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 -I dir Set an include directory search path
58 -Oi Optimize code, inline more code
59 -Or Enable register variables
60 -Os Inline some known functions
61 -T Include source as comment
62 -V Print the compiler version number
63 -W name[,name] Enable or disable warnings
65 -g Add debug info to object file
67 -j Default characters are signed
68 -o name Name the output file
69 -r Enable register variables
70 -t sys Set the target system
74 --add-source Include source as comment
75 --bss-name seg Set the name of the BSS segment
76 --check-stack Generate stack overflow checks
77 --code-name seg Set the name of the CODE segment
78 --codesize x Accept larger code by factor x
79 --cpu type Set cpu type
80 --create-dep Create a make dependency file
81 --data-name seg Set the name of the DATA segment
83 --debug-info Add debug info to object file
84 --forget-inc-paths Forget include search paths
85 --help Help (this text)
86 --include-dir dir Set an include directory search path
87 --register-space b Set space available for register variables
88 --register-vars Enable register variables
89 --rodata-name seg Set the name of the RODATA segment
90 --signed-chars Default characters are signed
91 --standard std Language standard (c89, c99, cc65)
92 --static-locals Make local variables static
93 --target sys Set the target system
94 --verbose Increase verbosity
95 --version Print the compiler version number
96 --writable-strings Make string literals writable
97 ---------------------------------------------------------------------------
101 <sect1>Command line options in detail<p>
103 Here is a description of all the command line options:
107 <label id="option-bss-name">
108 <tag><tt>--bss-name seg</tt></tag>
110 Set the name of the bss segment. See also <tt/<ref id="pragma-bss-name"
111 name="#pragma bss-name">/.
114 <label id="option-check-stack">
115 <tag><tt>--check-stack</tt></tag>
117 Tells the compiler to generate code that checks for stack overflows. See
118 <tt/<ref id="pragma-check-stack" name="#pragma check-stack">/ for an
119 explanation of this feature.
122 <label id="option-code-name">
123 <tag><tt>--code-name seg</tt></tag>
125 Set the name of the code segment. See also <tt/<ref id="pragma-code-name"
126 name="#pragma code-name">/
129 <label id="option-codesize">
130 <tag><tt>--codesize x</tt></tag>
132 This options allows finer control about speed vs. size decisions in the code
133 generation and optimization phases. It gives the allowed size increase
134 factor (in percent). The default is 100 when not using <tt/-Oi/ and 200 when
135 using <tt/-Oi/ (<tt/-Oi/ is the same as <tt/-O --codesize 200/).
138 <label id="option-cpu">
139 <tag><tt>--cpu CPU</tt></tag>
141 A new, still experimental option. You may specify "6502" or "65C02" as
142 the CPU. 6502 is the default, so this will not change anything.
143 Specifying 65C02 will use a few 65C02 instructions when generating code.
144 Don't expect too much from this option: It is still new (and may have
145 bugs), and the additional instructions for the 65C02 are not that
149 <label id="option-create-dep">
150 <tag><tt>--create-dep</tt></tag>
152 Tells the compiler to generate a file containing the dependency list for
153 the compiled module in makefile syntax. The file is named as the C input
154 file with the extension replaced by <tt/.u/.
157 <label id="option-data-name">
158 <tag><tt>--data-name seg</tt></tag>
160 Set the name of the data segment. See also <tt/<ref id="pragma-data-name"
161 name="#pragma data-name">/
164 <tag><tt>-d, --debug</tt></tag>
166 Enables debug mode, something that should not be needed for mere
170 <tag><tt>-D sym[=definition]</tt></tag>
172 Define a macro on the command line. If no definition is given, the macro
173 is defined to the value "1".
176 <tag><tt>--forget-inc-paths</tt></tag>
178 Forget the builtin include paths. This is most useful when building
179 customized C or runtime libraries, in which case the standard header
180 files should be ignored.
183 <tag><tt>-g, --debug-info</tt></tag>
185 This will cause the compiler to insert a <tt/.DEBUGINFO/ command into the
186 generated assembler code. This will cause the assembler to include all
187 symbols in a special section in the object file.
190 <tag><tt>-h, --help</tt></tag>
192 Print the short option summary shown above.
195 <tag><tt>-o name</tt></tag>
197 Specify the name of the output file. If you don't specify a name, the
198 name of the C input file is used, with the extension replaced by ".s".
