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. You can also use <tt><ref id="pragma-writable-strings"
304 name="#pragma writable-strings"></tt> to control this option from within
308 <label id="option-static-locals">
309 <tag><tt>-Cl, --static-locals</tt></tag>
311 Use static storage for local variables instead of storage on the stack.
312 Since the stack is emulated in software, this gives shorter and usually
313 faster code, but the code is no longer reentrant. The difference between
314 <tt/-Cl/ and declaring local variables as static yourself is, that
315 initializer code is executed each time, the function is entered. So when
326 the variable <tt/a/ will always have the value <tt/1/ when entering the
327 function and using <tt/-Cl/, while in
332 static unsigned a = 1;
337 the variable <tt/a/ will have the value <tt/1/ only the first time that the
338 function is entered, and will keep the old value from one call of the
339 function to the next.
341 You may also use <tt><ref id="pragma-static-locals"
342 name="#pragma static-locals"></tt> to change this setting in your
346 <label id="option-include-dir">
347 <tag><tt>-I dir, --include-dir dir</tt></tag>
349 Set a directory where the compiler searches for include files. You may
350 use this option multiple times to add more than one directory to the
354 <label id="option-O">
355 <tag><tt>-O, -Oi, -Or, -Os</tt></tag>
357 Enable an optimizer run over the produced code.
359 Using <tt/-Oi/, the code generator will inline some code where otherwise a
360 runtime functions would have been called, even if the generated code is
361 larger. This will not only remove the overhead for a function call, but will
362 make the code visible for the optimizer. <tt/-Oi/ is an alias for
363 <tt/-O --codesize 200/.
365 <tt/-Or/ will make the compiler honor the <tt/register/ keyword. Local
366 variables may be placed in registers (which are actually zero page
367 locations). See also the <tt/<ref id="option-register-vars"
368 name="--register-vars">/ command line option, and the <ref
369 id="register-vars" name="discussion of register variables"> below.
371 Using <tt/-Os/ will force the compiler to inline some known functions from
372 the C library like strlen. Note: This has two consequences:
375 <item>You may not use names of standard C functions in your own code. If you
376 do that, your program is not standard compliant anyway, but using
377 <tt/-Os/ will actually break things.
379 <item>The inlined string and memory functions will not handle strings or
380 memory areas larger than 255 bytes. Similarly, the inlined <tt/is..()/
381 functions will not work with values outside the char. range (such as
386 It is possible to concatenate the modifiers for <tt/-O/. For example, to
387 enable register variables and inlining of known functions, you may use
391 <tag><tt>-T, --add-source</tt></tag>
393 This include the source code as comments in the generated code. This is
397 <tag><tt>-V, --version</tt></tag>
399 Print the version number of the compiler. When submitting a bug report,
400 please include the operating system you're using, and the compiler
404 <label id="option-W">
405 <tag><tt>-W name[,name]</tt></tag>
407 This option allows to control warnings generated by the compiler. It is
408 followed by a comma separated list of warnings that should be enabled or
409 disabled. To disable a warning, its name is prefixed by a minus sign. If
410 no such prefix exists, or the name is prefixed by a plus sign, the warning
413 The following warning names are currently recognized:
415 <tag><tt/error/</tag>
416 Treat all warnings as errors.
417 <tag><tt/unknown-pragma/</tag>
418 Warn about known #pragmas.
419 <tag><tt/unused-label/</tag>
420 Warn about unused labels.
421 <tag><tt/unused-param/</tag>
422 Warn about unused function parameters.
423 <tag><tt/unused-var/</tag>
424 Warn about unused variables.
427 You may also use <tt><ref id="pragma-warn" name="#pragma warn"></tt> to
428 control this setting for smaller pieces of code from within your code.
433 <sect>Input and output<p>
435 The compiler will accept one C file per invocation and create a file with
436 the same base name, but with the extension replaced by ".s". The output
437 file contains assembler code suitable for the use with the ca65 macro
440 Include files in single quotes are searched in the following places:
442 <item>The current directory.
443 <item>The value of the environment variable <tt/CC65_INC/ if it is defined.
444 <item>Any directory added with the <tt/-I/ option on the command line.
