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 --cpu type Set cpu type
80 --debug-info Add debug info to object file
81 --help Help (this text)
82 --include-dir dir Set an include directory search path
83 --signed-chars Default characters are signed
84 --static-locals Make local variables static
85 --target sys Set the target system
86 --verbose Increase verbosity
87 --version Print the compiler version number
88 ---------------------------------------------------------------------------
92 <sect1>Command line options in detail<p>
94 Here is a description of all the command line options:
99 <tag><tt>-A, --ansi</tt></tag>
101 This option disables any compiler exensions. Have a look at section 5
102 for a discussion of compiler extensions. In addition, the macro
103 <tt/__STRICT_ANSI__/ is defined, when using one of these options.
106 <tag><tt>--cpu CPU</tt></tag>
108 A new, still experimental option. You may specify "6502" or "65C02" as
109 the CPU. 6502 is the default, so this will not change anything.
110 Specifying 65C02 will use a few 65C02 instructions when generating code.
111 Don't expect too much from this option: It is still new (and may have
112 bugs), and the additional instructions for the 65C02 are not that
116 <tag><tt>-d, --debug</tt></tag>
118 Enables debug mode, something that should not be needed for mere
122 <tag><tt>-D sym[=definition]</tt></tag>
124 Define a macro on the command line. If no definition is given, the macro
125 is defined to the value "1".
128 <tag><tt>-g, --debug-info</tt></tag>
130 This will cause the compiler to insert a <tt/.DEBUGINFO/ command into the
131 generated assembler code. This will cause the assembler to include all
132 symbols in a special section in the object file.
135 <tag><tt>-h, --help</tt></tag>
137 Print the short option summary shown above.
140 <tag><tt>-j, --signed-chars</tt></tag>
142 Using this option, you can make the default characters signed. Since the
143 6502 has no provisions for sign extending characters (which is needed on
144 almost any load operation), this will make the code larger and slower. A
145 better way is to declare characters explicitly as "signed" if needed. You
146 can also use <tt><ref id="pragma-signedchars" name="#pragma
147 signedchars"></tt> for better control of this option.
150 <tag><tt>-t target, --target target</tt></tag>
152 This option is used to set the target system. The target system
153 determines things like the character set that is used for strings and
154 character constants. The following target systems are supported:
162 <item>cbm610 (all CBM series-II computers with 80 column video)
163 <item>pet (all CBM PET systems except the 2001)
168 <tag><tt>-v, --verbose</tt></tag>
170 Using this option, the compiler will be somewhat more verbose if errors
171 or warnings are encountered.
174 <tag><tt>-Cl, --static-locals</tt></tag>
176 Use static storage for local variables instead of storage on the stack.
177 Since the stack is emulated in software, this gives shorter and usually
178 faster code, but the code is no longer reentrant. The difference between
179 <tt/-Cl/ and declaring local variables as static yourself is, that
180 initializer code is executed each time, the function is entered. So when
191 the variable a will always have the value 1 when entering the function
192 and using <tt/-Cl/, while in
197 static unsigned a = 1;
202 the variable a will have the value 1 only the first time, the function
203 is entered, and will keep the old value from one call of the function to
206 You may also use <tt><ref id="pragma-staticlocals" name="#pragma
207 staticlocals"></tt> to change this setting in your sources.
210 <tag><tt>-I dir, --include-dir dir</tt></tag>
212 Set a directory where the compiler searches for include files. You may
213 use this option multiple times to add more than one directory to the
217 <tag><tt>-o name</tt></tag>
219 Specify the name of the output file. If you don't specify a name, the
220 name of the C input file is used, with the extension replaced by ".s".
223 <tag><tt>-O, -Oi, -Or, -Os</tt></tag>
225 Enable an optimizer run over the produced code.
227 Using <tt/-Oi/, the code generator will inline some code where otherwise a
228 runtime functions would have been called, even if the generated code is
229 larger. This will not only remove the overhead for a function call, but will
230 make the code visible for the optimizer.
232 <tt/-Or/ will make the compiler honor the <tt/register/ keyword. Local
233 variables may be placed in registers (which are actually zero page
234 locations). There is some overhead involved with register variables, since
235 the old contents of the registers must be saved and restored. In addition,
236 the current implementation does not make good use of register variables, so
237 using <tt/-Or/ may make your program even slower and larger. Use with care!
