1 <!doctype linuxdoc system>
4 <title>cc65 Users Guide
5 <author>Ullrich von Bassewitz, <htmlurl url="mailto:uz@cc65.org" name="uz@cc65.org">
6 <date>2000-09-03, 2001-10-02, 2005-08-01
9 cc65 is a C compiler for 6502 targets. It supports several 6502 based home
10 computers like the Commodore and Atari machines, but it is easily retargetable.
13 <!-- Table of contents -->
16 <!-- Begin the document -->
21 cc65 was originally a C compiler for the Atari 8-bit machines written by
22 John R. Dunning. In prior releases I've described the compiler by listing
23 up the changes made by me. I have made many more changes in the meantime
24 (and rewritten major parts of the compiler), so I will no longer do that,
25 since the list would be too large and of no use to anyone. Instead I will
26 describe the compiler in respect to the ANSI/ISO C standard.
28 There are separate documents named <url url="library.html"> and <url
29 url="funcref.html"> that cover the library that is available for the compiler.
30 If you know C, and are interested in doing actual programming, the library
31 documentation is probably of much more use than this document.
33 If you need some hints for getting the best code out of the compiler, you
34 may have a look at <url url="coding.html"> which covers some code generation
41 The compiler translates C files into files containing assembly code that
42 may be translated by the ca65 macroassembler (for more information about
43 the assembler, have a look at <url url="ca65.html">).
46 <sect1>Command line option overview<p>
48 The compiler may be called as follows:
51 ---------------------------------------------------------------------------
52 Usage: cc65 [options] file
54 -Cl Make local variables static
55 -Dsym[=defn] Define a symbol
56 -E Stop after the preprocessing stage
57 -I dir Set an include directory search path
59 -Oi Optimize code, inline more code
60 -Or Enable register variables
61 -Os Inline some known functions
62 -T Include source as comment
63 -V Print the compiler version number
64 -W warning[,...] Suppress warnings
66 -g Add debug info to object file
68 -j Default characters are signed
69 -mm model Set the memory model
70 -o name Name the output file
71 -r Enable register variables
72 -t sys Set the target system
76 --add-source Include source as comment
77 --bss-name seg Set the name of the BSS segment
78 --check-stack Generate stack overflow checks
79 --code-name seg Set the name of the CODE segment
80 --codesize x Accept larger code by factor x
81 --cpu type Set cpu type (6502, 65c02)
82 --create-dep name Create a make dependency file
83 --create-full-dep name Create a full make dependency file
84 --data-name seg Set the name of the DATA segment
86 --debug-info Add debug info to object file
87 --debug-opt name Debug optimization steps
88 --dep-target target Use this dependency target
89 --disable-opt name Disable an optimization step
90 --enable-opt name Enable an optimization step
91 --forget-inc-paths Forget include search paths
92 --help Help (this text)
93 --include-dir dir Set an include directory search path
94 --list-opt-steps List all optimizer steps and exit
95 --list-warnings List available warning types for -W
96 --local-strings Emit string literals immediately
97 --memory-model model Set the memory model
98 --register-space b Set space available for register variables
99 --register-vars Enable register variables
100 --rodata-name seg Set the name of the RODATA segment
101 --signed-chars Default characters are signed
102 --standard std Language standard (c89, c99, cc65)
103 --static-locals Make local variables static
104 --target sys Set the target system
105 --verbose Increase verbosity
106 --version Print the compiler version number
107 --writable-strings Make string literals writable
108 ---------------------------------------------------------------------------
112 <sect1>Command line options in detail<p>
114 Here is a description of all the command line options:
118 <label id="option-bss-name">
119 <tag><tt>--bss-name seg</tt></tag>
121 Set the name of the bss segment. See also <tt/<ref id="pragma-bss-name"
122 name="#pragma bss-name">/.
125 <label id="option-check-stack">
126 <tag><tt>--check-stack</tt></tag>
128 Tells the compiler to generate code that checks for stack overflows. See
129 <tt/<ref id="pragma-check-stack" name="#pragma check-stack">/ for an
130 explanation of this feature.
133 <label id="option-code-name">
134 <tag><tt>--code-name seg</tt></tag>
136 Set the name of the code segment. See also <tt/<ref id="pragma-code-name"
137 name="#pragma code-name">/
140 <label id="option-codesize">
141 <tag><tt>--codesize x</tt></tag>
143 This options allows finer control about speed vs. size decisions in the code
144 generation and optimization phases. It gives the allowed size increase
145 factor (in percent). The default is 100 when not using <tt/-Oi/ and 200 when
146 using <tt/-Oi/ (<tt/-Oi/ is the same as <tt/-O --codesize 200/).
149 <label id="option--cpu">
150 <tag><tt>--cpu CPU</tt></tag>
152 Set the CPU, the compiler generates code for. You may specify "6502" or
153 "65C02" as the CPU. The default depends on the selected target (see option
154 <tt/<ref id="option-t" name="-t">/). It is the 6502 CPU for most targets or
155 if no target has been set. Specifying 65C02 will use a few 65C02
156 instructions when generating code. Don't expect too much from this option:
