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 --disable-opt name Disable an optimization step
89 --enable-opt name Enable an optimization step
90 --forget-inc-paths Forget include search paths
91 --help Help (this text)
92 --include-dir dir Set an include directory search path
93 --list-opt-steps List all optimizer steps and exit
94 --local-strings Emit string literals immediately
95 --memory-model model Set the memory model
96 --register-space b Set space available for register variables
97 --register-vars Enable register variables
98 --rodata-name seg Set the name of the RODATA segment
99 --signed-chars Default characters are signed
100 --standard std Language standard (c89, c99, cc65)
101 --static-locals Make local variables static
102 --target sys Set the target system
103 --verbose Increase verbosity
104 --version Print the compiler version number
105 --writable-strings Make string literals writable
106 ---------------------------------------------------------------------------
110 <sect1>Command line options in detail<p>
112 Here is a description of all the command line options:
116 <label id="option-bss-name">
117 <tag><tt>--bss-name seg</tt></tag>
119 Set the name of the bss segment. See also <tt/<ref id="pragma-bss-name"
120 name="#pragma bss-name">/.
123 <label id="option-check-stack">
124 <tag><tt>--check-stack</tt></tag>
126 Tells the compiler to generate code that checks for stack overflows. See
127 <tt/<ref id="pragma-check-stack" name="#pragma check-stack">/ for an
128 explanation of this feature.
131 <label id="option-code-name">
132 <tag><tt>--code-name seg</tt></tag>
134 Set the name of the code segment. See also <tt/<ref id="pragma-code-name"
135 name="#pragma code-name">/
138 <label id="option-codesize">
139 <tag><tt>--codesize x</tt></tag>
141 This options allows finer control about speed vs. size decisions in the code
142 generation and optimization phases. It gives the allowed size increase
143 factor (in percent). The default is 100 when not using <tt/-Oi/ and 200 when
144 using <tt/-Oi/ (<tt/-Oi/ is the same as <tt/-O --codesize 200/).
147 <label id="option-cpu">
148 <tag><tt>--cpu CPU</tt></tag>
150 A new, still experimental option. You may specify "6502" or "65C02" as the
151 CPU. 6502 is the default, so this will not change anything. Specifying 65C02
152 will use a few 65C02 instructions when generating code. Don't expect too
153 much from this option: It is still new (and may have bugs), and the
154 additional instructions for the 65C02 are not that overwhelming.
157 <label id="option-create-dep">
158 <tag><tt>--create-dep name</tt></tag>
160 Tells the compiler to generate a file containing the dependency list for the
161 compiled module in makefile syntax. The output is written to a file with the
162 given name. The output does not include system include files (in angle
166 <label id="option-create-full-dep">
167 <tag><tt>--create-full-dep name</tt></tag>
169 Tells the compiler to generate a file containing the dependency list for the
170 compiled module in makefile syntax. The output is written to a file with the
171 given name. The output does include system include files (in angle
175 <label id="option-data-name">
176 <tag><tt>--data-name seg</tt></tag>
178 Set the name of the data segment. See also <tt/<ref id="pragma-data-name"
179 name="#pragma data-name">/
182 <tag><tt>-d, --debug</tt></tag>
184 Enables debug mode, something that should not be needed for mere
188 <tag><tt>-D sym[=definition]</tt></tag>
190 Define a macro on the command line. If no definition is given, the macro
191 is defined to the value "1".
194 <tag><tt>--forget-inc-paths</tt></tag>
196 Forget the builtin include paths. This is most useful when building
197 customized C or runtime libraries, in which case the standard header
198 files should be ignored.
201 <tag><tt>-g, --debug-info</tt></tag>
203 This will cause the compiler to insert a <tt/.DEBUGINFO/ command into the
204 generated assembler code. This will cause the assembler to include all
205 symbols in a special section in the object file.
208 <tag><tt>-h, --help</tt></tag>
210 Print the short option summary shown above.
213 <label id="option-local-strings">
214 <tag><tt>--local-strings</tt></tag>
216 Emit string literals to the data segment when they're encountered in the
217 source. The default is to keep string literals until end of assembly, merge
218 read only literals if possible, and then output the literals into the data
219 or rodata segment that is active at that point. Use of this option prevents
220 merging of duplicate strings, but the options that change the name of one of
221 the data segments will work.
223 You can also use <tt><ref id="pragma-local-strings"
224 name="#pragma local-strings"></tt> for fine grained control.
227 <tag><tt>-o name</tt></tag>
229 Specify the name of the output file. If you don't specify a name, the
230 name of the C input file is used, with the extension replaced by ".s".
