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 to the data segment when they're encountered in the
237 source. The default is to keep string literals until end of assembly, merge
238 read only literals if possible, and then output the literals into the data
239 or rodata segment that is active at that point. Use of this option prevents
240 merging of duplicate strings, but the options that change the name of one of
241 the data segments will work.
243 You can also use <tt><ref id="pragma-local-strings"
244 name="#pragma local-strings"></tt> for fine grained control.
247 <tag><tt>-o name</tt></tag>
249 Specify the name of the output file. If you don't specify a name, the
250 name of the C input file is used, with the extension replaced by ".s".
253 <label id="option-register-vars">
254 <tag><tt>-r, --register-vars</tt></tag>
256 <tt/-r/ will make the compiler honor the <tt/register/ keyword. Local
257 variables may be placed in registers (which are actually zero page
258 locations). There is some overhead involved with register variables, since
259 the old contents of the registers must be saved and restored. Since register
260 variables are of limited use without the optimizer, there is also a combined
261 switch: <tt/-Or/ will enable both, the optimizer and register variables.
263 For more information about register variables see <ref id="register-vars"
264 name="register variables">.
266 The compiler setting can also be changed within the source file by using
267 <tt/<ref id="pragma-register-vars" name="#pragma register-vars">/.
270 <label id="option-register-space">
271 <tag><tt>--register-space</tt></tag>
273 This option takes a numeric parameter and is used to specify, how much
274 zero page register space is available. Please note that just giving this
275 option will not increase or decrease by itself, it will just tell the
276 compiler about the available space. You will have to allocate that space
277 yourself using an assembler module with the necessary allocations, and a
278 linker configuration that matches the assembler module. The default value
279 for this option is 6 (bytes).
281 If you don't know what all this means, please don't use this option.
284 <label id="option-rodata-name">
285 <tag><tt>--rodata-name seg</tt></tag>
287 Set the name of the rodata segment (the segment used for readonly data).
288 See also <tt/<ref id="pragma-rodata-name" name="#pragma rodata-name">/
290 <label id="option-signed-chars">
291 <tag><tt>-j, --signed-chars</tt></tag>
293 Using this option, you can make the default characters signed. Since the
294 6502 has no provisions for sign extending characters (which is needed on
295 almost any load operation), this will make the code larger and slower. A
296 better way is to declare characters explicitly as "signed" if needed. You
297 can also use <tt><ref id="pragma-signed-chars"
298 name="#pragma signed-chars"></tt> for better control of this option.
301 <label id="option--standard">
302 <tag><tt>--standard std</tt></tag>
304 This option allows to set the language standard supported. The argument is
308 This disables anything that is illegal in C89/C90. Among those things
309 are <tt>//</tt> comments and the non-standard keywords without
310 underscores. Please note that cc65 is not a fully C89 compliant compiler
311 despite this option. A few more things (like floats) are missing.
314 This enables a few features from the C99 standard. With this option,
315 <tt>//</tt> comments are allowed. It will also cause warnings and even
316 errors in a few situations that are allowed with <tt/--standard c89/.
317 For example, a call to a function without a prototype is an error in
321 This is the default mode. It is like c99 mode, but additional features
322 are enabled. Among these are "void data", non-standard keywords without
323 the underlines, unnamed function parameters and the requirement for
324 main() to return an int.
327 Please note that the compiler does not support the C99 standard and never
328 will. c99 mode is actually c89 mode with a few selected C99 extensions.
331 <label id="option-t">
332 <tag><tt>-t target, --target target</tt></tag>
334 This option is used to set the target system. The target system determines
335 the character set that is used for strings and character constants and the
336 default CPU. The CPU setting can be overriden by use of the <tt/<ref
337 id="option--cpu" name="--cpu">/ option.
339 The following target systems are supported:
347 <item>c16 (works also for the c116 with memory up to 32K)
350 <item>cbm510 (CBM-II series with 40 column video)
351 <item>cbm610 (all CBM-II II computers with 80 column video)
357 <item>pet (all CBM PET systems except the 2001)
363 <tag><tt>-v, --verbose</tt></tag>
365 Using this option, the compiler will be somewhat more verbose if errors
366 or warnings are encountered.
