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
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 --local-strings Emit string literals immediately
96 --memory-model model Set the memory model
97 --register-space b Set space available for register variables
98 --register-vars Enable register variables
99 --rodata-name seg Set the name of the RODATA segment
100 --signed-chars Default characters are signed
101 --standard std Language standard (c89, c99, cc65)
102 --static-locals Make local variables static
103 --target sys Set the target system
104 --verbose Increase verbosity
105 --version Print the compiler version number
106 --writable-strings Make string literals writable
107 ---------------------------------------------------------------------------
111 <sect1>Command line options in detail<p>
113 Here is a description of all the command line options:
117 <label id="option-bss-name">
118 <tag><tt>--bss-name seg</tt></tag>
120 Set the name of the bss segment. See also <tt/<ref id="pragma-bss-name"
121 name="#pragma bss-name">/.
124 <label id="option-check-stack">
125 <tag><tt>--check-stack</tt></tag>
127 Tells the compiler to generate code that checks for stack overflows. See
128 <tt/<ref id="pragma-check-stack" name="#pragma check-stack">/ for an
129 explanation of this feature.
132 <label id="option-code-name">
133 <tag><tt>--code-name seg</tt></tag>
135 Set the name of the code segment. See also <tt/<ref id="pragma-code-name"
136 name="#pragma code-name">/
139 <label id="option-codesize">
140 <tag><tt>--codesize x</tt></tag>
142 This options allows finer control about speed vs. size decisions in the code
143 generation and optimization phases. It gives the allowed size increase
144 factor (in percent). The default is 100 when not using <tt/-Oi/ and 200 when
145 using <tt/-Oi/ (<tt/-Oi/ is the same as <tt/-O --codesize 200/).
148 <label id="option--cpu">
149 <tag><tt>--cpu CPU</tt></tag>
151 Set the CPU, the compiler generates code for. You may specify "6502" or
152 "65C02" as the CPU. The default depends on the selected target (see option
153 <tt/<ref id="option-t" name="-t">/). It is the 6502 CPU for most targets or
154 if no target has been set. Specifying 65C02 will use a few 65C02
155 instructions when generating code. Don't expect too much from this option:
156 In most cases the difference in size and speed is just 1-2%.
159 <label id="option-create-dep">
160 <tag><tt>--create-dep name</tt></tag>
162 Tells the compiler to generate a file containing the dependency list for the
163 compiled module in makefile syntax. The output is written to a file with the
164 given name. The output does not include system include files (in angle
168 <label id="option-create-full-dep">
169 <tag><tt>--create-full-dep name</tt></tag>
171 Tells the compiler to generate a file containing the dependency list for the
172 compiled module in makefile syntax. The output is written to a file with the
173 given name. The output does include system include files (in angle
177 <label id="option-data-name">
178 <tag><tt>--data-name seg</tt></tag>
180 Set the name of the data segment. See also <tt/<ref id="pragma-data-name"
181 name="#pragma data-name">/
184 <tag><tt>-d, --debug</tt></tag>
186 Enables debug mode, something that should not be needed for mere
190 <label id="option-dep-target">
191 <tag><tt>--dep-target target</tt></tag>
193 When generating a dependency file, don't use the actual output file as the
194 target of the dependency, but the file specified with this option. The
195 option has no effect if neither <tt/<ref id="option-create-dep"
196 name="--create-dep">/ nor <tt/<ref id="option-create-full-dep"
197 name="--create-full-dep">/ is specified.
200 <tag><tt>-D sym[=definition]</tt></tag>
202 Define a macro on the command line. If no definition is given, the macro
203 is defined to the value "1".
206 <tag><tt>--forget-inc-paths</tt></tag>
208 Forget the builtin include paths. This is most useful when building
209 customized C or runtime libraries, in which case the standard header
210 files should be ignored.
213 <tag><tt>-g, --debug-info</tt></tag>
215 This will cause the compiler to insert a <tt/.DEBUGINFO/ command into the
216 generated assembler code. This will cause the assembler to include all
217 symbols in a special section in the object file.
220 <tag><tt>-h, --help</tt></tag>
222 Print the short option summary shown above.
225 <label id="option-local-strings">
226 <tag><tt>--local-strings</tt></tag>
228 Emit string literals to the data segment when they're encountered in the
229 source. The default is to keep string literals until end of assembly, merge
230 read only literals if possible, and then output the literals into the data
231 or rodata segment that is active at that point. Use of this option prevents
232 merging of duplicate strings, but the options that change the name of one of
233 the data segments will work.
235 You can also use <tt><ref id="pragma-local-strings"
236 name="#pragma local-strings"></tt> for fine grained control.
239 <tag><tt>-o name</tt></tag>
241 Specify the name of the output file. If you don't specify a name, the
242 name of the C input file is used, with the extension replaced by ".s".