239 Using <tt/-Os/ will force the compiler to inline some known functions from
240 the C library like strlen. Note: This has two consequences:
243 <item>You may not use names of standard C functions in your own code. If you
244 do that, your program is not standard compliant anyway, but using
245 <tt/-Os/ will actually break things.
247 <item>The inlined string and memory functions will not handle strings or
248 memory areas larger than 255 bytes. Similar, the inlined <tt/is..()/
249 functions will not work with values outside char range.
253 It is possible to concatenate the modifiers for <tt/-O/. For example, to
254 enable register variables and inlining of known functions, you may use
258 <tag><tt>-T</tt></tag>
260 This include the source code as comments in the generated code. This is
264 <tag><tt>-V, --version</tt></tag>
266 Print the version number of the compiler. When submitting a bug report,
267 please include the operating system you're using, and the compiler
271 <tag><tt>-W</tt></tag>
273 This option will suppress any warnings generated by the compiler. Since
274 any source file may be written in a manner that it will not produce
275 compiler warnings, using this option is usually not a good idea.
280 <sect>Input and output<p>
282 The compiler will accept one C file per invocation and create a file with
283 the same base name, but with the extension replaced by ".s". The output
284 file contains assembler code suitable for the use with the ca65 macro
287 In addition to the paths named in the <tt/-I/ option on the command line, the
288 directory named in the environment variable <tt/CC65_INC/ is added to the
289 search path for include files on startup.
293 <sect>Differences to the ISO standard<p>
295 Here is a list of differences between the language, the compiler accepts,
296 and the one defined by the ISO standard:
300 <item> The compiler allows single line comments that start with //. This
301 feature is disabled in strict ANSI mode.
303 <item> The compiler allows unnamed parameters in parameter lists. The
304 compiler will not issue warnings about unused parameters that don't
305 have a name. This feature is disabled in strict ANSI mode.
307 <item> The compiler has some additional keywords:
313 <item><tt/__fastcall__/
317 <item><tt/__attribute__/
320 The keywords without the underlines are disabled in strict ANSI mode.
322 <item> The datatypes "float" and "double" are not available.
324 <item> The compiler does not support bit fields.
326 <item> Initialization of local variables is only possible for scalar data
327 types (that is, not for arrays and structs).
329 <item> Because of the "wrong" order of the parameters on the stack, there is
330 an additional macro needed to access parameters in a variable
331 parameter list in a C function.
333 <item> Functions may not return structs. However, struct assignment *is*
336 <item> Part of the C library is available only with fastcall calling
337 conventions (see below). This means, that you may not mix pointers to
338 those functions with pointers to user written functions.
342 There may be some more minor differences, I'm currently not aware off. The
343 biggest problem is the missing float data type. With this limitation in
344 mind, you should be able to write fairly portable code.
350 This cc65 version has some extensions to the ISO C standard.
354 <item> The compiler allows // comments (like in C++ and in the proposed C9x
355 standard). This feature is disabled by <tt><ref id="option-A"
359 <item> The compiler allows to insert assembler statements into the output
363 asm (<string literal>) ;
367 __asm__ (<string literal>) ;
370 The first form is in the user namespace and is disabled if the <tt/-A/
373 The given string is inserted literally into the output file, and a
374 newline is appended. The statements in this string are not checked by
375 the compiler, so be careful!
377 The asm statement may be used inside a function and on global file
381 <item> There is a special calling convention named "fastcall". This calling
382 convention is currently only usable for functions written in
383 assembler. The syntax for a function declaration using fastcall is
386 <tt/<return type> fastcall <function name> (<parameter list>)/
390 <tt/<return type> __fastcall__ <function name> (<parameter list>)/
394 <tt/void __fastcall__ f (unsigned char c)/
396 The first form of the fastcall keyword is in the user namespace and is
397 therefore disabled in strict ANSI mode.
399 For functions declared as <tt/fastcall/, the rightmost parameter is not
400 pushed on the stack but left in the primary register when the function
401 is called. This will reduce the cost when calling assembler functions
402 significantly, especially when the function itself is rather small.
405 <item> There are two pseudo variables named <tt/__AX__/ and <tt/__EAX__/.
