video)
208 <item>cbm610 (all CBM-II II computers with 80 column video)
209 <item>pet (all CBM PET systems except the 2001)
214 <tag><tt>-v, --verbose</tt></tag>
216 Using this option, the compiler will be somewhat more verbose if errors
217 or warnings are encountered.
220 <tag><tt>-Cl, --static-locals</tt></tag>
222 Use static storage for local variables instead of storage on the stack.
223 Since the stack is emulated in software, this gives shorter and usually
224 faster code, but the code is no longer reentrant. The difference between
225 <tt/-Cl/ and declaring local variables as static yourself is, that
226 initializer code is executed each time, the function is entered. So when
237 the variable a will always have the value 1 when entering the function
238 and using <tt/-Cl/, while in
243 static unsigned a = 1;
248 the variable a will have the value 1 only the first time, the function
249 is entered, and will keep the old value from one call of the function to
252 You may also use <tt><ref id="pragma-staticlocals" name="#pragma
253 staticlocals"></tt> to change this setting in your sources.
256 <tag><tt>-I dir, --include-dir dir</tt></tag>
258 Set a directory where the compiler searches for include files. You may
259 use this option multiple times to add more than one directory to the
263 <tag><tt>-o name</tt></tag>
265 Specify the name of the output file. If you don't specify a name, the
266 name of the C input file is used, with the extension replaced by ".s".
269 <tag><tt>-O, -Oi, -Or, -Os</tt></tag>
271 Enable an optimizer run over the produced code.
273 Using <tt/-Oi/, the code generator will inline some code where otherwise a
274 runtime functions would have been called, even if the generated code is
275 larger. This will not only remove the overhead for a function call, but will
276 make the code visible for the optimizer. <tt/-Oi/ is an alias for
279 <tt/-Or/ will make the compiler honor the <tt/register/ keyword. Local
280 variables may be placed in registers (which are actually zero page
281 locations). There is some overhead involved with register variables, since
282 the old contents of the registers must be saved and restored. In addition,
283 the current implementation does not make good use of register variables, so
284 using <tt/-Or/ may make your program even slower and larger. Use with care!
286 Using <tt/-Os/ will force the compiler to inline some known functions from
287 the C library like strlen. Note: This has two consequences:
290 <item>You may not use names of standard C functions in your own code. If you
291 do that, your program is not standard compliant anyway, but using
292 <tt/-Os/ will actually break things.
294 <item>The inlined string and memory functions will not handle strings or
295 memory areas larger than 255 bytes. Similar, the inlined <tt/is..()/
296 functions will not work with values outside char range.
300 It is possible to concatenate the modifiers for <tt/-O/. For example, to
301 enable register variables and inlining of known functions, you may use
305 <tag><tt>-T, --add-source</tt></tag>
307 This include the source code as comments in the generated code. This is
311 <tag><tt>-V, --version</tt></tag>
313 Print the version number of the compiler. When submitting a bug report,
314 please include the operating system you're using, and the compiler
318 <tag><tt>-W</tt></tag>
320 This option will suppress any warnings generated by the compiler. Since
321 any source file may be written in a manner that it will not produce
322 compiler warnings, using this option is usually not a good idea.
327 <sect>Input and output<p>
329 The compiler will accept one C file per invocation and create a file with
330 the same base name, but with the extension replaced by ".s". The output
331 file contains assembler code suitable for the use with the ca65 macro
334 In addition to the paths named in the <tt/-I/ option on the command line, the
335 directory named in the environment variable <tt/CC65_INC/ is added to the
336 search path for include files on startup.
340 <sect>Differences to the ISO standard<p>
342 Here is a list of differences between the language, the compiler accepts,
343 and the one defined by the ISO standard:
347 <item> The compiler allows single line comments that start with //. This
348 feature is disabled in strict ANSI mode.
350 <item> The compiler allows unnamed parameters in parameter lists. The
351 compiler will not issue warnings about unused parameters that don't
352 have a name. This feature is disabled in strict ANSI mode.