245 <label id="option-register-vars">
246 <tag><tt>-r, --register-vars</tt></tag>
248 <tt/-r/ will make the compiler honor the <tt/register/ keyword. Local
249 variables may be placed in registers (which are actually zero page
250 locations). There is some overhead involved with register variables, since
251 the old contents of the registers must be saved and restored. Since register
252 variables are of limited use without the optimizer, there is also a combined
253 switch: <tt/-Or/ will enable both, the optimizer and register variables.
255 For more information about register variables see <ref id="register-vars"
256 name="register variables">.
258 The compiler setting can also be changed within the source file by using
259 <tt/<ref id="pragma-register-vars" name="#pragma register-vars">/.
262 <label id="option-register-space">
263 <tag><tt>--register-space</tt></tag>
265 This option takes a numeric parameter and is used to specify, how much
266 zero page register space is available. Please note that just giving this
267 option will not increase or decrease by itself, it will just tell the
268 compiler about the available space. You will have to allocate that space
269 yourself using an assembler module with the necessary allocations, and a
270 linker configuration that matches the assembler module. The default value
271 for this option is 6 (bytes).
273 If you don't know what all this means, please don't use this option.
276 <label id="option-rodata-name">
277 <tag><tt>--rodata-name seg</tt></tag>
279 Set the name of the rodata segment (the segment used for readonly data).
280 See also <tt/<ref id="pragma-rodata-name" name="#pragma rodata-name">/
282 <label id="option-signed-chars">
283 <tag><tt>-j, --signed-chars</tt></tag>
285 Using this option, you can make the default characters signed. Since the
286 6502 has no provisions for sign extending characters (which is needed on
287 almost any load operation), this will make the code larger and slower. A
288 better way is to declare characters explicitly as "signed" if needed. You
289 can also use <tt><ref id="pragma-signed-chars"
290 name="#pragma signed-chars"></tt> for better control of this option.
293 <label id="option--standard">
294 <tag><tt>--standard std</tt></tag>
296 This option allows to set the language standard supported. The argument is
300 This disables anything that is illegal in C89/C90. Among those things
301 are <tt>//</tt> comments and the non-standard keywords without
302 underscores. Please note that cc65 is not a fully C89 compliant compiler
303 despite this option. A few more things (like floats) are missing.
306 This enables a few features from the C99 standard. With this option,
307 <tt>//</tt> comments are allowed. It will also cause warnings and even
308 errors in a few situations that are allowed with <tt/--standard c89/.
309 For example, a call to a function without a prototype is an error in
313 This is the default mode. It is like c99 mode, but additional features
314 are enabled. Among these are "void data", non-standard keywords without
315 the underlines, unnamed function parameters and the requirement for
316 main() to return an int.
319 Please note that the compiler does not support the C99 standard and never
320 will. c99 mode is actually c89 mode with a few selected C99 extensions.
323 <label id="option-t">
324 <tag><tt>-t target, --target target</tt></tag>
326 This option is used to set the target system. The target system determines
327 the character set that is used for strings and character constants and the
328 default CPU. The CPU setting can be overriden by use of the <tt/<ref
329 id="option--cpu" name="--cpu">/ option.
331 The following target systems are supported:
339 <item>c16 (works also for the c116 with memory up to 32K)
342 <item>cbm510 (CBM-II series with 40 column video)
343 <item>cbm610 (all CBM-II II computers with 80 column video)
348 <item>pet (all CBM PET systems except the 2001)
354 <tag><tt>-v, --verbose</tt></tag>
356 Using this option, the compiler will be somewhat more verbose if errors
357 or warnings are encountered.
360 <label id="option-writable-strings">
361 <tag><tt>--writable-strings</tt></tag>
363 Make string literals writable by placing them into the data segment instead
364 of the rodata segment. You can also use <tt><ref id="pragma-writable-strings"
365 name="#pragma writable-strings"></tt> to control this option from within
369 <label id="option-static-locals">
370 <tag><tt>-Cl, --static-locals</tt></tag>
372 Use static storage for local variables instead of storage on the stack.
373 Since the stack is emulated in software, this gives shorter and usually
374 faster code, but the code is no longer reentrant. The difference between
375 <tt/-Cl/ and declaring local variables as static yourself is, that
376 initializer code is executed each time, the function is entered. So when
387 the variable <tt/a/ will always have the value <tt/1/ when entering the
388 function and using <tt/-Cl/, while in
393 static unsigned a = 1;
398 the variable <tt/a/ will have the value <tt/1/ only the first time that the
399 function is entered, and will keep the old value from one call of the
400 function to the next.
402 You may also use <tt><ref id="pragma-static-locals"
403 name="#pragma static-locals"></tt> to change this setting in your
407 <label id="option-include-dir">
408 <tag><tt>-I dir, --include-dir dir</tt></tag>
410 Set a directory where the compiler searches for include files. You may
411 use this option multiple times to add more than one directory to the
415 <label id="option-O">
416 <tag><tt>-O, -Oi, -Or, -Os</tt></tag>
418 Enable an optimizer run over the produced code.
420 Using <tt/-Oi/, the code generator will inline some code where otherwise a
421 runtime functions would have been called, even if the generated code is
422 larger. This will not only remove the overhead for a function call, but will
423 make the code visible for the optimizer. <tt/-Oi/ is an alias for
424 <tt/-O --codesize 200/.
