1 <!doctype linuxdoc system>
4 <title>cc65 Users Guide
5 <author>Ullrich von Bassewitz, <htmlurl url="mailto:uz@cc65.org" name="uz@cc65.org">
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>cbm610 (all CBM series-II computers with 80 column video)
199 <item>pet (all CBM PET systems except the 2001)
204 <tag><tt>-v, --verbose</tt></tag>
206 Using this option, the compiler will be somewhat more verbose if errors
207 or warnings are encountered.
210 <tag><tt>-Cl, --static-locals</tt></tag>
212 Use static storage for local variables instead of storage on the stack.
213 Since the stack is emulated in software, this gives shorter and usually
214 faster code, but the code is no longer reentrant. The difference between
215 <tt/-Cl/ and declaring local variables as static yourself is, that
216 initializer code is executed each time, the function is entered. So when
227 the variable a will always have the value 1 when entering the function
228 and using <tt/-Cl/, while in
233 static unsigned a = 1;
238 the variable a will have the value 1 only the first time, the function
239 is entered, and will keep the old value from one call of the function to
242 You may also use <tt><ref id="pragma-staticlocals" name="#pragma
243 staticlocals"></tt> to change this setting in your sources.
246 <tag><tt>-I dir, --include-dir dir</tt></tag>
248 Set a directory where the compiler searches for include files. You may
249 use this option multiple times to add more than one directory to the
253 <tag><tt>-o name</tt></tag>
255 Specify the name of the output file. If you don't specify a name, the
256 name of the C input file is used, with the extension replaced by ".s".
259 <tag><tt>-O, -Oi, -Or, -Os</tt></tag>
261 Enable an optimizer run over the produced code.
263 Using <tt/-Oi/, the code generator will inline some code where otherwise a
264 runtime functions would have been called, even if the generated code is
265 larger. This will not only remove the overhead for a function call, but will
266 make the code visible for the optimizer. <tt/-Oi/ is an alias for
269 <tt/-Or/ will make the compiler honor the <tt/register/ keyword. Local
270 variables may be placed in registers (which are actually zero page
271 locations). There is some overhead involved with register variables, since
272 the old contents of the registers must be saved and restored. In addition,
273 the current implementation does not make good use of register variables, so
274 using <tt/-Or/ may make your program even slower and larger. Use with care!
276 Using <tt/-Os/ will force the compiler to inline some known functions from
277 the C library like strlen. Note: This has two consequences:
280 <item>You may not use names of standard C functions in your own code. If you
281 do that, your program is not standard compliant anyway, but using
282 <tt/-Os/ will actually break things.
284 <item>The inlined string and memory functions will not handle strings or
285 memory areas larger than 255 bytes. Similar, the inlined <tt/is..()/
286 functions will not work with values outside char range.
290 It is possible to concatenate the modifiers for <tt/-O/. For example, to
291 enable register variables and inlining of known functions, you may use
295 <tag><tt>-T</tt></tag>
297 This include the source code as comments in the generated code. This is
301 <tag><tt>-V, --version</tt></tag>
303 Print the version number of the compiler. When submitting a bug report,
304 please include the operating system you're using, and the compiler
308 <tag><tt>-W</tt></tag>
310 This option will suppress any warnings generated by the compiler. Since
311 any source file may be written in a manner that it will not produce
312 compiler warnings, using this option is usually not a good idea.
317 <sect>Input and output<p>
319 The compiler will accept one C file per invocation and create a file with
320 the same base name, but with the extension replaced by ".s". The output
321 file contains assembler code suitable for the use with the ca65 macro
324 In addition to the paths named in the <tt/-I/ option on the command line, the
325 directory named in the environment variable <tt/CC65_INC/ is added to the
326 search path for include files on startup.
330 <sect>Differences to the ISO standard<p>
332 Here is a list of differences between the language, the compiler accepts,
333 and the one defined by the ISO standard:
337 <item> The compiler allows single line comments that start with //. This
338 feature is disabled in strict ANSI mode.