157 In most cases the difference in size and speed is just 1-2%.
160 <label id="option-create-dep">
161 <tag><tt>--create-dep name</tt></tag>
163 Tells the compiler to generate a file containing the dependency list for the
164 compiled module in makefile syntax. The output is written to a file with the
165 given name. The output does not include system include files (in angle
169 <label id="option-create-full-dep">
170 <tag><tt>--create-full-dep name</tt></tag>
172 Tells the compiler to generate a file containing the dependency list for the
173 compiled module in makefile syntax. The output is written to a file with the
174 given name. The output does include system include files (in angle
178 <label id="option-data-name">
179 <tag><tt>--data-name seg</tt></tag>
181 Set the name of the data segment. See also <tt/<ref id="pragma-data-name"
182 name="#pragma data-name">/
185 <tag><tt>-d, --debug</tt></tag>
187 Enables debug mode, something that should not be needed for mere
191 <label id="option-dep-target">
192 <tag><tt>--dep-target target</tt></tag>
194 When generating a dependency file, don't use the actual output file as the
195 target of the dependency, but the file specified with this option. The
196 option has no effect if neither <tt/<ref id="option-create-dep"
197 name="--create-dep">/ nor <tt/<ref id="option-create-full-dep"
198 name="--create-full-dep">/ is specified.
201 <tag><tt>-D sym[=definition]</tt></tag>
203 Define a macro on the command line. If no definition is given, the macro
204 is defined to the value "1".
207 <tag><tt>--forget-inc-paths</tt></tag>
209 Forget the builtin include paths. This is most useful when building
210 customized C or runtime libraries, in which case the standard header
211 files should be ignored.
214 <tag><tt>-g, --debug-info</tt></tag>
216 This will cause the compiler to insert a <tt/.DEBUGINFO/ command into the
217 generated assembler code. This will cause the assembler to include all
218 symbols in a special section in the object file.
221 <tag><tt>-h, --help</tt></tag>
223 Print the short option summary shown above.
226 <label id="option-list-warnings">
227 <tag><tt>--list-warnings</tt></tag>
229 List the names of warning types available for use with <tt><ref
230 id="option-W" name="-W"></tt>.
233 <label id="option-local-strings">
234 <tag><tt>--local-strings</tt></tag>
236 Emit string literals into the rodata segment as soon as they're encountered
237 in the source (even if you do nothing but get the sizeof those strings). The
238 default is to keep string literals until end of assembly, merge read only
239 literals if possible, and then output the literals into the data or rodata
240 segment that is active at that point. Use of this option prevents merging of
241 duplicate strings, but the options that change the name of one of the data
244 You can also use <tt><ref id="pragma-local-strings"
245 name="#pragma local-strings"></tt> for fine grained control.
248 <tag><tt>-o name</tt></tag>
250 Specify the name of the output file. If you don't specify a name, the
251 name of the C input file is used, with the extension replaced by ".s".
254 <label id="option-register-vars">
255 <tag><tt>-r, --register-vars</tt></tag>
257 <tt/-r/ will make the compiler honor the <tt/register/ keyword. Local
258 variables may be placed in registers (which are actually zero page
259 locations). There is some overhead involved with register variables, since
260 the old contents of the registers must be saved and restored. Since register
261 variables are of limited use without the optimizer, there is also a combined
262 switch: <tt/-Or/ will enable both, the optimizer and register variables.
264 For more information about register variables see <ref id="register-vars"
265 name="register variables">.
267 The compiler setting can also be changed within the source file by using
268 <tt/<ref id="pragma-register-vars" name="#pragma register-vars">/.
271 <label id="option-register-space">
272 <tag><tt>--register-space</tt></tag>
274 This option takes a numeric parameter and is used to specify, how much
275 zero page register space is available. Please note that just giving this
276 option will not increase or decrease by itself, it will just tell the
277 compiler about the available space. You will have to allocate that space
278 yourself using an assembler module with the necessary allocations, and a
279 linker configuration that matches the assembler module. The default value
280 for this option is 6 (bytes).
282 If you don't know what all this means, please don't use this option.
285 <label id="option-rodata-name">
286 <tag><tt>--rodata-name seg</tt></tag>
288 Set the name of the rodata segment (the segment used for readonly data).
289 See also <tt/<ref id="pragma-rodata-name" name="#pragma rodata-name">/
291 <label id="option-signed-chars">
292 <tag><tt>-j, --signed-chars</tt></tag>
294 Using this option, you can make the default characters signed. Since the
295 6502 has no provisions for sign extending characters (which is needed on
296 almost any load operation), this will make the code larger and slower. A
297 better way is to declare characters explicitly as "signed" if needed. You
298 can also use <tt><ref id="pragma-signed-chars"
299 name="#pragma signed-chars"></tt> for better control of this option.
302 <label id="option--standard">
303 <tag><tt>--standard std</tt></tag>
305 This option allows to set the language standard supported. The argument is
309 This disables anything that is illegal in C89/C90. Among those things
310 are <tt>//</tt> comments and the non-standard keywords without
311 underscores. Please note that cc65 is not a fully C89 compliant compiler
312 despite this option. A few more things (like floats) are missing.
315 This enables a few features from the C99 standard. With this option,
316 <tt>//</tt> comments are allowed. It will also cause warnings and even
317 errors in a few situations that are allowed with <tt/--standard c89/.
318 For example, a call to a function without a prototype is an error in
322 This is the default mode. It is like c99 mode, but additional features
323 are enabled. Among these are "void data", non-standard keywords without
324 the underlines, unnamed function parameters and the requirement for
325 main() to return an int.
328 Please note that the compiler does not support the C99 standard and never
329 will. c99 mode is actually c89 mode with a few selected C99 extensions.