233 <label id="option-register-vars">
234 <tag><tt>-r, --register-vars</tt></tag>
236 <tt/-r/ will make the compiler honor the <tt/register/ keyword. Local
237 variables may be placed in registers (which are actually zero page
238 locations). There is some overhead involved with register variables, since
239 the old contents of the registers must be saved and restored. Since register
240 variables are of limited use without the optimizer, there is also a combined
241 switch: <tt/-Or/ will enable both, the optimizer and register variables.
243 For more information about register variables see <ref id="register-vars"
244 name="register variables">.
246 The compiler setting can also be changed within the source file by using
247 <tt/<ref id="pragma-register-vars" name="#pragma register-vars">/.
250 <label id="option-register-space">
251 <tag><tt>--register-space</tt></tag>
253 This option takes a numeric parameter and is used to specify, how much
254 zero page register space is available. Please note that just giving this
255 option will not increase or decrease by itself, it will just tell the
256 compiler about the available space. You will have to allocate that space
257 yourself using an assembler module with the necessary allocations, and a
258 linker configuration that matches the assembler module. The default value
259 for this option is 6 (bytes).
261 If you don't know what all this means, please don't use this option.
264 <label id="option-rodata-name">
265 <tag><tt>--rodata-name seg</tt></tag>
267 Set the name of the rodata segment (the segment used for readonly data).
268 See also <tt/<ref id="pragma-rodata-name" name="#pragma rodata-name">/
270 <label id="option-signed-chars">
271 <tag><tt>-j, --signed-chars</tt></tag>
273 Using this option, you can make the default characters signed. Since the
274 6502 has no provisions for sign extending characters (which is needed on
275 almost any load operation), this will make the code larger and slower. A
276 better way is to declare characters explicitly as "signed" if needed. You
277 can also use <tt><ref id="pragma-signed-chars"
278 name="#pragma signed-chars"></tt> for better control of this option.
281 <label id="option--standard">
282 <tag><tt>--standard std</tt></tag>
284 This option allows to set the language standard supported. The argument is
292 Please note that the compiler does not support the c99 standard and never
293 will. c99 mode is actually c89 mode with a few selected c99 extensions
294 (// comments for example).
297 <label id="option-standard">
298 <tag><tt>-t target, --target target</tt></tag>
300 This option is used to set the target system. The target system
301 determines things like the character set that is used for strings and
302 character constants. The following target systems are supported:
310 <item>c16 (works also for the c116 with memory up to 32K)
313 <item>cbm510 (CBM-II series with 40 column video)
314 <item>cbm610 (all CBM-II II computers with 80 column video)
319 <item>pet (all CBM PET systems except the 2001)
325 <tag><tt>-v, --verbose</tt></tag>
327 Using this option, the compiler will be somewhat more verbose if errors
328 or warnings are encountered.
331 <label id="option-writable-strings">
332 <tag><tt>--writable-strings</tt></tag>
334 Make string literals writable by placing them into the data segment instead
335 of the rodata segment. You can also use <tt><ref id="pragma-writable-strings"
336 name="#pragma writable-strings"></tt> to control this option from within
340 <label id="option-static-locals">
341 <tag><tt>-Cl, --static-locals</tt></tag>
343 Use static storage for local variables instead of storage on the stack.
344 Since the stack is emulated in software, this gives shorter and usually
345 faster code, but the code is no longer reentrant. The difference between
346 <tt/-Cl/ and declaring local variables as static yourself is, that
347 initializer code is executed each time, the function is entered. So when
358 the variable <tt/a/ will always have the value <tt/1/ when entering the
359 function and using <tt/-Cl/, while in
364 static unsigned a = 1;
369 the variable <tt/a/ will have the value <tt/1/ only the first time that the
370 function is entered, and will keep the old value from one call of the
371 function to the next.
373 You may also use <tt><ref id="pragma-static-locals"
374 name="#pragma static-locals"></tt> to change this setting in your
378 <label id="option-include-dir">
379 <tag><tt>-I dir, --include-dir dir</tt></tag>
381 Set a directory where the compiler searches for include files. You may
382 use this option multiple times to add more than one directory to the
386 <label id="option-O">
387 <tag><tt>-O, -Oi, -Or, -Os</tt></tag>
389 Enable an optimizer run over the produced code.
391 Using <tt/-Oi/, the code generator will inline some code where otherwise a
392 runtime functions would have been called, even if the generated code is
393 larger. This will not only remove the overhead for a function call, but will
394 make the code visible for the optimizer. <tt/-Oi/ is an alias for
395 <tt/-O --codesize 200/.
397 <tt/-Or/ will make the compiler honor the <tt/register/ keyword. Local
398 variables may be placed in registers (which are actually zero page
399 locations). See also the <tt/<ref id="option-register-vars"
400 name="--register-vars">/ command line option, and the <ref
401 id="register-vars" name="discussion of register variables"> below.