354 <item> The compiler has some additional keywords:
360 <item><tt/__fastcall__/
364 <item><tt/__attribute__/
367 The keywords without the underlines are disabled in strict ANSI mode.
369 <item> The datatypes "float" and "double" are not available.
371 <item> The compiler does not support bit fields.
373 <item> Because of the "wrong" order of the parameters on the stack, there is
374 an additional macro needed to access parameters in a variable
375 parameter list in a C function.
377 <item> Functions may not return structs (or unions), and structs may not be
378 passed as parameters by value. However, struct assignment *is*
381 <item> Part of the C library is available only with fastcall calling
382 conventions (see below). This means, that you may not mix pointers to
383 those functions with pointers to user written functions.
387 There may be some more minor differences, I'm currently not aware off. The
388 biggest problem is the missing float data type. With this limitation in
389 mind, you should be able to write fairly portable code.
395 This cc65 version has some extensions to the ISO C standard.
399 <item> The compiler allows // comments (like in C++ and in the proposed C9x
400 standard). This feature is disabled by <tt><ref id="option-A"
404 <item> The compiler allows to insert assembler statements into the output
408 asm (<string literal>[, optional parameters]) ;
412 __asm__ (<string literal>[, optional parameters]) ;
415 The first form is in the user namespace and is disabled if the <tt/-A/
418 There is a whole section covering inline assembler statements,
419 <ref id="inline-asm" name="see there">.
422 <item> There is a special calling convention named "fastcall". This calling
423 convention is currently only usable for functions written in
424 assembler. The syntax for a function declaration using fastcall is
427 <return type> fastcall <function name> (<parameter list>)
431 <return type> __fastcall__ <function name> (<parameter list>)
435 void __fastcall__ f (unsigned char c)
437 The first form of the fastcall keyword is in the user namespace and is
438 therefore disabled in strict ANSI mode.
440 For functions declared as <tt/fastcall/, the rightmost parameter is not
441 pushed on the stack but left in the primary register when the function
442 is called. This will reduce the cost when calling assembler functions
443 significantly, especially when the function itself is rather small.
446 <item> There are two pseudo variables named <tt/__AX__/ and <tt/__EAX__/.
447 Both refer to the primary register that is used by the compiler to
448 evaluate expressions or return function results. <tt/__AX__/ is of
449 type <tt/unsigned int/ and <tt/__EAX__/ of type <tt/long unsigned int/
450 respectively. The pseudo variables may be used as lvalue and rvalue as
451 every other variable. They are most useful together with short
452 sequences of assembler code. For example, the macro
455 #define hi(x) (__AX__=(x),asm("\ttxa\n\tldx\t#$00",__AX__)
458 will give the high byte of any unsigned value.
461 <item> Inside a function, the identifier <tt/__func__/ gives the name of the
462 current function as a string. Outside of functions, <tt/__func__/ is
467 #define PRINT_DEBUG(s) printf ("%s: %s\n", __func__, s);
470 The macro will print the name of the current function plus a given
474 <item> cc65 allows the initialization of <tt/void/ variables. This may be
475 used to create variable structures that are more compatible with
476 interfaces written for assembler languages. Here is an example:
479 void GCmd = { (char)3, (unsigned)0x2000, (unsigned)0x3000 };
482 This will be translated as follows:
491 Since the variable is of type <tt/void/ you may not use it as is.
492 However, taking the address of the variable results in a <tt/void*/
493 which may be passed to any function expecting a pointer.
495 See the <htmlurl url="geos.html" name="GEOS library"> for examples on
496 how to use this feature.