426 <tt/-Or/ will make the compiler honor the <tt/register/ keyword. Local
427 variables may be placed in registers (which are actually zero page
428 locations). See also the <tt/<ref id="option-register-vars"
429 name="--register-vars">/ command line option, and the <ref
430 id="register-vars" name="discussion of register variables"> below.
432 Using <tt/-Os/ will force the compiler to inline some known functions from
433 the C library like strlen. Note: This has two consequences:
436 <item>You may not use names of standard C functions in your own code. If you
437 do that, your program is not standard compliant anyway, but using
438 <tt/-Os/ will actually break things.
440 <item>The inlined string and memory functions will not handle strings or
441 memory areas larger than 255 bytes. Similarly, the inlined <tt/is..()/
442 functions will not work with values outside the char. range (such as
447 It is possible to concatenate the modifiers for <tt/-O/. For example, to
448 enable register variables and inlining of known functions, you may use
452 <tag><tt>-T, --add-source</tt></tag>
454 This include the source code as comments in the generated code. This is
458 <tag><tt>-V, --version</tt></tag>
460 Print the version number of the compiler. When submitting a bug report,
461 please include the operating system you're using, and the compiler
465 <label id="option-W">
466 <tag><tt>-W name[,name]</tt></tag>
468 This option allows to control warnings generated by the compiler. It is
469 followed by a comma separated list of warnings that should be enabled or
470 disabled. To disable a warning, its name is prefixed by a minus sign. If
471 no such prefix exists, or the name is prefixed by a plus sign, the warning
474 The following warning names are currently recognized:
476 <tag><tt/const-comparison/</tag>
477 Warn if the result of a comparison is constant.
478 <tag><tt/error/</tag>
479 Treat all warnings as errors.
480 <tag><tt/no-effect/</tag>
481 Warn about statements that don't have an effect.
482 <tag><tt/struct-param/</tag>
483 Warn when passing structs by value.
484 <tag><tt/unknown-pragma/</tag>
485 Warn about known #pragmas.
486 <tag><tt/unused-label/</tag>
487 Warn about unused labels.
488 <tag><tt/unused-param/</tag>
489 Warn about unused function parameters.
490 <tag><tt/unused-var/</tag>
491 Warn about unused variables.
494 You may also use <tt><ref id="pragma-warn" name="#pragma warn"></tt> to
495 control this setting for smaller pieces of code from within your code.
500 <sect>Input and output<p>
502 The compiler will accept one C file per invocation and create a file with
503 the same base name, but with the extension replaced by ".s". The output
504 file contains assembler code suitable for the use with the ca65 macro
507 Include files in single quotes are searched in the following places:
509 <item>The current directory.
510 <item>The value of the environment variable <tt/CC65_INC/ if it is defined.
511 <item>Any directory added with the <tt/-I/ option on the command line.
514 Include files in angle brackets are searched in the following places:
516 <item>A compiled in directory which is often <tt>/usr/lib/cc65/include</tt> on
518 <item>The value of the environment variable <tt/CC65_INC/ if it is defined.
519 <item>A subdirectory named <tt/include/ of the directory defined in the
520 environment variable <tt/CC65_HOME/, if it is defined.
521 <item>Any directory added with the <tt/-I/ option on the command line.
526 <sect>Differences to the ISO standard<p>
528 Apart from the things listed below, the compiler does support additional
529 keywords, has several functions in the standard headers with names outside the
530 reserved namespace and a few syntax extensions. All these can be disabled with
531 the <tt><ref id="option--standard" name="--standard"></tt> command line
532 option. Its use for maximum standards compatibility is advised.
534 Here is a list of differences between the language, the compiler accepts,
535 and the one defined by the ISO standard:
539 <item> The datatypes "float" and "double" are not available.
541 <item> C Functions may not return structs (or unions), and structs may not
542 be passed as parameters by value. However, struct assignment *is*
545 <item> Part of the C library is available only with fastcall calling
546 conventions (see below). It means that you must not mix pointers to
547 those functions with pointers to user-written, not-fastcall functions.
549 <item> The <tt/volatile/ keyword doesn't have an effect. This is not as bad
550 as it sounds, since the 6502 has so few registers that it isn't
551 possible to keep values in registers anyway.
555 There may be some more minor differences I'm currently not aware of. The
556 biggest problem is the missing float data type. With this limitation in
557 mind, you should be able to write fairly portable code.
563 This cc65 version has some extensions to the ISO C standard.
567 <item> The compiler allows to insert assembler statements into the output
571 asm (<string literal>[, optional parameters]) ;
575 __asm__ (<string literal>[, optional parameters]) ;
578 The first form is in the user namespace and is disabled if the <tt/-A/
581 There is a whole section covering inline assembler statements,
582 <ref id="inline-asm" name="see there">.