332 <label id="option-t">
333 <tag><tt>-t target, --target target</tt></tag>
335 This option is used to set the target system. The target system determines
336 the character set that is used for strings and character constants and the
337 default CPU. The CPU setting can be overriden by use of the <tt/<ref
338 id="option--cpu" name="--cpu">/ option.
340 The following target systems are supported:
348 <item>c16 (works also for the c116 with memory up to 32K)
351 <item>cbm510 (CBM-II series with 40 column video)
352 <item>cbm610 (all CBM-II II computers with 80 column video)
358 <item>pet (all CBM PET systems except the 2001)
364 <tag><tt>-v, --verbose</tt></tag>
366 Using this option, the compiler will be somewhat more verbose if errors
367 or warnings are encountered.
370 <label id="option-writable-strings">
371 <tag><tt>--writable-strings</tt></tag>
373 Make string literals writable by placing them into the data segment instead
374 of the rodata segment. You can also use <tt><ref id="pragma-writable-strings"
375 name="#pragma writable-strings"></tt> to control this option from within
379 <label id="option-static-locals">
380 <tag><tt>-Cl, --static-locals</tt></tag>
382 Use static storage for local variables instead of storage on the stack.
383 Since the stack is emulated in software, this gives shorter and usually
384 faster code, but the code is no longer reentrant. The difference between
385 <tt/-Cl/ and declaring local variables as static yourself is, that
386 initializer code is executed each time, the function is entered. So when
397 the variable <tt/a/ will always have the value <tt/1/ when entering the
398 function and using <tt/-Cl/, while in
403 static unsigned a = 1;
408 the variable <tt/a/ will have the value <tt/1/ only the first time that the
409 function is entered, and will keep the old value from one call of the
410 function to the next.
412 You may also use <tt><ref id="pragma-static-locals"
413 name="#pragma static-locals"></tt> to change this setting in your
417 <label id="option-include-dir">
418 <tag><tt>-I dir, --include-dir dir</tt></tag>
420 Set a directory where the compiler searches for include files. You may
421 use this option multiple times to add more than one directory to the
425 <label id="option-O">
426 <tag><tt>-O, -Oi, -Or, -Os</tt></tag>
428 Enable an optimizer run over the produced code.
430 Using <tt/-Oi/, the code generator will inline some code where otherwise a
431 runtime functions would have been called, even if the generated code is
432 larger. This will not only remove the overhead for a function call, but will
433 make the code visible for the optimizer. <tt/-Oi/ is an alias for
434 <tt/-O --codesize 200/.
436 <tt/-Or/ will make the compiler honor the <tt/register/ keyword. Local
437 variables may be placed in registers (which are actually zero page
438 locations). See also the <tt/<ref id="option-register-vars"
439 name="--register-vars">/ command line option, and the <ref
440 id="register-vars" name="discussion of register variables"> below.
442 Using <tt/-Os/ will force the compiler to inline some known functions from
443 the C library like strlen. Note: This has two consequences:
446 <item>You may not use names of standard C functions in your own code. If you
447 do that, your program is not standard compliant anyway, but using
448 <tt/-Os/ will actually break things.
450 <item>The inlined string and memory functions will not handle strings or
451 memory areas larger than 255 bytes. Similarly, the inlined <tt/is..()/
452 functions will not work with values outside the char. range (such as
457 It is possible to concatenate the modifiers for <tt/-O/. For example, to
458 enable register variables and inlining of known functions, you may use
462 <tag><tt>-T, --add-source</tt></tag>
464 This include the source code as comments in the generated code. This is
468 <tag><tt>-V, --version</tt></tag>
470 Print the version number of the compiler. When submitting a bug report,
471 please include the operating system you're using, and the compiler
475 <label id="option-W">
476 <tag><tt>-W name[,name]</tt></tag>
478 This option allows to control warnings generated by the compiler. It is
479 followed by a comma separated list of warnings that should be enabled or
480 disabled. To disable a warning, its name is prefixed by a minus sign. If
481 no such prefix exists, or the name is prefixed by a plus sign, the warning
484 The following warning names are currently recognized:
486 <tag><tt/const-comparison/</tag>
487 Warn if the result of a comparison is constant.
488 <tag><tt/error/</tag>
489 Treat all warnings as errors.
490 <tag><tt/no-effect/</tag>
491 Warn about statements that don't have an effect.
492 <tag><tt/struct-param/</tag>
493 Warn when passing structs by value.
494 <tag><tt/unknown-pragma/</tag>
495 Warn about known #pragmas.
496 <tag><tt/unused-label/</tag>
497 Warn about unused labels.
498 <tag><tt/unused-param/</tag>
499 Warn about unused function parameters.
500 <tag><tt/unused-var/</tag>
501 Warn about unused variables.
504 The full list of available warning names may be retrieved by using the
505 option <tt><ref id="option-list-warnings" name="--list-warnings"></tt>.
507 You may also use <tt><ref id="pragma-warn" name="#pragma warn"></tt> to
508 control this setting for smaller pieces of code from within your code.
513 <sect>Input and output<p>
515 The compiler will accept one C file per invocation and create a file with
516 the same base name, but with the extension replaced by ".s". The output
517 file contains assembler code suitable for the use with the ca65 macro
520 Include files in single quotes are searched in the following places:
522 <item>The current directory.
523 <item>The value of the environment variable <tt/CC65_INC/ if it is defined.
524 <item>Any directory added with the <tt/-I/ option on the command line.
527 Include files in angle brackets are searched in the following places:
529 <item>A compiled in directory which is often <tt>/usr/lib/cc65/include</tt> on
531 <item>The value of the environment variable <tt/CC65_INC/ if it is defined.