447 Include files in angle brackets are searched in the following places:
449 <item>A compiled in directory which is often <tt>/usr/lib/cc65/include</tt> on
451 <item>The value of the environment variable <tt/CC65_INC/ if it is defined.
452 <item>A subdirectory named <tt/include/ of the directory defined in the
453 environment variable <tt/CC65_HOME/, if it is defined.
454 <item>Any directory added with the <tt/-I/ option on the command line.
459 <sect>Differences to the ISO standard<p>
461 Apart from the things listed below, the compiler does support additional
462 keywords, has several functions in the standard headers with names outside the
463 reserved namespace and a few syntax extensions. All these can be disabled with
464 the <tt><ref id="option--standard" name="--standard"></tt> command line
465 option. Its use for maximum standards compatibility is advised.
467 Here is a list of differences between the language, the compiler accepts,
468 and the one defined by the ISO standard:
472 <item> The datatypes "float" and "double" are not available.
474 <item> C Functions may not return structs (or unions), and structs may not
475 be passed as parameters by value. However, struct assignment *is*
478 <item> Part of the C library is available only with fastcall calling
479 conventions (see below). It means that you must not mix pointers to
480 those functions with pointers to user-written, not-fastcall functions.
482 <item> The <tt/volatile/ keyword doesn't have an effect. This is not as bad
483 as it sounds, since the 6502 has so few registers that it isn't
484 possible to keep values in registers anyway.
488 There may be some more minor differences I'm currently not aware of. The
489 biggest problem is the missing float data type. With this limitation in
490 mind, you should be able to write fairly portable code.
496 This cc65 version has some extensions to the ISO C standard.
500 <item> The compiler allows to insert assembler statements into the output
504 asm (<string literal>[, optional parameters]) ;
508 __asm__ (<string literal>[, optional parameters]) ;
511 The first form is in the user namespace and is disabled if the <tt/-A/
514 There is a whole section covering inline assembler statements,
515 <ref id="inline-asm" name="see there">.
518 <item> There is a special calling convention named "fastcall".
519 The syntax for a function declaration using fastcall is
522 <return type> fastcall <function name> (<parameter list>)
526 <return type> __fastcall__ <function name> (<parameter list>)
530 void __fastcall__ f (unsigned char c)
532 The first form of the fastcall keyword is in the user namespace and can
533 therefore be disabled with the <tt><ref id="option--standard"
534 name="--standard"></tt> command line option.
536 For functions declared as <tt/fastcall/, the rightmost parameter is not
537 pushed on the stack but left in the primary register when the function
538 is called. This will reduce the cost when calling assembler functions
539 significantly, especially when the function itself is rather small.
542 <item> There are two pseudo variables named <tt/__AX__/ and <tt/__EAX__/.
543 Both refer to the primary register that is used by the compiler to
544 evaluate expressions or return function results. <tt/__AX__/ is of
545 type <tt/unsigned int/ and <tt/__EAX__/ of type <tt/long unsigned int/
546 respectively. The pseudo variables may be used as lvalue and rvalue as
547 every other variable. They are most useful together with short
548 sequences of assembler code. For example, the macro
558 will give the high byte of any unsigned value.
561 <item> Inside a function, the identifier <tt/__func__/ gives the name of the
562 current function as a string. Outside of functions, <tt/__func__/ is
567 #define PRINT_DEBUG(s) printf ("%s: %s\n", __func__, s);
570 The macro will print the name of the current function plus a given
574 <item> cc65 allows the initialization of <tt/void/ variables. This may be
575 used to create variable structures that are more compatible with
576 interfaces written for assembler languages. Here is an example:
579 void GCmd = { (char)3, (unsigned)0x2000, (unsigned)0x3000 };
582 This will be translated as follows:
591 Since the variable is of type <tt/void/ you may not use it as is.
592 However, taking the address of the variable results in a <tt/void*/
593 which may be passed to any function expecting a pointer.
595 See the <url url="geos.html" name="GEOS library document"> for examples
596 on how to use this feature.
599 <item> cc65 implements flexible array struct members as defined in the C99 ISO
600 standard. As an extension, these fields may be initialized. There are
601 several exceptions, however (which is probably the reason why the
602 standard does not define this feature, because it is highly
603 unorthogonal). Flexible array members cannot be initialized ...