369 <label id="option-writable-strings">
370 <tag><tt>--writable-strings</tt></tag>
372 Make string literals writable by placing them into the data segment instead
373 of the rodata segment. You can also use <tt><ref id="pragma-writable-strings"
374 name="#pragma writable-strings"></tt> to control this option from within
378 <label id="option-static-locals">
379 <tag><tt>-Cl, --static-locals</tt></tag>
381 Use static storage for local variables instead of storage on the stack.
382 Since the stack is emulated in software, this gives shorter and usually
383 faster code, but the code is no longer reentrant. The difference between
384 <tt/-Cl/ and declaring local variables as static yourself is, that
385 initializer code is executed each time, the function is entered. So when
396 the variable <tt/a/ will always have the value <tt/1/ when entering the
397 function and using <tt/-Cl/, while in
402 static unsigned a = 1;
407 the variable <tt/a/ will have the value <tt/1/ only the first time that the
408 function is entered, and will keep the old value from one call of the
409 function to the next.
411 You may also use <tt><ref id="pragma-static-locals"
412 name="#pragma static-locals"></tt> to change this setting in your
416 <label id="option-include-dir">
417 <tag><tt>-I dir, --include-dir dir</tt></tag>
419 Set a directory where the compiler searches for include files. You may
420 use this option multiple times to add more than one directory to the
424 <label id="option-O">
425 <tag><tt>-O, -Oi, -Or, -Os</tt></tag>
427 Enable an optimizer run over the produced code.
429 Using <tt/-Oi/, the code generator will inline some code where otherwise a
430 runtime functions would have been called, even if the generated code is
431 larger. This will not only remove the overhead for a function call, but will
432 make the code visible for the optimizer. <tt/-Oi/ is an alias for
433 <tt/-O --codesize 200/.
435 <tt/-Or/ will make the compiler honor the <tt/register/ keyword. Local
436 variables may be placed in registers (which are actually zero page
437 locations). See also the <tt/<ref id="option-register-vars"
438 name="--register-vars">/ command line option, and the <ref
439 id="register-vars" name="discussion of register variables"> below.
441 Using <tt/-Os/ will force the compiler to inline some known functions from
442 the C library like strlen. Note: This has two consequences:
445 <item>You may not use names of standard C functions in your own code. If you
446 do that, your program is not standard compliant anyway, but using
447 <tt/-Os/ will actually break things.
449 <item>The inlined string and memory functions will not handle strings or
450 memory areas larger than 255 bytes. Similarly, the inlined <tt/is..()/
451 functions will not work with values outside the char. range (such as
456 It is possible to concatenate the modifiers for <tt/-O/. For example, to
457 enable register variables and inlining of known functions, you may use
461 <tag><tt>-T, --add-source</tt></tag>
463 This include the source code as comments in the generated code. This is
467 <tag><tt>-V, --version</tt></tag>
469 Print the version number of the compiler. When submitting a bug report,
470 please include the operating system you're using, and the compiler
474 <label id="option-W">
475 <tag><tt>-W name[,name]</tt></tag>
477 This option allows to control warnings generated by the compiler. It is
478 followed by a comma separated list of warnings that should be enabled or
479 disabled. To disable a warning, its name is prefixed by a minus sign. If
480 no such prefix exists, or the name is prefixed by a plus sign, the warning
483 The following warning names are currently recognized:
485 <tag><tt/const-comparison/</tag>
486 Warn if the result of a comparison is constant.
487 <tag><tt/error/</tag>
488 Treat all warnings as errors.
489 <tag><tt/no-effect/</tag>
490 Warn about statements that don't have an effect.
491 <tag><tt/struct-param/</tag>
492 Warn when passing structs by value.
493 <tag><tt/unknown-pragma/</tag>
494 Warn about known #pragmas.
495 <tag><tt/unused-label/</tag>
496 Warn about unused labels.
497 <tag><tt/unused-param/</tag>
498 Warn about unused function parameters.
499 <tag><tt/unused-var/</tag>
500 Warn about unused variables.
503 The full list of available warning names may be retrieved by using the
504 option <tt><ref id="option-list-warnings" name="--list-warnings"></tt>.
506 You may also use <tt><ref id="pragma-warn" name="#pragma warn"></tt> to
507 control this setting for smaller pieces of code from within your code.
512 <sect>Input and output<p>
514 The compiler will accept one C file per invocation and create a file with
515 the same base name, but with the extension replaced by ".s". The output
516 file contains assembler code suitable for the use with the ca65 macro
519 Include files in single quotes are searched in the following places:
521 <item>The current directory.
522 <item>The value of the environment variable <tt/CC65_INC/ if it is defined.
523 <item>Any directory added with the <tt/-I/ option on the command line.
526 Include files in angle brackets are searched in the following places:
528 <item>A compiled in directory which is often <tt>/usr/lib/cc65/include</tt> on
530 <item>The value of the environment variable <tt/CC65_INC/ if it is defined.