403 Using <tt/-Os/ will force the compiler to inline some known functions from
404 the C library like strlen. Note: This has two consequences:
407 <item>You may not use names of standard C functions in your own code. If you
408 do that, your program is not standard compliant anyway, but using
409 <tt/-Os/ will actually break things.
411 <item>The inlined string and memory functions will not handle strings or
412 memory areas larger than 255 bytes. Similarly, the inlined <tt/is..()/
413 functions will not work with values outside the char. range (such as
418 It is possible to concatenate the modifiers for <tt/-O/. For example, to
419 enable register variables and inlining of known functions, you may use
423 <tag><tt>-T, --add-source</tt></tag>
425 This include the source code as comments in the generated code. This is
429 <tag><tt>-V, --version</tt></tag>
431 Print the version number of the compiler. When submitting a bug report,
432 please include the operating system you're using, and the compiler
436 <label id="option-W">
437 <tag><tt>-W name[,name]</tt></tag>
439 This option allows to control warnings generated by the compiler. It is
440 followed by a comma separated list of warnings that should be enabled or
441 disabled. To disable a warning, its name is prefixed by a minus sign. If
442 no such prefix exists, or the name is prefixed by a plus sign, the warning
445 The following warning names are currently recognized:
447 <tag><tt/error/</tag>
448 Treat all warnings as errors.
449 <tag><tt/unknown-pragma/</tag>
450 Warn about known #pragmas.
451 <tag><tt/unused-label/</tag>
452 Warn about unused labels.
453 <tag><tt/unused-param/</tag>
454 Warn about unused function parameters.
455 <tag><tt/unused-var/</tag>
456 Warn about unused variables.
459 You may also use <tt><ref id="pragma-warn" name="#pragma warn"></tt> to
460 control this setting for smaller pieces of code from within your code.
465 <sect>Input and output<p>
467 The compiler will accept one C file per invocation and create a file with
468 the same base name, but with the extension replaced by ".s". The output
469 file contains assembler code suitable for the use with the ca65 macro
472 Include files in single quotes are searched in the following places:
474 <item>The current directory.
475 <item>The value of the environment variable <tt/CC65_INC/ if it is defined.
476 <item>Any directory added with the <tt/-I/ option on the command line.
479 Include files in angle brackets are searched in the following places:
481 <item>A compiled in directory which is often <tt>/usr/lib/cc65/include</tt> on
483 <item>The value of the environment variable <tt/CC65_INC/ if it is defined.
484 <item>A subdirectory named <tt/include/ of the directory defined in the
485 environment variable <tt/CC65_HOME/, if it is defined.
486 <item>Any directory added with the <tt/-I/ option on the command line.
491 <sect>Differences to the ISO standard<p>
493 Apart from the things listed below, the compiler does support additional
494 keywords, has several functions in the standard headers with names outside the
495 reserved namespace and a few syntax extensions. All these can be disabled with
496 the <tt><ref id="option--standard" name="--standard"></tt> command line
497 option. Its use for maximum standards compatibility is advised.
499 Here is a list of differences between the language, the compiler accepts,
500 and the one defined by the ISO standard:
504 <item> The datatypes "float" and "double" are not available.
506 <item> C Functions may not return structs (or unions), and structs may not
507 be passed as parameters by value. However, struct assignment *is*
510 <item> Part of the C library is available only with fastcall calling
511 conventions (see below). It means that you must not mix pointers to
512 those functions with pointers to user-written, not-fastcall functions.
514 <item> The <tt/volatile/ keyword doesn't have an effect. This is not as bad
515 as it sounds, since the 6502 has so few registers that it isn't
516 possible to keep values in registers anyway.
520 There may be some more minor differences I'm currently not aware of. The
521 biggest problem is the missing float data type. With this limitation in
522 mind, you should be able to write fairly portable code.
528 This cc65 version has some extensions to the ISO C standard.
532 <item> The compiler allows to insert assembler statements into the output
536 asm (<string literal>[, optional parameters]) ;
540 __asm__ (<string literal>[, optional parameters]) ;
543 The first form is in the user namespace and is disabled if the <tt/-A/
546 There is a whole section covering inline assembler statements,
547 <ref id="inline-asm" name="see there">.
550 <item> There is a special calling convention named "fastcall".
551 The syntax for a function declaration using fastcall is
554 <return type> fastcall <function name> (<parameter list>)
558 <return type> __fastcall__ <function name> (<parameter list>)
562 void __fastcall__ f (unsigned char c)
564 The first form of the fastcall keyword is in the user namespace and can
565 therefore be disabled with the <tt><ref id="option--standard"
566 name="--standard"></tt> command line option.
