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 A new, still experimental option. You may specify "6502" or "65C02" as the
152 CPU. 6502 is the default, so this will not change anything. Specifying 65C02
153 will use a few 65C02 instructions when generating code. Don't expect too
154 much from this option: It is still new (and may have bugs), and the
155 additional instructions for the 65C02 are not that overwhelming.
158 <label id="option-create-dep">
159 <tag><tt>--create-dep name</tt></tag>
161 Tells the compiler to generate a file containing the dependency list for the
162 compiled module in makefile syntax. The output is written to a file with the
163 given name. The output does not include system include files (in angle
167 <label id="option-create-full-dep">
168 <tag><tt>--create-full-dep name</tt></tag>
170 Tells the compiler to generate a file containing the dependency list for the
171 compiled module in makefile syntax. The output is written to a file with the
172 given name. The output does include system include files (in angle
176 <label id="option-data-name">
177 <tag><tt>--data-name seg</tt></tag>
179 Set the name of the data segment. See also <tt/<ref id="pragma-data-name"
180 name="#pragma data-name">/
183 <tag><tt>-d, --debug</tt></tag>
185 Enables debug mode, something that should not be needed for mere
189 <label id="option-dep-target">
190 <tag><tt>--dep-target target</tt></tag>
192 When generating a dependency file, don't use the actual output file as the
193 target of the dependency, but the file specified with this option. The
194 option has no effect if neither <tt/<ref id="option-create-dep"
195 name="--create-dep">/ nor <tt/<ref id="option-create-full-dep"
196 name="--create-full-dep">/ is specified.
199 <tag><tt>-D sym[=definition]</tt></tag>
201 Define a macro on the command line. If no definition is given, the macro
202 is defined to the value "1".
205 <tag><tt>--forget-inc-paths</tt></tag>
207 Forget the builtin include paths. This is most useful when building
208 customized C or runtime libraries, in which case the standard header
209 files should be ignored.
212 <tag><tt>-g, --debug-info</tt></tag>
214 This will cause the compiler to insert a <tt/.DEBUGINFO/ command into the
215 generated assembler code. This will cause the assembler to include all
216 symbols in a special section in the object file.
219 <tag><tt>-h, --help</tt></tag>
221 Print the short option summary shown above.
224 <label id="option-local-strings">
225 <tag><tt>--local-strings</tt></tag>
227 Emit string literals to the data segment when they're encountered in the
228 source. The default is to keep string literals until end of assembly, merge
229 read only literals if possible, and then output the literals into the data
230 or rodata segment that is active at that point. Use of this option prevents
231 merging of duplicate strings, but the options that change the name of one of
232 the data segments will work.
234 You can also use <tt><ref id="pragma-local-strings"
235 name="#pragma local-strings"></tt> for fine grained control.
238 <tag><tt>-o name</tt></tag>
240 Specify the name of the output file. If you don't specify a name, the
241 name of the C input file is used, with the extension replaced by ".s".
244 <label id="option-register-vars">
245 <tag><tt>-r, --register-vars</tt></tag>
247 <tt/-r/ will make the compiler honor the <tt/register/ keyword. Local
248 variables may be placed in registers (which are actually zero page
249 locations). There is some overhead involved with register variables, since
250 the old contents of the registers must be saved and restored. Since register
251 variables are of limited use without the optimizer, there is also a combined
252 switch: <tt/-Or/ will enable both, the optimizer and register variables.
254 For more information about register variables see <ref id="register-vars"
255 name="register variables">.
257 The compiler setting can also be changed within the source file by using
258 <tt/<ref id="pragma-register-vars" name="#pragma register-vars">/.
261 <label id="option-register-space">
262 <tag><tt>--register-space</tt></tag>
264 This option takes a numeric parameter and is used to specify, how much
265 zero page register space is available. Please note that just giving this
266 option will not increase or decrease by itself, it will just tell the
267 compiler about the available space. You will have to allocate that space
268 yourself using an assembler module with the necessary allocations, and a
269 linker configuration that matches the assembler module. The default value
270 for this option is 6 (bytes).
272 If you don't know what all this means, please don't use this option.
275 <label id="option-rodata-name">
276 <tag><tt>--rodata-name seg</tt></tag>
278 Set the name of the rodata segment (the segment used for readonly data).
279 See also <tt/<ref id="pragma-rodata-name" name="#pragma rodata-name">/
281 <label id="option-signed-chars">
282 <tag><tt>-j, --signed-chars</tt></tag>
284 Using this option, you can make the default characters signed. Since the
285 6502 has no provisions for sign extending characters (which is needed on
286 almost any load operation), this will make the code larger and slower. A
287 better way is to declare characters explicitly as "signed" if needed. You
288 can also use <tt><ref id="pragma-signed-chars"
289 name="#pragma signed-chars"></tt> for better control of this option.