531 <item>A subdirectory named <tt/include/ of the directory defined in the
532 environment variable <tt/CC65_HOME/, if it is defined.
533 <item>Any directory added with the <tt/-I/ option on the command line.
538 <sect>Differences to the ISO standard<p>
540 Apart from the things listed below, the compiler does support additional
541 keywords, has several functions in the standard headers with names outside the
542 reserved namespace and a few syntax extensions. All these can be disabled with
543 the <tt><ref id="option--standard" name="--standard"></tt> command line
544 option. Its use for maximum standards compatibility is advised.
546 Here is a list of differences between the language, the compiler accepts,
547 and the one defined by the ISO standard:
551 <item> The datatypes "float" and "double" are not available.
553 <item> C Functions may not return structs (or unions), and structs may not
554 be passed as parameters by value. However, struct assignment *is*
557 <item> Part of the C library is available only with fastcall calling
558 conventions (see below). It means that you must not mix pointers to
559 those functions with pointers to user-written, not-fastcall functions.
561 <item> The <tt/volatile/ keyword doesn't have an effect. This is not as bad
562 as it sounds, since the 6502 has so few registers that it isn't
563 possible to keep values in registers anyway.
567 There may be some more minor differences I'm currently not aware of. The
568 biggest problem is the missing float data type. With this limitation in
569 mind, you should be able to write fairly portable code.
575 This cc65 version has some extensions to the ISO C standard.
579 <item> The compiler allows to insert assembler statements into the output
583 asm (<string literal>[, optional parameters]) ;
587 __asm__ (<string literal>[, optional parameters]) ;
590 The first form is in the user namespace and is disabled if the <tt/-A/
593 There is a whole section covering inline assembler statements,
594 <ref id="inline-asm" name="see there">.
597 <item> There is a special calling convention named "fastcall".
598 The syntax for a function declaration using fastcall is
601 <return type> fastcall <function name> (<parameter list>)
605 <return type> __fastcall__ <function name> (<parameter list>)
609 void __fastcall__ f (unsigned char c)
611 The first form of the fastcall keyword is in the user namespace and can
612 therefore be disabled with the <tt><ref id="option--standard"
613 name="--standard"></tt> command line option.
615 For functions declared as <tt/fastcall/, the rightmost parameter is not
616 pushed on the stack but left in the primary register when the function
617 is called. This will reduce the cost when calling assembler functions
618 significantly, especially when the function itself is rather small.
621 <item> There are two pseudo variables named <tt/__AX__/ and <tt/__EAX__/.
622 Both refer to the primary register that is used by the compiler to
623 evaluate expressions or return function results. <tt/__AX__/ is of
624 type <tt/unsigned int/ and <tt/__EAX__/ of type <tt/long unsigned int/
625 respectively. The pseudo variables may be used as lvalue and rvalue as
626 every other variable. They are most useful together with short
627 sequences of assembler code. For example, the macro
637 will give the high byte of any unsigned value.
640 <item> Inside a function, the identifier <tt/__func__/ gives the name of the
641 current function as a string. Outside of functions, <tt/__func__/ is
646 #define PRINT_DEBUG(s) printf ("%s: %s\n", __func__, s);
649 The macro will print the name of the current function plus a given
653 <item> cc65 allows the initialization of <tt/void/ variables. This may be
654 used to create variable structures that are more compatible with
655 interfaces written for assembler languages. Here is an example:
658 void GCmd = { (char)3, (unsigned)0x2000, (unsigned)0x3000 };
661 This will be translated as follows:
670 Since the variable is of type <tt/void/ you may not use it as is.
671 However, taking the address of the variable results in a <tt/void*/
672 which may be passed to any function expecting a pointer.
674 See the <url url="geos.html" name="GEOS library document"> for examples
675 on how to use this feature.
678 <item> cc65 implements flexible array struct members as defined in the C99 ISO
679 standard. As an extension, these fields may be initialized. There are
680 several exceptions, however (which is probably the reason why the
681 standard does not define this feature, because it is highly
682 unorthogonal). Flexible array members cannot be initialized ...
685 <item>... when defining an array of structs with flexible
687 <item>... if such a struct is a member field of another struct
688 which is not the last field.
689 <item>... if the struct which contains a flexible array member is
690 declared as <tt/register/, and the size and compiler settings
691 do allow the compiler actually to place the struct into the
692 register bank in the zero page.
695 Please note that -- as defined in the ISO C standard -- the <tt/sizeof/
696 operator returns the struct size with the flexible array member having
697 size zero, even if it is initialized.