585 <item> There is a special calling convention named "fastcall".
586 The syntax for a function declaration using fastcall is
589 <return type> fastcall <function name> (<parameter list>)
593 <return type> __fastcall__ <function name> (<parameter list>)
597 void __fastcall__ f (unsigned char c)
599 The first form of the fastcall keyword is in the user namespace and can
600 therefore be disabled with the <tt><ref id="option--standard"
601 name="--standard"></tt> command line option.
603 For functions declared as <tt/fastcall/, the rightmost parameter is not
604 pushed on the stack but left in the primary register when the function
605 is called. This will reduce the cost when calling assembler functions
606 significantly, especially when the function itself is rather small.
609 <item> There are two pseudo variables named <tt/__AX__/ and <tt/__EAX__/.
610 Both refer to the primary register that is used by the compiler to
611 evaluate expressions or return function results. <tt/__AX__/ is of
612 type <tt/unsigned int/ and <tt/__EAX__/ of type <tt/long unsigned int/
613 respectively. The pseudo variables may be used as lvalue and rvalue as
614 every other variable. They are most useful together with short
615 sequences of assembler code. For example, the macro
625 will give the high byte of any unsigned value.
628 <item> Inside a function, the identifier <tt/__func__/ gives the name of the
629 current function as a string. Outside of functions, <tt/__func__/ is
634 #define PRINT_DEBUG(s) printf ("%s: %s\n", __func__, s);
637 The macro will print the name of the current function plus a given
641 <item> cc65 allows the initialization of <tt/void/ variables. This may be
642 used to create variable structures that are more compatible with
643 interfaces written for assembler languages. Here is an example:
646 void GCmd = { (char)3, (unsigned)0x2000, (unsigned)0x3000 };
649 This will be translated as follows:
658 Since the variable is of type <tt/void/ you may not use it as is.
659 However, taking the address of the variable results in a <tt/void*/
660 which may be passed to any function expecting a pointer.
662 See the <url url="geos.html" name="GEOS library document"> for examples
663 on how to use this feature.
666 <item> cc65 implements flexible array struct members as defined in the C99 ISO
667 standard. As an extension, these fields may be initialized. There are
668 several exceptions, however (which is probably the reason why the
669 standard does not define this feature, because it is highly
670 unorthogonal). Flexible array members cannot be initialized ...
673 <item>... when defining an array of structs with flexible
675 <item>... if such a struct is a member field of another struct
676 which is not the last field.
677 <item>... if the struct which contains a flexible array member is
678 declared as <tt/register/, and the size and compiler settings
679 do allow the compiler actually to place the struct into the
680 register bank in the zero page.
683 Please note that -- as defined in the ISO C standard -- the <tt/sizeof/
684 operator returns the struct size with the flexible array member having
685 size zero, even if it is initialized.
692 <sect>Predefined macros<p>
694 The compiler defines several macros at startup:
697 <tag><tt>__APPLE2__</tt></tag>
699 This macro is defined if the target is the Apple ][ (-t apple2).
701 <tag><tt>__APPLE2ENH__</tt></tag>
703 This macro is defined if the target is the enhanced Apple //e (-t apple2enh).
705 <tag><tt>__ATARI__</tt></tag>
707 This macro is defined if the target is one of the Atari computers
708 (400/800/130XL/800XL).
710 <tag><tt>__ATMOS__</tt></tag>
712 This macro is defined if the target is the Oric Atmos (-t atmos).
714 <tag><tt>__C128__</tt></tag>
716 This macro is defined if the target is the c128 (-t c128).
718 <tag><tt>__C16__</tt></tag>
720 This macro is defined if the target is the c16 (-t c16).
722 <tag><tt>__C64__</tt></tag>
724 This macro is defined if the target is the c64 (-t c64).
726 <tag><tt>__CBM__</tt></tag>
728 This macro is defined if the target system is one of the CBM targets.
730 <tag><tt>__CBM510__</tt></tag>
732 This macro is defined if the target is the CBM 500 series of computers.
734 <tag><tt>__CBM610__</tt></tag>
736 This macro is defined if the target is one of the CBM 600/700 family of
737 computers (called B series in the US).
739 <tag><tt>__CC65__</tt></tag>
741 This macro is always defined. Its value is the version number of the
742 compiler in hex. For example, version 2.10.1 of the compiler has this macro
743 defined as <tt/0x02A1/.
745 <tag><tt>__CC65_STD__</tt></tag>
747 This macro is defined to one of the following depending on the <tt><ref
748 id="option--standard" name="--standard"></tt> command line option:
750 <item><tt/__CC65_STD_C89__/
751 <item><tt/__CC65_STD_C99__/
752 <item><tt/__CC65_STD_CC65__/
755 <tag><tt>__DATE__</tt></tag>
757 This macro expands to the date of translation of the preprocessing
758 translation unit in the form "Mmm dd yyyy".