292 <label id="option--standard">
293 <tag><tt>--standard std</tt></tag>
295 This option allows to set the language standard supported. The argument is
299 This disables anything that is illegal in C89/C90. Among those things
300 are <tt>//</tt> comments and the non-standard keywords without
301 underscores. Please note that cc65 is not a fully C89 compliant compiler
302 despite this option. A few more things (like floats) are missing.
305 This enables a few features from the C99 standard. With this option,
306 <tt>//</tt> comments are allowed. It will also cause warnings and even
307 errors in a few situations that are allowed with <tt/--standard c89/.
308 For example, a call to a function without a prototype is an error in
312 This is the default mode. It is like c99 mode, but additional features
313 are enabled. Among these are "void data", non-standard keywords without
314 the underlines, unnamed function parameters and the requirement for
315 main() to return an int.
318 Please note that the compiler does not support the C99 standard and never
319 will. c99 mode is actually c89 mode with a few selected C99 extensions.
322 <label id="option-standard">
323 <tag><tt>-t target, --target target</tt></tag>
325 This option is used to set the target system. The target system
326 determines things like the character set that is used for strings and
327 character constants. The following target systems are supported:
335 <item>c16 (works also for the c116 with memory up to 32K)
338 <item>cbm510 (CBM-II series with 40 column video)
339 <item>cbm610 (all CBM-II II computers with 80 column video)
344 <item>pet (all CBM PET systems except the 2001)
350 <tag><tt>-v, --verbose</tt></tag>
352 Using this option, the compiler will be somewhat more verbose if errors
353 or warnings are encountered.
356 <label id="option-writable-strings">
357 <tag><tt>--writable-strings</tt></tag>
359 Make string literals writable by placing them into the data segment instead
360 of the rodata segment. You can also use <tt><ref id="pragma-writable-strings"
361 name="#pragma writable-strings"></tt> to control this option from within
365 <label id="option-static-locals">
366 <tag><tt>-Cl, --static-locals</tt></tag>
368 Use static storage for local variables instead of storage on the stack.
369 Since the stack is emulated in software, this gives shorter and usually
370 faster code, but the code is no longer reentrant. The difference between
371 <tt/-Cl/ and declaring local variables as static yourself is, that
372 initializer code is executed each time, the function is entered. So when
383 the variable <tt/a/ will always have the value <tt/1/ when entering the
384 function and using <tt/-Cl/, while in
389 static unsigned a = 1;
394 the variable <tt/a/ will have the value <tt/1/ only the first time that the
395 function is entered, and will keep the old value from one call of the
396 function to the next.
398 You may also use <tt><ref id="pragma-static-locals"
399 name="#pragma static-locals"></tt> to change this setting in your
403 <label id="option-include-dir">
404 <tag><tt>-I dir, --include-dir dir</tt></tag>
406 Set a directory where the compiler searches for include files. You may
407 use this option multiple times to add more than one directory to the
411 <label id="option-O">
412 <tag><tt>-O, -Oi, -Or, -Os</tt></tag>
414 Enable an optimizer run over the produced code.
416 Using <tt/-Oi/, the code generator will inline some code where otherwise a
417 runtime functions would have been called, even if the generated code is
418 larger. This will not only remove the overhead for a function call, but will
419 make the code visible for the optimizer. <tt/-Oi/ is an alias for
420 <tt/-O --codesize 200/.
422 <tt/-Or/ will make the compiler honor the <tt/register/ keyword. Local
423 variables may be placed in registers (which are actually zero page
424 locations). See also the <tt/<ref id="option-register-vars"
425 name="--register-vars">/ command line option, and the <ref
426 id="register-vars" name="discussion of register variables"> below.
428 Using <tt/-Os/ will force the compiler to inline some known functions from
429 the C library like strlen. Note: This has two consequences:
432 <item>You may not use names of standard C functions in your own code. If you
433 do that, your program is not standard compliant anyway, but using
434 <tt/-Os/ will actually break things.