201 <label id="option-register-vars">
202 <tag><tt>-r, --register-vars</tt></tag>
204 <tt/-r/ will make the compiler honor the <tt/register/ keyword. Local
205 variables may be placed in registers (which are actually zero page
206 locations). There is some overhead involved with register variables, since
207 the old contents of the registers must be saved and restored. Since register
208 variables are of limited use without the optimizer, there is also a combined
209 switch: <tt/-Or/ will enable both, the optimizer and register variables.
211 For more information about register variables see <ref id="register-vars"
212 name="register variables">.
214 The compiler setting can also be changed within the source file by using
215 <tt/<ref id="pragma-register-vars" name="#pragma register-vars">/.
218 <label id="option-register-space">
219 <tag><tt>--register-space</tt></tag>
221 This option takes a numeric parameter and is used to specify, how much
222 zero page register space is available. Please note that just giving this
223 option will not increase or decrease by itself, it will just tell the
224 compiler about the available space. You will have to allocate that space
225 yourself using an assembler module with the necessary allocations, and a
226 linker configuration that matches the assembler module. The default value
227 for this option is 6 (bytes).
229 If you don't know what all this means, please don't use this option.
232 <label id="option-rodata-name">
233 <tag><tt>--rodata-name seg</tt></tag>
235 Set the name of the rodata segment (the segment used for readonly data).
236 See also <tt/<ref id="pragma-rodata-name" name="#pragma rodata-name">/
238 <label id="option-signed-chars">
239 <tag><tt>-j, --signed-chars</tt></tag>
241 Using this option, you can make the default characters signed. Since the
242 6502 has no provisions for sign extending characters (which is needed on
243 almost any load operation), this will make the code larger and slower. A
244 better way is to declare characters explicitly as "signed" if needed. You
245 can also use <tt><ref id="pragma-signed-chars"
246 name="#pragma signed-chars"></tt> for better control of this option.
249 <label id="option--standard">
250 <tag><tt>--standard std</tt></tag>
252 This option allows to set the language standard supported. The argument is
260 Please note that the compiler does not support the c99 standard and never
261 will. c99 mode is actually c89 mode with a few selected c99 extensions
262 (// comments for example).
265 <label id="option-standard">
266 <tag><tt>-t target, --target target</tt></tag>
268 This option is used to set the target system. The target system
269 determines things like the character set that is used for strings and
270 character constants. The following target systems are supported:
278 <item>c16 (works also for the c116 with memory up to 32K)
281 <item>cbm510 (CBM-II series with 40 column video)
282 <item>cbm610 (all CBM-II II computers with 80 column video)
287 <item>pet (all CBM PET systems except the 2001)
293 <tag><tt>-v, --verbose</tt></tag>
295 Using this option, the compiler will be somewhat more verbose if errors
296 or warnings are encountered.
299 <label id="option-writable-strings">
300 <tag><tt>--writable-strings</tt></tag>
302 Make string literals writable by placing them into the data segment instead
303 of the rodata segment.
306 <label id="option-static-locals">
307 <tag><tt>-Cl, --static-locals</tt></tag>
309 Use static storage for local variables instead of storage on the stack.
310 Since the stack is emulated in software, this gives shorter and usually
311 faster code, but the code is no longer reentrant. The difference between
312 <tt/-Cl/ and declaring local variables as static yourself is, that
313 initializer code is executed each time, the function is entered. So when
324 the variable <tt/a/ will always have the value <tt/1/ when entering the
325 function and using <tt/-Cl/, while in
330 static unsigned a = 1;
335 the variable <tt/a/ will have the value <tt/1/ only the first time that the
336 function is entered, and will keep the old value from one call of the
337 function to the next.
339 You may also use <tt><ref id="pragma-static-locals"
340 name="#pragma static-locals"></tt> to change this setting in your
344 <label id="option-include-dir">
345 <tag><tt>-I dir, --include-dir dir</tt></tag>
347 Set a directory where the compiler searches for include files. You may
348 use this option multiple times to add more than one directory to the
352 <label id="option-O">
353 <tag><tt>-O, -Oi, -Or, -Os</tt></tag>
355 Enable an optimizer run over the produced code.
357 Using <tt/-Oi/, the code generator will inline some code where otherwise a
358 runtime functions would have been called, even if the generated code is
359 larger. This will not only remove the overhead for a function call, but will
360 make the code visible for the optimizer. <tt/-Oi/ is an alias for
361 <tt/-O --codesize 200/.