503 <sect>Predefined macros<p>
505 The compiler defines several macros at startup:
509 <tag><tt>__CC65__</tt></tag>
511 This macro is always defined. Its value is the version number of the
512 compiler in hex. Version 2.0.1 of the compiler will have this macro defined
515 <tag><tt>__CBM__</tt></tag>
517 This macro is defined if the target system is one of the CBM targets.
519 <tag><tt>__C64__</tt></tag>
521 This macro is defined if the target is the c64 (-t c64).
523 <tag><tt>__C128__</tt></tag>
525 This macro is defined if the target is the c128 (-t c128).
527 <tag><tt>__PLUS4__</tt></tag>
529 This macro is defined if the target is the plus/4 (-t plus4).
531 <tag><tt>__CBM510__</tt></tag>
533 This macro is defined if the target is the CBM 500 series of computers.
535 <tag><tt>__CBM610__</tt></tag>
537 This macro is defined if the target is one of the CBM 600/700 family of
538 computers (called B series in the US).
540 <tag><tt>__PET__</tt></tag>
542 This macro is defined if the target is the PET family of computers (-t pet).
544 <tag><tt>__ATARI__</tt></tag>
546 This macro is defined if the target is one of the Atari computers
547 (400/800/130XL/800XL).
549 <tag><tt>__APPLE2__</tt></tag>
551 This macro is defined if the target is the Apple ][ (-t apple2).
553 <tag><tt>__GEOS__</tt></tag>
555 This macro is defined if you are compiling for the GEOS system (-t geos).
557 <tag><tt>__FILE__</tt></tag>
559 This macro expands to a string containing the name of the C source file.
561 <tag><tt>__LINE__</tt></tag>
563 This macro expands to the current line number.
565 <tag><tt>__STRICT_ANSI__</tt></tag>
567 This macro is defined to 1 if the <tt/-A/ compiler option was given, and
570 <tag><tt>__OPT__</tt></tag>
572 Is defined if the compiler was called with the <tt/-O/ command line option.
574 <tag><tt>__OPT_i__</tt></tag>
576 Is defined if the compiler was called with the <tt/-Oi/ command line option.
578 <tag><tt>__OPT_r__</tt></tag>
580 Is defined if the compiler was called with the <tt/-Or/ command line option.
582 <tag><tt>__OPT_s__</tt></tag>
584 Is defined if the compiler was called with the <tt/-Os/ command line option.
589 <sect>#pragmas<label id="pragmas"><p>
591 The compiler understands some pragmas that may be used to change code
592 generation and other stuff.
595 <sect1><tt>#pragma bssseg (<name>)</tt><p>
597 This pragma changes the name used for the BSS segment (the BSS segment
598 is used to store uninitialized data). The argument is a string enclosed
601 Note: The default linker configuration file does only map the standard
602 segments. If you use other segments, you have to create a new linker
605 Beware: The startup code will zero only the default BSS segment. If you
606 use another BSS segment, you have to do that yourself, otherwise
607 uninitialized variables do not have the value zero.
611 #pragma bssseg ("MyBSS")
615 <sect1><tt>#pragma charmap (<index>, <code>)</tt><p>
617 Each literal string and each literal character in the source is translated
618 by use of a translation table. This translation table is preset when the
619 compiler is started depending on the target system, for example to map
620 ISO-8859-1 characters into PETSCII if the target is a commodore machine.
622 This pragma allows to change entries in the translation table, so the
623 translation for individual characters, or even the complete table may be
626 Both arguments are assumed to be unsigned characters with a valid range of
629 Beware of two pitfalls:
632 <item>The character index is actually the code of the character in the
633 C source, so character mappings do always depend on the source
634 character set. This means that <tt/#pragma charmap/ is not portable
635 - it depends on the build environment.
636 <item>While it is possible to use character literals as indices, the
637 result may be somewhat unexpected, since character literals are
638 itself translated. For this reason I would suggest to avoid
639 character literals and use numeric character codes instead.