436 <item>The inlined string and memory functions will not handle strings or
437 memory areas larger than 255 bytes. Similarly, the inlined <tt/is..()/
438 functions will not work with values outside the char. range (such as
443 It is possible to concatenate the modifiers for <tt/-O/. For example, to
444 enable register variables and inlining of known functions, you may use
448 <tag><tt>-T, --add-source</tt></tag>
450 This include the source code as comments in the generated code. This is
454 <tag><tt>-V, --version</tt></tag>
456 Print the version number of the compiler. When submitting a bug report,
457 please include the operating system you're using, and the compiler
461 <label id="option-W">
462 <tag><tt>-W name[,name]</tt></tag>
464 This option allows to control warnings generated by the compiler. It is
465 followed by a comma separated list of warnings that should be enabled or
466 disabled. To disable a warning, its name is prefixed by a minus sign. If
467 no such prefix exists, or the name is prefixed by a plus sign, the warning
470 The following warning names are currently recognized:
472 <tag><tt/error/</tag>
473 Treat all warnings as errors.
474 <tag><tt/unknown-pragma/</tag>
475 Warn about known #pragmas.
476 <tag><tt/unused-label/</tag>
477 Warn about unused labels.
478 <tag><tt/unused-param/</tag>
479 Warn about unused function parameters.
480 <tag><tt/unused-var/</tag>
481 Warn about unused variables.
484 You may also use <tt><ref id="pragma-warn" name="#pragma warn"></tt> to
485 control this setting for smaller pieces of code from within your code.
490 <sect>Input and output<p>
492 The compiler will accept one C file per invocation and create a file with
493 the same base name, but with the extension replaced by ".s". The output
494 file contains assembler code suitable for the use with the ca65 macro
497 Include files in single quotes are searched in the following places:
499 <item>The current directory.
500 <item>The value of the environment variable <tt/CC65_INC/ if it is defined.
501 <item>Any directory added with the <tt/-I/ option on the command line.
504 Include files in angle brackets are searched in the following places:
506 <item>A compiled in directory which is often <tt>/usr/lib/cc65/include</tt> on
508 <item>The value of the environment variable <tt/CC65_INC/ if it is defined.
509 <item>A subdirectory named <tt/include/ of the directory defined in the
510 environment variable <tt/CC65_HOME/, if it is defined.
511 <item>Any directory added with the <tt/-I/ option on the command line.
516 <sect>Differences to the ISO standard<p>
518 Apart from the things listed below, the compiler does support additional
519 keywords, has several functions in the standard headers with names outside the
520 reserved namespace and a few syntax extensions. All these can be disabled with
521 the <tt><ref id="option--standard" name="--standard"></tt> command line
522 option. Its use for maximum standards compatibility is advised.
524 Here is a list of differences between the language, the compiler accepts,
525 and the one defined by the ISO standard:
529 <item> The datatypes "float" and "double" are not available.
531 <item> C Functions may not return structs (or unions), and structs may not
532 be passed as parameters by value. However, struct assignment *is*
535 <item> Part of the C library is available only with fastcall calling
536 conventions (see below). It means that you must not mix pointers to
537 those functions with pointers to user-written, not-fastcall functions.
539 <item> The <tt/volatile/ keyword doesn't have an effect. This is not as bad
540 as it sounds, since the 6502 has so few registers that it isn't
541 possible to keep values in registers anyway.
545 There may be some more minor differences I'm currently not aware of. The
546 biggest problem is the missing float data type. With this limitation in
547 mind, you should be able to write fairly portable code.
553 This cc65 version has some extensions to the ISO C standard.
557 <item> The compiler allows to insert assembler statements into the output
561 asm (<string literal>[, optional parameters]) ;
565 __asm__ (<string literal>[, optional parameters]) ;
568 The first form is in the user namespace and is disabled if the <tt/-A/
571 There is a whole section covering inline assembler statements,
572 <ref id="inline-asm" name="see there">.
575 <item> There is a special calling convention named "fastcall".
576 The syntax for a function declaration using fastcall is
579 <return type> fastcall <function name> (<parameter list>)
583 <return type> __fastcall__ <function name> (<parameter list>)
587 void __fastcall__ f (unsigned char c)
589 The first form of the fastcall keyword is in the user namespace and can
590 therefore be disabled with the <tt><ref id="option--standard"
591 name="--standard"></tt> command line option.
593 For functions declared as <tt/fastcall/, the rightmost parameter is not
594 pushed on the stack but left in the primary register when the function
595 is called. This will reduce the cost when calling assembler functions
596 significantly, especially when the function itself is rather small.
599 <item> There are two pseudo variables named <tt/__AX__/ and <tt/__EAX__/.
600 Both refer to the primary register that is used by the compiler to
601 evaluate expressions or return function results. <tt/__AX__/ is of
602 type <tt/unsigned int/ and <tt/__EAX__/ of type <tt/long unsigned int/
603 respectively. The pseudo variables may be used as lvalue and rvalue as
604 every other variable. They are most useful together with short
605 sequences of assembler code. For example, the macro
615 will give the high byte of any unsigned value.