406 Both refer to the primary register that is used by the compiler to
407 evaluate expressions or return function results. <tt/__AX__/ is of
408 type <tt/unsigned int/ and <tt/__EAX__/ of type <tt/long unsigned int/
409 respectively. The pseudo variables may be used as lvalue and rvalue as
410 every other variable. They are most useful together with short
411 sequences of assembler code. For example, the macro
414 #define hi(x) (__AX__=(x),asm("\ttxa\n\tldx\t#$00",__AX__)
417 will give the high byte of any unsigned value.
420 <item> Inside a function, the identifier <tt/__func__/ gives the name of the
421 current function as a string. Outside of functions, <tt/__func__/ is
426 #define PRINT_DEBUG(s) printf ("%s: %s\n", __func__, s);
429 The macro will print the name of the current function plus a given
436 <sect>Predefined macros<p>
438 The compiler defines several macros at startup:
442 <tag><tt>__CC65__</tt></tag>
444 This macro is always defined. Its value is the version number of the
445 compiler in hex. Version 2.0.1 of the compiler will have this macro defined
448 <tag><tt>__CBM__</tt></tag>
450 This macro is defined if the target system is one of the CBM targets.
452 <tag><tt>__C64__</tt></tag>
454 This macro is defined if the target is the c64 (-t c64).
456 <tag><tt>__C128__</tt></tag>
458 This macro is defined if the target is the c128 (-t c128).
460 <tag><tt>__PLUS4__</tt></tag>
462 This macro is defined if the target is the plus/4 (-t plus4).
464 <tag><tt>__CBM610__</tt></tag>
466 This macro is defined if the target is one of the CBM 600/700 family of
467 computers (called B series in the US).
469 <tag><tt>__PET__</tt></tag>
471 This macro is defined if the target is the PET family of computers (-t pet).
473 <tag><tt>__ATARI__</tt></tag>
475 This macro is defined if the target is one of the Atari computers
476 (400/800/130XL/800XL).
478 <tag><tt>__APPLE2__</tt></tag>
480 This macro is defined if the target is the Apple ][ (-t apple2).
482 <tag><tt>__GEOS__</tt></tag>
484 This macro is defined if you are compiling for the GEOS system (-t geos).
486 <tag><tt>__FILE__</tt></tag>
488 This macro expands to a string containing the name of the C source file.
490 <tag><tt>__LINE__</tt></tag>
492 This macro expands to the current line number.
494 <tag><tt>__STRICT_ANSI__</tt></tag>
496 This macro is defined to 1 if the <tt/-A/ compiler option was given, and
499 <tag><tt>__OPT__</tt></tag>
501 Is defined if the compiler was called with the <tt/-O/ command line option.
503 <tag><tt>__OPT_i__</tt></tag>
505 Is defined if the compiler was called with the <tt/-Oi/ command line option.
507 <tag><tt>__OPT_r__</tt></tag>
509 Is defined if the compiler was called with the <tt/-Or/ command line option.
511 <tag><tt>__OPT_s__</tt></tag>
513 Is defined if the compiler was called with the <tt/-Os/ command line option.
518 <sect>#pragmas<label id="pragmas"><p>
520 The compiler understands some pragmas that may be used to change code
521 generation and other stuff.
524 <sect1><tt>#pragma bssseg (<name>)</tt><p>
526 This pragma changes the name used for the BSS segment (the BSS segment
527 is used to store uninitialized data). The argument is a string enclosed
530 Note: The default linker configuration file does only map the standard
531 segments. If you use other segments, you have to create a new linker
534 Beware: The startup code will zero only the default BSS segment. If you
535 use another BSS segment, you have to do that yourself, otherwise
536 uninitialized variables do not have the value zero.
540 #pragma bssseg ("MyBSS")
544 <sect1><tt>#pragma codeseg (<name>)</tt><p>
546 This pragma changes the name used for the CODE segment (the CODE segment
547 is used to store executable code). The argument is a string enclosed in
550 Note: The default linker configuration file does only map the standard
551 segments. If you use other segments, you have to create a new linker
556 #pragma bssseg ("MyCODE")
560 <sect1><tt>#pragma dataseg (<name>)</tt><p>
562 This pragma changes the name used for the DATA segment (the DATA segment
563 is used to store initialized data). The argument is a string enclosed in
566 Note: The default linker configuration file does only map the standard
567 segments. If you use other segments, you have to create a new linker
572 #pragma bssseg ("MyDATA")
576 <sect1><tt>#pragma rodataseg (<name>)</tt><p>
578 This pragma changes the name used for the RODATA segment (the RODATA
579 segment is used to store readonly data). The argument is a string
580 enclosed in double quotes.