760 <tag><tt>__FILE__</tt></tag>
762 This macro expands to a string containing the name of the C source file.
764 <tag><tt>__GEOS__</tt></tag>
766 This macro is defined if you are compiling for the GEOS system (-t geos).
768 <tag><tt>__LINE__</tt></tag>
770 This macro expands to the current line number.
772 <tag><tt>__LUNIX__</tt></tag>
774 This macro is defined if you are compiling for the LUnix system (-t lunix).
776 <tag><tt>__LYNX__</tt></tag>
778 This macro is defined if the target is the Atari Lynx (-t lynx).
780 <tag><tt>__NES__</tt></tag>
782 This macro is defined if the target is the NES (-t nes).
784 <tag><tt>__OPT__</tt></tag>
786 Is defined if the compiler was called with the <tt/-O/ command line option.
788 <tag><tt>__OPT_i__</tt></tag>
790 Is defined if the compiler was called with the <tt/-Oi/ command line option.
792 <tag><tt>__OPT_r__</tt></tag>
794 Is defined if the compiler was called with the <tt/-Or/ command line option.
796 <tag><tt>__OPT_s__</tt></tag>
798 Is defined if the compiler was called with the <tt/-Os/ command line option.
800 <tag><tt>__PET__</tt></tag>
802 This macro is defined if the target is the PET family of computers (-t pet).
804 <tag><tt>__PLUS4__</tt></tag>
806 This macro is defined if the target is the plus/4 (-t plus4).
808 <tag><tt>__STDC_HOSTED__</tt></tag>
810 This macro is expands to the integer constant 1.
812 <tag><tt>__SUPERVISION__</tt></tag>
814 This macro is defined if the target is the supervision (-t supervision).
816 <tag><tt>__TIME__</tt></tag>
818 This macro expands to the time of translation of the preprocessing
819 translation unit in the form "hh:mm:ss".
821 <tag><tt>__VIC20__</tt></tag>
823 This macro is defined if the target is the vic20 (-t vic20).
827 <sect>#pragmas<label id="pragmas"><p>
829 The compiler understands some pragmas that may be used to change code
830 generation and other stuff. Some of these pragmas understand a special form:
831 If the first parameter is <tt/push/, the old value is saved onto a stack
832 before changing it. The value may later be restored by using the <tt/pop/
833 parameter with the <tt/#pragma/.
835 <sect1><tt>#pragma bss-name ([push,] <name>)</tt><label id="pragma-bss-name"><p>
837 This pragma changes the name used for the BSS segment (the BSS segment
838 is used to store uninitialized data). The argument is a string enclosed
841 Note: The default linker configuration file does only map the standard
842 segments. If you use other segments, you have to create a new linker
845 Beware: The startup code will zero only the default BSS segment. If you
846 use another BSS segment, you have to do that yourself, otherwise
847 uninitialized variables do not have the value zero.
849 The <tt/#pragma/ understands the push and pop parameters as explained above.
853 #pragma bss-name ("MyBSS")
857 <sect1><tt>#pragma charmap (<index>, <code>)</tt><label id="pragma-charmap"><p>
859 Each literal string and each literal character in the source is translated
860 by use of a translation table. This translation table is preset when the
861 compiler is started depending on the target system, for example to map
862 ISO-8859-1 characters into PETSCII if the target is a commodore machine.
864 This pragma allows to change entries in the translation table, so the
865 translation for individual characters, or even the complete table may be
868 Both arguments are assumed to be unsigned characters with a valid range of
871 Beware of two pitfalls:
874 <item>The character index is actually the code of the character in the
875 C source, so character mappings do always depend on the source
876 character set. This means that <tt/#pragma charmap/ is not
877 portable -- it depends on the build environment.
878 <item>While it is possible to use character literals as indices, the
879 result may be somewhat unexpected, since character literals are
880 itself translated. For this reason I would suggest to avoid
881 character literals and use numeric character codes instead.
886 /* Use a space wherever an 'a' occurs in ISO-8859-1 source */
887 #pragma charmap (0x61, 0x20);
891 <sect1><tt>#pragma check-stack ([push,] on|off)</tt><label id="pragma-check-stack"><p>
893 Tells the compiler to insert calls to a stack checking subroutine to detect
894 stack overflows. The stack checking code will lead to somewhat larger and
895 slower programs, so you may want to use this pragma when debugging your
896 program and switch it off for the release version. If a stack overflow is
897 detected, the program is aborted.