532 <item>A subdirectory named <tt/include/ of the directory defined in the
533 environment variable <tt/CC65_HOME/, if it is defined.
534 <item>Any directory added with the <tt/-I/ option on the command line.
539 <sect>Differences to the ISO standard<p>
541 Apart from the things listed below, the compiler does support additional
542 keywords, has several functions in the standard headers with names outside the
543 reserved namespace and a few syntax extensions. All these can be disabled with
544 the <tt><ref id="option--standard" name="--standard"></tt> command line
545 option. Its use for maximum standards compatibility is advised.
547 Here is a list of differences between the language, the compiler accepts,
548 and the one defined by the ISO standard:
552 <item> The datatypes "float" and "double" are not available.
554 <item> C Functions may not return structs (or unions), and structs may not
555 be passed as parameters by value. However, struct assignment *is*
558 <item> Part of the C library is available only with fastcall calling
559 conventions (see below). It means that you must not mix pointers to
560 those functions with pointers to user-written, not-fastcall functions.
562 <item> The <tt/volatile/ keyword doesn't have an effect. This is not as bad
563 as it sounds, since the 6502 has so few registers that it isn't
564 possible to keep values in registers anyway.
568 There may be some more minor differences I'm currently not aware of. The
569 biggest problem is the missing float data type. With this limitation in
570 mind, you should be able to write fairly portable code.
576 This cc65 version has some extensions to the ISO C standard.
580 <item> The compiler allows to insert assembler statements into the output
584 asm (<string literal>[, optional parameters]) ;
588 __asm__ (<string literal>[, optional parameters]) ;
591 The first form is in the user namespace and is disabled if the <tt/-A/
594 There is a whole section covering inline assembler statements,
595 <ref id="inline-asm" name="see there">.
598 <item> There is a special calling convention named "fastcall".
599 The syntax for a function declaration using fastcall is
602 <return type> fastcall <function name> (<parameter list>)
606 <return type> __fastcall__ <function name> (<parameter list>)
610 void __fastcall__ f (unsigned char c)
612 The first form of the fastcall keyword is in the user namespace and can
613 therefore be disabled with the <tt><ref id="option--standard"
614 name="--standard"></tt> command line option.
616 For functions declared as <tt/fastcall/, the rightmost parameter is not
617 pushed on the stack but left in the primary register when the function
618 is called. This will reduce the cost when calling assembler functions
619 significantly, especially when the function itself is rather small.
622 <item> There are two pseudo variables named <tt/__AX__/ and <tt/__EAX__/.
623 Both refer to the primary register that is used by the compiler to
624 evaluate expressions or return function results. <tt/__AX__/ is of
625 type <tt/unsigned int/ and <tt/__EAX__/ of type <tt/long unsigned int/
626 respectively. The pseudo variables may be used as lvalue and rvalue as
627 every other variable. They are most useful together with short
628 sequences of assembler code. For example, the macro
638 will give the high byte of any unsigned value.
641 <item> Inside a function, the identifier <tt/__func__/ gives the name of the
642 current function as a string. Outside of functions, <tt/__func__/ is
647 #define PRINT_DEBUG(s) printf ("%s: %s\n", __func__, s);
650 The macro will print the name of the current function plus a given
654 <item> cc65 allows the initialization of <tt/void/ variables. This may be
655 used to create variable structures that are more compatible with
656 interfaces written for assembler languages. Here is an example:
659 void GCmd = { (char)3, (unsigned)0x2000, (unsigned)0x3000 };
662 This will be translated as follows:
671 Since the variable is of type <tt/void/ you may not use it as is.
672 However, taking the address of the variable results in a <tt/void*/
673 which may be passed to any function expecting a pointer.
675 See the <url url="geos.html" name="GEOS library document"> for examples
676 on how to use this feature.
679 <item> cc65 implements flexible array struct members as defined in the C99 ISO
680 standard. As an extension, these fields may be initialized. There are
681 several exceptions, however (which is probably the reason why the
682 standard does not define this feature, because it is highly
683 unorthogonal). Flexible array members cannot be initialized ...
686 <item>... when defining an array of structs with flexible
688 <item>... if such a struct is a member field of another struct
689 which is not the last field.
690 <item>... if the struct which contains a flexible array member is
691 declared as <tt/register/, and the size and compiler settings
692 do allow the compiler actually to place the struct into the
693 register bank in the zero page.
696 Please note that -- as defined in the ISO C standard -- the <tt/sizeof/
697 operator returns the struct size with the flexible array member having
698 size zero, even if it is initialized.
705 <sect>Predefined macros<p>
707 The compiler defines several macros at startup:
710 <tag><tt>__APPLE2__</tt></tag>
712 This macro is defined if the target is the Apple ][ (-t apple2).
714 <tag><tt>__APPLE2ENH__</tt></tag>
716 This macro is defined if the target is the enhanced Apple //e (-t apple2enh).
718 <tag><tt>__ATARI__</tt></tag>
720 This macro is defined if the target is one of the Atari computers
721 (400/800/130XL/800XL).