606 <item>... when defining an array of structs with flexible
608 <item>... if such a struct is a member field of another struct
609 which is not the last field.
610 <item>... if the struct which contains a flexible array member is
611 declared as <tt/register/, and the size and compiler settings
612 do allow the compiler actually to place the struct into the
613 register bank in the zero page.
616 Please note that -- as defined in the ISO C standard -- the <tt/sizeof/
617 operator returns the struct size with the flexible array member having
618 size zero, even if it is initialized.
625 <sect>Predefined macros<p>
627 The compiler defines several macros at startup:
631 <tag><tt>__CC65__</tt></tag>
633 This macro is always defined. Its value is the version number of the
634 compiler in hex. For example, version 2.10.1 of the compiler has this macro
635 defined as <tt/0x02A1/.
637 <tag><tt>__APPLE2__</tt></tag>
639 This macro is defined if the target is the Apple ][ (-t apple2).
641 <tag><tt>__APPLE2ENH__</tt></tag>
643 This macro is defined if the target is the enhanced Apple //e (-t apple2enh).
645 <tag><tt>__ATARI__</tt></tag>
647 This macro is defined if the target is one of the Atari computers
648 (400/800/130XL/800XL).
650 <tag><tt>__ATMOS__</tt></tag>
652 This macro is defined if the target is the Oric Atmos (-t atmos).
654 <tag><tt>__CBM__</tt></tag>
656 This macro is defined if the target system is one of the CBM targets.
658 <tag><tt>__C16__</tt></tag>
660 This macro is defined if the target is the c16 (-t c16).
662 <tag><tt>__C64__</tt></tag>
664 This macro is defined if the target is the c64 (-t c64).
666 <tag><tt>__C128__</tt></tag>
668 This macro is defined if the target is the c128 (-t c128).
670 <tag><tt>__CBM510__</tt></tag>
672 This macro is defined if the target is the CBM 500 series of computers.
674 <tag><tt>__CBM610__</tt></tag>
676 This macro is defined if the target is one of the CBM 600/700 family of
677 computers (called B series in the US).
679 <tag><tt>__GEOS__</tt></tag>
681 This macro is defined if you are compiling for the GEOS system (-t geos).
683 <tag><tt>__LUNIX__</tt></tag>
685 This macro is defined if you are compiling for the LUnix system (-t lunix).
687 <tag><tt>__LYNX__</tt></tag>
689 This macro is defined if the target is the Atari Lynx (-t lynx).
691 <tag><tt>__NES__</tt></tag>
693 This macro is defined if the target is the NES (-t nes).
695 <tag><tt>__PET__</tt></tag>
697 This macro is defined if the target is the PET family of computers (-t pet).
699 <tag><tt>__PLUS4__</tt></tag>
701 This macro is defined if the target is the plus/4 (-t plus4).
703 <tag><tt>__SUPERVISION__</tt></tag>
705 This macro is defined if the target is the supervision (-t supervision).
707 <tag><tt>__VIC20__</tt></tag>
709 This macro is defined if the target is the vic20 (-t vic20).
711 <tag><tt>__FILE__</tt></tag>
713 This macro expands to a string containing the name of the C source file.
715 <tag><tt>__LINE__</tt></tag>
717 This macro expands to the current line number.
719 <tag><tt>__CC65_STD__</tt></tag>
721 This macro is defined to one of the following depending on the <tt><ref
722 id="option--standard" name="--standard"></tt> command line option:
724 <item><tt/__CC65_STD_C89__/
725 <item><tt/__CC65_STD_C99__/
726 <item><tt/__CC65_STD_CC65__/
729 <tag><tt>__OPT__</tt></tag>
731 Is defined if the compiler was called with the <tt/-O/ command line option.
733 <tag><tt>__OPT_i__</tt></tag>
735 Is defined if the compiler was called with the <tt/-Oi/ command line option.
737 <tag><tt>__OPT_r__</tt></tag>
739 Is defined if the compiler was called with the <tt/-Or/ command line option.
741 <tag><tt>__OPT_s__</tt></tag>
743 Is defined if the compiler was called with the <tt/-Os/ command line option.
748 <sect>#pragmas<label id="pragmas"><p>
750 The compiler understands some pragmas that may be used to change code
751 generation and other stuff. Some of these pragmas understand a special form:
752 If the first parameter is <tt/push/, the old value is saved onto a stack
753 before changing it. The value may later be restored by using the <tt/pop/
754 parameter with the <tt/#pragma/.
