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 -g Add debug info to object file
60 -j Default characters are signed
61 -o name Name the output file
62 -t sys Set the target system
65 -Cl Make local variables static
66 -Dsym[=defn] Define a symbol
67 -I dir Set an include directory search path
69 -Oi Optimize code, inline more code
70 -Or Enable register variables
71 -Os Inline some known functions
72 -T Include source as comment
73 -V Print the compiler version number
77 --ansi Strict ANSI mode
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
83 --data-name seg Set the name of the DATA segment
85 --debug-info Add debug info to object file
86 --help Help (this text)
87 --include-dir dir Set an include directory search path
88 --rodata-name seg Set the name of the RODATA segment
89 --signed-chars Default characters are signed
90 --static-locals Make local variables static
91 --target sys Set the target system
92 --verbose Increase verbosity
93 --version Print the compiler version number
94 ---------------------------------------------------------------------------
98 <sect1>Command line options in detail<p>
100 Here is a description of all the command line options:
104 <label id="option-A">
105 <tag><tt>-A, --ansi</tt></tag>
107 This option disables any compiler exensions. Have a look at section 5
108 for a discussion of compiler extensions. In addition, the macro
109 <tt/__STRICT_ANSI__/ is defined, when using one of these options.
112 <tag><tt>--bss-name seg</tt></tag>
114 Set the name of the bss segment.
117 <tag><tt>--check-stack</tt></tag>
119 Tells the compiler to generate code that checks for stack overflows. See
120 <tt><ref id="pragma-checkstack" name="#pragma checkstack"></tt> for an
121 explanation of this feature.
124 <tag><tt>--code-name seg</tt></tag>
126 Set the name of the code segment.
129 <tag><tt>--codesize x</tt></tag>
131 This options allows finer control about speed vs. size decisions in the
132 code generation phase. It gives the allowed size increase factor (in
133 percent). The default is 100 when not using <tt/-Oi/ and 200 when using
134 <tt/-Oi/ (<tt/-Oi/ is the same as <tt/--codesize 200/).
137 <tag><tt>--cpu CPU</tt></tag>
139 A new, still experimental option. You may specify "6502" or "65C02" as
140 the CPU. 6502 is the default, so this will not change anything.
141 Specifying 65C02 will use a few 65C02 instructions when generating code.
142 Don't expect too much from this option: It is still new (and may have
143 bugs), and the additional instructions for the 65C02 are not that
147 <tag><tt>-d, --debug</tt></tag>
149 Enables debug mode, something that should not be needed for mere
153 <tag><tt>-D sym[=definition]</tt></tag>
155 Define a macro on the command line. If no definition is given, the macro
156 is defined to the value "1".
159 <tag><tt>-g, --debug-info</tt></tag>
161 This will cause the compiler to insert a <tt/.DEBUGINFO/ command into the
162 generated assembler code. This will cause the assembler to include all
163 symbols in a special section in the object file.
166 <tag><tt>-h, --help</tt></tag>
168 Print the short option summary shown above.
171 <tag><tt>--rodata-name seg</tt></tag>
173 Set the name of the rodata segment (the segment used for readonly data).
176 <tag><tt>-j, --signed-chars</tt></tag>
178 Using this option, you can make the default characters signed. Since the
179 6502 has no provisions for sign extending characters (which is needed on
180 almost any load operation), this will make the code larger and slower. A
181 better way is to declare characters explicitly as "signed" if needed. You
182 can also use <tt><ref id="pragma-signedchars" name="#pragma
183 signedchars"></tt> for better control of this option.
186 <tag><tt>-t target, --target target</tt></tag>
188 This option is used to set the target system. The target system
189 determines things like the character set that is used for strings and
190 character constants. The following target systems are supported:
198 <item>cbm510 (CBM-II series with 40 column video)
199 <item>cbm610 (all CBM-II II computers with 80 column video)
200 <item>pet (all CBM PET systems except the 2001)
205 <tag><tt>-v, --verbose</tt></tag>
207 Using this option, the compiler will be somewhat more verbose if errors
208 or warnings are encountered.