363 <tt/-Or/ will make the compiler honor the <tt/register/ keyword. Local
364 variables may be placed in registers (which are actually zero page
365 locations). See also the <tt/<ref id="option-register-vars"
366 name="--register-vars">/ command line option, and the <ref
367 id="register-vars" name="discussion of register variables"> below.
369 Using <tt/-Os/ will force the compiler to inline some known functions from
370 the C library like strlen. Note: This has two consequences:
373 <item>You may not use names of standard C functions in your own code. If you
374 do that, your program is not standard compliant anyway, but using
375 <tt/-Os/ will actually break things.
377 <item>The inlined string and memory functions will not handle strings or
378 memory areas larger than 255 bytes. Similarly, the inlined <tt/is..()/
379 functions will not work with values outside the char. range (such as
384 It is possible to concatenate the modifiers for <tt/-O/. For example, to
385 enable register variables and inlining of known functions, you may use
389 <tag><tt>-T, --add-source</tt></tag>
391 This include the source code as comments in the generated code. This is
395 <tag><tt>-V, --version</tt></tag>
397 Print the version number of the compiler. When submitting a bug report,
398 please include the operating system you're using, and the compiler
402 <label id="option-W">
403 <tag><tt>-W name[,name]</tt></tag>
405 This option allows to control warnings generated by the compiler. It is
406 followed by a comma separated list of warnings that should be enabled or
407 disabled. To disable a warning, its name is prefixed by a minus sign. If
408 no such prefix exists, or the name is prefixed by a plus sign, the warning
411 The following warning names are currently recognized:
413 <tag><tt/error/</tag>
414 Treat all warnings as errors.
415 <tag><tt/unknown-pragma/</tag>
416 Warn about known #pragmas.
417 <tag><tt/unused-label/</tag>
418 Warn about unused labels.
419 <tag><tt/unused-param/</tag>
420 Warn about unused function parameters.
421 <tag><tt/unused-var/</tag>
422 Warn about unused variables.
425 You may also use <tt><ref id="pragma-warn" name="#pragma warn"></tt> to
426 control this setting for smaller pieces of code from within your code.
431 <sect>Input and output<p>
433 The compiler will accept one C file per invocation and create a file with
434 the same base name, but with the extension replaced by ".s". The output
435 file contains assembler code suitable for the use with the ca65 macro
438 Include files in single quotes are searched in the following places:
440 <item>The current directory.
441 <item>The value of the environment variable <tt/CC65_INC/ if it is defined.
442 <item>Any directory added with the <tt/-I/ option on the command line.
445 Include files in angle brackets are searched in the following places:
447 <item>A compiled in directory which is often <tt>/usr/lib/cc65/include</tt> on
449 <item>The value of the environment variable <tt/CC65_INC/ if it is defined.
450 <item>A subdirectory named <tt/include/ of the directory defined in the
451 environment variable <tt/CC65_HOME/, if it is defined.
452 <item>Any directory added with the <tt/-I/ option on the command line.
457 <sect>Differences to the ISO standard<p>
459 Apart from the things listed below, the compiler does support additional
460 keywords, has several functions in the standard headers with names outside the
461 reserved namespace and a few syntax extensions. All these can be disabled with
462 the <tt><ref id="option--standard" name="--standard"></tt> command line
463 option. Its use for maximum standards compatibility is advised.
465 Here is a list of differences between the language, the compiler accepts,
466 and the one defined by the ISO standard:
470 <item> The datatypes "float" and "double" are not available.
472 <item> C Functions may not return structs (or unions), and structs may not
473 be passed as parameters by value. However, struct assignment *is*
476 <item> Part of the C library is available only with fastcall calling
477 conventions (see below). It means that you must not mix pointers to
478 those functions with pointers to user-written, not-fastcall functions.
480 <item> The <tt/volatile/ keyword doesn't have an effect. This is not as bad
481 as it sounds, since the 6502 has so few registers that it isn't
482 possible to keep values in registers anyway.
486 There may be some more minor differences I'm currently not aware of. The
487 biggest problem is the missing float data type. With this limitation in
488 mind, you should be able to write fairly portable code.
494 This cc65 version has some extensions to the ISO C standard.
498 <item> The compiler allows to insert assembler statements into the output
502 asm (<string literal>[, optional parameters]) ;
506 __asm__ (<string literal>[, optional parameters]) ;
509 The first form is in the user namespace and is disabled if the <tt/-A/
512 There is a whole section covering inline assembler statements,
513 <ref id="inline-asm" name="see there">.
516 <item> There is a special calling convention named "fastcall".