704 <sect>Predefined macros<p>
706 The compiler defines several macros at startup:
709 <tag><tt>__APPLE2__</tt></tag>
711 This macro is defined if the target is the Apple ][ (-t apple2).
713 <tag><tt>__APPLE2ENH__</tt></tag>
715 This macro is defined if the target is the enhanced Apple //e (-t apple2enh).
717 <tag><tt>__ATARI__</tt></tag>
719 This macro is defined if the target is one of the Atari computers
720 (400/800/130XL/800XL).
722 <tag><tt>__ATMOS__</tt></tag>
724 This macro is defined if the target is the Oric Atmos (-t atmos).
726 <tag><tt>__C128__</tt></tag>
728 This macro is defined if the target is the c128 (-t c128).
730 <tag><tt>__C16__</tt></tag>
732 This macro is defined if the target is the c16 (-t c16).
734 <tag><tt>__C64__</tt></tag>
736 This macro is defined if the target is the c64 (-t c64).
738 <tag><tt>__CBM__</tt></tag>
740 This macro is defined if the target system is one of the CBM targets.
742 <tag><tt>__CBM510__</tt></tag>
744 This macro is defined if the target is the CBM 500 series of computers.
746 <tag><tt>__CBM610__</tt></tag>
748 This macro is defined if the target is one of the CBM 600/700 family of
749 computers (called B series in the US).
751 <tag><tt>__CC65__</tt></tag>
753 This macro is always defined. Its value is the version number of the
754 compiler in hex. For example, version 2.10.1 of the compiler has this macro
755 defined as <tt/0x02A1/.
757 <tag><tt>__CC65_STD__</tt></tag>
759 This macro is defined to one of the following depending on the <tt><ref
760 id="option--standard" name="--standard"></tt> command line option:
762 <item><tt/__CC65_STD_C89__/
763 <item><tt/__CC65_STD_C99__/
764 <item><tt/__CC65_STD_CC65__/
767 <tag><tt>__DATE__</tt></tag>
769 This macro expands to the date of translation of the preprocessing
770 translation unit in the form "Mmm dd yyyy".
772 <tag><tt>__FILE__</tt></tag>
774 This macro expands to a string containing the name of the C source file.
776 <tag><tt>__GEOS__</tt></tag>
778 This macro is defined if you are compiling for the GEOS system (-t geos).
780 <tag><tt>__LINE__</tt></tag>
782 This macro expands to the current line number.
784 <tag><tt>__LUNIX__</tt></tag>
786 This macro is defined if you are compiling for the LUnix system (-t lunix).
788 <tag><tt>__LYNX__</tt></tag>
790 This macro is defined if the target is the Atari Lynx (-t lynx).
792 <tag><tt>__NES__</tt></tag>
794 This macro is defined if the target is the NES (-t nes).
796 <tag><tt>__OPT__</tt></tag>
798 Is defined if the compiler was called with the <tt/-O/ command line option.
800 <tag><tt>__OPT_i__</tt></tag>
802 Is defined if the compiler was called with the <tt/-Oi/ command line option.
804 <tag><tt>__OPT_r__</tt></tag>
806 Is defined if the compiler was called with the <tt/-Or/ command line option.
808 <tag><tt>__OPT_s__</tt></tag>
810 Is defined if the compiler was called with the <tt/-Os/ command line option.
812 <tag><tt>__PET__</tt></tag>
814 This macro is defined if the target is the PET family of computers (-t pet).
816 <tag><tt>__PLUS4__</tt></tag>
818 This macro is defined if the target is the plus/4 (-t plus4).
820 <tag><tt>__STDC_HOSTED__</tt></tag>
822 This macro is expands to the integer constant 1.
824 <tag><tt>__SUPERVISION__</tt></tag>
826 This macro is defined if the target is the supervision (-t supervision).
828 <tag><tt>__TIME__</tt></tag>
830 This macro expands to the time of translation of the preprocessing
831 translation unit in the form "hh:mm:ss".
833 <tag><tt>__VIC20__</tt></tag>
835 This macro is defined if the target is the vic20 (-t vic20).
839 <sect>#pragmas<label id="pragmas"><p>
841 The compiler understands some pragmas that may be used to change code
842 generation and other stuff. Some of these pragmas understand a special form:
843 If the first parameter is <tt/push/, the old value is saved onto a stack
844 before changing it. The value may later be restored by using the <tt/pop/
845 parameter with the <tt/#pragma/.