568 For functions declared as <tt/fastcall/, the rightmost parameter is not
569 pushed on the stack but left in the primary register when the function
570 is called. This will reduce the cost when calling assembler functions
571 significantly, especially when the function itself is rather small.
574 <item> There are two pseudo variables named <tt/__AX__/ and <tt/__EAX__/.
575 Both refer to the primary register that is used by the compiler to
576 evaluate expressions or return function results. <tt/__AX__/ is of
577 type <tt/unsigned int/ and <tt/__EAX__/ of type <tt/long unsigned int/
578 respectively. The pseudo variables may be used as lvalue and rvalue as
579 every other variable. They are most useful together with short
580 sequences of assembler code. For example, the macro
590 will give the high byte of any unsigned value.
593 <item> Inside a function, the identifier <tt/__func__/ gives the name of the
594 current function as a string. Outside of functions, <tt/__func__/ is
599 #define PRINT_DEBUG(s) printf ("%s: %s\n", __func__, s);
602 The macro will print the name of the current function plus a given
606 <item> cc65 allows the initialization of <tt/void/ variables. This may be
607 used to create variable structures that are more compatible with
608 interfaces written for assembler languages. Here is an example:
611 void GCmd = { (char)3, (unsigned)0x2000, (unsigned)0x3000 };
614 This will be translated as follows:
623 Since the variable is of type <tt/void/ you may not use it as is.
624 However, taking the address of the variable results in a <tt/void*/
625 which may be passed to any function expecting a pointer.
627 See the <url url="geos.html" name="GEOS library document"> for examples
628 on how to use this feature.
631 <item> cc65 implements flexible array struct members as defined in the C99 ISO
632 standard. As an extension, these fields may be initialized. There are
633 several exceptions, however (which is probably the reason why the
634 standard does not define this feature, because it is highly
635 unorthogonal). Flexible array members cannot be initialized ...
638 <item>... when defining an array of structs with flexible
640 <item>... if such a struct is a member field of another struct
641 which is not the last field.
642 <item>... if the struct which contains a flexible array member is
643 declared as <tt/register/, and the size and compiler settings
644 do allow the compiler actually to place the struct into the
645 register bank in the zero page.
648 Please note that -- as defined in the ISO C standard -- the <tt/sizeof/
649 operator returns the struct size with the flexible array member having
650 size zero, even if it is initialized.
657 <sect>Predefined macros<p>
659 The compiler defines several macros at startup:
663 <tag><tt>__CC65__</tt></tag>
665 This macro is always defined. Its value is the version number of the
666 compiler in hex. For example, version 2.10.1 of the compiler has this macro
667 defined as <tt/0x02A1/.
669 <tag><tt>__APPLE2__</tt></tag>
671 This macro is defined if the target is the Apple ][ (-t apple2).
673 <tag><tt>__APPLE2ENH__</tt></tag>
675 This macro is defined if the target is the enhanced Apple //e (-t apple2enh).
677 <tag><tt>__ATARI__</tt></tag>
679 This macro is defined if the target is one of the Atari computers
680 (400/800/130XL/800XL).
682 <tag><tt>__ATMOS__</tt></tag>
684 This macro is defined if the target is the Oric Atmos (-t atmos).
686 <tag><tt>__CBM__</tt></tag>
688 This macro is defined if the target system is one of the CBM targets.
690 <tag><tt>__C16__</tt></tag>
692 This macro is defined if the target is the c16 (-t c16).
694 <tag><tt>__C64__</tt></tag>
696 This macro is defined if the target is the c64 (-t c64).
698 <tag><tt>__C128__</tt></tag>
700 This macro is defined if the target is the c128 (-t c128).
702 <tag><tt>__CBM510__</tt></tag>
704 This macro is defined if the target is the CBM 500 series of computers.
706 <tag><tt>__CBM610__</tt></tag>
708 This macro is defined if the target is one of the CBM 600/700 family of
709 computers (called B series in the US).