756 <sect1><tt>#pragma bss-name ([push,] <name>)</tt><label id="pragma-bss-name"><p>
758 This pragma changes the name used for the BSS segment (the BSS segment
759 is used to store uninitialized data). The argument is a string enclosed
762 Note: The default linker configuration file does only map the standard
763 segments. If you use other segments, you have to create a new linker
766 Beware: The startup code will zero only the default BSS segment. If you
767 use another BSS segment, you have to do that yourself, otherwise
768 uninitialized variables do not have the value zero.
770 The <tt/#pragma/ understands the push and pop parameters as explained above.
774 #pragma bss-name ("MyBSS")
778 <sect1><tt>#pragma charmap (<index>, <code>)</tt><label id="pragma-charmap"><p>
780 Each literal string and each literal character in the source is translated
781 by use of a translation table. This translation table is preset when the
782 compiler is started depending on the target system, for example to map
783 ISO-8859-1 characters into PETSCII if the target is a commodore machine.
785 This pragma allows to change entries in the translation table, so the
786 translation for individual characters, or even the complete table may be
789 Both arguments are assumed to be unsigned characters with a valid range of
792 Beware of two pitfalls:
795 <item>The character index is actually the code of the character in the
796 C source, so character mappings do always depend on the source
797 character set. This means that <tt/#pragma charmap/ is not
798 portable -- it depends on the build environment.
799 <item>While it is possible to use character literals as indices, the
800 result may be somewhat unexpected, since character literals are
801 itself translated. For this reason I would suggest to avoid
802 character literals and use numeric character codes instead.
807 /* Use a space wherever an 'a' occurs in ISO-8859-1 source */
808 #pragma charmap (0x61, 0x20);
812 <sect1><tt>#pragma check-stack ([push,] on|off)</tt><label id="pragma-check-stack"><p>
814 Tells the compiler to insert calls to a stack checking subroutine to detect
815 stack overflows. The stack checking code will lead to somewhat larger and
816 slower programs, so you may want to use this pragma when debugging your
817 program and switch it off for the release version. If a stack overflow is
818 detected, the program is aborted.
820 If the argument is "off", stack checks are disabled (the default), otherwise
823 The <tt/#pragma/ understands the push and pop parameters as explained above.
825 <sect1><tt>#pragma code-name ([push,] <name>)</tt><label id="pragma-code-name"><p>
827 This pragma changes the name used for the CODE segment (the CODE segment
828 is used to store executable code). The argument is a string enclosed in
831 Note: The default linker configuration file does only map the standard
832 segments. If you use other segments, you have to create a new linker
835 The <tt/#pragma/ understands the push and pop parameters as explained above.
839 #pragma code-name ("MyCODE")
843 <sect1><tt>#pragma codesize ([push,] <int>)</tt><label id="pragma-codesize"><p>
845 This pragma allows finer control about speed vs. size decisions in the code
846 generation and optimization phase. It gives the allowed size increase factor
847 (in percent). The default is can be changed by use of the <tt/<ref
848 id="option-codesize" name="--codesize">/ compiler option.
850 The <tt/#pragma/ understands the push and pop parameters as explained above.
853 <sect1><tt>#pragma data-name ([push,] <name>)</tt><label id="pragma-data-name"><p>
855 This pragma changes the name used for the DATA segment (the DATA segment
856 is used to store initialized data). The argument is a string enclosed in
859 Note: The default linker configuration file does only map the standard
860 segments. If you use other segments, you have to create a new linker
863 The <tt/#pragma/ understands the push and pop parameters as explained above.
867 #pragma data-name ("MyDATA")
871 <sect1><tt>#pragma optimize ([push,] on|off)</tt><label id="pragma-optimize"><p>
873 Switch optimization on or off. If the argument is "off", optimization is
874 disabled, otherwise it is enabled. Please note that this pragma only effects
875 whole functions. The setting in effect when the function is encountered will
876 determine if the generated code is optimized or not.