618 <item> Inside a function, the identifier <tt/__func__/ gives the name of the
619 current function as a string. Outside of functions, <tt/__func__/ is
624 #define PRINT_DEBUG(s) printf ("%s: %s\n", __func__, s);
627 The macro will print the name of the current function plus a given
631 <item> cc65 allows the initialization of <tt/void/ variables. This may be
632 used to create variable structures that are more compatible with
633 interfaces written for assembler languages. Here is an example:
636 void GCmd = { (char)3, (unsigned)0x2000, (unsigned)0x3000 };
639 This will be translated as follows:
648 Since the variable is of type <tt/void/ you may not use it as is.
649 However, taking the address of the variable results in a <tt/void*/
650 which may be passed to any function expecting a pointer.
652 See the <url url="geos.html" name="GEOS library document"> for examples
653 on how to use this feature.
656 <item> cc65 implements flexible array struct members as defined in the C99 ISO
657 standard. As an extension, these fields may be initialized. There are
658 several exceptions, however (which is probably the reason why the
659 standard does not define this feature, because it is highly
660 unorthogonal). Flexible array members cannot be initialized ...
663 <item>... when defining an array of structs with flexible
665 <item>... if such a struct is a member field of another struct
666 which is not the last field.
667 <item>... if the struct which contains a flexible array member is
668 declared as <tt/register/, and the size and compiler settings
669 do allow the compiler actually to place the struct into the
670 register bank in the zero page.
673 Please note that -- as defined in the ISO C standard -- the <tt/sizeof/
674 operator returns the struct size with the flexible array member having
675 size zero, even if it is initialized.
682 <sect>Predefined macros<p>
684 The compiler defines several macros at startup:
688 <tag><tt>__CC65__</tt></tag>
690 This macro is always defined. Its value is the version number of the
691 compiler in hex. For example, version 2.10.1 of the compiler has this macro
692 defined as <tt/0x02A1/.
694 <tag><tt>__APPLE2__</tt></tag>
696 This macro is defined if the target is the Apple ][ (-t apple2).
698 <tag><tt>__APPLE2ENH__</tt></tag>
700 This macro is defined if the target is the enhanced Apple //e (-t apple2enh).
702 <tag><tt>__ATARI__</tt></tag>
704 This macro is defined if the target is one of the Atari computers
705 (400/800/130XL/800XL).
707 <tag><tt>__ATMOS__</tt></tag>
709 This macro is defined if the target is the Oric Atmos (-t atmos).
711 <tag><tt>__CBM__</tt></tag>
713 This macro is defined if the target system is one of the CBM targets.
715 <tag><tt>__C16__</tt></tag>
717 This macro is defined if the target is the c16 (-t c16).
719 <tag><tt>__C64__</tt></tag>
721 This macro is defined if the target is the c64 (-t c64).
723 <tag><tt>__C128__</tt></tag>
725 This macro is defined if the target is the c128 (-t c128).
727 <tag><tt>__CBM510__</tt></tag>
729 This macro is defined if the target is the CBM 500 series of computers.
731 <tag><tt>__CBM610__</tt></tag>
733 This macro is defined if the target is one of the CBM 600/700 family of
734 computers (called B series in the US).