711 <tag><tt>__GEOS__</tt></tag>
713 This macro is defined if you are compiling for the GEOS system (-t geos).
715 <tag><tt>__LUNIX__</tt></tag>
717 This macro is defined if you are compiling for the LUnix system (-t lunix).
719 <tag><tt>__LYNX__</tt></tag>
721 This macro is defined if the target is the Atari Lynx (-t lynx).
723 <tag><tt>__NES__</tt></tag>
725 This macro is defined if the target is the NES (-t nes).
727 <tag><tt>__PET__</tt></tag>
729 This macro is defined if the target is the PET family of computers (-t pet).
731 <tag><tt>__PLUS4__</tt></tag>
733 This macro is defined if the target is the plus/4 (-t plus4).
735 <tag><tt>__SUPERVISION__</tt></tag>
737 This macro is defined if the target is the supervision (-t supervision).
739 <tag><tt>__VIC20__</tt></tag>
741 This macro is defined if the target is the vic20 (-t vic20).
743 <tag><tt>__FILE__</tt></tag>
745 This macro expands to a string containing the name of the C source file.
747 <tag><tt>__LINE__</tt></tag>
749 This macro expands to the current line number.
751 <tag><tt>__CC65_STD__</tt></tag>
753 This macro is defined to one of the following depending on the <tt><ref
754 id="option--standard" name="--standard"></tt> command line option:
756 <item><tt/__CC65_STD_C89__/
757 <item><tt/__CC65_STD_C99__/
758 <item><tt/__CC65_STD_CC65__/
761 <tag><tt>__OPT__</tt></tag>
763 Is defined if the compiler was called with the <tt/-O/ command line option.
765 <tag><tt>__OPT_i__</tt></tag>
767 Is defined if the compiler was called with the <tt/-Oi/ command line option.
769 <tag><tt>__OPT_r__</tt></tag>
771 Is defined if the compiler was called with the <tt/-Or/ command line option.
773 <tag><tt>__OPT_s__</tt></tag>
775 Is defined if the compiler was called with the <tt/-Os/ command line option.
780 <sect>#pragmas<label id="pragmas"><p>
782 The compiler understands some pragmas that may be used to change code
783 generation and other stuff. Some of these pragmas understand a special form:
784 If the first parameter is <tt/push/, the old value is saved onto a stack
785 before changing it. The value may later be restored by using the <tt/pop/
786 parameter with the <tt/#pragma/.
788 <sect1><tt>#pragma bss-name ([push,] <name>)</tt><label id="pragma-bss-name"><p>
790 This pragma changes the name used for the BSS segment (the BSS segment
791 is used to store uninitialized data). The argument is a string enclosed
794 Note: The default linker configuration file does only map the standard
795 segments. If you use other segments, you have to create a new linker
798 Beware: The startup code will zero only the default BSS segment. If you
799 use another BSS segment, you have to do that yourself, otherwise
800 uninitialized variables do not have the value zero.
802 The <tt/#pragma/ understands the push and pop parameters as explained above.
806 #pragma bss-name ("MyBSS")
810 <sect1><tt>#pragma charmap (<index>, <code>)</tt><label id="pragma-charmap"><p>
812 Each literal string and each literal character in the source is translated
813 by use of a translation table. This translation table is preset when the
814 compiler is started depending on the target system, for example to map
815 ISO-8859-1 characters into PETSCII if the target is a commodore machine.
817 This pragma allows to change entries in the translation table, so the
818 translation for individual characters, or even the complete table may be
821 Both arguments are assumed to be unsigned characters with a valid range of
824 Beware of two pitfalls:
827 <item>The character index is actually the code of the character in the
828 C source, so character mappings do always depend on the source
829 character set. This means that <tt/#pragma charmap/ is not
830 portable -- it depends on the build environment.
831 <item>While it is possible to use character literals as indices, the
832 result may be somewhat unexpected, since character literals are
833 itself translated. For this reason I would suggest to avoid
834 character literals and use numeric character codes instead.
839 /* Use a space wherever an 'a' occurs in ISO-8859-1 source */
840 #pragma charmap (0x61, 0x20);
844 <sect1><tt>#pragma check-stack ([push,] on|off)</tt><label id="pragma-check-stack"><p>
846 Tells the compiler to insert calls to a stack checking subroutine to detect
847 stack overflows. The stack checking code will lead to somewhat larger and
848 slower programs, so you may want to use this pragma when debugging your
849 program and switch it off for the release version. If a stack overflow is
850 detected, the program is aborted.
852 If the argument is "off", stack checks are disabled (the default), otherwise
855 The <tt/#pragma/ understands the push and pop parameters as explained above.
857 <sect1><tt>#pragma code-name ([push,] <name>)</tt><label id="pragma-code-name"><p>
859 This pragma changes the name used for the CODE segment (the CODE segment
860 is used to store executable code). The argument is a string enclosed in
863 Note: The default linker configuration file does only map the standard
864 segments. If you use other segments, you have to create a new linker
867 The <tt/#pragma/ understands the push and pop parameters as explained above.
871 #pragma code-name ("MyCODE")
875 <sect1><tt>#pragma codesize ([push,] <int>)</tt><label id="pragma-codesize"><p>
877 This pragma allows finer control about speed vs. size decisions in the code
878 generation and optimization phase. It gives the allowed size increase factor
879 (in percent). The default is can be changed by use of the <tt/<ref
880 id="option-codesize" name="--codesize">/ compiler option.