847 <sect1><tt>#pragma bss-name ([push,] <name>)</tt><label id="pragma-bss-name"><p>
849 This pragma changes the name used for the BSS segment (the BSS segment
850 is used to store uninitialized data). The argument is a string enclosed
853 Note: The default linker configuration file does only map the standard
854 segments. If you use other segments, you have to create a new linker
857 Beware: The startup code will zero only the default BSS segment. If you
858 use another BSS segment, you have to do that yourself, otherwise
859 uninitialized variables do not have the value zero.
861 The <tt/#pragma/ understands the push and pop parameters as explained above.
865 #pragma bss-name ("MyBSS")
869 <sect1><tt>#pragma charmap (<index>, <code>)</tt><label id="pragma-charmap"><p>
871 Each literal string and each literal character in the source is translated
872 by use of a translation table. This translation table is preset when the
873 compiler is started depending on the target system, for example to map
874 ISO-8859-1 characters into PETSCII if the target is a commodore machine.
876 This pragma allows to change entries in the translation table, so the
877 translation for individual characters, or even the complete table may be
880 Both arguments are assumed to be unsigned characters with a valid range of
883 Beware of two pitfalls:
886 <item>The character index is actually the code of the character in the
887 C source, so character mappings do always depend on the source
888 character set. This means that <tt/#pragma charmap/ is not
889 portable -- it depends on the build environment.
890 <item>While it is possible to use character literals as indices, the
891 result may be somewhat unexpected, since character literals are
892 itself translated. For this reason I would suggest to avoid
893 character literals and use numeric character codes instead.
898 /* Use a space wherever an 'a' occurs in ISO-8859-1 source */
899 #pragma charmap (0x61, 0x20);
903 <sect1><tt>#pragma check-stack ([push,] on|off)</tt><label id="pragma-check-stack"><p>
905 Tells the compiler to insert calls to a stack checking subroutine to detect
906 stack overflows. The stack checking code will lead to somewhat larger and
907 slower programs, so you may want to use this pragma when debugging your
908 program and switch it off for the release version. If a stack overflow is
909 detected, the program is aborted.
911 If the argument is "off", stack checks are disabled (the default), otherwise
914 The <tt/#pragma/ understands the push and pop parameters as explained above.
916 <sect1><tt>#pragma code-name ([push,] <name>)</tt><label id="pragma-code-name"><p>
918 This pragma changes the name used for the CODE segment (the CODE segment
919 is used to store executable code). The argument is a string enclosed in
922 Note: The default linker configuration file does only map the standard
923 segments. If you use other segments, you have to create a new linker
926 The <tt/#pragma/ understands the push and pop parameters as explained above.
930 #pragma code-name ("MyCODE")
934 <sect1><tt>#pragma codesize ([push,] <int>)</tt><label id="pragma-codesize"><p>
936 This pragma allows finer control about speed vs. size decisions in the code
937 generation and optimization phase. It gives the allowed size increase factor
938 (in percent). The default is can be changed by use of the <tt/<ref
939 id="option-codesize" name="--codesize">/ compiler option.
941 The <tt/#pragma/ understands the push and pop parameters as explained above.
944 <sect1><tt>#pragma data-name ([push,] <name>)</tt><label id="pragma-data-name"><p>
946 This pragma changes the name used for the DATA segment (the DATA segment
947 is used to store initialized data). The argument is a string enclosed in
950 Note: The default linker configuration file does only map the standard
951 segments. If you use other segments, you have to create a new linker
954 The <tt/#pragma/ understands the push and pop parameters as explained above.
958 #pragma data-name ("MyDATA")
962 <sect1><tt>#pragma local-strings ([push,] on|off)</tt><label id="pragma-local-strings"><p>
964 When "on", emit string literals to the data segment when they're encountered
965 in the source. The default ("off") is to keep string literals until end of
966 assembly, merge read only literals if possible, and then output the literals
967 into the data or rodata segment that is active at that point.
969 Using this <tt/#pragma/ it is possible to control the behaviour from within
970 the source. When <tt/#pragma local-strings/ is active, string literals are
971 output immediately, which means that they go into the currently active data
972 or rodata segment, but cannot be merged. When inactive, string literals are
973 remembered and output as a whole when translation is finished.
976 <sect1><tt>#pragma optimize ([push,] on|off)</tt><label id="pragma-optimize"><p>
978 Switch optimization on or off. If the argument is "off", optimization is
979 disabled, otherwise it is enabled. Please note that this pragma only effects
980 whole functions. The setting in effect when the function is encountered will
981 determine if the generated code is optimized or not.
983 Optimization and code generation is also controlled by the <ref
984 id="pragma-codesize" name="codesize pragma">.