644 /* Use a space wherever an 'a' occurs in ISO-8859-1 source */
645 #pragma charmap (0x61, 0x20);
649 <sect1><tt>#pragma checkstack (on|off)</tt><label
650 id="pragma-checkstack"><p>
652 Tells the compiler to insert calls to a stack checking subroutine to detect
653 stack overflows. The stack checking code will lead to somewhat larger and
654 slower programs, so you may want to use this pragma when debugging your
655 program and switch it off for the release version. If a stack overflow is
656 detected, the program is aborted.
658 If the argument is "off", stack checks are disabled (the default), otherwise
662 <sect1><tt>#pragma codeseg (<name>)</tt><p>
664 This pragma changes the name used for the CODE segment (the CODE segment
665 is used to store executable code). The argument is a string enclosed in
668 Note: The default linker configuration file does only map the standard
669 segments. If you use other segments, you have to create a new linker
674 #pragma codeseg ("MyCODE")
678 <sect1><tt>#pragma dataseg (<name>)</tt><p>
680 This pragma changes the name used for the DATA segment (the DATA segment
681 is used to store initialized data). The argument is a string enclosed in
684 Note: The default linker configuration file does only map the standard
685 segments. If you use other segments, you have to create a new linker
690 #pragma dataseg ("MyDATA")
694 <sect1><tt>#pragma rodataseg (<name>)</tt><p>
696 This pragma changes the name used for the RODATA segment (the RODATA
697 segment is used to store readonly data). The argument is a string
698 enclosed in double quotes.
700 Note: The default linker configuration file does only map the standard
701 segments. If you use other segments, you have to create a new linker
706 #pragma rodataseg ("MyRODATA")
710 <sect1><tt>#pragma regvaraddr (on|off)</tt><p>
712 The compiler does not allow to take the address of register variables.
713 The regvaraddr pragma changes this. Taking the address of a register
714 variable is allowed after using this pragma with "on" as argument.
715 Using "off" as an argument switches back to the default behaviour.
717 Beware: The C standard does not allow taking the address of a variable
718 declared as register. So your programs become non-portable if you use
719 this pragma. In addition, your program may not work. This is usually the
720 case if a subroutine is called with the address of a register variable,
721 and this subroutine (or a subroutine called from there) uses itself
722 register variables. So be careful with this #pragma.
726 #pragma regvaraddr(1) /* Allow taking the address
727 * of register variables
732 <sect1><tt>#pragma signedchars (on|off)</tt><label id="pragma-signedchars"><p>
734 Changes the signedness of the default character type. If the argument is
735 "on", default characters are signed, otherwise characters are unsigned.
736 The compiler default is to make characters unsigned since this creates a
737 lot better code. This default may be overridden by the <tt/--signed-chars/
741 <sect1><tt>#pragma staticlocals (on|off)</tt><label
742 id="pragma-staticlocals"<p>
744 Use variables in the bss segment instead of variables on the stack. This
745 pragma changes the default set by the compiler option <tt/-Cl/. If the
746 argument is "on", local variables are allocated in the BSS segment,
747 leading to shorter and in most cases faster, but non-reentrant code.
750 <sect1><tt>#pragma zpsym (<name>)</tt><p>
752 Tell the compiler that the - previously as external declared - symbol with
753 the given name is a zero page symbol (usually from an assembler file).
754 The compiler will create a matching import declaration for the assembler.
759 #pragma zpsym ("foo"); /* foo is in the zeropage */
765 <sect>Inline assembler<label id="inline-asm"><p>
767 The compiler allows to insert assembler statements into the output file. The
771 asm (<string literal>[, optional parameters]) ;
775 __asm__ (<string literal>[, optional parameters]) ;
779 The first form is in the user namespace and is disabled by <tt><ref
780 id="option-A" name="-A"></tt>.
782 The asm statement may be used inside a function and on global file level. An
783 inline assembler statement is a primary expression, so it may also be used as
784 part of an expression. Please note however that the result of an expression
785 containing just an inline assembler statement is always of type <tt/void/.