882 The <tt/#pragma/ understands the push and pop parameters as explained above.
885 <sect1><tt>#pragma data-name ([push,] <name>)</tt><label id="pragma-data-name"><p>
887 This pragma changes the name used for the DATA segment (the DATA segment
888 is used to store initialized data). The argument is a string enclosed in
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 data-name ("MyDATA")
903 <sect1><tt>#pragma local-strings ([push,] on|off)</tt><label id="pragma-local-strings"><p>
905 When "on", emit string literals to the data segment when they're encountered
906 in the source. The default ("off") is to keep string literals until end of
907 assembly, merge read only literals if possible, and then output the literals
908 into the data or rodata segment that is active at that point.
910 Using this <tt/#pragma/ it is possible to control the behaviour from within
911 the source. When <tt/#pragma local-strings/ is active, string literals are
912 output immediately, which means that they go into the currently active data
913 or rodata segment, but cannot be merged. When inactive, string literals are
914 remembered and output as a whole when translation is finished.
917 <sect1><tt>#pragma optimize ([push,] on|off)</tt><label id="pragma-optimize"><p>
919 Switch optimization on or off. If the argument is "off", optimization is
920 disabled, otherwise it is enabled. Please note that this pragma only effects
921 whole functions. The setting in effect when the function is encountered will
922 determine if the generated code is optimized or not.
924 Optimization and code generation is also controlled by the <ref
925 id="pragma-codesize" name="codesize pragma">.
927 The default is "off", but may be changed with the <tt/<ref name="-O"
928 id="option-O">/ compiler option.
930 The <tt/#pragma/ understands the push and pop parameters as explained above.
933 <sect1><tt>#pragma rodata-name ([push,] <name>)</tt><label id="pragma-rodata-name"><p>
935 This pragma changes the name used for the RODATA segment (the RODATA
936 segment is used to store readonly data). The argument is a string
937 enclosed in double quotes.
939 Note: The default linker configuration file does only map the standard
940 segments. If you use other segments, you have to create a new linker
943 The <tt/#pragma/ understands the push and pop parameters as explained above.
947 #pragma rodata-name ("MyRODATA")
951 <sect1><tt>#pragma regvaraddr ([push,] on|off)</tt><label id="pragma-regvaraddr"><p>
953 The compiler does not allow to take the address of register variables.
954 The regvaraddr pragma changes this. Taking the address of a register
955 variable is allowed after using this pragma with "on" as argument.
956 Using "off" as an argument switches back to the default behaviour.
958 Beware: The C standard does not allow taking the address of a variable
959 declared as register. So your programs become non-portable if you use
960 this pragma. In addition, your program may not work. This is usually the
961 case if a subroutine is called with the address of a register variable,
962 and this subroutine (or a subroutine called from there) uses
963 register variables. So be careful with this #pragma.
965 The <tt/#pragma/ understands the push and pop parameters as explained above.
969 #pragma regvaraddr(on) /* Allow taking the address
970 * of register variables
975 <sect1><tt>#pragma register-vars ([push,] on|off)</tt><label id="pragma-register-vars"><p>
977 Enables or disables use of register variables. If register variables are
978 disabled (the default), the <tt/register/ keyword is ignored. Register
979 variables are explained in more detail in <ref id="register-vars" name="a separate
982 The <tt/#pragma/ understands the push and pop parameters as explained above.
985 <sect1><tt>#pragma signed-chars ([push,] on|off)</tt><label id="pragma-signed-chars"><p>
987 Changes the signedness of the default character type. If the argument is
988 "on", default characters are signed, otherwise characters are unsigned. The
989 compiler default is to make characters unsigned since this creates a lot
990 better code. This default may be overridden by the <tt/<ref
991 name="--signed-chars" id="option-signed-chars">/ command line option.
993 The <tt/#pragma/ understands the push and pop parameters as explained above.
996 <sect1><tt>#pragma static-locals ([push,] on|off)</tt><label id="pragma-static-locals"<p>
998 Use variables in the bss segment instead of variables on the stack. This
999 pragma changes the default set by the compiler option <tt/<ref
1000 name="--static-locals" id="option-static-locals">/. If the argument is "on",
1001 local variables are allocated in the BSS segment, leading to shorter and in
1002 most cases faster, but non-reentrant code.