736 <tag><tt>__GEOS__</tt></tag>
738 This macro is defined if you are compiling for the GEOS system (-t geos).
740 <tag><tt>__LUNIX__</tt></tag>
742 This macro is defined if you are compiling for the LUnix system (-t lunix).
744 <tag><tt>__LYNX__</tt></tag>
746 This macro is defined if the target is the Atari Lynx (-t lynx).
748 <tag><tt>__NES__</tt></tag>
750 This macro is defined if the target is the NES (-t nes).
752 <tag><tt>__PET__</tt></tag>
754 This macro is defined if the target is the PET family of computers (-t pet).
756 <tag><tt>__PLUS4__</tt></tag>
758 This macro is defined if the target is the plus/4 (-t plus4).
760 <tag><tt>__SUPERVISION__</tt></tag>
762 This macro is defined if the target is the supervision (-t supervision).
764 <tag><tt>__VIC20__</tt></tag>
766 This macro is defined if the target is the vic20 (-t vic20).
768 <tag><tt>__FILE__</tt></tag>
770 This macro expands to a string containing the name of the C source file.
772 <tag><tt>__LINE__</tt></tag>
774 This macro expands to the current line number.
776 <tag><tt>__CC65_STD__</tt></tag>
778 This macro is defined to one of the following depending on the <tt><ref
779 id="option--standard" name="--standard"></tt> command line option:
781 <item><tt/__CC65_STD_C89__/
782 <item><tt/__CC65_STD_C99__/
783 <item><tt/__CC65_STD_CC65__/
786 <tag><tt>__OPT__</tt></tag>
788 Is defined if the compiler was called with the <tt/-O/ command line option.
790 <tag><tt>__OPT_i__</tt></tag>
792 Is defined if the compiler was called with the <tt/-Oi/ command line option.
794 <tag><tt>__OPT_r__</tt></tag>
796 Is defined if the compiler was called with the <tt/-Or/ command line option.
798 <tag><tt>__OPT_s__</tt></tag>
800 Is defined if the compiler was called with the <tt/-Os/ command line option.
805 <sect>#pragmas<label id="pragmas"><p>
807 The compiler understands some pragmas that may be used to change code
808 generation and other stuff. Some of these pragmas understand a special form:
809 If the first parameter is <tt/push/, the old value is saved onto a stack
810 before changing it. The value may later be restored by using the <tt/pop/
811 parameter with the <tt/#pragma/.
813 <sect1><tt>#pragma bss-name ([push,] <name>)</tt><label id="pragma-bss-name"><p>
815 This pragma changes the name used for the BSS segment (the BSS segment
816 is used to store uninitialized data). The argument is a string enclosed
819 Note: The default linker configuration file does only map the standard
820 segments. If you use other segments, you have to create a new linker
823 Beware: The startup code will zero only the default BSS segment. If you
824 use another BSS segment, you have to do that yourself, otherwise
825 uninitialized variables do not have the value zero.
827 The <tt/#pragma/ understands the push and pop parameters as explained above.
831 #pragma bss-name ("MyBSS")
835 <sect1><tt>#pragma charmap (<index>, <code>)</tt><label id="pragma-charmap"><p>
837 Each literal string and each literal character in the source is translated
838 by use of a translation table. This translation table is preset when the
839 compiler is started depending on the target system, for example to map
840 ISO-8859-1 characters into PETSCII if the target is a commodore machine.
842 This pragma allows to change entries in the translation table, so the
843 translation for individual characters, or even the complete table may be
846 Both arguments are assumed to be unsigned characters with a valid range of
849 Beware of two pitfalls:
852 <item>The character index is actually the code of the character in the
853 C source, so character mappings do always depend on the source
854 character set. This means that <tt/#pragma charmap/ is not
855 portable -- it depends on the build environment.
856 <item>While it is possible to use character literals as indices, the
857 result may be somewhat unexpected, since character literals are
858 itself translated. For this reason I would suggest to avoid
859 character literals and use numeric character codes instead.
864 /* Use a space wherever an 'a' occurs in ISO-8859-1 source */
865 #pragma charmap (0x61, 0x20);
869 <sect1><tt>#pragma check-stack ([push,] on|off)</tt><label id="pragma-check-stack"><p>
871 Tells the compiler to insert calls to a stack checking subroutine to detect
872 stack overflows. The stack checking code will lead to somewhat larger and
873 slower programs, so you may want to use this pragma when debugging your
874 program and switch it off for the release version. If a stack overflow is
875 detected, the program is aborted.
877 If the argument is "off", stack checks are disabled (the default), otherwise
880 The <tt/#pragma/ understands the push and pop parameters as explained above.
882 <sect1><tt>#pragma code-name ([push,] <name>)</tt><label id="pragma-code-name"><p>
884 This pragma changes the name used for the CODE segment (the CODE segment
885 is used to store executable code). The argument is a string enclosed in
888 Note: The default linker configuration file does only map the standard
889 segments. If you use other segments, you have to create a new linker
892 The <tt/#pragma/ understands the push and pop parameters as explained above.
896 #pragma code-name ("MyCODE")
900 <sect1><tt>#pragma codesize ([push,] <int>)</tt><label id="pragma-codesize"><p>
902 This pragma allows finer control about speed vs. size decisions in the code
903 generation and optimization phase. It gives the allowed size increase factor
904 (in percent). The default is can be changed by use of the <tt/<ref
905 id="option-codesize" name="--codesize">/ compiler option.