582 Note: The default linker configuration file does only map the standard
583 segments. If you use other segments, you have to create a new linker
588 #pragma bssseg ("MyRODATA")
592 <sect1><tt>#pragma regvaraddr (<const int>)</tt><p>
594 The compiler does not allow to take the address of register variables.
595 The regvaraddr pragma changes this. Taking the address of a register
596 variable is allowed after using this pragma, if the argument is not
597 zero. Using an argument of zero changes back to the default behaviour.
599 Beware: The C standard does not allow taking the address of a variable
600 declared as register. So your programs become non-portable if you use
601 this pragma. In addition, your program may not work. This is usually the
602 case if a subroutine is called with the address of a register variable,
603 and this subroutine (or a subroutine called from there) uses itself
604 register variables. So be careful with this #pragma.
608 #pragma regvaraddr(1) /* Allow taking the address
609 * of register variables
614 <sect1><tt>#pragma signedchars (<const int>)</tt><label
615 id="pragma-signedchars"><p>
617 Changed the signedness of the default character type. If the argument
618 is not zero, default characters are signed, otherwise characters are
619 unsigned. The compiler default is to make characters unsigned since this
620 creates a lot better code. This default may be overridden by the
621 <tt/--signed-chars/ command line option.
624 <sect1><tt>#pragma staticlocals (<const int>)</tt><label
625 id="pragma-staticlocals"<p>
627 Use variables in the bss segment instead of variables on the stack. This
628 pragma changes the default set by the compiler option <tt/-Cl/. If the
629 argument is not zero, local variables are allocated in the BSS segment,
630 leading to shorter and in most cases faster, but non-reentrant code.
633 <sect1><tt>#pragma zpsym (<name>)</tt><p>
635 Tell the compiler that the - previously as external declared - symbol with
636 the given name is a zero page symbol (usually from an assembler file).
637 The compiler will create a matching import declaration for the assembler.
642 #pragma zpsym ("foo"); /* foo is in the zeropage */
648 <sect>Bugs/Feedback<p>
650 If you have problems using the compiler, if you find any bugs, or if you're
651 doing something interesting with it, I would be glad to hear from you. Feel
652 free to contact me by email (<htmlurl url="mailto:uz@cc65.org" name="uz@cc65.org">).
658 This is the original compiler copyright:
661 --------------------------------------------------------------------------
664 This is the copyright notice for RA65, LINK65, LIBR65, and other
665 Atari 8-bit programs. Said programs are Copyright 1989, by John R.
666 Dunning. All rights reserved, with the following exceptions:
668 Anyone may copy or redistribute these programs, provided that:
670 1: You don't charge anything for the copy. It is permissable to
671 charge a nominal fee for media, etc.
673 2: All source code and documentation for the programs is made
674 available as part of the distribution.
676 3: This copyright notice is preserved verbatim, and included in
679 You are allowed to modify these programs, and redistribute the
680 modified versions, provided that the modifications are clearly noted.
682 There is NO WARRANTY with this software, it comes as is, and is
683 distributed in the hope that it may be useful.
685 This copyright notice applies to any program which contains
686 this text, or the refers to this file.
688 This copyright notice is based on the one published by the Free
689 Software Foundation, sometimes known as the GNU project. The idea
690 is the same as theirs, ie the software is free, and is intended to
691 stay that way. Everybody has the right to copy, modify, and re-
692 distribute this software. Nobody has the right to prevent anyone
693 else from copying, modifying or redistributing it.
695 --------------------------------------------------------------------------
698 In acknowledgment of this copyright, I will place my own changes to the
699 compiler under the same copyright. Please note however, that the library
700 and all binutils are covered by another copyright, and that I'm planning
701 to do a complete rewrite of the compiler, after which the compiler
702 copyright will also change.
704 For the list of changes requested by this copyright see newvers.txt.