723 <tag><tt>__ATMOS__</tt></tag>
725 This macro is defined if the target is the Oric Atmos (-t atmos).
727 <tag><tt>__C128__</tt></tag>
729 This macro is defined if the target is the c128 (-t c128).
731 <tag><tt>__C16__</tt></tag>
733 This macro is defined if the target is the c16 (-t c16).
735 <tag><tt>__C64__</tt></tag>
737 This macro is defined if the target is the c64 (-t c64).
739 <tag><tt>__CBM__</tt></tag>
741 This macro is defined if the target system is one of the CBM targets.
743 <tag><tt>__CBM510__</tt></tag>
745 This macro is defined if the target is the CBM 500 series of computers.
747 <tag><tt>__CBM610__</tt></tag>
749 This macro is defined if the target is one of the CBM 600/700 family of
750 computers (called B series in the US).
752 <tag><tt>__CC65__</tt></tag>
754 This macro is always defined. Its value is the version number of the
755 compiler in hex. For example, version 2.10.1 of the compiler has this macro
756 defined as <tt/0x02A1/.
758 <tag><tt>__CC65_STD__</tt></tag>
760 This macro is defined to one of the following depending on the <tt><ref
761 id="option--standard" name="--standard"></tt> command line option:
763 <item><tt/__CC65_STD_C89__/
764 <item><tt/__CC65_STD_C99__/
765 <item><tt/__CC65_STD_CC65__/
768 <tag><tt>__DATE__</tt></tag>
770 This macro expands to the date of translation of the preprocessing
771 translation unit in the form "Mmm dd yyyy".
773 <tag><tt>__FILE__</tt></tag>
775 This macro expands to a string containing the name of the C source file.
777 <tag><tt>__GEOS__</tt></tag>
779 This macro is defined if you are compiling for the GEOS system (-t geos).
781 <tag><tt>__LINE__</tt></tag>
783 This macro expands to the current line number.
785 <tag><tt>__LUNIX__</tt></tag>
787 This macro is defined if you are compiling for the LUnix system (-t lunix).
789 <tag><tt>__LYNX__</tt></tag>
791 This macro is defined if the target is the Atari Lynx (-t lynx).
793 <tag><tt>__NES__</tt></tag>
795 This macro is defined if the target is the NES (-t nes).
797 <tag><tt>__OPT__</tt></tag>
799 Is defined if the compiler was called with the <tt/-O/ command line option.
801 <tag><tt>__OPT_i__</tt></tag>
803 Is defined if the compiler was called with the <tt/-Oi/ command line option.
805 <tag><tt>__OPT_r__</tt></tag>
807 Is defined if the compiler was called with the <tt/-Or/ command line option.
809 <tag><tt>__OPT_s__</tt></tag>
811 Is defined if the compiler was called with the <tt/-Os/ command line option.
813 <tag><tt>__PET__</tt></tag>
815 This macro is defined if the target is the PET family of computers (-t pet).
817 <tag><tt>__PLUS4__</tt></tag>
819 This macro is defined if the target is the plus/4 (-t plus4).
821 <tag><tt>__STDC_HOSTED__</tt></tag>
823 This macro is expands to the integer constant 1.
825 <tag><tt>__SUPERVISION__</tt></tag>
827 This macro is defined if the target is the supervision (-t supervision).
829 <tag><tt>__TIME__</tt></tag>
831 This macro expands to the time of translation of the preprocessing
832 translation unit in the form "hh:mm:ss".
834 <tag><tt>__VIC20__</tt></tag>
836 This macro is defined if the target is the vic20 (-t vic20).
840 <sect>#pragmas<label id="pragmas"><p>
842 The compiler understands some pragmas that may be used to change code
843 generation and other stuff. Some of these pragmas understand a special form:
844 If the first parameter is <tt/push/, the old value is saved onto a stack
845 before changing it. The value may later be restored by using the <tt/pop/
846 parameter with the <tt/#pragma/.
848 <sect1><tt>#pragma bss-name ([push,] <name>)</tt><label id="pragma-bss-name"><p>
850 This pragma changes the name used for the BSS segment (the BSS segment
851 is used to store uninitialized data). The argument is a string enclosed
854 Note: The default linker configuration file does only map the standard
855 segments. If you use other segments, you have to create a new linker
858 Beware: The startup code will zero only the default BSS segment. If you
859 use another BSS segment, you have to do that yourself, otherwise
860 uninitialized variables do not have the value zero.
862 The <tt/#pragma/ understands the push and pop parameters as explained above.
866 #pragma bss-name ("MyBSS")
870 <sect1><tt>#pragma charmap (<index>, <code>)</tt><label id="pragma-charmap"><p>
872 Each literal string and each literal character in the source is translated
873 by use of a translation table. This translation table is preset when the
874 compiler is started depending on the target system, for example to map
875 ISO-8859-1 characters into PETSCII if the target is a commodore machine.
877 This pragma allows to change entries in the translation table, so the
878 translation for individual characters, or even the complete table may be
881 Both arguments are assumed to be unsigned characters with a valid range of
884 Beware of two pitfalls:
887 <item>The character index is actually the code of the character in the
888 C source, so character mappings do always depend on the source
889 character set. This means that <tt/#pragma charmap/ is not
890 portable -- it depends on the build environment.
891 <item>While it is possible to use character literals as indices, the
892 result may be somewhat unexpected, since character literals are
893 itself translated. For this reason I would suggest to avoid
894 character literals and use numeric character codes instead.
899 /* Use a space wherever an 'a' occurs in ISO-8859-1 source */
900 #pragma charmap (0x61, 0x20);
904 <sect1><tt>#pragma check-stack ([push,] on|off)</tt><label id="pragma-check-stack"><p>
906 Tells the compiler to insert calls to a stack checking subroutine to detect
907 stack overflows. The stack checking code will lead to somewhat larger and
908 slower programs, so you may want to use this pragma when debugging your
909 program and switch it off for the release version. If a stack overflow is
910 detected, the program is aborted.