907 The <tt/#pragma/ understands the push and pop parameters as explained above.
910 <sect1><tt>#pragma data-name ([push,] <name>)</tt><label id="pragma-data-name"><p>
912 This pragma changes the name used for the DATA segment (the DATA segment
913 is used to store initialized data). The argument is a string enclosed in
916 Note: The default linker configuration file does only map the standard
917 segments. If you use other segments, you have to create a new linker
920 The <tt/#pragma/ understands the push and pop parameters as explained above.
924 #pragma data-name ("MyDATA")
928 <sect1><tt>#pragma local-strings ([push,] on|off)</tt><label id="pragma-local-strings"><p>
930 When "on", emit string literals to the data segment when they're encountered
931 in the source. The default ("off") is to keep string literals until end of
932 assembly, merge read only literals if possible, and then output the literals
933 into the data or rodata segment that is active at that point.
935 Using this <tt/#pragma/ it is possible to control the behaviour from within
936 the source. When <tt/#pragma local-strings/ is active, string literals are
937 output immediately, which means that they go into the currently active data
938 or rodata segment, but cannot be merged. When inactive, string literals are
939 remembered and output as a whole when translation is finished.
942 <sect1><tt>#pragma optimize ([push,] on|off)</tt><label id="pragma-optimize"><p>
944 Switch optimization on or off. If the argument is "off", optimization is
945 disabled, otherwise it is enabled. Please note that this pragma only effects
946 whole functions. The setting in effect when the function is encountered will
947 determine if the generated code is optimized or not.
949 Optimization and code generation is also controlled by the <ref
950 id="pragma-codesize" name="codesize pragma">.
952 The default is "off", but may be changed with the <tt/<ref name="-O"
953 id="option-O">/ compiler option.
955 The <tt/#pragma/ understands the push and pop parameters as explained above.
958 <sect1><tt>#pragma rodata-name ([push,] <name>)</tt><label id="pragma-rodata-name"><p>
960 This pragma changes the name used for the RODATA segment (the RODATA
961 segment is used to store readonly data). The argument is a string
962 enclosed in double quotes.
964 Note: The default linker configuration file does only map the standard
965 segments. If you use other segments, you have to create a new linker
968 The <tt/#pragma/ understands the push and pop parameters as explained above.
972 #pragma rodata-name ("MyRODATA")
976 <sect1><tt>#pragma regvaraddr ([push,] on|off)</tt><label id="pragma-regvaraddr"><p>
978 The compiler does not allow to take the address of register variables.
979 The regvaraddr pragma changes this. Taking the address of a register
980 variable is allowed after using this pragma with "on" as argument.
981 Using "off" as an argument switches back to the default behaviour.
983 Beware: The C standard does not allow taking the address of a variable
984 declared as register. So your programs become non-portable if you use
985 this pragma. In addition, your program may not work. This is usually the
986 case if a subroutine is called with the address of a register variable,
987 and this subroutine (or a subroutine called from there) uses
988 register variables. So be careful with this #pragma.
990 The <tt/#pragma/ understands the push and pop parameters as explained above.
994 #pragma regvaraddr(on) /* Allow taking the address
995 * of register variables
1000 <sect1><tt>#pragma register-vars ([push,] on|off)</tt><label id="pragma-register-vars"><p>
1002 Enables or disables use of register variables. If register variables are
1003 disabled (the default), the <tt/register/ keyword is ignored. Register
1004 variables are explained in more detail in <ref id="register-vars" name="a separate
1007 The <tt/#pragma/ understands the push and pop parameters as explained above.
1010 <sect1><tt>#pragma signed-chars ([push,] on|off)</tt><label id="pragma-signed-chars"><p>
1012 Changes the signedness of the default character type. If the argument is
1013 "on", default characters are signed, otherwise characters are unsigned. The
1014 compiler default is to make characters unsigned since this creates a lot
1015 better code. This default may be overridden by the <tt/<ref
1016 name="--signed-chars" id="option-signed-chars">/ command line option.
1018 The <tt/#pragma/ understands the push and pop parameters as explained above.
1021 <sect1><tt>#pragma static-locals ([push,] on|off)</tt><label id="pragma-static-locals"<p>
1023 Use variables in the bss segment instead of variables on the stack. This
1024 pragma changes the default set by the compiler option <tt/<ref
1025 name="--static-locals" id="option-static-locals">/. If the argument is "on",
1026 local variables are allocated in the BSS segment, leading to shorter and in
1027 most cases faster, but non-reentrant code.