878 Optimization and code generation is also controlled by the <ref
879 id="pragma-codesize" name="codesize pragma">.
881 The default is "off", but may be changed with the <tt/<ref name="-O"
882 id="option-O">/ compiler option.
884 The <tt/#pragma/ understands the push and pop parameters as explained above.
887 <sect1><tt>#pragma rodata-name ([push,] <name>)</tt><label id="pragma-rodata-name"><p>
889 This pragma changes the name used for the RODATA segment (the RODATA
890 segment is used to store readonly data). The argument is a string
891 enclosed in double quotes.
893 Note: The default linker configuration file does only map the standard
894 segments. If you use other segments, you have to create a new linker
897 The <tt/#pragma/ understands the push and pop parameters as explained above.
901 #pragma rodata-name ("MyRODATA")
905 <sect1><tt>#pragma regvaraddr ([push,] on|off)</tt><label id="pragma-regvaraddr"><p>
907 The compiler does not allow to take the address of register variables.
908 The regvaraddr pragma changes this. Taking the address of a register
909 variable is allowed after using this pragma with "on" as argument.
910 Using "off" as an argument switches back to the default behaviour.
912 Beware: The C standard does not allow taking the address of a variable
913 declared as register. So your programs become non-portable if you use
914 this pragma. In addition, your program may not work. This is usually the
915 case if a subroutine is called with the address of a register variable,
916 and this subroutine (or a subroutine called from there) uses
917 register variables. So be careful with this #pragma.
919 The <tt/#pragma/ understands the push and pop parameters as explained above.
923 #pragma regvaraddr(on) /* Allow taking the address
924 * of register variables
929 <sect1><tt>#pragma register-vars ([push,] on|off)</tt><label id="pragma-register-vars"><p>
931 Enables or disables use of register variables. If register variables are
932 disabled (the default), the <tt/register/ keyword is ignored. Register
933 variables are explained in more detail in <ref id="register-vars" name="a separate
936 The <tt/#pragma/ understands the push and pop parameters as explained above.
939 <sect1><tt>#pragma signed-chars ([push,] on|off)</tt><label id="pragma-signed-chars"><p>
941 Changes the signedness of the default character type. If the argument is
942 "on", default characters are signed, otherwise characters are unsigned. The
943 compiler default is to make characters unsigned since this creates a lot
944 better code. This default may be overridden by the <tt/<ref
945 name="--signed-chars" id="option-signed-chars">/ command line option.
947 The <tt/#pragma/ understands the push and pop parameters as explained above.
950 <sect1><tt>#pragma static-locals ([push,] on|off)</tt><label id="pragma-static-locals"<p>
952 Use variables in the bss segment instead of variables on the stack. This
953 pragma changes the default set by the compiler option <tt/<ref
954 name="--static-locals" id="option-static-locals">/. If the argument is "on",
955 local variables are allocated in the BSS segment, leading to shorter and in
956 most cases faster, but non-reentrant code.
958 The <tt/#pragma/ understands the push and pop parameters as explained above.
961 <sect1><tt>#pragma warn (name, [push,] on|off)</tt><label id="pragma-warn"><p>
963 Switch compiler warnings on or off. "name" is the name of a warning (see the
964 <tt/<ref name="-W" id="option-W">/ compiler option for a list). The name is
965 either followed by "pop", which restores the last pushed state, or by "on" or
966 "off", optionally preceeded by "push" to push the current state before
971 /* Don't warn about the unused parameter in function func */
972 #pragma warn (unused-param, push, off)
973 static int func (int unused)
977 #pragma warn (unused-param, pop)
980 <sect1><tt>#pragma writable-strings ([push,] on|off)</tt><label id="pragma-writable-strings"><p>
982 Changes the storage location of string literals. For historical reasons,
983 the C standard defines that string literals are of type "char[]", but
984 writing to such a literal causes undefined behaviour. Most compilers
985 (including cc65) place string literals in the read-only data segment, which
986 may cause problems with old C code that writes to string literals.