912 If the argument is "off", stack checks are disabled (the default), otherwise
915 The <tt/#pragma/ understands the push and pop parameters as explained above.
917 <sect1><tt>#pragma code-name ([push,] <name>)</tt><label id="pragma-code-name"><p>
919 This pragma changes the name used for the CODE segment (the CODE segment
920 is used to store executable code). The argument is a string enclosed in
923 Note: The default linker configuration file does only map the standard
924 segments. If you use other segments, you have to create a new linker
927 The <tt/#pragma/ understands the push and pop parameters as explained above.
931 #pragma code-name ("MyCODE")
935 <sect1><tt>#pragma codesize ([push,] <int>)</tt><label id="pragma-codesize"><p>
937 This pragma allows finer control about speed vs. size decisions in the code
938 generation and optimization phase. It gives the allowed size increase factor
939 (in percent). The default is can be changed by use of the <tt/<ref
940 id="option-codesize" name="--codesize">/ compiler option.
942 The <tt/#pragma/ understands the push and pop parameters as explained above.
945 <sect1><tt>#pragma data-name ([push,] <name>)</tt><label id="pragma-data-name"><p>
947 This pragma changes the name used for the DATA segment (the DATA segment
948 is used to store initialized data). The argument is a string enclosed in
951 Note: The default linker configuration file does only map the standard
952 segments. If you use other segments, you have to create a new linker
955 The <tt/#pragma/ understands the push and pop parameters as explained above.
959 #pragma data-name ("MyDATA")
963 <sect1><tt>#pragma local-strings ([push,] on|off)</tt><label id="pragma-local-strings"><p>
965 When "on", emit string literals to the data segment when they're encountered
966 in the source. The default ("off") is to keep string literals until end of
967 assembly, merge read only literals if possible, and then output the literals
968 into the data or rodata segment that is active at that point.
970 Using this <tt/#pragma/ it is possible to control the behaviour from within
971 the source. When <tt/#pragma local-strings/ is active, string literals are
972 output immediately, which means that they go into the currently active data
973 or rodata segment, but cannot be merged. When inactive, string literals are
974 remembered and output as a whole when translation is finished.
977 <sect1><tt>#pragma optimize ([push,] on|off)</tt><label id="pragma-optimize"><p>
979 Switch optimization on or off. If the argument is "off", optimization is
980 disabled, otherwise it is enabled. Please note that this pragma only effects
981 whole functions. The setting in effect when the function is encountered will
982 determine if the generated code is optimized or not.
984 Optimization and code generation is also controlled by the <ref
985 id="pragma-codesize" name="codesize pragma">.
987 The default is "off", but may be changed with the <tt/<ref name="-O"
988 id="option-O">/ compiler option.
990 The <tt/#pragma/ understands the push and pop parameters as explained above.
993 <sect1><tt>#pragma rodata-name ([push,] <name>)</tt><label id="pragma-rodata-name"><p>
995 This pragma changes the name used for the RODATA segment (the RODATA
996 segment is used to store readonly data). The argument is a string
997 enclosed in double quotes.
999 Note: The default linker configuration file does only map the standard
1000 segments. If you use other segments, you have to create a new linker
1003 The <tt/#pragma/ understands the push and pop parameters as explained above.
1007 #pragma rodata-name ("MyRODATA")
1011 <sect1><tt>#pragma regvaraddr ([push,] on|off)</tt><label id="pragma-regvaraddr"><p>
1013 The compiler does not allow to take the address of register variables.
1014 The regvaraddr pragma changes this. Taking the address of a register
1015 variable is allowed after using this pragma with "on" as argument.
1016 Using "off" as an argument switches back to the default behaviour.
1018 Beware: The C standard does not allow taking the address of a variable
1019 declared as register. So your programs become non-portable if you use
1020 this pragma. In addition, your program may not work. This is usually the
1021 case if a subroutine is called with the address of a register variable,
1022 and this subroutine (or a subroutine called from there) uses
1023 register variables. So be careful with this #pragma.
1025 The <tt/#pragma/ understands the push and pop parameters as explained above.
1029 #pragma regvaraddr(on) /* Allow taking the address
1030 * of register variables
1035 <sect1><tt>#pragma register-vars ([push,] on|off)</tt><label id="pragma-register-vars"><p>
1037 Enables or disables use of register variables. If register variables are
1038 disabled (the default), the <tt/register/ keyword is ignored. Register
1039 variables are explained in more detail in <ref id="register-vars" name="a separate
1042 The <tt/#pragma/ understands the push and pop parameters as explained above.
1045 <sect1><tt>#pragma signed-chars ([push,] on|off)</tt><label id="pragma-signed-chars"><p>
1047 Changes the signedness of the default character type. If the argument is
1048 "on", default characters are signed, otherwise characters are unsigned. The
1049 compiler default is to make characters unsigned since this creates a lot
1050 better code. This default may be overridden by the <tt/<ref
1051 name="--signed-chars" id="option-signed-chars">/ command line option.
1053 The <tt/#pragma/ understands the push and pop parameters as explained above.
1056 <sect1><tt>#pragma static-locals ([push,] on|off)</tt><label id="pragma-static-locals"<p>
1058 Use variables in the bss segment instead of variables on the stack. This
1059 pragma changes the default set by the compiler option <tt/<ref
1060 name="--static-locals" id="option-static-locals">/. If the argument is "on",
1061 local variables are allocated in the BSS segment, leading to shorter and in
1062 most cases faster, but non-reentrant code.