1029 The <tt/#pragma/ understands the push and pop parameters as explained above.
1032 <sect1><tt>#pragma warn (name, [push,] on|off)</tt><label id="pragma-warn"><p>
1034 Switch compiler warnings on or off. "name" is the name of a warning (see the
1035 <tt/<ref name="-W" id="option-W">/ compiler option for a list). The name is
1036 either followed by "pop", which restores the last pushed state, or by "on" or
1037 "off", optionally preceeded by "push" to push the current state before
1042 /* Don't warn about the unused parameter in function func */
1043 #pragma warn (unused-param, push, off)
1044 static int func (int unused)
1048 #pragma warn (unused-param, pop)
1051 <sect1><tt>#pragma writable-strings ([push,] on|off)</tt><label id="pragma-writable-strings"><p>
1053 Changes the storage location of string literals. For historical reasons,
1054 the C standard defines that string literals are of type "char[]", but
1055 writing to such a literal causes undefined behaviour. Most compilers
1056 (including cc65) place string literals in the read-only data segment, which
1057 may cause problems with old C code that writes to string literals.
1059 Using this pragma (or the corresponding command line option <tt/<ref
1060 name="--writable-strings" id="option-writable-strings">/) causes the
1061 literals to be placed in the data segment so they can be written to without
1064 The <tt/#pragma/ understands the push and pop parameters as explained above.
1067 <sect1><tt>#pragma zpsym (<name>)</tt><p>
1069 Tell the compiler that the -- previously as external declared -- symbol with
1070 the given name is a zero page symbol (usually from an assembler file).
1071 The compiler will create a matching import declaration for the assembler.
1076 #pragma zpsym ("foo"); /* foo is in the zeropage */
1082 <sect>Register variables<label id="register-vars"><p>
1084 The runtime for all supported platforms has 6 bytes of zero page space
1085 available for register variables (this could be increased, but I think it's a
1086 good value). So you can declare register variables up to a total size of 6 per
1087 function. The compiler will allocate register space on a "first come, first
1088 served" base and convert any <tt/register/ declarations that exceed the
1089 available register space silently to <tt/auto/. Parameters can also be
1090 declared as <tt/register/, this will in fact give slightly shorter code than
1091 using a register variable.
1093 Since a function must save the current values of the registers on entry and
1094 restore them on exit, there is an overhead associated with register variables,
1095 and this overhead is quite high (about 20 bytes per variable). This means that
1096 just declaring anything as <tt/register/ is not a good idea.
1098 The best use for register variables are pointers, especially those that point
1099 to structures. The magic number here is about 3 uses of a struct field: If the
1100 function contains this number or even more, the generated code will be usually
1101 shorter and faster when using a register variable for the struct pointer. The
1102 reason for this is that the register variable can in many cases be used as a
1103 pointer directly. Having a pointer in an auto variable means that this pointer
1104 must first be copied into a zero page location, before it can be dereferenced.
1106 Second best use for register variables are counters. However, there is not
1107 much difference in the code generated for counters, so you will need at least
1108 100 operations on this variable (for example in a loop) to make it worth the
1109 trouble. The only savings you get here are by the use of a zero page variable
1110 instead of one on the stack or in the data segment.
1112 Register variables must be explicitly enabled, either by using <tt/<ref
1113 name="-Or" id="option-O">/ or <tt/<ref name="--register-vars"
1114 id="option-register-vars">/ on the command line or by use of <tt/<ref
1115 name="#pragma register-vars" id="pragma-register-vars">/. Register variables
1116 are only accepted on function top level, register variables declared in
1117 interior blocks are silently converted to <tt/auto/. With register variables
1118 disabled, all variables declared as <tt/register/ are actually auto variables.
1120 Please take care when using register variables: While they are helpful and can
1121 lead to a tremendous speedup when used correctly, improper usage will cause
1122 bloated code and a slowdown.
1126 <sect>Inline assembler<label id="inline-asm"><p>
1128 The compiler allows to insert assembler statements into the output file. The
1132 asm (<string literal>[, optional parameters]) ;
1136 __asm__ (<string literal>[, optional parameters]) ;
1140 The first form is in the user namespace and is disabled by <tt><ref
1141 id="option--standard" name="--standard"></tt> if the argument is not <tt/cc65/.
1143 The asm statement may be used inside a function and on global file level. An
1144 inline assembler statement is a primary expression, so it may also be used as
1145 part of an expression. Please note however that the result of an expression
1146 containing just an inline assembler statement is always of type <tt/void/.
1148 The contents of the string literal are preparsed by the compiler and inserted
1149 into the generated assembly output, so that the can be further processed by
1150 the backend and especially the optimizer. For this reason, the compiler does
1151 only allow regular 6502 opcodes to be used with the inline assembler. Pseudo
1152 instructions (like <tt/.import/, <tt/.byte/ and so on) are <em/not/ allowed,
1153 even if the ca65 assembler (which is used to translate the generated assembler
1154 code) would accept them. The builtin inline assembler is not a replacement for
1155 the full blown macro assembler which comes with the compiler.