517 The syntax for a function declaration using fastcall is
520 <return type> fastcall <function name> (<parameter list>)
524 <return type> __fastcall__ <function name> (<parameter list>)
528 void __fastcall__ f (unsigned char c)
530 The first form of the fastcall keyword is in the user namespace and can
531 therefore be disabled with the <tt><ref id="option--standard"
532 name="--standard"></tt> command line option.
534 For functions declared as <tt/fastcall/, the rightmost parameter is not
535 pushed on the stack but left in the primary register when the function
536 is called. This will reduce the cost when calling assembler functions
537 significantly, especially when the function itself is rather small.
540 <item> There are two pseudo variables named <tt/__AX__/ and <tt/__EAX__/.
541 Both refer to the primary register that is used by the compiler to
542 evaluate expressions or return function results. <tt/__AX__/ is of
543 type <tt/unsigned int/ and <tt/__EAX__/ of type <tt/long unsigned int/
544 respectively. The pseudo variables may be used as lvalue and rvalue as
545 every other variable. They are most useful together with short
546 sequences of assembler code. For example, the macro
556 will give the high byte of any unsigned value.
559 <item> Inside a function, the identifier <tt/__func__/ gives the name of the
560 current function as a string. Outside of functions, <tt/__func__/ is
565 #define PRINT_DEBUG(s) printf ("%s: %s\n", __func__, s);
568 The macro will print the name of the current function plus a given
572 <item> cc65 allows the initialization of <tt/void/ variables. This may be
573 used to create variable structures that are more compatible with
574 interfaces written for assembler languages. Here is an example:
577 void GCmd = { (char)3, (unsigned)0x2000, (unsigned)0x3000 };
580 This will be translated as follows:
589 Since the variable is of type <tt/void/ you may not use it as is.
590 However, taking the address of the variable results in a <tt/void*/
591 which may be passed to any function expecting a pointer.
593 See the <url url="geos.html" name="GEOS library document"> for examples
594 on how to use this feature.
597 <item> cc65 implements flexible array struct members as defined in the C99 ISO
598 standard. As an extension, these fields may be initialized. There are
599 several exceptions, however (which is probably the reason why the
600 standard does not define this feature, because it is highly
601 unorthogonal). Flexible array members cannot be initialized ...
604 <item>... when defining an array of structs with flexible
606 <item>... if such a struct is a member field of another struct
607 which is not the last field.
608 <item>... if the struct which contains a flexible array member is
609 declared as <tt/register/, and the size and compiler settings
610 do allow the compiler actually to place the struct into the
611 register bank in the zero page.
614 Please note that -- as defined in the ISO C standard -- the <tt/sizeof/
615 operator returns the struct size with the flexible array member having
616 size zero, even if it is initialized.
623 <sect>Predefined macros<p>
625 The compiler defines several macros at startup:
629 <tag><tt>__CC65__</tt></tag>
631 This macro is always defined. Its value is the version number of the
632 compiler in hex. For example, version 2.10.1 of the compiler has this macro
633 defined as <tt/0x02A1/.
635 <tag><tt>__APPLE2__</tt></tag>
637 This macro is defined if the target is the Apple ][ (-t apple2).
639 <tag><tt>__APPLE2ENH__</tt></tag>
641 This macro is defined if the target is the enhanced Apple //e (-t apple2enh).
643 <tag><tt>__ATARI__</tt></tag>
645 This macro is defined if the target is one of the Atari computers
646 (400/800/130XL/800XL).
648 <tag><tt>__ATMOS__</tt></tag>
650 This macro is defined if the target is the Oric Atmos (-t atmos).
652 <tag><tt>__CBM__</tt></tag>
654 This macro is defined if the target system is one of the CBM targets.
656 <tag><tt>__C16__</tt></tag>
658 This macro is defined if the target is the c16 (-t c16).
660 <tag><tt>__C64__</tt></tag>
662 This macro is defined if the target is the c64 (-t c64).
664 <tag><tt>__C128__</tt></tag>
666 This macro is defined if the target is the c128 (-t c128).
668 <tag><tt>__CBM510__</tt></tag>
670 This macro is defined if the target is the CBM 500 series of computers.
672 <tag><tt>__CBM610__</tt></tag>
674 This macro is defined if the target is one of the CBM 600/700 family of
675 computers (called B series in the US).