986 The default is "off", but may be changed with the <tt/<ref name="-O"
987 id="option-O">/ compiler option.
989 The <tt/#pragma/ understands the push and pop parameters as explained above.
992 <sect1><tt>#pragma rodata-name ([push,] <name>)</tt><label id="pragma-rodata-name"><p>
994 This pragma changes the name used for the RODATA segment (the RODATA
995 segment is used to store readonly data). The argument is a string
996 enclosed in double quotes.
998 Note: The default linker configuration file does only map the standard
999 segments. If you use other segments, you have to create a new linker
1002 The <tt/#pragma/ understands the push and pop parameters as explained above.
1006 #pragma rodata-name ("MyRODATA")
1010 <sect1><tt>#pragma regvaraddr ([push,] on|off)</tt><label id="pragma-regvaraddr"><p>
1012 The compiler does not allow to take the address of register variables.
1013 The regvaraddr pragma changes this. Taking the address of a register
1014 variable is allowed after using this pragma with "on" as argument.
1015 Using "off" as an argument switches back to the default behaviour.
1017 Beware: The C standard does not allow taking the address of a variable
1018 declared as register. So your programs become non-portable if you use
1019 this pragma. In addition, your program may not work. This is usually the
1020 case if a subroutine is called with the address of a register variable,
1021 and this subroutine (or a subroutine called from there) uses
1022 register variables. So be careful with this #pragma.
1024 The <tt/#pragma/ understands the push and pop parameters as explained above.
1028 #pragma regvaraddr(on) /* Allow taking the address
1029 * of register variables
1034 <sect1><tt>#pragma register-vars ([push,] on|off)</tt><label id="pragma-register-vars"><p>
1036 Enables or disables use of register variables. If register variables are
1037 disabled (the default), the <tt/register/ keyword is ignored. Register
1038 variables are explained in more detail in <ref id="register-vars" name="a separate
1041 The <tt/#pragma/ understands the push and pop parameters as explained above.
1044 <sect1><tt>#pragma signed-chars ([push,] on|off)</tt><label id="pragma-signed-chars"><p>
1046 Changes the signedness of the default character type. If the argument is
1047 "on", default characters are signed, otherwise characters are unsigned. The
1048 compiler default is to make characters unsigned since this creates a lot
1049 better code. This default may be overridden by the <tt/<ref
1050 name="--signed-chars" id="option-signed-chars">/ command line option.
1052 The <tt/#pragma/ understands the push and pop parameters as explained above.
1055 <sect1><tt>#pragma static-locals ([push,] on|off)</tt><label id="pragma-static-locals"<p>
1057 Use variables in the bss segment instead of variables on the stack. This
1058 pragma changes the default set by the compiler option <tt/<ref
1059 name="--static-locals" id="option-static-locals">/. If the argument is "on",
1060 local variables are allocated in the BSS segment, leading to shorter and in
1061 most cases faster, but non-reentrant code.
1063 The <tt/#pragma/ understands the push and pop parameters as explained above.
1066 <sect1><tt>#pragma warn (name, [push,] on|off)</tt><label id="pragma-warn"><p>
1068 Switch compiler warnings on or off. "name" is the name of a warning (see the
1069 <tt/<ref name="-W" id="option-W">/ compiler option for a list). The name is
1070 either followed by "pop", which restores the last pushed state, or by "on" or
1071 "off", optionally preceeded by "push" to push the current state before
1076 /* Don't warn about the unused parameter in function func */
1077 #pragma warn (unused-param, push, off)
1078 static int func (int unused)
1082 #pragma warn (unused-param, pop)
1085 <sect1><tt>#pragma writable-strings ([push,] on|off)</tt><label id="pragma-writable-strings"><p>
1087 Changes the storage location of string literals. For historical reasons,
1088 the C standard defines that string literals are of type "char[]", but
1089 writing to such a literal causes undefined behaviour. Most compilers
1090 (including cc65) place string literals in the read-only data segment, which
1091 may cause problems with old C code that writes to string literals.
1093 Using this pragma (or the corresponding command line option <tt/<ref
1094 name="--writable-strings" id="option-writable-strings">/) causes the
1095 literals to be placed in the data segment so they can be written to without
1098 The <tt/#pragma/ understands the push and pop parameters as explained above.
1101 <sect1><tt>#pragma zpsym (<name>)</tt><p>
1103 Tell the compiler that the -- previously as external declared -- symbol with
1104 the given name is a zero page symbol (usually from an assembler file).