340 <item> The compiler allows unnamed parameters in parameter lists. The
341 compiler will not issue warnings about unused parameters that don't
342 have a name. This feature is disabled in strict ANSI mode.
344 <item> The compiler has some additional keywords:
350 <item><tt/__fastcall__/
354 <item><tt/__attribute__/
357 The keywords without the underlines are disabled in strict ANSI mode.
359 <item> The datatypes "float" and "double" are not available.
361 <item> The compiler does not support bit fields.
363 <item> Initialization of local variables is only possible for scalar data
364 types (that is, not for arrays and structs).
366 <item> Because of the "wrong" order of the parameters on the stack, there is
367 an additional macro needed to access parameters in a variable
368 parameter list in a C function.
370 <item> Functions may not return structs. However, struct assignment *is*
373 <item> Part of the C library is available only with fastcall calling
374 conventions (see below). This means, that you may not mix pointers to
375 those functions with pointers to user written functions.
379 There may be some more minor differences, I'm currently not aware off. The
380 biggest problem is the missing float data type. With this limitation in
381 mind, you should be able to write fairly portable code.
387 This cc65 version has some extensions to the ISO C standard.
391 <item> The compiler allows // comments (like in C++ and in the proposed C9x
392 standard). This feature is disabled by <tt><ref id="option-A"
396 <item> The compiler allows to insert assembler statements into the output
400 asm (<string literal>) ;
404 __asm__ (<string literal>) ;
407 The first form is in the user namespace and is disabled if the <tt/-A/
410 The given string is inserted literally into the output file, and a
411 newline is appended. The statements in this string are not checked by
412 the compiler, so be careful!
414 The asm statement may be used inside a function and on global file
418 <item> There is a special calling convention named "fastcall". This calling
419 convention is currently only usable for functions written in
420 assembler. The syntax for a function declaration using fastcall is
423 <tt/<return type> fastcall <function name> (<parameter list>)/
427 <tt/<return type> __fastcall__ <function name> (<parameter list>)/
431 <tt/void __fastcall__ f (unsigned char c)/
433 The first form of the fastcall keyword is in the user namespace and is
434 therefore disabled in strict ANSI mode.
436 For functions declared as <tt/fastcall/, the rightmost parameter is not
437 pushed on the stack but left in the primary register when the function
438 is called. This will reduce the cost when calling assembler functions
439 significantly, especially when the function itself is rather small.
442 <item> There are two pseudo variables named <tt/__AX__/ and <tt/__EAX__/.
443 Both refer to the primary register that is used by the compiler to
444 evaluate expressions or return function results. <tt/__AX__/ is of
445 type <tt/unsigned int/ and <tt/__EAX__/ of type <tt/long unsigned int/
446 respectively. The pseudo variables may be used as lvalue and rvalue as
447 every other variable. They are most useful together with short
448 sequences of assembler code. For example, the macro
451 #define hi(x) (__AX__=(x),asm("\ttxa\n\tldx\t#$00",__AX__)
454 will give the high byte of any unsigned value.
457 <item> Inside a function, the identifier <tt/__func__/ gives the name of the
458 current function as a string. Outside of functions, <tt/__func__/ is
463 #define PRINT_DEBUG(s) printf ("%s: %s\n", __func__, s);
466 The macro will print the name of the current function plus a given
470 <item> cc65 allows the initialization of <tt/void/ variables. This may be
471 used to create variable structures that are more compatible with
472 interfaces written for assembler languages. Here is an example:
475 void GCmd = { (char)3, (unsigned)0x2000, (unsigned)0x3000 };
478 This will be translated as follows:
487 Since the variable is of type <tt/void/ you may not use it as is.
488 However, taking the address of the variable results in a <tt/void*/
489 which may be passed to any function expecting a pointer.
491 See the <htmlurl url="geos.html" name="GEOS library"> for examples on
492 how to use this feature.