1064 The <tt/#pragma/ understands the push and pop parameters as explained above.
1067 <sect1><tt>#pragma warn (name, [push,] on|off)</tt><label id="pragma-warn"><p>
1069 Switch compiler warnings on or off. "name" is the name of a warning (see the
1070 <tt/<ref name="-W" id="option-W">/ compiler option for a list). The name is
1071 either followed by "pop", which restores the last pushed state, or by "on" or
1072 "off", optionally preceeded by "push" to push the current state before
1077 /* Don't warn about the unused parameter in function func */
1078 #pragma warn (unused-param, push, off)
1079 static int func (int unused)
1083 #pragma warn (unused-param, pop)
1086 <sect1><tt>#pragma writable-strings ([push,] on|off)</tt><label id="pragma-writable-strings"><p>
1088 Changes the storage location of string literals. For historical reasons,
1089 the C standard defines that string literals are of type "char[]", but
1090 writing to such a literal causes undefined behaviour. Most compilers
1091 (including cc65) place string literals in the read-only data segment, which
1092 may cause problems with old C code that writes to string literals.
1094 Using this pragma (or the corresponding command line option <tt/<ref
1095 name="--writable-strings" id="option-writable-strings">/) causes the
1096 literals to be placed in the data segment so they can be written to without
1099 The <tt/#pragma/ understands the push and pop parameters as explained above.
1102 <sect1><tt>#pragma zpsym (<name>)</tt><p>
1104 Tell the compiler that the -- previously as external declared -- symbol with
1105 the given name is a zero page symbol (usually from an assembler file).
1106 The compiler will create a matching import declaration for the assembler.
1111 #pragma zpsym ("foo"); /* foo is in the zeropage */
1117 <sect>Register variables<label id="register-vars"><p>
1119 The runtime for all supported platforms has 6 bytes of zero page space
1120 available for register variables (this could be increased, but I think it's a
1121 good value). So you can declare register variables up to a total size of 6 per
1122 function. The compiler will allocate register space on a "first come, first
1123 served" base and convert any <tt/register/ declarations that exceed the
1124 available register space silently to <tt/auto/. Parameters can also be
1125 declared as <tt/register/, this will in fact give slightly shorter code than
1126 using a register variable.
1128 Since a function must save the current values of the registers on entry and
1129 restore them on exit, there is an overhead associated with register variables,
1130 and this overhead is quite high (about 20 bytes per variable). This means that
1131 just declaring anything as <tt/register/ is not a good idea.
1133 The best use for register variables are pointers, especially those that point
1134 to structures. The magic number here is about 3 uses of a struct field: If the
1135 function contains this number or even more, the generated code will be usually
1136 shorter and faster when using a register variable for the struct pointer. The
1137 reason for this is that the register variable can in many cases be used as a
1138 pointer directly. Having a pointer in an auto variable means that this pointer
1139 must first be copied into a zero page location, before it can be dereferenced.
1141 Second best use for register variables are counters. However, there is not
1142 much difference in the code generated for counters, so you will need at least
1143 100 operations on this variable (for example in a loop) to make it worth the
1144 trouble. The only savings you get here are by the use of a zero page variable
1145 instead of one on the stack or in the data segment.
1147 Register variables must be explicitly enabled, either by using <tt/<ref
1148 name="-Or" id="option-O">/ or <tt/<ref name="--register-vars"
1149 id="option-register-vars">/ on the command line or by use of <tt/<ref
1150 name="#pragma register-vars" id="pragma-register-vars">/. Register variables
1151 are only accepted on function top level, register variables declared in
1152 interior blocks are silently converted to <tt/auto/. With register variables
1153 disabled, all variables declared as <tt/register/ are actually auto variables.
1155 Please take care when using register variables: While they are helpful and can
1156 lead to a tremendous speedup when used correctly, improper usage will cause
1157 bloated code and a slowdown.
1161 <sect>Inline assembler<label id="inline-asm"><p>
1163 The compiler allows to insert assembler statements into the output file. The
1167 asm (<string literal>[, optional parameters]) ;
1171 __asm__ (<string literal>[, optional parameters]) ;
1175 The first form is in the user namespace and is disabled by <tt><ref
1176 id="option--standard" name="--standard"></tt> if the argument is not <tt/cc65/.
1178 The asm statement may be used inside a function and on global file level. An
1179 inline assembler statement is a primary expression, so it may also be used as
1180 part of an expression. Please note however that the result of an expression
1181 containing just an inline assembler statement is always of type <tt/void/.
1183 The contents of the string literal are preparsed by the compiler and inserted
1184 into the generated assembly output, so that the can be further processed by
1185 the backend and especially the optimizer. For this reason, the compiler does
1186 only allow regular 6502 opcodes to be used with the inline assembler. Pseudo
1187 instructions (like <tt/.import/, <tt/.byte/ and so on) are <em/not/ allowed,
1188 even if the ca65 assembler (which is used to translate the generated assembler
1189 code) would accept them. The builtin inline assembler is not a replacement for
1190 the full blown macro assembler which comes with the compiler.
1192 Note: Inline assembler statements are subject to all optimizations done by the
1193 compiler. There is currently no way to protect an inline assembler statement
1194 from being moved or removed completely by the optimizer. If in doubt, check
1195 the generated assembler output, or disable optimizations.