1105 The compiler will create a matching import declaration for the assembler.
1110 #pragma zpsym ("foo"); /* foo is in the zeropage */
1116 <sect>Register variables<label id="register-vars"><p>
1118 The runtime for all supported platforms has 6 bytes of zero page space
1119 available for register variables (this could be increased, but I think it's a
1120 good value). So you can declare register variables up to a total size of 6 per
1121 function. The compiler will allocate register space on a "first come, first
1122 served" base and convert any <tt/register/ declarations that exceed the
1123 available register space silently to <tt/auto/. Parameters can also be
1124 declared as <tt/register/, this will in fact give slightly shorter code than
1125 using a register variable.
1127 Since a function must save the current values of the registers on entry and
1128 restore them on exit, there is an overhead associated with register variables,
1129 and this overhead is quite high (about 20 bytes per variable). This means that
1130 just declaring anything as <tt/register/ is not a good idea.
1132 The best use for register variables are pointers, especially those that point
1133 to structures. The magic number here is about 3 uses of a struct field: If the
1134 function contains this number or even more, the generated code will be usually
1135 shorter and faster when using a register variable for the struct pointer. The
1136 reason for this is that the register variable can in many cases be used as a
1137 pointer directly. Having a pointer in an auto variable means that this pointer
1138 must first be copied into a zero page location, before it can be dereferenced.
1140 Second best use for register variables are counters. However, there is not
1141 much difference in the code generated for counters, so you will need at least
1142 100 operations on this variable (for example in a loop) to make it worth the
1143 trouble. The only savings you get here are by the use of a zero page variable
1144 instead of one on the stack or in the data segment.
1146 Register variables must be explicitly enabled, either by using <tt/<ref
1147 name="-Or" id="option-O">/ or <tt/<ref name="--register-vars"
1148 id="option-register-vars">/ on the command line or by use of <tt/<ref
1149 name="#pragma register-vars" id="pragma-register-vars">/. Register variables
1150 are only accepted on function top level, register variables declared in
1151 interior blocks are silently converted to <tt/auto/. With register variables
1152 disabled, all variables declared as <tt/register/ are actually auto variables.
1154 Please take care when using register variables: While they are helpful and can
1155 lead to a tremendous speedup when used correctly, improper usage will cause
1156 bloated code and a slowdown.
1160 <sect>Inline assembler<label id="inline-asm"><p>
1162 The compiler allows to insert assembler statements into the output file. The
1166 asm (<string literal>[, optional parameters]) ;
1170 __asm__ (<string literal>[, optional parameters]) ;
1174 The first form is in the user namespace and is disabled by <tt><ref
1175 id="option--standard" name="--standard"></tt> if the argument is not <tt/cc65/.
1177 The asm statement may be used inside a function and on global file level. An
1178 inline assembler statement is a primary expression, so it may also be used as
1179 part of an expression. Please note however that the result of an expression
1180 containing just an inline assembler statement is always of type <tt/void/.
1182 The contents of the string literal are preparsed by the compiler and inserted
1183 into the generated assembly output, so that the can be further processed by
1184 the backend and especially the optimizer. For this reason, the compiler does
1185 only allow regular 6502 opcodes to be used with the inline assembler. Pseudo
1186 instructions (like <tt/.import/, <tt/.byte/ and so on) are <em/not/ allowed,
1187 even if the ca65 assembler (which is used to translate the generated assembler
1188 code) would accept them. The builtin inline assembler is not a replacement for
1189 the full blown macro assembler which comes with the compiler.
1191 Note: Inline assembler statements are subject to all optimizations done by the
1192 compiler. There is currently no way to protect an inline assembler statement
1193 from being moved or removed completely by the optimizer. If in doubt, check
1194 the generated assembler output, or disable optimizations.
1196 The string literal may contain format specifiers from the following list. For
1197 each format specifier, an argument is expected which is inserted instead of
1198 the format specifier before passing the assembly code line to the backend.