211 <tag><tt>-Cl, --static-locals</tt></tag>
213 Use static storage for local variables instead of storage on the stack.
214 Since the stack is emulated in software, this gives shorter and usually
215 faster code, but the code is no longer reentrant. The difference between
216 <tt/-Cl/ and declaring local variables as static yourself is, that
217 initializer code is executed each time, the function is entered. So when
228 the variable a will always have the value 1 when entering the function
229 and using <tt/-Cl/, while in
234 static unsigned a = 1;
239 the variable a will have the value 1 only the first time, the function
240 is entered, and will keep the old value from one call of the function to
243 You may also use <tt><ref id="pragma-staticlocals" name="#pragma
244 staticlocals"></tt> to change this setting in your sources.
247 <tag><tt>-I dir, --include-dir dir</tt></tag>
249 Set a directory where the compiler searches for include files. You may
250 use this option multiple times to add more than one directory to the
254 <tag><tt>-o name</tt></tag>
256 Specify the name of the output file. If you don't specify a name, the
257 name of the C input file is used, with the extension replaced by ".s".
260 <tag><tt>-O, -Oi, -Or, -Os</tt></tag>
262 Enable an optimizer run over the produced code.
264 Using <tt/-Oi/, the code generator will inline some code where otherwise a
265 runtime functions would have been called, even if the generated code is
266 larger. This will not only remove the overhead for a function call, but will
267 make the code visible for the optimizer. <tt/-Oi/ is an alias for
270 <tt/-Or/ will make the compiler honor the <tt/register/ keyword. Local
271 variables may be placed in registers (which are actually zero page
272 locations). There is some overhead involved with register variables, since
273 the old contents of the registers must be saved and restored. In addition,
274 the current implementation does not make good use of register variables, so
275 using <tt/-Or/ may make your program even slower and larger. Use with care!
277 Using <tt/-Os/ will force the compiler to inline some known functions from
278 the C library like strlen. Note: This has two consequences:
281 <item>You may not use names of standard C functions in your own code. If you
282 do that, your program is not standard compliant anyway, but using
283 <tt/-Os/ will actually break things.
285 <item>The inlined string and memory functions will not handle strings or
286 memory areas larger than 255 bytes. Similar, the inlined <tt/is..()/
287 functions will not work with values outside char range.
291 It is possible to concatenate the modifiers for <tt/-O/. For example, to
292 enable register variables and inlining of known functions, you may use
296 <tag><tt>-T</tt></tag>
298 This include the source code as comments in the generated code. This is
302 <tag><tt>-V, --version</tt></tag>
304 Print the version number of the compiler. When submitting a bug report,
305 please include the operating system you're using, and the compiler
309 <tag><tt>-W</tt></tag>
311 This option will suppress any warnings generated by the compiler. Since
312 any source file may be written in a manner that it will not produce
313 compiler warnings, using this option is usually not a good idea.
318 <sect>Input and output<p>
320 The compiler will accept one C file per invocation and create a file with
321 the same base name, but with the extension replaced by ".s". The output
322 file contains assembler code suitable for the use with the ca65 macro
325 In addition to the paths named in the <tt/-I/ option on the command line, the
326 directory named in the environment variable <tt/CC65_INC/ is added to the
327 search path for include files on startup.
331 <sect>Differences to the ISO standard<p>
333 Here is a list of differences between the language, the compiler accepts,
334 and the one defined by the ISO standard:
338 <item> The compiler allows single line comments that start with //. This
339 feature is disabled in strict ANSI mode.
341 <item> The compiler allows unnamed parameters in parameter lists. The
342 compiler will not issue warnings about unused parameters that don't
343 have a name. This feature is disabled in strict ANSI mode.
345 <item> The compiler has some additional keywords:
351 <item><tt/__fastcall__/
355 <item><tt/__attribute__/
358 The keywords without the underlines are disabled in strict ANSI mode.
360 <item> The datatypes "float" and "double" are not available.
362 <item> The compiler does not support bit fields.
364 <item> Initialization of local variables is only possible for scalar data
365 types (that is, not for arrays and structs).
367 <item> Because of the "wrong" order of the parameters on the stack, there is
368 an additional macro needed to access parameters in a variable
369 parameter list in a C function.
371 <item> Functions may not return structs (or unions), and structs may not be
372 passed as parameters by value. However, struct assignment *is*
375 <item> Part of the C library is available only with fastcall calling
376 conventions (see below). This means, that you may not mix pointers to
377 those functions with pointers to user written functions.
381 There may be some more minor differences, I'm currently not aware off. The
382 biggest problem is the missing float data type. With this limitation in
383 mind, you should be able to write fairly portable code.