499 <sect>Predefined macros<p>
501 The compiler defines several macros at startup:
505 <tag><tt>__CC65__</tt></tag>
507 This macro is always defined. Its value is the version number of the
508 compiler in hex. Version 2.0.1 of the compiler will have this macro defined
511 <tag><tt>__CBM__</tt></tag>
513 This macro is defined if the target system is one of the CBM targets.
515 <tag><tt>__C64__</tt></tag>
517 This macro is defined if the target is the c64 (-t c64).
519 <tag><tt>__C128__</tt></tag>
521 This macro is defined if the target is the c128 (-t c128).
523 <tag><tt>__PLUS4__</tt></tag>
525 This macro is defined if the target is the plus/4 (-t plus4).
527 <tag><tt>__CBM610__</tt></tag>
529 This macro is defined if the target is one of the CBM 600/700 family of
530 computers (called B series in the US).
532 <tag><tt>__PET__</tt></tag>
534 This macro is defined if the target is the PET family of computers (-t pet).
536 <tag><tt>__ATARI__</tt></tag>
538 This macro is defined if the target is one of the Atari computers
539 (400/800/130XL/800XL).
541 <tag><tt>__APPLE2__</tt></tag>
543 This macro is defined if the target is the Apple ][ (-t apple2).
545 <tag><tt>__GEOS__</tt></tag>
547 This macro is defined if you are compiling for the GEOS system (-t geos).
549 <tag><tt>__FILE__</tt></tag>
551 This macro expands to a string containing the name of the C source file.
553 <tag><tt>__LINE__</tt></tag>
555 This macro expands to the current line number.
557 <tag><tt>__STRICT_ANSI__</tt></tag>
559 This macro is defined to 1 if the <tt/-A/ compiler option was given, and
562 <tag><tt>__OPT__</tt></tag>
564 Is defined if the compiler was called with the <tt/-O/ command line option.
566 <tag><tt>__OPT_i__</tt></tag>
568 Is defined if the compiler was called with the <tt/-Oi/ command line option.
570 <tag><tt>__OPT_r__</tt></tag>
572 Is defined if the compiler was called with the <tt/-Or/ command line option.
574 <tag><tt>__OPT_s__</tt></tag>
576 Is defined if the compiler was called with the <tt/-Os/ command line option.
581 <sect>#pragmas<label id="pragmas"><p>
583 The compiler understands some pragmas that may be used to change code
584 generation and other stuff.
587 <sect1><tt>#pragma bssseg (<name>)</tt><p>
589 This pragma changes the name used for the BSS segment (the BSS segment
590 is used to store uninitialized data). The argument is a string enclosed
593 Note: The default linker configuration file does only map the standard
594 segments. If you use other segments, you have to create a new linker
597 Beware: The startup code will zero only the default BSS segment. If you
598 use another BSS segment, you have to do that yourself, otherwise
599 uninitialized variables do not have the value zero.
603 #pragma bssseg ("MyBSS")
607 <sect1><tt>#pragma checkstack (<const int>)</tt><label
608 id="pragma-checkstack"><p>
610 Tells the compiler to insert calls to a stack checking subroutine to detect
611 stack overflows. The stack checking code will lead to somewhat larger and
612 slower programs, so you may want to use this pragma when debugging your
613 program and switch it off for the release version. If a stack overflow is
614 detected, the program is aborted.
616 If the argument is zero, stack checks are disabled (the default), otherwise
620 <sect1><tt>#pragma codeseg (<name>)</tt><p>
622 This pragma changes the name used for the CODE segment (the CODE segment
623 is used to store executable code). The argument is a string enclosed in
626 Note: The default linker configuration file does only map the standard
627 segments. If you use other segments, you have to create a new linker
632 #pragma bssseg ("MyCODE")
636 <sect1><tt>#pragma dataseg (<name>)</tt><p>
638 This pragma changes the name used for the DATA segment (the DATA segment
639 is used to store initialized data). The argument is a string enclosed in
642 Note: The default linker configuration file does only map the standard
643 segments. If you use other segments, you have to create a new linker
648 #pragma bssseg ("MyDATA")
652 <sect1><tt>#pragma rodataseg (<name>)</tt><p>
654 This pragma changes the name used for the RODATA segment (the RODATA
655 segment is used to store readonly data). The argument is a string
656 enclosed in double quotes.