1201 <item><tt/%b/ - Numerical 8-bit value
1202 <item><tt/%w/ - Numerical 16-bit value
1203 <item><tt/%l/ - Numerical 32-bit value
1204 <item><tt/%v/ - Assembler name of a global variable or function
1205 <item><tt/%o/ - Stack offset of a local variable
1206 <item><tt/%g/ - Assembler name of a C label
1207 <item><tt/%s/ - The argument is converted to a string
1208 <item><tt/%%/ - The % sign itself
1211 Using these format specifiers, you can access C <tt/#defines/, variables or
1212 similar stuff from the inline assembler. For example, to load the value of
1213 a C <tt/#define/ into the Y register, one would use
1217 __asm__ ("ldy #%b", OFFS);
1220 Or, to access a struct member of a static variable:
1226 unsigned char color;
1228 static pixel_t pixel;
1229 __asm__ ("ldy #%b", offsetof(pixel_t, color));
1230 __asm__ ("lda %v,y", pixel);
1233 The next example shows how to use global variables to exchange data between C
1234 an assembler and how to handle assembler jumps:
1237 unsigned char globalSubA, globalSubB, globalSubResult;
1239 /* return a-b, return 255 if b>a */
1240 unsigned char sub (unsigned char a, unsigned char b)
1245 __asm__ ("lda %v", globalSubA);
1246 __asm__ ("sbc %v", globalSubB);
1247 __asm__ ("bcs %g", jumpSubNoError);
1248 __asm__ ("lda #$FF");
1250 __asm__ ("sta %v", globalSubResult);
1251 return globalSubResult;
1256 Arrays can also be accessed:
1259 unsigned char globalSquareTable[] = {
1260 0, 1, 4, 9, 16, 25, 36, 49, 64, 81,
1261 100, 121, 144, 169, 196, 225
1263 unsigned char globalSquareA, globalSquareResult;
1265 /* return a*a for a<16, else 255 */
1266 unsigned char square (unsigned char a)
1272 __asm__ ("ldx %v", globalSquareA);
1273 __asm__ ("lda %v,x", globalSquareTable);
1274 __asm__ ("sta %v", globalSquareResult);
1275 return globalSquareResult;
1280 Note: Do not embed the assembler labels that are used as names of global
1281 variables or functions into your asm statements. Code like this
1285 int bar () { return 1; }
1286 __asm__ ("lda _foo"); /* DON'T DO THAT! */
1288 __asm__ ("jsr _bar"); /* DON'T DO THAT EITHER! */
1292 may stop working if the way, the compiler generates these names is changed in
1293 a future version. Instead use the format specifiers from the table above:
1296 __asm__ ("lda %v", foo); /* OK */
1298 __asm__ ("jsr %v", bar); /* OK */
1303 <sect>Implementation-defined behavior<p>
1305 This section describes the behavior of cc65 when the standard describes the
1306 behavior as implementation-defined.
1310 <sect>Bugs/Feedback<p>
1312 If you have problems using the compiler, if you find any bugs, or if you're
1313 doing something interesting with it, I would be glad to hear from you. Feel
1314 free to contact me by email (<htmlurl url="mailto:uz@cc65.org"
1315 name="uz@cc65.org">).
1321 This is the original compiler copyright:
1324 --------------------------------------------------------------------------
1327 This is the copyright notice for RA65, LINK65, LIBR65, and other
1328 Atari 8-bit programs. Said programs are Copyright 1989, by John R.
1329 Dunning. All rights reserved, with the following exceptions:
1331 Anyone may copy or redistribute these programs, provided that:
1333 1: You don't charge anything for the copy. It is permissable to
1334 charge a nominal fee for media, etc.
1336 2: All source code and documentation for the programs is made
1337 available as part of the distribution.
1339 3: This copyright notice is preserved verbatim, and included in
1342 You are allowed to modify these programs, and redistribute the
1343 modified versions, provided that the modifications are clearly noted.
1345 There is NO WARRANTY with this software, it comes as is, and is
1346 distributed in the hope that it may be useful.
1348 This copyright notice applies to any program which contains
1349 this text, or the refers to this file.
1351 This copyright notice is based on the one published by the Free
1352 Software Foundation, sometimes known as the GNU project. The idea
1353 is the same as theirs, ie the software is free, and is intended to
1354 stay that way. Everybody has the right to copy, modify, and re-
1355 distribute this software. Nobody has the right to prevent anyone
1356 else from copying, modifying or redistributing it.
1358 --------------------------------------------------------------------------
1361 Small parts of the compiler (parts of the preprocessor and main parser) are
1362 still covered by this copyright. The main portion is covered by the usual
1363 cc65 license, which reads:
1365 This software is provided 'as-is', without any expressed or implied
1366 warranty. In no event will the authors be held liable for any damages
1367 arising from the use of this software.
1369 Permission is granted to anyone to use this software for any purpose,
1370 including commercial applications, and to alter it and redistribute it
1371 freely, subject to the following restrictions:
1374 <item> The origin of this software must not be misrepresented; you must not
1375 claim that you wrote the original software. If you use this software
1376 in a product, an acknowledgment in the product documentation would be
1377 appreciated but is not required.
1378 <item> Altered source versions must be plainly marked as such, and must not
1379 be misrepresented as being the original software.
1380 <item> This notice may not be removed or altered from any source