988 Using this pragma (or the corresponding command line option <tt/<ref
989 name="--writable-strings" id="option-writable-strings">/) causes the
990 literals to be placed in the data segment so they can be written to without
993 The <tt/#pragma/ understands the push and pop parameters as explained above.
996 <sect1><tt>#pragma zpsym (<name>)</tt><p>
998 Tell the compiler that the -- previously as external declared -- symbol with
999 the given name is a zero page symbol (usually from an assembler file).
1000 The compiler will create a matching import declaration for the assembler.
1005 #pragma zpsym ("foo"); /* foo is in the zeropage */
1011 <sect>Register variables<label id="register-vars"><p>
1013 The runtime for all supported platforms has 6 bytes of zero page space
1014 available for register variables (this could be increased, but I think it's a
1015 good value). So you can declare register variables up to a total size of 6 per
1016 function. The compiler will allocate register space on a "first come, first
1017 served" base and convert any <tt/register/ declarations that exceed the
1018 available register space silently to <tt/auto/. Parameters can also be
1019 declared as <tt/register/, this will in fact give slightly shorter code than
1020 using a register variable.
1022 Since a function must save the current values of the registers on entry and
1023 restore them on exit, there is an overhead associated with register variables,
1024 and this overhead is quite high (about 20 bytes per variable). This means that
1025 just declaring anything as <tt/register/ is not a good idea.
1027 The best use for register variables are pointers, especially those that point
1028 to structures. The magic number here is about 3 uses of a struct field: If the
1029 function contains this number or even more, the generated code will be usually
1030 shorter and faster when using a register variable for the struct pointer. The
1031 reason for this is that the register variable can in many cases be used as a
1032 pointer directly. Having a pointer in an auto variable means that this pointer
1033 must first be copied into a zero page location, before it can be dereferenced.
1035 Second best use for register variables are counters. However, there is not
1036 much difference in the code generated for counters, so you will need at least
1037 100 operations on this variable (for example in a loop) to make it worth the
1038 trouble. The only savings you get here are by the use of a zero page variable
1039 instead of one on the stack or in the data segment.
1041 Register variables must be explicitly enabled, either by using <tt/<ref
1042 name="-Or" id="option-O">/ or <tt/<ref name="--register-vars"
1043 id="option-register-vars">/ on the command line or by use of <tt/<ref
1044 name="#pragma register-vars" id="pragma-register-vars">/. Register variables
1045 are only accepted on function top level, register variables declared in
1046 interior blocks are silently converted to <tt/auto/. With register variables
1047 disabled, all variables declared as <tt/register/ are actually auto variables.
1049 Please take care when using register variables: While they are helpful and can
1050 lead to a tremendous speedup when used correctly, improper usage will cause
1051 bloated code and a slowdown.
1055 <sect>Inline assembler<label id="inline-asm"><p>
1057 The compiler allows to insert assembler statements into the output file. The
1061 asm (<string literal>[, optional parameters]) ;
1065 __asm__ (<string literal>[, optional parameters]) ;
1069 The first form is in the user namespace and is disabled by <tt><ref
1070 id="option--standard" name="--standard"></tt> if the argument is not <tt/cc65/.
1072 The asm statement may be used inside a function and on global file level. An
1073 inline assembler statement is a primary expression, so it may also be used as
1074 part of an expression. Please note however that the result of an expression
1075 containing just an inline assembler statement is always of type <tt/void/.
1077 The contents of the string literal are preparsed by the compiler and inserted
1078 into the generated assembly output, so that the can be further processed by
1079 the backend and especially the optimizer. For this reason, the compiler does
1080 only allow regular 6502 opcodes to be used with the inline assembler. Pseudo
1081 instructions (like <tt/.import/, <tt/.byte/ and so on) are <em/not/ allowed,
1082 even if the ca65 assembler (which is used to translate the generated assembler
1083 code) would accept them. The builtin inline assembler is not a replacement for
1084 the full blown macro assembler which comes with the compiler.
1086 Note: Inline assembler statements are subject to all optimizations done by the
1087 compiler. There is currently no way to protect an inline assembler statement
1088 from being moved or removed completely by the optimizer. If in doubt, check
1089 the generated assembler output, or disable optimizations.
1091 The string literal may contain format specifiers from the following list. For
1092 each format specifier, an argument is expected which is inserted instead of
1093 the format specifier before passing the assembly code line to the backend.