1004 The <tt/#pragma/ understands the push and pop parameters as explained above.
1007 <sect1><tt>#pragma warn (name, [push,] on|off)</tt><label id="pragma-warn"><p>
1009 Switch compiler warnings on or off. "name" is the name of a warning (see the
1010 <tt/<ref name="-W" id="option-W">/ compiler option for a list). The name is
1011 either followed by "pop", which restores the last pushed state, or by "on" or
1012 "off", optionally preceeded by "push" to push the current state before
1017 /* Don't warn about the unused parameter in function func */
1018 #pragma warn (unused-param, push, off)
1019 static int func (int unused)
1023 #pragma warn (unused-param, pop)
1026 <sect1><tt>#pragma writable-strings ([push,] on|off)</tt><label id="pragma-writable-strings"><p>
1028 Changes the storage location of string literals. For historical reasons,
1029 the C standard defines that string literals are of type "char[]", but
1030 writing to such a literal causes undefined behaviour. Most compilers
1031 (including cc65) place string literals in the read-only data segment, which
1032 may cause problems with old C code that writes to string literals.
1034 Using this pragma (or the corresponding command line option <tt/<ref
1035 name="--writable-strings" id="option-writable-strings">/) causes the
1036 literals to be placed in the data segment so they can be written to without
1039 The <tt/#pragma/ understands the push and pop parameters as explained above.
1042 <sect1><tt>#pragma zpsym (<name>)</tt><p>
1044 Tell the compiler that the -- previously as external declared -- symbol with
1045 the given name is a zero page symbol (usually from an assembler file).
1046 The compiler will create a matching import declaration for the assembler.
1051 #pragma zpsym ("foo"); /* foo is in the zeropage */
1057 <sect>Register variables<label id="register-vars"><p>
1059 The runtime for all supported platforms has 6 bytes of zero page space
1060 available for register variables (this could be increased, but I think it's a
1061 good value). So you can declare register variables up to a total size of 6 per
1062 function. The compiler will allocate register space on a "first come, first
1063 served" base and convert any <tt/register/ declarations that exceed the
1064 available register space silently to <tt/auto/. Parameters can also be
1065 declared as <tt/register/, this will in fact give slightly shorter code than
1066 using a register variable.
1068 Since a function must save the current values of the registers on entry and
1069 restore them on exit, there is an overhead associated with register variables,
1070 and this overhead is quite high (about 20 bytes per variable). This means that
1071 just declaring anything as <tt/register/ is not a good idea.
1073 The best use for register variables are pointers, especially those that point
1074 to structures. The magic number here is about 3 uses of a struct field: If the
1075 function contains this number or even more, the generated code will be usually
1076 shorter and faster when using a register variable for the struct pointer. The
1077 reason for this is that the register variable can in many cases be used as a
1078 pointer directly. Having a pointer in an auto variable means that this pointer
1079 must first be copied into a zero page location, before it can be dereferenced.
1081 Second best use for register variables are counters. However, there is not
1082 much difference in the code generated for counters, so you will need at least
1083 100 operations on this variable (for example in a loop) to make it worth the
1084 trouble. The only savings you get here are by the use of a zero page variable
1085 instead of one on the stack or in the data segment.
1087 Register variables must be explicitly enabled, either by using <tt/<ref
1088 name="-Or" id="option-O">/ or <tt/<ref name="--register-vars"
1089 id="option-register-vars">/ on the command line or by use of <tt/<ref
1090 name="#pragma register-vars" id="pragma-register-vars">/. Register variables
1091 are only accepted on function top level, register variables declared in
1092 interior blocks are silently converted to <tt/auto/. With register variables
1093 disabled, all variables declared as <tt/register/ are actually auto variables.
1095 Please take care when using register variables: While they are helpful and can
1096 lead to a tremendous speedup when used correctly, improper usage will cause
1097 bloated code and a slowdown.
1101 <sect>Inline assembler<label id="inline-asm"><p>
1103 The compiler allows to insert assembler statements into the output file. The
1107 asm (<string literal>[, optional parameters]) ;
1111 __asm__ (<string literal>[, optional parameters]) ;
1115 The first form is in the user namespace and is disabled by <tt><ref
1116 id="option--standard" name="--standard"></tt> if the argument is not <tt/cc65/.
1118 The asm statement may be used inside a function and on global file level. An
1119 inline assembler statement is a primary expression, so it may also be used as
1120 part of an expression. Please note however that the result of an expression
1121 containing just an inline assembler statement is always of type <tt/void/.
1123 The contents of the string literal are preparsed by the compiler and inserted
1124 into the generated assembly output, so that the can be further processed by
1125 the backend and especially the optimizer. For this reason, the compiler does
1126 only allow regular 6502 opcodes to be used with the inline assembler. Pseudo
1127 instructions (like <tt/.import/, <tt/.byte/ and so on) are <em/not/ allowed,
1128 even if the ca65 assembler (which is used to translate the generated assembler
1129 code) would accept them. The builtin inline assembler is not a replacement for
1130 the full blown macro assembler which comes with the compiler.