677 <tag><tt>__GEOS__</tt></tag>
679 This macro is defined if you are compiling for the GEOS system (-t geos).
681 <tag><tt>__LUNIX__</tt></tag>
683 This macro is defined if you are compiling for the LUnix system (-t lunix).
685 <tag><tt>__LYNX__</tt></tag>
687 This macro is defined if the target is the Atari Lynx (-t lynx).
689 <tag><tt>__NES__</tt></tag>
691 This macro is defined if the target is the NES (-t nes).
693 <tag><tt>__PET__</tt></tag>
695 This macro is defined if the target is the PET family of computers (-t pet).
697 <tag><tt>__PLUS4__</tt></tag>
699 This macro is defined if the target is the plus/4 (-t plus4).
701 <tag><tt>__SUPERVISION__</tt></tag>
703 This macro is defined if the target is the supervision (-t supervision).
705 <tag><tt>__VIC20__</tt></tag>
707 This macro is defined if the target is the vic20 (-t vic20).
709 <tag><tt>__FILE__</tt></tag>
711 This macro expands to a string containing the name of the C source file.
713 <tag><tt>__LINE__</tt></tag>
715 This macro expands to the current line number.
717 <tag><tt>__CC65_STD__</tt></tag>
719 This macro is defined to one of the following depending on the <tt><ref
720 id="option--standard" name="--standard"></tt> command line option:
722 <item><tt/__CC65_STD_C89__/
723 <item><tt/__CC65_STD_C99__/
724 <item><tt/__CC65_STD_CC65__/
727 <tag><tt>__OPT__</tt></tag>
729 Is defined if the compiler was called with the <tt/-O/ command line option.
731 <tag><tt>__OPT_i__</tt></tag>
733 Is defined if the compiler was called with the <tt/-Oi/ command line option.
735 <tag><tt>__OPT_r__</tt></tag>
737 Is defined if the compiler was called with the <tt/-Or/ command line option.
739 <tag><tt>__OPT_s__</tt></tag>
741 Is defined if the compiler was called with the <tt/-Os/ command line option.
746 <sect>#pragmas<label id="pragmas"><p>
748 The compiler understands some pragmas that may be used to change code
749 generation and other stuff. Some of these pragmas understand a special form:
750 If the first parameter is <tt/push/, the old value is saved onto a stack
751 before changing it. The value may later be restored by using the <tt/pop/
752 parameter with the <tt/#pragma/.
754 <sect1><tt>#pragma bss-name ([push,] <name>)</tt><label id="pragma-bss-name"><p>
756 This pragma changes the name used for the BSS segment (the BSS segment
757 is used to store uninitialized data). The argument is a string enclosed
760 Note: The default linker configuration file does only map the standard
761 segments. If you use other segments, you have to create a new linker
764 Beware: The startup code will zero only the default BSS segment. If you
765 use another BSS segment, you have to do that yourself, otherwise
766 uninitialized variables do not have the value zero.
768 The <tt/#pragma/ understands the push and pop parameters as explained above.
772 #pragma bss-name ("MyBSS")
776 <sect1><tt>#pragma charmap (<index>, <code>)</tt><label id="pragma-charmap"><p>
778 Each literal string and each literal character in the source is translated
779 by use of a translation table. This translation table is preset when the
780 compiler is started depending on the target system, for example to map
781 ISO-8859-1 characters into PETSCII if the target is a commodore machine.
783 This pragma allows to change entries in the translation table, so the
784 translation for individual characters, or even the complete table may be
787 Both arguments are assumed to be unsigned characters with a valid range of
790 Beware of two pitfalls:
793 <item>The character index is actually the code of the character in the
794 C source, so character mappings do always depend on the source
795 character set. This means that <tt/#pragma charmap/ is not
796 portable -- it depends on the build environment.
797 <item>While it is possible to use character literals as indices, the
798 result may be somewhat unexpected, since character literals are
799 itself translated. For this reason I would suggest to avoid
800 character literals and use numeric character codes instead.
805 /* Use a space wherever an 'a' occurs in ISO-8859-1 source */
806 #pragma charmap (0x61, 0x20);
810 <sect1><tt>#pragma check-stack ([push,] on|off)</tt><label id="pragma-check-stack"><p>
812 Tells the compiler to insert calls to a stack checking subroutine to detect
813 stack overflows. The stack checking code will lead to somewhat larger and
814 slower programs, so you may want to use this pragma when debugging your
815 program and switch it off for the release version. If a stack overflow is
816 detected, the program is aborted.