1157 Note: Inline assembler statements are subject to all optimizations done by the
1158 compiler. There is currently no way to protect an inline assembler statement
1159 from being moved or removed completely by the optimizer. If in doubt, check
1160 the generated assembler output, or disable optimizations.
1162 The string literal may contain format specifiers from the following list. For
1163 each format specifier, an argument is expected which is inserted instead of
1164 the format specifier before passing the assembly code line to the backend.
1167 <item><tt/%b/ - Numerical 8-bit value
1168 <item><tt/%w/ - Numerical 16-bit value
1169 <item><tt/%l/ - Numerical 32-bit value
1170 <item><tt/%v/ - Assembler name of a (global) variable or function
1171 <item><tt/%o/ - Stack offset of a (local) variable
1172 <item><tt/%g/ - Assembler name of a C label
1173 <item><tt/%s/ - The argument is converted to a string
1174 <item><tt/%%/ - The % sign itself
1177 Using these format specifiers, you can access C <tt/#defines/, variables or
1178 similar stuff from the inline assembler. For example, to load the value of
1179 a C <tt/#define/ into the Y register, one would use
1183 __asm__ ("ldy #%b", OFFS);
1186 Or, to access a struct member of a static variable:
1192 unsigned char color;
1194 static pixel_t pixel;
1195 __asm__ ("ldy #%b", offsetof(pixel_t, color));
1196 __asm__ ("lda %v,y", pixel);
1200 Note: Do not embed the assembler labels that are used as names of global
1201 variables or functions into your asm statements. Code like this
1205 int bar () { return 1; }
1206 __asm__ ("lda _foo"); /* DON'T DO THAT! */
1208 __asm__ ("jsr _bar"); /* DON'T DO THAT EITHER! */
1212 may stop working if the way, the compiler generates these names is changed in
1213 a future version. Instead use the format specifiers from the table above:
1216 __asm__ ("lda %v", foo); /* OK */
1218 __asm__ ("jsr %v", bar); /* OK */
1223 <sect>Implementation-defined behavior<p>
1225 This section describes the behavior of cc65 when the standard describes the
1226 behavior as implementation-defined.
1230 <sect>Bugs/Feedback<p>
1232 If you have problems using the compiler, if you find any bugs, or if you're
1233 doing something interesting with it, I would be glad to hear from you. Feel
1234 free to contact me by email (<htmlurl url="mailto:uz@cc65.org"
1235 name="uz@cc65.org">).
1241 This is the original compiler copyright:
1244 --------------------------------------------------------------------------
1247 This is the copyright notice for RA65, LINK65, LIBR65, and other
1248 Atari 8-bit programs. Said programs are Copyright 1989, by John R.
1249 Dunning. All rights reserved, with the following exceptions:
1251 Anyone may copy or redistribute these programs, provided that:
1253 1: You don't charge anything for the copy. It is permissable to
1254 charge a nominal fee for media, etc.
1256 2: All source code and documentation for the programs is made
1257 available as part of the distribution.
1259 3: This copyright notice is preserved verbatim, and included in
1262 You are allowed to modify these programs, and redistribute the
1263 modified versions, provided that the modifications are clearly noted.
1265 There is NO WARRANTY with this software, it comes as is, and is
1266 distributed in the hope that it may be useful.
1268 This copyright notice applies to any program which contains
1269 this text, or the refers to this file.
1271 This copyright notice is based on the one published by the Free
1272 Software Foundation, sometimes known as the GNU project. The idea
1273 is the same as theirs, ie the software is free, and is intended to
1274 stay that way. Everybody has the right to copy, modify, and re-
1275 distribute this software. Nobody has the right to prevent anyone
1276 else from copying, modifying or redistributing it.
1278 --------------------------------------------------------------------------
1281 Small parts of the compiler (parts of the preprocessor and main parser) are
1282 still covered by this copyright. The main portion is covered by the usual
1283 cc65 license, which reads:
1285 This software is provided 'as-is', without any expressed or implied
1286 warranty. In no event will the authors be held liable for any damages
1287 arising from the use of this software.
1289 Permission is granted to anyone to use this software for any purpose,
1290 including commercial applications, and to alter it and redistribute it
1291 freely, subject to the following restrictions:
1294 <item> The origin of this software must not be misrepresented; you must not
1295 claim that you wrote the original software. If you use this software
1296 in a product, an acknowledgment in the product documentation would be
1297 appreciated but is not required.
1298 <item> Altered source versions must be plainly marked as such, and must not
1299 be misrepresented as being the original software.
1300 <item> This notice may not be removed or altered from any source