1132 Note: Inline assembler statements are subject to all optimizations done by the
1133 compiler. There is currently no way to protect an inline assembler statement
1134 from being moved or removed completely by the optimizer. If in doubt, check
1135 the generated assembler output, or disable optimizations.
1137 The string literal may contain format specifiers from the following list. For
1138 each format specifier, an argument is expected which is inserted instead of
1139 the format specifier before passing the assembly code line to the backend.
1142 <item><tt/%b/ - Numerical 8-bit value
1143 <item><tt/%w/ - Numerical 16-bit value
1144 <item><tt/%l/ - Numerical 32-bit value
1145 <item><tt/%v/ - Assembler name of a (global) variable or function
1146 <item><tt/%o/ - Stack offset of a (local) variable
1147 <item><tt/%g/ - Assembler name of a C label
1148 <item><tt/%s/ - The argument is converted to a string
1149 <item><tt/%%/ - The % sign itself
1152 Using these format specifiers, you can access C <tt/#defines/, variables or
1153 similar stuff from the inline assembler. For example, to load the value of
1154 a C <tt/#define/ into the Y register, one would use
1158 __asm__ ("ldy #%b", OFFS);
1161 Or, to access a struct member of a static variable:
1167 unsigned char color;
1169 static pixel_t pixel;
1170 __asm__ ("ldy #%b", offsetof(pixel_t, color));
1171 __asm__ ("lda %v,y", pixel);
1175 Note: Do not embed the assembler labels that are used as names of global
1176 variables or functions into your asm statements. Code like this
1180 int bar () { return 1; }
1181 __asm__ ("lda _foo"); /* DON'T DO THAT! */
1183 __asm__ ("jsr _bar"); /* DON'T DO THAT EITHER! */
1187 may stop working if the way, the compiler generates these names is changed in
1188 a future version. Instead use the format specifiers from the table above:
1191 __asm__ ("lda %v", foo); /* OK */
1193 __asm__ ("jsr %v", bar); /* OK */
1198 <sect>Implementation-defined behavior<p>
1200 This section describes the behavior of cc65 when the standard describes the
1201 behavior as implementation-defined.
1205 <sect>Bugs/Feedback<p>
1207 If you have problems using the compiler, if you find any bugs, or if you're
1208 doing something interesting with it, I would be glad to hear from you. Feel
1209 free to contact me by email (<htmlurl url="mailto:uz@cc65.org"
1210 name="uz@cc65.org">).
1216 This is the original compiler copyright:
1219 --------------------------------------------------------------------------
1222 This is the copyright notice for RA65, LINK65, LIBR65, and other
1223 Atari 8-bit programs. Said programs are Copyright 1989, by John R.
1224 Dunning. All rights reserved, with the following exceptions:
1226 Anyone may copy or redistribute these programs, provided that:
1228 1: You don't charge anything for the copy. It is permissable to
1229 charge a nominal fee for media, etc.
1231 2: All source code and documentation for the programs is made
1232 available as part of the distribution.
1234 3: This copyright notice is preserved verbatim, and included in
1237 You are allowed to modify these programs, and redistribute the
1238 modified versions, provided that the modifications are clearly noted.
1240 There is NO WARRANTY with this software, it comes as is, and is
1241 distributed in the hope that it may be useful.
1243 This copyright notice applies to any program which contains
1244 this text, or the refers to this file.
1246 This copyright notice is based on the one published by the Free
1247 Software Foundation, sometimes known as the GNU project. The idea
1248 is the same as theirs, ie the software is free, and is intended to
1249 stay that way. Everybody has the right to copy, modify, and re-
1250 distribute this software. Nobody has the right to prevent anyone
1251 else from copying, modifying or redistributing it.
1253 --------------------------------------------------------------------------
1256 Small parts of the compiler (parts of the preprocessor and main parser) are
1257 still covered by this copyright. The main portion is covered by the usual
1258 cc65 license, which reads:
1260 This software is provided 'as-is', without any expressed or implied
1261 warranty. In no event will the authors be held liable for any damages
1262 arising from the use of this software.
1264 Permission is granted to anyone to use this software for any purpose,
1265 including commercial applications, and to alter it and redistribute it
1266 freely, subject to the following restrictions:
1269 <item> The origin of this software must not be misrepresented; you must not
1270 claim that you wrote the original software. If you use this software
1271 in a product, an acknowledgment in the product documentation would be
1272 appreciated but is not required.
1273 <item> Altered source versions must be plainly marked as such, and must not
1274 be misrepresented as being the original software.
1275 <item> This notice may not be removed or altered from any source