787 The contents of the string literal are preparsed by the compiler and inserted
788 into the generated assembly output, so that the can be further processed by
789 the backend and especially the optimizer. For this reason, the compiler does
790 only allow regular 6502 opcodes to be used with the inline assembler. Pseudo
791 instructions (like <tt/.import/, <tt/.byte/ and so on) are <em/not/ allowed,
792 even if the ca65 assembler (which is used to translate the generated assembler
793 code) would accept them. The builtin inline assembler is not a replacement for
794 the full blown macro assembler which comes with the compiler.
796 Note: Inline assembler statements are subject to all optimizations done by the
797 compiler. There is currently no way to protect an inline assembler statement
798 from being moved or removed completely by the optimizer. If in doubt, check
799 the generated assembler output, or disable optimizations.
801 The string literal may contain format specifiers from the following list. For
802 each format specifier, an argument is expected which is inserted instead of
803 the format specifier before passing the assembly code line to the backend.
806 <item><tt/%b/ - Numerical 8 bit value
807 <item><tt/%w/ - Numerical 16 bit value
808 <item><tt/%l/ - Numerical 32 bit value
809 <item><tt/%v/ - Assembler name of a (global) variable or function
810 <item><tt/%o/ - Stack offset of a (local) variable
811 <item><tt/%%/ - The % sign itself
814 Using these format specifiers, you can access C <tt/#defines/, variables or
815 similar stuff from the inline assembler. For example, to load the value of
816 a C <tt/#define/ into the Y register, one would use
820 __asm__ ("ldy #%b", OFFS);
823 Or, to access a struct member of a static variable:
831 static pixel_t pixel;
832 __asm__ ("ldy #%b", offsetof(pixel_t, color));
833 __asm__ ("lda %v,y", pixel);
837 Note: Do not embedd the assembler labels that are used as names of global
838 variables or functions into your asm statements. Code like this
842 int bar () { return 1; }
843 __asm__ ("lda _foo"); /* DON'T DO THAT! */
845 __asm__ ("jsr _bar"); /* DON'T DO THAT EITHER! */
849 may stop working if the way, the compiler generates these names is changed in
854 <sect>Bugs/Feedback<p>
856 If you have problems using the compiler, if you find any bugs, or if you're
857 doing something interesting with it, I would be glad to hear from you. Feel
858 free to contact me by email (<htmlurl url="mailto:uz@cc65.org" name="uz@cc65.org">).
864 This is the original compiler copyright:
867 --------------------------------------------------------------------------
870 This is the copyright notice for RA65, LINK65, LIBR65, and other
871 Atari 8-bit programs. Said programs are Copyright 1989, by John R.
872 Dunning. All rights reserved, with the following exceptions:
874 Anyone may copy or redistribute these programs, provided that:
876 1: You don't charge anything for the copy. It is permissable to
877 charge a nominal fee for media, etc.
879 2: All source code and documentation for the programs is made
880 available as part of the distribution.
882 3: This copyright notice is preserved verbatim, and included in
885 You are allowed to modify these programs, and redistribute the
886 modified versions, provided that the modifications are clearly noted.
888 There is NO WARRANTY with this software, it comes as is, and is
889 distributed in the hope that it may be useful.
891 This copyright notice applies to any program which contains
892 this text, or the refers to this file.
894 This copyright notice is based on the one published by the Free
895 Software Foundation, sometimes known as the GNU project. The idea
896 is the same as theirs, ie the software is free, and is intended to
897 stay that way. Everybody has the right to copy, modify, and re-
898 distribute this software. Nobody has the right to prevent anyone
899 else from copying, modifying or redistributing it.
901 --------------------------------------------------------------------------
904 In acknowledgment of this copyright, I will place my own changes to the
905 compiler under the same copyright. Please note however, that the library
906 and all binutils are covered by another copyright, and that I'm planning
907 to do a complete rewrite of the compiler, after which the compiler
908 copyright will also change.
910 For the list of changes requested by this copyright see newvers.txt.