818 If the argument is "off", stack checks are disabled (the default), otherwise
821 The <tt/#pragma/ understands the push and pop parameters as explained above.
823 <sect1><tt>#pragma code-name ([push,] <name>)</tt><label id="pragma-code-name"><p>
825 This pragma changes the name used for the CODE segment (the CODE segment
826 is used to store executable code). The argument is a string enclosed in
829 Note: The default linker configuration file does only map the standard
830 segments. If you use other segments, you have to create a new linker
833 The <tt/#pragma/ understands the push and pop parameters as explained above.
837 #pragma code-name ("MyCODE")
841 <sect1><tt>#pragma codesize ([push,] <int>)</tt><label id="pragma-codesize"><p>
843 This pragma allows finer control about speed vs. size decisions in the code
844 generation and optimization phase. It gives the allowed size increase factor
845 (in percent). The default is can be changed by use of the <tt/<ref
846 id="option-codesize" name="--codesize">/ compiler option.
848 The <tt/#pragma/ understands the push and pop parameters as explained above.
851 <sect1><tt>#pragma data-name ([push,] <name>)</tt><label id="pragma-data-name"><p>
853 This pragma changes the name used for the DATA segment (the DATA segment
854 is used to store initialized data). The argument is a string enclosed in
857 Note: The default linker configuration file does only map the standard
858 segments. If you use other segments, you have to create a new linker
861 The <tt/#pragma/ understands the push and pop parameters as explained above.
865 #pragma data-name ("MyDATA")
869 <sect1><tt>#pragma optimize ([push,] on|off)</tt><label id="pragma-optimize"><p>
871 Switch optimization on or off. If the argument is "off", optimization is
872 disabled, otherwise it is enabled. Please note that this pragma only effects
873 whole functions. The setting in effect when the function is encountered will
874 determine if the generated code is optimized or not.
876 Optimization and code generation is also controlled by the <ref
877 id="pragma-codesize" name="codesize pragma">.
879 The default is "off", but may be changed with the <tt/<ref name="-O"
880 id="option-O">/ compiler option.
882 The <tt/#pragma/ understands the push and pop parameters as explained above.
885 <sect1><tt>#pragma rodata-name ([push,] <name>)</tt><label id="pragma-rodata-name"><p>
887 This pragma changes the name used for the RODATA segment (the RODATA
888 segment is used to store readonly data). The argument is a string
889 enclosed in double quotes.
891 Note: The default linker configuration file does only map the standard
892 segments. If you use other segments, you have to create a new linker
895 The <tt/#pragma/ understands the push and pop parameters as explained above.
899 #pragma rodata-name ("MyRODATA")
903 <sect1><tt>#pragma regvaraddr ([push,] on|off)</tt><label id="pragma-regvaraddr"><p>
905 The compiler does not allow to take the address of register variables.
906 The regvaraddr pragma changes this. Taking the address of a register
907 variable is allowed after using this pragma with "on" as argument.
908 Using "off" as an argument switches back to the default behaviour.
910 Beware: The C standard does not allow taking the address of a variable
911 declared as register. So your programs become non-portable if you use
912 this pragma. In addition, your program may not work. This is usually the
913 case if a subroutine is called with the address of a register variable,
914 and this subroutine (or a subroutine called from there) uses
915 register variables. So be careful with this #pragma.
917 The <tt/#pragma/ understands the push and pop parameters as explained above.
921 #pragma regvaraddr(on) /* Allow taking the address
922 * of register variables
927 <sect1><tt>#pragma register-vars ([push,] on|off)</tt><label id="pragma-register-vars"><p>
929 Enables or disables use of register variables. If register variables are
930 disabled (the default), the <tt/register/ keyword is ignored. Register
931 variables are explained in more detail in <ref id="register-vars" name="a separate
934 The <tt/#pragma/ understands the push and pop parameters as explained above.
937 <sect1><tt>#pragma signed-chars ([push,] on|off)</tt><label id="pragma-signed-chars"><p>
939 Changes the signedness of the default character type. If the argument is
940 "on", default characters are signed, otherwise characters are unsigned. The
941 compiler default is to make characters unsigned since this creates a lot
942 better code. This default may be overridden by the <tt/<ref
943 name="--signed-chars" id="option-signed-chars">/ command line option.
945 The <tt/#pragma/ understands the push and pop parameters as explained above.
948 <sect1><tt>#pragma static-locals ([push,] on|off)</tt><label id="pragma-static-locals"<p>
950 Use variables in the bss segment instead of variables on the stack. This
951 pragma changes the default set by the compiler option <tt/<ref
952 name="--static-locals" id="option-static-locals">/. If the argument is "on",
953 local variables are allocated in the BSS segment, leading to shorter and in
954 most cases faster, but non-reentrant code.