389 This cc65 version has some extensions to the ISO C standard.
393 <item> The compiler allows // comments (like in C++ and in the proposed C9x
394 standard). This feature is disabled by <tt><ref id="option-A"
398 <item> The compiler allows to insert assembler statements into the output
402 asm (<string literal>[, optional parameters]) ;
406 __asm__ (<string literal>[, optional parameters]) ;
409 The first form is in the user namespace and is disabled if the <tt/-A/
412 There is a whole section covering inline assembler statements,
413 <ref id="inline-asm" name="see there">.
416 <item> There is a special calling convention named "fastcall". This calling
417 convention is currently only usable for functions written in
418 assembler. The syntax for a function declaration using fastcall is
421 <tt/<return type> fastcall <function name> (<parameter list>)/
425 <tt/<return type> __fastcall__ <function name> (<parameter list>)/
429 <tt/void __fastcall__ f (unsigned char c)/
431 The first form of the fastcall keyword is in the user namespace and is
432 therefore disabled in strict ANSI mode.
434 For functions declared as <tt/fastcall/, the rightmost parameter is not
435 pushed on the stack but left in the primary register when the function
436 is called. This will reduce the cost when calling assembler functions
437 significantly, especially when the function itself is rather small.
440 <item> There are two pseudo variables named <tt/__AX__/ and <tt/__EAX__/.
441 Both refer to the primary register that is used by the compiler to
442 evaluate expressions or return function results. <tt/__AX__/ is of
443 type <tt/unsigned int/ and <tt/__EAX__/ of type <tt/long unsigned int/
444 respectively. The pseudo variables may be used as lvalue and rvalue as
445 every other variable. They are most useful together with short
446 sequences of assembler code. For example, the macro
449 #define hi(x) (__AX__=(x),asm("\ttxa\n\tldx\t#$00",__AX__)
452 will give the high byte of any unsigned value.
455 <item> Inside a function, the identifier <tt/__func__/ gives the name of the
456 current function as a string. Outside of functions, <tt/__func__/ is
461 #define PRINT_DEBUG(s) printf ("%s: %s\n", __func__, s);
464 The macro will print the name of the current function plus a given
468 <item> cc65 allows the initialization of <tt/void/ variables. This may be
469 used to create variable structures that are more compatible with
470 interfaces written for assembler languages. Here is an example:
473 void GCmd = { (char)3, (unsigned)0x2000, (unsigned)0x3000 };
476 This will be translated as follows:
485 Since the variable is of type <tt/void/ you may not use it as is.
486 However, taking the address of the variable results in a <tt/void*/
487 which may be passed to any function expecting a pointer.
489 See the <htmlurl url="geos.html" name="GEOS library"> for examples on
490 how to use this feature.
497 <sect>Predefined macros<p>
499 The compiler defines several macros at startup:
503 <tag><tt>__CC65__</tt></tag>
505 This macro is always defined. Its value is the version number of the
506 compiler in hex. Version 2.0.1 of the compiler will have this macro defined
509 <tag><tt>__CBM__</tt></tag>
511 This macro is defined if the target system is one of the CBM targets.
513 <tag><tt>__C64__</tt></tag>
515 This macro is defined if the target is the c64 (-t c64).
517 <tag><tt>__C128__</tt></tag>
519 This macro is defined if the target is the c128 (-t c128).
521 <tag><tt>__PLUS4__</tt></tag>
523 This macro is defined if the target is the plus/4 (-t plus4).
525 <tag><tt>__CBM510__</tt></tag>
527 This macro is defined if the target is the CBM 500 series of computers.
529 <tag><tt>__CBM610__</tt></tag>
531 This macro is defined if the target is one of the CBM 600/700 family of
532 computers (called B series in the US).
534 <tag><tt>__PET__</tt></tag>
536 This macro is defined if the target is the PET family of computers (-t pet).
538 <tag><tt>__ATARI__</tt></tag>
540 This macro is defined if the target is one of the Atari computers
541 (400/800/130XL/800XL).