1197 The string literal may contain format specifiers from the following list. For
1198 each format specifier, an argument is expected which is inserted instead of
1199 the format specifier before passing the assembly code line to the backend.
1202 <item><tt/%b/ - Numerical 8-bit value
1203 <item><tt/%w/ - Numerical 16-bit value
1204 <item><tt/%l/ - Numerical 32-bit value
1205 <item><tt/%v/ - Assembler name of a global variable or function
1206 <item><tt/%o/ - Stack offset of a local variable
1207 <item><tt/%g/ - Assembler name of a C label
1208 <item><tt/%s/ - The argument is converted to a string
1209 <item><tt/%%/ - The % sign itself
1212 Using these format specifiers, you can access C <tt/#defines/, variables or
1213 similar stuff from the inline assembler. For example, to load the value of
1214 a C <tt/#define/ into the Y register, one would use
1218 __asm__ ("ldy #%b", OFFS);
1221 Or, to access a struct member of a static variable:
1227 unsigned char color;
1229 static pixel_t pixel;
1230 __asm__ ("ldy #%b", offsetof(pixel_t, color));
1231 __asm__ ("lda %v,y", pixel);
1234 The next example shows how to use global variables to exchange data between C
1235 an assembler and how to handle assembler jumps:
1238 unsigned char globalSubA, globalSubB, globalSubResult;
1240 /* return a-b, return 255 if b>a */
1241 unsigned char sub (unsigned char a, unsigned char b)
1246 __asm__ ("lda %v", globalSubA);
1247 __asm__ ("sbc %v", globalSubB);
1248 __asm__ ("bcs %g", jumpSubNoError);
1249 __asm__ ("lda #$FF");
1251 __asm__ ("sta %v", globalSubResult);
1252 return globalSubResult;
1257 Arrays can also be accessed:
1260 unsigned char globalSquareTable[] = {
1261 0, 1, 4, 9, 16, 25, 36, 49, 64, 81,
1262 100, 121, 144, 169, 196, 225
1264 unsigned char globalSquareA, globalSquareResult;
1266 /* return a*a for a<16, else 255 */
1267 unsigned char square (unsigned char a)
1273 __asm__ ("ldx %v", globalSquareA);
1274 __asm__ ("lda %v,x", globalSquareTable);
1275 __asm__ ("sta %v", globalSquareResult);
1276 return globalSquareResult;
1281 Note: Do not embed the assembler labels that are used as names of global
1282 variables or functions into your asm statements. Code like this
1286 int bar () { return 1; }
1287 __asm__ ("lda _foo"); /* DON'T DO THAT! */
1289 __asm__ ("jsr _bar"); /* DON'T DO THAT EITHER! */
1293 may stop working if the way, the compiler generates these names is changed in
1294 a future version. Instead use the format specifiers from the table above:
1297 __asm__ ("lda %v", foo); /* OK */
1299 __asm__ ("jsr %v", bar); /* OK */
1304 <sect>Implementation-defined behavior<p>
1306 This section describes the behavior of cc65 when the standard describes the
1307 behavior as implementation-defined.
1311 <sect>Bugs/Feedback<p>
1313 If you have problems using the compiler, if you find any bugs, or if you're
1314 doing something interesting with it, I would be glad to hear from you. Feel
1315 free to contact me by email (<htmlurl url="mailto:uz@cc65.org"
1316 name="uz@cc65.org">).
1322 This is the original compiler copyright:
1325 --------------------------------------------------------------------------
1328 This is the copyright notice for RA65, LINK65, LIBR65, and other
1329 Atari 8-bit programs. Said programs are Copyright 1989, by John R.
1330 Dunning. All rights reserved, with the following exceptions:
1332 Anyone may copy or redistribute these programs, provided that:
1334 1: You don't charge anything for the copy. It is permissable to
1335 charge a nominal fee for media, etc.
1337 2: All source code and documentation for the programs is made
1338 available as part of the distribution.
1340 3: This copyright notice is preserved verbatim, and included in
1343 You are allowed to modify these programs, and redistribute the
1344 modified versions, provided that the modifications are clearly noted.
1346 There is NO WARRANTY with this software, it comes as is, and is
1347 distributed in the hope that it may be useful.
1349 This copyright notice applies to any program which contains
1350 this text, or the refers to this file.
1352 This copyright notice is based on the one published by the Free
1353 Software Foundation, sometimes known as the GNU project. The idea
1354 is the same as theirs, ie the software is free, and is intended to
1355 stay that way. Everybody has the right to copy, modify, and re-
1356 distribute this software. Nobody has the right to prevent anyone
1357 else from copying, modifying or redistributing it.
1359 --------------------------------------------------------------------------
1362 Small parts of the compiler (parts of the preprocessor and main parser) are
1363 still covered by this copyright. The main portion is covered by the usual
1364 cc65 license, which reads:
1366 This software is provided 'as-is', without any expressed or implied
1367 warranty. In no event will the authors be held liable for any damages
1368 arising from the use of this software.
1370 Permission is granted to anyone to use this software for any purpose,
1371 including commercial applications, and to alter it and redistribute it
1372 freely, subject to the following restrictions:
1375 <item> The origin of this software must not be misrepresented; you must not
1376 claim that you wrote the original software. If you use this software
1377 in a product, an acknowledgment in the product documentation would be
1378 appreciated but is not required.
1379 <item> Altered source versions must be plainly marked as such, and must not
1380 be misrepresented as being the original software.
1381 <item> This notice may not be removed or altered from any source