956 The <tt/#pragma/ understands the push and pop parameters as explained above.
959 <sect1><tt>#pragma warn (name, [push,] on|off)</tt><label id="pragma-warn"><p>
961 Switch compiler warnings on or off. "name" is the name of a warning (see the
962 <tt/<ref name="-W" id="option-W">/ compiler option for a list). The name is
963 either followed by "pop", which restores the last pushed state, or by "on" or
964 "off", optionally preceeded by "push" to push the current state before
969 /* Don't warn about the unused parameter in function func */
970 #pragma warn (unused-param, push, off)
971 static int func (int unused)
975 #pragma warn (unused-param, pop)
978 <sect1><tt>#pragma zpsym (<name>)</tt><p>
980 Tell the compiler that the -- previously as external declared -- symbol with
981 the given name is a zero page symbol (usually from an assembler file).
982 The compiler will create a matching import declaration for the assembler.
987 #pragma zpsym ("foo"); /* foo is in the zeropage */
993 <sect>Register variables<label id="register-vars"><p>
995 The runtime for all supported platforms has 6 bytes of zero page space
996 available for register variables (this could be increased, but I think it's a
997 good value). So you can declare register variables up to a total size of 6 per
998 function. The compiler will allocate register space on a "first come, first
999 served" base and convert any <tt/register/ declarations that exceed the
1000 available register space silently to <tt/auto/. Parameters can also be
1001 declared as <tt/register/, this will in fact give slightly shorter code than
1002 using a register variable.
1004 Since a function must save the current values of the registers on entry and
1005 restore them on exit, there is an overhead associated with register variables,
1006 and this overhead is quite high (about 20 bytes per variable). This means that
1007 just declaring anything as <tt/register/ is not a good idea.
1009 The best use for register variables are pointers, especially those that point
1010 to structures. The magic number here is about 3 uses of a struct field: If the
1011 function contains this number or even more, the generated code will be usually
1012 shorter and faster when using a register variable for the struct pointer. The
1013 reason for this is that the register variable can in many cases be used as a
1014 pointer directly. Having a pointer in an auto variable means that this pointer
1015 must first be copied into a zero page location, before it can be dereferenced.
1017 Second best use for register variables are counters. However, there is not
1018 much difference in the code generated for counters, so you will need at least
1019 100 operations on this variable (for example in a loop) to make it worth the
1020 trouble. The only savings you get here are by the use of a zero page variable
1021 instead of one on the stack or in the data segment.
1023 Register variables must be explicitly enabled, either by using <tt/<ref
1024 name="-Or" id="option-O">/ or <tt/<ref name="--register-vars"
1025 id="option-register-vars">/ on the command line or by use of <tt/<ref
1026 name="#pragma register-vars" id="pragma-register-vars">/. Register variables
1027 are only accepted on function top level, register variables declared in
1028 interior blocks are silently converted to <tt/auto/. With register variables
1029 disabled, all variables declared as <tt/register/ are actually auto variables.
1031 Please take care when using register variables: While they are helpful and can
1032 lead to a tremendous speedup when used correctly, improper usage will cause
1033 bloated code and a slowdown.
1037 <sect>Inline assembler<label id="inline-asm"><p>
1039 The compiler allows to insert assembler statements into the output file. The
1043 asm (<string literal>[, optional parameters]) ;
1047 __asm__ (<string literal>[, optional parameters]) ;
1051 The first form is in the user namespace and is disabled by <tt><ref
1052 id="option--standard" name="--standard"></tt> if the argument is not <tt/cc65/.
1054 The asm statement may be used inside a function and on global file level. An
1055 inline assembler statement is a primary expression, so it may also be used as
1056 part of an expression. Please note however that the result of an expression
1057 containing just an inline assembler statement is always of type <tt/void/.
1059 The contents of the string literal are preparsed by the compiler and inserted
1060 into the generated assembly output, so that the can be further processed by
1061 the backend and especially the optimizer. For this reason, the compiler does
1062 only allow regular 6502 opcodes to be used with the inline assembler. Pseudo
1063 instructions (like <tt/.import/, <tt/.byte/ and so on) are <em/not/ allowed,
1064 even if the ca65 assembler (which is used to translate the generated assembler
1065 code) would accept them. The builtin inline assembler is not a replacement for
1066 the full blown macro assembler which comes with the compiler.