543 <tag><tt>__APPLE2__</tt></tag>
545 This macro is defined if the target is the Apple ][ (-t apple2).
547 <tag><tt>__GEOS__</tt></tag>
549 This macro is defined if you are compiling for the GEOS system (-t geos).
551 <tag><tt>__FILE__</tt></tag>
553 This macro expands to a string containing the name of the C source file.
555 <tag><tt>__LINE__</tt></tag>
557 This macro expands to the current line number.
559 <tag><tt>__STRICT_ANSI__</tt></tag>
561 This macro is defined to 1 if the <tt/-A/ compiler option was given, and
564 <tag><tt>__OPT__</tt></tag>
566 Is defined if the compiler was called with the <tt/-O/ command line option.
568 <tag><tt>__OPT_i__</tt></tag>
570 Is defined if the compiler was called with the <tt/-Oi/ command line option.
572 <tag><tt>__OPT_r__</tt></tag>
574 Is defined if the compiler was called with the <tt/-Or/ command line option.
576 <tag><tt>__OPT_s__</tt></tag>
578 Is defined if the compiler was called with the <tt/-Os/ command line option.
583 <sect>#pragmas<label id="pragmas"><p>
585 The compiler understands some pragmas that may be used to change code
586 generation and other stuff.
589 <sect1><tt>#pragma bssseg (<name>)</tt><p>
591 This pragma changes the name used for the BSS segment (the BSS segment
592 is used to store uninitialized data). The argument is a string enclosed
595 Note: The default linker configuration file does only map the standard
596 segments. If you use other segments, you have to create a new linker
599 Beware: The startup code will zero only the default BSS segment. If you
600 use another BSS segment, you have to do that yourself, otherwise
601 uninitialized variables do not have the value zero.
605 #pragma bssseg ("MyBSS")
609 <sect1><tt>#pragma checkstack (<const int>)</tt><label
610 id="pragma-checkstack"><p>
612 Tells the compiler to insert calls to a stack checking subroutine to detect
613 stack overflows. The stack checking code will lead to somewhat larger and
614 slower programs, so you may want to use this pragma when debugging your
615 program and switch it off for the release version. If a stack overflow is
616 detected, the program is aborted.
618 If the argument is zero, stack checks are disabled (the default), otherwise
622 <sect1><tt>#pragma codeseg (<name>)</tt><p>
624 This pragma changes the name used for the CODE segment (the CODE segment
625 is used to store executable code). The argument is a string enclosed in
628 Note: The default linker configuration file does only map the standard
629 segments. If you use other segments, you have to create a new linker
634 #pragma codeseg ("MyCODE")
638 <sect1><tt>#pragma dataseg (<name>)</tt><p>
640 This pragma changes the name used for the DATA segment (the DATA segment
641 is used to store initialized data). The argument is a string enclosed in
644 Note: The default linker configuration file does only map the standard
645 segments. If you use other segments, you have to create a new linker
650 #pragma dataseg ("MyDATA")
654 <sect1><tt>#pragma rodataseg (<name>)</tt><p>
656 This pragma changes the name used for the RODATA segment (the RODATA
657 segment is used to store readonly data). The argument is a string
658 enclosed in double quotes.
660 Note: The default linker configuration file does only map the standard
661 segments. If you use other segments, you have to create a new linker
666 #pragma rodataseg ("MyRODATA")
670 <sect1><tt>#pragma regvaraddr (<const int>)</tt><p>
672 The compiler does not allow to take the address of register variables.
673 The regvaraddr pragma changes this. Taking the address of a register
674 variable is allowed after using this pragma, if the argument is not
675 zero. Using an argument of zero changes back to the default behaviour.
677 Beware: The C standard does not allow taking the address of a variable
678 declared as register. So your programs become non-portable if you use
679 this pragma. In addition, your program may not work. This is usually the
680 case if a subroutine is called with the address of a register variable,
681 and this subroutine (or a subroutine called from there) uses itself
682 register variables. So be careful with this #pragma.
686 #pragma regvaraddr(1) /* Allow taking the address
687 * of register variables
692 <sect1><tt>#pragma signedchars (<const int>)</tt><label
693 id="pragma-signedchars"><p>
695 Changes the signedness of the default character type. If the argument
696 is not zero, default characters are signed, otherwise characters are
697 unsigned. The compiler default is to make characters unsigned since this
698 creates a lot better code. This default may be overridden by the
699 <tt/--signed-chars/ command line option.
702 <sect1><tt>#pragma staticlocals (<const int>)</tt><label
703 id="pragma-staticlocals"<p>
705 Use variables in the bss segment instead of variables on the stack. This
706 pragma changes the default set by the compiler option <tt/-Cl/. If the
707 argument is not zero, local variables are allocated in the BSS segment,
708 leading to shorter and in most cases faster, but non-reentrant code.
711 <sect1><tt>#pragma zpsym (<name>)</tt><p>
713 Tell the compiler that the - previously as external declared - symbol with
714 the given name is a zero page symbol (usually from an assembler file).