899 If the argument is "off", stack checks are disabled (the default), otherwise
902 The <tt/#pragma/ understands the push and pop parameters as explained above.
904 <sect1><tt>#pragma code-name ([push,] <name>)</tt><label id="pragma-code-name"><p>
906 This pragma changes the name used for the CODE segment (the CODE segment
907 is used to store executable code). The argument is a string enclosed in
910 Note: The default linker configuration file does only map the standard
911 segments. If you use other segments, you have to create a new linker
914 The <tt/#pragma/ understands the push and pop parameters as explained above.
918 #pragma code-name ("MyCODE")
922 <sect1><tt>#pragma codesize ([push,] <int>)</tt><label id="pragma-codesize"><p>
924 This pragma allows finer control about speed vs. size decisions in the code
925 generation and optimization phase. It gives the allowed size increase factor
926 (in percent). The default is can be changed by use of the <tt/<ref
927 id="option-codesize" name="--codesize">/ compiler option.
929 The <tt/#pragma/ understands the push and pop parameters as explained above.
932 <sect1><tt>#pragma data-name ([push,] <name>)</tt><label id="pragma-data-name"><p>
934 This pragma changes the name used for the DATA segment (the DATA segment
935 is used to store initialized data). The argument is a string enclosed in
938 Note: The default linker configuration file does only map the standard
939 segments. If you use other segments, you have to create a new linker
942 The <tt/#pragma/ understands the push and pop parameters as explained above.
946 #pragma data-name ("MyDATA")
950 <sect1><tt>#pragma local-strings ([push,] on|off)</tt><label id="pragma-local-strings"><p>
952 When "on", emit string literals to the data segment when they're encountered
953 in the source. The default ("off") is to keep string literals until end of
954 assembly, merge read only literals if possible, and then output the literals
955 into the data or rodata segment that is active at that point.
957 Using this <tt/#pragma/ it is possible to control the behaviour from within
958 the source. When <tt/#pragma local-strings/ is active, string literals are
959 output immediately, which means that they go into the currently active data
960 or rodata segment, but cannot be merged. When inactive, string literals are
961 remembered and output as a whole when translation is finished.
964 <sect1><tt>#pragma optimize ([push,] on|off)</tt><label id="pragma-optimize"><p>
966 Switch optimization on or off. If the argument is "off", optimization is
967 disabled, otherwise it is enabled. Please note that this pragma only effects
968 whole functions. The setting in effect when the function is encountered will
969 determine if the generated code is optimized or not.
971 Optimization and code generation is also controlled by the <ref
972 id="pragma-codesize" name="codesize pragma">.
974 The default is "off", but may be changed with the <tt/<ref name="-O"
975 id="option-O">/ compiler option.
977 The <tt/#pragma/ understands the push and pop parameters as explained above.
980 <sect1><tt>#pragma rodata-name ([push,] <name>)</tt><label id="pragma-rodata-name"><p>
982 This pragma changes the name used for the RODATA segment (the RODATA
983 segment is used to store readonly data). The argument is a string
984 enclosed in double quotes.
986 Note: The default linker configuration file does only map the standard
987 segments. If you use other segments, you have to create a new linker
990 The <tt/#pragma/ understands the push and pop parameters as explained above.
994 #pragma rodata-name ("MyRODATA")
998 <sect1><tt>#pragma regvaraddr ([push,] on|off)</tt><label id="pragma-regvaraddr"><p>
1000 The compiler does not allow to take the address of register variables.
1001 The regvaraddr pragma changes this. Taking the address of a register
1002 variable is allowed after using this pragma with "on" as argument.
1003 Using "off" as an argument switches back to the default behaviour.
1005 Beware: The C standard does not allow taking the address of a variable
1006 declared as register. So your programs become non-portable if you use
1007 this pragma. In addition, your program may not work. This is usually the
1008 case if a subroutine is called with the address of a register variable,
1009 and this subroutine (or a subroutine called from there) uses
1010 register variables. So be careful with this #pragma.
1012 The <tt/#pragma/ understands the push and pop parameters as explained above.
1016 #pragma regvaraddr(on) /* Allow taking the address
1017 * of register variables
1022 <sect1><tt>#pragma register-vars ([push,] on|off)</tt><label id="pragma-register-vars"><p>
1024 Enables or disables use of register variables. If register variables are
1025 disabled (the default), the <tt/register/ keyword is ignored. Register
1026 variables are explained in more detail in <ref id="register-vars" name="a separate
1029 The <tt/#pragma/ understands the push and pop parameters as explained above.
1032 <sect1><tt>#pragma signed-chars ([push,] on|off)</tt><label id="pragma-signed-chars"><p>
1034 Changes the signedness of the default character type. If the argument is
1035 "on", default characters are signed, otherwise characters are unsigned. The
1036 compiler default is to make characters unsigned since this creates a lot
1037 better code. This default may be overridden by the <tt/<ref
1038 name="--signed-chars" id="option-signed-chars">/ command line option.
1040 The <tt/#pragma/ understands the push and pop parameters as explained above.
1043 <sect1><tt>#pragma static-locals ([push,] on|off)</tt><label id="pragma-static-locals"<p>
1045 Use variables in the bss segment instead of variables on the stack. This
1046 pragma changes the default set by the compiler option <tt/<ref
1047 name="--static-locals" id="option-static-locals">/. If the argument is "on",
1048 local variables are allocated in the BSS segment, leading to shorter and in
1049 most cases faster, but non-reentrant code.