1096 <item><tt/%b/ - Numerical 8-bit value
1097 <item><tt/%w/ - Numerical 16-bit value
1098 <item><tt/%l/ - Numerical 32-bit value
1099 <item><tt/%v/ - Assembler name of a (global) variable or function
1100 <item><tt/%o/ - Stack offset of a (local) variable
1101 <item><tt/%g/ - Assembler name of a C label
1102 <item><tt/%s/ - The argument is converted to a string
1103 <item><tt/%%/ - The % sign itself
1106 Using these format specifiers, you can access C <tt/#defines/, variables or
1107 similar stuff from the inline assembler. For example, to load the value of
1108 a C <tt/#define/ into the Y register, one would use
1112 __asm__ ("ldy #%b", OFFS);
1115 Or, to access a struct member of a static variable:
1121 unsigned char color;
1123 static pixel_t pixel;
1124 __asm__ ("ldy #%b", offsetof(pixel_t, color));
1125 __asm__ ("lda %v,y", pixel);
1129 Note: Do not embed the assembler labels that are used as names of global
1130 variables or functions into your asm statements. Code like this
1134 int bar () { return 1; }
1135 __asm__ ("lda _foo"); /* DON'T DO THAT! */
1137 __asm__ ("jsr _bar"); /* DON'T DO THAT EITHER! */
1141 may stop working if the way, the compiler generates these names is changed in
1142 a future version. Instead use the format specifiers from the table above:
1145 __asm__ ("lda %v", foo); /* OK */
1147 __asm__ ("jsr %v", bar); /* OK */
1152 <sect>Implementation-defined behavior<p>
1154 This section describes the behavior of cc65 when the standard describes the
1155 behavior as implementation-defined.
1159 <sect>Bugs/Feedback<p>
1161 If you have problems using the compiler, if you find any bugs, or if you're
1162 doing something interesting with it, I would be glad to hear from you. Feel
1163 free to contact me by email (<htmlurl url="mailto:uz@cc65.org"
1164 name="uz@cc65.org">).
1170 This is the original compiler copyright:
1173 --------------------------------------------------------------------------
1176 This is the copyright notice for RA65, LINK65, LIBR65, and other
1177 Atari 8-bit programs. Said programs are Copyright 1989, by John R.
1178 Dunning. All rights reserved, with the following exceptions:
1180 Anyone may copy or redistribute these programs, provided that:
1182 1: You don't charge anything for the copy. It is permissable to
1183 charge a nominal fee for media, etc.
1185 2: All source code and documentation for the programs is made
1186 available as part of the distribution.
1188 3: This copyright notice is preserved verbatim, and included in
1191 You are allowed to modify these programs, and redistribute the
1192 modified versions, provided that the modifications are clearly noted.
1194 There is NO WARRANTY with this software, it comes as is, and is
1195 distributed in the hope that it may be useful.
1197 This copyright notice applies to any program which contains
1198 this text, or the refers to this file.
1200 This copyright notice is based on the one published by the Free
1201 Software Foundation, sometimes known as the GNU project. The idea
1202 is the same as theirs, ie the software is free, and is intended to
1203 stay that way. Everybody has the right to copy, modify, and re-
1204 distribute this software. Nobody has the right to prevent anyone
1205 else from copying, modifying or redistributing it.
1207 --------------------------------------------------------------------------
1210 Small parts of the compiler (parts of the preprocessor and main parser) are
1211 still covered by this copyright. The main portion is covered by the usual
1212 cc65 license, which reads:
1214 This software is provided 'as-is', without any expressed or implied
1215 warranty. In no event will the authors be held liable for any damages
1216 arising from the use of this software.
1218 Permission is granted to anyone to use this software for any purpose,
1219 including commercial applications, and to alter it and redistribute it
1220 freely, subject to the following restrictions:
1223 <item> The origin of this software must not be misrepresented; you must not
1224 claim that you wrote the original software. If you use this software
1225 in a product, an acknowledgment in the product documentation would be
1226 appreciated but is not required.
1227 <item> Altered source versions must be plainly marked as such, and must not
1228 be misrepresented as being the original software.
1229 <item> This notice may not be removed or altered from any source