715 The compiler will create a matching import declaration for the assembler.
720 #pragma zpsym ("foo"); /* foo is in the zeropage */
726 <sect>Inline assembler<label id="inline-asm"><p>
728 The compiler allows to insert assembler statements into the output file. The
732 asm (<string literal>[, optional parameters]) ;
736 __asm__ (<string literal>[, optional parameters]) ;
740 The first form is in the user namespace and is disabled by <tt><ref
741 id="option-A" name="-A"></tt>.
743 The asm statement may be used inside a function and on global file level. An
744 inline assembler statement is a primary expression, so it may also be used as
745 part of an expression. Please note however that the result of an expression
746 containing just an inline assembler statement is always of type <tt/void/.
748 The contents of the string literal are preparsed by the compiler and inserted
749 into the generated assembly output, so that the can be further processed by
750 the backend and especially the optimizer. For this reason, the compiler does
751 only allow regular 6502 opcodes to be used with the inline assembler. Pseudo
752 instructions (like <tt/.import/, <tt/.byte/ and so on) are <em/not/ allowed,
753 even if the ca65 assembler (which is used to translate the generated assembler
754 code) would accept them. The builtin inline assembler is not a replacement for
755 the full blown macro assembler which comes with the compiler.
757 Note: Inline assembler statements are subject to all optimizations done by the
758 compiler. There is currently no way to protect an inline assembler statement
759 from being moved or removed completely by the optimizer. If in doubt, check
760 the generated assembler output, or disable optimizations.
762 The string literal may contain format specifiers from the following list. For
763 each format specifier, an argument is expected which is inserted instead of
764 the format specifier before passing the assembly code line to the backend.
767 <item><tt/%b/ - Numerical 8 bit value
768 <item><tt/%w/ - Numerical 16 bit value
769 <item><tt/%l/ - Numerical 32 bit value
770 <item><tt/%v/ - Assembler name of a (global) variable
771 <item><tt/%o/ - Stack offset of a (local) variable
772 <item><tt/%%/ - The % sign itself
775 Using these format specifiers, you can access C <tt/#defines/, variables or
776 similar stuff from the inline assembler. For example, to load the value of
777 a C <tt/#define/ into the Y register, one would use
781 __asm__ ("ldy #%b", OFFS);
784 Or, to access a struct member of a static variable:
792 static pixel_t pixel;
793 __asm__ ("ldy #%b", offsetof(pixel, color));
794 __asm__ ("lda %v,y", pixel);
800 <sect>Bugs/Feedback<p>
802 If you have problems using the compiler, if you find any bugs, or if you're
803 doing something interesting with it, I would be glad to hear from you. Feel
804 free to contact me by email (<htmlurl url="mailto:uz@cc65.org" name="uz@cc65.org">).
810 This is the original compiler copyright:
813 --------------------------------------------------------------------------
816 This is the copyright notice for RA65, LINK65, LIBR65, and other
817 Atari 8-bit programs. Said programs are Copyright 1989, by John R.
818 Dunning. All rights reserved, with the following exceptions:
820 Anyone may copy or redistribute these programs, provided that:
822 1: You don't charge anything for the copy. It is permissable to
823 charge a nominal fee for media, etc.
825 2: All source code and documentation for the programs is made
826 available as part of the distribution.
828 3: This copyright notice is preserved verbatim, and included in
831 You are allowed to modify these programs, and redistribute the
832 modified versions, provided that the modifications are clearly noted.
834 There is NO WARRANTY with this software, it comes as is, and is
835 distributed in the hope that it may be useful.
837 This copyright notice applies to any program which contains
838 this text, or the refers to this file.
840 This copyright notice is based on the one published by the Free
841 Software Foundation, sometimes known as the GNU project. The idea
842 is the same as theirs, ie the software is free, and is intended to
843 stay that way. Everybody has the right to copy, modify, and re-
844 distribute this software. Nobody has the right to prevent anyone
845 else from copying, modifying or redistributing it.
847 --------------------------------------------------------------------------
850 In acknowledgment of this copyright, I will place my own changes to the
851 compiler under the same copyright. Please note however, that the library
852 and all binutils are covered by another copyright, and that I'm planning
853 to do a complete rewrite of the compiler, after which the compiler
854 copyright will also change.
856 For the list of changes requested by this copyright see newvers.txt.