658 Note: The default linker configuration file does only map the standard
659 segments. If you use other segments, you have to create a new linker
664 #pragma bssseg ("MyRODATA")
668 <sect1><tt>#pragma regvaraddr (<const int>)</tt><p>
670 The compiler does not allow to take the address of register variables.
671 The regvaraddr pragma changes this. Taking the address of a register
672 variable is allowed after using this pragma, if the argument is not
673 zero. Using an argument of zero changes back to the default behaviour.
675 Beware: The C standard does not allow taking the address of a variable
676 declared as register. So your programs become non-portable if you use
677 this pragma. In addition, your program may not work. This is usually the
678 case if a subroutine is called with the address of a register variable,
679 and this subroutine (or a subroutine called from there) uses itself
680 register variables. So be careful with this #pragma.
684 #pragma regvaraddr(1) /* Allow taking the address
685 * of register variables
690 <sect1><tt>#pragma signedchars (<const int>)</tt><label
691 id="pragma-signedchars"><p>
693 Changes the signedness of the default character type. If the argument
694 is not zero, default characters are signed, otherwise characters are
695 unsigned. The compiler default is to make characters unsigned since this
696 creates a lot better code. This default may be overridden by the
697 <tt/--signed-chars/ command line option.
700 <sect1><tt>#pragma staticlocals (<const int>)</tt><label
701 id="pragma-staticlocals"<p>
703 Use variables in the bss segment instead of variables on the stack. This
704 pragma changes the default set by the compiler option <tt/-Cl/. If the
705 argument is not zero, local variables are allocated in the BSS segment,
706 leading to shorter and in most cases faster, but non-reentrant code.
709 <sect1><tt>#pragma zpsym (<name>)</tt><p>
711 Tell the compiler that the - previously as external declared - symbol with
712 the given name is a zero page symbol (usually from an assembler file).
713 The compiler will create a matching import declaration for the assembler.
718 #pragma zpsym ("foo"); /* foo is in the zeropage */
724 <sect>Bugs/Feedback<p>
726 If you have problems using the compiler, if you find any bugs, or if you're
727 doing something interesting with it, I would be glad to hear from you. Feel
728 free to contact me by email (<htmlurl url="mailto:uz@cc65.org" name="uz@cc65.org">).
734 This is the original compiler copyright:
737 --------------------------------------------------------------------------
740 This is the copyright notice for RA65, LINK65, LIBR65, and other
741 Atari 8-bit programs. Said programs are Copyright 1989, by John R.
742 Dunning. All rights reserved, with the following exceptions:
744 Anyone may copy or redistribute these programs, provided that:
746 1: You don't charge anything for the copy. It is permissable to
747 charge a nominal fee for media, etc.
749 2: All source code and documentation for the programs is made
750 available as part of the distribution.
752 3: This copyright notice is preserved verbatim, and included in
755 You are allowed to modify these programs, and redistribute the
756 modified versions, provided that the modifications are clearly noted.
758 There is NO WARRANTY with this software, it comes as is, and is
759 distributed in the hope that it may be useful.
761 This copyright notice applies to any program which contains
762 this text, or the refers to this file.
764 This copyright notice is based on the one published by the Free
765 Software Foundation, sometimes known as the GNU project. The idea
766 is the same as theirs, ie the software is free, and is intended to
767 stay that way. Everybody has the right to copy, modify, and re-
768 distribute this software. Nobody has the right to prevent anyone
769 else from copying, modifying or redistributing it.
771 --------------------------------------------------------------------------
774 In acknowledgment of this copyright, I will place my own changes to the
775 compiler under the same copyright. Please note however, that the library
776 and all binutils are covered by another copyright, and that I'm planning
777 to do a complete rewrite of the compiler, after which the compiler
778 copyright will also change.
780 For the list of changes requested by this copyright see newvers.txt.