1051 The <tt/#pragma/ understands the push and pop parameters as explained above.
1054 <sect1><tt>#pragma warn (name, [push,] on|off)</tt><label id="pragma-warn"><p>
1056 Switch compiler warnings on or off. "name" is the name of a warning (see the
1057 <tt/<ref name="-W" id="option-W">/ compiler option for a list). The name is
1058 either followed by "pop", which restores the last pushed state, or by "on" or
1059 "off", optionally preceeded by "push" to push the current state before
1064 /* Don't warn about the unused parameter in function func */
1065 #pragma warn (unused-param, push, off)
1066 static int func (int unused)
1070 #pragma warn (unused-param, pop)
1073 <sect1><tt>#pragma writable-strings ([push,] on|off)</tt><label id="pragma-writable-strings"><p>
1075 Changes the storage location of string literals. For historical reasons,
1076 the C standard defines that string literals are of type "char[]", but
1077 writing to such a literal causes undefined behaviour. Most compilers
1078 (including cc65) place string literals in the read-only data segment, which
1079 may cause problems with old C code that writes to string literals.
1081 Using this pragma (or the corresponding command line option <tt/<ref
1082 name="--writable-strings" id="option-writable-strings">/) causes the
1083 literals to be placed in the data segment so they can be written to without
1086 The <tt/#pragma/ understands the push and pop parameters as explained above.
1089 <sect1><tt>#pragma zpsym (<name>)</tt><p>
1091 Tell the compiler that the -- previously as external declared -- symbol with
1092 the given name is a zero page symbol (usually from an assembler file).
1093 The compiler will create a matching import declaration for the assembler.
1098 #pragma zpsym ("foo"); /* foo is in the zeropage */
1104 <sect>Register variables<label id="register-vars"><p>
1106 The runtime for all supported platforms has 6 bytes of zero page space
1107 available for register variables (this could be increased, but I think it's a
1108 good value). So you can declare register variables up to a total size of 6 per
1109 function. The compiler will allocate register space on a "first come, first
1110 served" base and convert any <tt/register/ declarations that exceed the
1111 available register space silently to <tt/auto/. Parameters can also be
1112 declared as <tt/register/, this will in fact give slightly shorter code than
1113 using a register variable.
1115 Since a function must save the current values of the registers on entry and
1116 restore them on exit, there is an overhead associated with register variables,
1117 and this overhead is quite high (about 20 bytes per variable). This means that
1118 just declaring anything as <tt/register/ is not a good idea.
1120 The best use for register variables are pointers, especially those that point
1121 to structures. The magic number here is about 3 uses of a struct field: If the
1122 function contains this number or even more, the generated code will be usually
1123 shorter and faster when using a register variable for the struct pointer. The
1124 reason for this is that the register variable can in many cases be used as a
1125 pointer directly. Having a pointer in an auto variable means that this pointer
1126 must first be copied into a zero page location, before it can be dereferenced.
1128 Second best use for register variables are counters. However, there is not
1129 much difference in the code generated for counters, so you will need at least
1130 100 operations on this variable (for example in a loop) to make it worth the
1131 trouble. The only savings you get here are by the use of a zero page variable
1132 instead of one on the stack or in the data segment.
1134 Register variables must be explicitly enabled, either by using <tt/<ref
1135 name="-Or" id="option-O">/ or <tt/<ref name="--register-vars"
1136 id="option-register-vars">/ on the command line or by use of <tt/<ref
1137 name="#pragma register-vars" id="pragma-register-vars">/. Register variables
1138 are only accepted on function top level, register variables declared in
1139 interior blocks are silently converted to <tt/auto/. With register variables
1140 disabled, all variables declared as <tt/register/ are actually auto variables.
1142 Please take care when using register variables: While they are helpful and can
1143 lead to a tremendous speedup when used correctly, improper usage will cause
1144 bloated code and a slowdown.
1148 <sect>Inline assembler<label id="inline-asm"><p>
1150 The compiler allows to insert assembler statements into the output file. The
1154 asm (<string literal>[, optional parameters]) ;
1158 __asm__ (<string literal>[, optional parameters]) ;
1162 The first form is in the user namespace and is disabled by <tt><ref
1163 id="option--standard" name="--standard"></tt> if the argument is not <tt/cc65/.
1165 The asm statement may be used inside a function and on global file level. An
1166 inline assembler statement is a primary expression, so it may also be used as
1167 part of an expression. Please note however that the result of an expression
1168 containing just an inline assembler statement is always of type <tt/void/.