1068 Note: Inline assembler statements are subject to all optimizations done by the
1069 compiler. There is currently no way to protect an inline assembler statement
1070 from being moved or removed completely by the optimizer. If in doubt, check
1071 the generated assembler output, or disable optimizations.
1073 The string literal may contain format specifiers from the following list. For
1074 each format specifier, an argument is expected which is inserted instead of
1075 the format specifier before passing the assembly code line to the backend.
1078 <item><tt/%b/ - Numerical 8-bit value
1079 <item><tt/%w/ - Numerical 16-bit value
1080 <item><tt/%l/ - Numerical 32-bit value
1081 <item><tt/%v/ - Assembler name of a (global) variable or function
1082 <item><tt/%o/ - Stack offset of a (local) variable
1083 <item><tt/%g/ - Assembler name of a C label
1084 <item><tt/%s/ - The argument is converted to a string
1085 <item><tt/%%/ - The % sign itself
1088 Using these format specifiers, you can access C <tt/#defines/, variables or
1089 similar stuff from the inline assembler. For example, to load the value of
1090 a C <tt/#define/ into the Y register, one would use
1094 __asm__ ("ldy #%b", OFFS);
1097 Or, to access a struct member of a static variable:
1103 unsigned char color;
1105 static pixel_t pixel;
1106 __asm__ ("ldy #%b", offsetof(pixel_t, color));
1107 __asm__ ("lda %v,y", pixel);
1111 Note: Do not embed the assembler labels that are used as names of global
1112 variables or functions into your asm statements. Code like this
1116 int bar () { return 1; }
1117 __asm__ ("lda _foo"); /* DON'T DO THAT! */
1119 __asm__ ("jsr _bar"); /* DON'T DO THAT EITHER! */
1123 may stop working if the way, the compiler generates these names is changed in
1124 a future version. Instead use the format specifiers from the table above:
1127 __asm__ ("lda %v", foo); /* OK */
1129 __asm__ ("jsr %v", bar); /* OK */
1134 <sect>Implementation-defined behavior<p>
1136 This section describes the behavior of cc65 when the standard describes the
1137 behavior as implementation-defined.
1141 <sect>Bugs/Feedback<p>
1143 If you have problems using the compiler, if you find any bugs, or if you're
1144 doing something interesting with it, I would be glad to hear from you. Feel
1145 free to contact me by email (<htmlurl url="mailto:uz@cc65.org"
1146 name="uz@cc65.org">).
1152 This is the original compiler copyright:
1155 --------------------------------------------------------------------------
1158 This is the copyright notice for RA65, LINK65, LIBR65, and other
1159 Atari 8-bit programs. Said programs are Copyright 1989, by John R.
1160 Dunning. All rights reserved, with the following exceptions:
1162 Anyone may copy or redistribute these programs, provided that:
1164 1: You don't charge anything for the copy. It is permissable to
1165 charge a nominal fee for media, etc.
1167 2: All source code and documentation for the programs is made
1168 available as part of the distribution.
1170 3: This copyright notice is preserved verbatim, and included in
1173 You are allowed to modify these programs, and redistribute the
1174 modified versions, provided that the modifications are clearly noted.
1176 There is NO WARRANTY with this software, it comes as is, and is
1177 distributed in the hope that it may be useful.
1179 This copyright notice applies to any program which contains
1180 this text, or the refers to this file.
1182 This copyright notice is based on the one published by the Free
1183 Software Foundation, sometimes known as the GNU project. The idea
1184 is the same as theirs, ie the software is free, and is intended to
1185 stay that way. Everybody has the right to copy, modify, and re-
1186 distribute this software. Nobody has the right to prevent anyone
1187 else from copying, modifying or redistributing it.
1189 --------------------------------------------------------------------------
1192 Small parts of the compiler (parts of the preprocessor and main parser) are
1193 still covered by this copyright. The main portion is covered by the usual
1194 cc65 license, which reads:
1196 This software is provided 'as-is', without any expressed or implied
1197 warranty. In no event will the authors be held liable for any damages
1198 arising from the use of this software.
1200 Permission is granted to anyone to use this software for any purpose,
1201 including commercial applications, and to alter it and redistribute it
1202 freely, subject to the following restrictions:
1205 <item> The origin of this software must not be misrepresented; you must not
1206 claim that you wrote the original software. If you use this software
1207 in a product, an acknowledgment in the product documentation would be
1208 appreciated but is not required.
1209 <item> Altered source versions must be plainly marked as such, and must not
1210 be misrepresented as being the original software.
1211 <item> This notice may not be removed or altered from any source