1170 The contents of the string literal are preparsed by the compiler and inserted
1171 into the generated assembly output, so that the can be further processed by
1172 the backend and especially the optimizer. For this reason, the compiler does
1173 only allow regular 6502 opcodes to be used with the inline assembler. Pseudo
1174 instructions (like <tt/.import/, <tt/.byte/ and so on) are <em/not/ allowed,
1175 even if the ca65 assembler (which is used to translate the generated assembler
1176 code) would accept them. The builtin inline assembler is not a replacement for
1177 the full blown macro assembler which comes with the compiler.
1179 Note: Inline assembler statements are subject to all optimizations done by the
1180 compiler. There is currently no way to protect an inline assembler statement
1181 from being moved or removed completely by the optimizer. If in doubt, check
1182 the generated assembler output, or disable optimizations.
1184 The string literal may contain format specifiers from the following list. For
1185 each format specifier, an argument is expected which is inserted instead of
1186 the format specifier before passing the assembly code line to the backend.
1189 <item><tt/%b/ - Numerical 8-bit value
1190 <item><tt/%w/ - Numerical 16-bit value
1191 <item><tt/%l/ - Numerical 32-bit value
1192 <item><tt/%v/ - Assembler name of a (global) variable or function
1193 <item><tt/%o/ - Stack offset of a (local) variable
1194 <item><tt/%g/ - Assembler name of a C label
1195 <item><tt/%s/ - The argument is converted to a string
1196 <item><tt/%%/ - The % sign itself
1199 Using these format specifiers, you can access C <tt/#defines/, variables or
1200 similar stuff from the inline assembler. For example, to load the value of
1201 a C <tt/#define/ into the Y register, one would use
1205 __asm__ ("ldy #%b", OFFS);
1208 Or, to access a struct member of a static variable:
1214 unsigned char color;
1216 static pixel_t pixel;
1217 __asm__ ("ldy #%b", offsetof(pixel_t, color));
1218 __asm__ ("lda %v,y", pixel);
1222 Note: Do not embed the assembler labels that are used as names of global
1223 variables or functions into your asm statements. Code like this
1227 int bar () { return 1; }
1228 __asm__ ("lda _foo"); /* DON'T DO THAT! */
1230 __asm__ ("jsr _bar"); /* DON'T DO THAT EITHER! */
1234 may stop working if the way, the compiler generates these names is changed in
1235 a future version. Instead use the format specifiers from the table above:
1238 __asm__ ("lda %v", foo); /* OK */
1240 __asm__ ("jsr %v", bar); /* OK */
1245 <sect>Implementation-defined behavior<p>
1247 This section describes the behavior of cc65 when the standard describes the
1248 behavior as implementation-defined.
1252 <sect>Bugs/Feedback<p>
1254 If you have problems using the compiler, if you find any bugs, or if you're
1255 doing something interesting with it, I would be glad to hear from you. Feel
1256 free to contact me by email (<htmlurl url="mailto:uz@cc65.org"
1257 name="uz@cc65.org">).
1263 This is the original compiler copyright:
1266 --------------------------------------------------------------------------
1269 This is the copyright notice for RA65, LINK65, LIBR65, and other
1270 Atari 8-bit programs. Said programs are Copyright 1989, by John R.
1271 Dunning. All rights reserved, with the following exceptions:
1273 Anyone may copy or redistribute these programs, provided that:
1275 1: You don't charge anything for the copy. It is permissable to
1276 charge a nominal fee for media, etc.
1278 2: All source code and documentation for the programs is made
1279 available as part of the distribution.
1281 3: This copyright notice is preserved verbatim, and included in
1284 You are allowed to modify these programs, and redistribute the
1285 modified versions, provided that the modifications are clearly noted.
1287 There is NO WARRANTY with this software, it comes as is, and is
1288 distributed in the hope that it may be useful.
1290 This copyright notice applies to any program which contains
1291 this text, or the refers to this file.
1293 This copyright notice is based on the one published by the Free
1294 Software Foundation, sometimes known as the GNU project. The idea
1295 is the same as theirs, ie the software is free, and is intended to
1296 stay that way. Everybody has the right to copy, modify, and re-
1297 distribute this software. Nobody has the right to prevent anyone
1298 else from copying, modifying or redistributing it.
1300 --------------------------------------------------------------------------
1303 Small parts of the compiler (parts of the preprocessor and main parser) are
1304 still covered by this copyright. The main portion is covered by the usual
1305 cc65 license, which reads:
1307 This software is provided 'as-is', without any expressed or implied
1308 warranty. In no event will the authors be held liable for any damages
1309 arising from the use of this software.
1311 Permission is granted to anyone to use this software for any purpose,
1312 including commercial applications, and to alter it and redistribute it
1313 freely, subject to the following restrictions:
1316 <item> The origin of this software must not be misrepresented; you must not
1317 claim that you wrote the original software. If you use this software
1318 in a product, an acknowledgment in the product documentation would be
1319 appreciated but is not required.
1320 <item> Altered source versions must be plainly marked as such, and must not
1321 be misrepresented as being the original software.
1322 <item> This notice may not be removed or altered from any source