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 --local-strings Emit string literals immediately
88 --register-space b Set space available for register variables
89 --register-vars Enable register variables
90 --rodata-name seg Set the name of the RODATA segment
91 --signed-chars Default characters are signed
92 --standard std Language standard (c89, c99, cc65)
93 --static-locals Make local variables static
94 --target sys Set the target system
95 --verbose Increase verbosity
96 --version Print the compiler version number
97 --writable-strings Make string literals writable
98 ---------------------------------------------------------------------------
102 <sect1>Command line options in detail<p>
104 Here is a description of all the command line options:
108 <label id="option-bss-name">
109 <tag><tt>--bss-name seg</tt></tag>
111 Set the name of the bss segment. See also <tt/<ref id="pragma-bss-name"
112 name="#pragma bss-name">/.
115 <label id="option-check-stack">
116 <tag><tt>--check-stack</tt></tag>
118 Tells the compiler to generate code that checks for stack overflows. See
119 <tt/<ref id="pragma-check-stack" name="#pragma check-stack">/ for an
120 explanation of this feature.
123 <label id="option-code-name">
124 <tag><tt>--code-name seg</tt></tag>
126 Set the name of the code segment. See also <tt/<ref id="pragma-code-name"
127 name="#pragma code-name">/
130 <label id="option-codesize">
131 <tag><tt>--codesize x</tt></tag>
133 This options allows finer control about speed vs. size decisions in the code
134 generation and optimization phases. It gives the allowed size increase
135 factor (in percent). The default is 100 when not using <tt/-Oi/ and 200 when
136 using <tt/-Oi/ (<tt/-Oi/ is the same as <tt/-O --codesize 200/).
139 <label id="option-cpu">
140 <tag><tt>--cpu CPU</tt></tag>
142 A new, still experimental option. You may specify "6502" or "65C02" as
143 the CPU. 6502 is the default, so this will not change anything.
144 Specifying 65C02 will use a few 65C02 instructions when generating code.
145 Don't expect too much from this option: It is still new (and may have
146 bugs), and the additional instructions for the 65C02 are not that
150 <label id="option-create-dep">
151 <tag><tt>--create-dep</tt></tag>
153 Tells the compiler to generate a file containing the dependency list for
154 the compiled module in makefile syntax. The file is named as the C input
155 file with the extension replaced by <tt/.u/.
158 <label id="option-data-name">
159 <tag><tt>--data-name seg</tt></tag>
161 Set the name of the data segment. See also <tt/<ref id="pragma-data-name"
162 name="#pragma data-name">/
165 <tag><tt>-d, --debug</tt></tag>
167 Enables debug mode, something that should not be needed for mere
171 <tag><tt>-D sym[=definition]</tt></tag>
173 Define a macro on the command line. If no definition is given, the macro
174 is defined to the value "1".
177 <tag><tt>--forget-inc-paths</tt></tag>
179 Forget the builtin include paths. This is most useful when building
180 customized C or runtime libraries, in which case the standard header
181 files should be ignored.
184 <tag><tt>-g, --debug-info</tt></tag>
186 This will cause the compiler to insert a <tt/.DEBUGINFO/ command into the
187 generated assembler code. This will cause the assembler to include all
188 symbols in a special section in the object file.
191 <tag><tt>-h, --help</tt></tag>
193 Print the short option summary shown above.
196 <label id="option-local-strings">
197 <tag><tt>--local-strings</tt></tag>
199 Emit string literals to the data segment when they're encountered in the
200 source. The default is to keep string literals until end of assembly, merge
201 read only literals if possible, and then output the literals into the data
202 or rodata segment that is active at that point. Use of this option prevents
203 merging of duplicate strings, but the options that change the name of one of
204 the data segments will work.
206 You can also use <tt><ref id="pragma-local-strings"
207 name="#pragma local-strings"></tt> for fine grained control.
210 <tag><tt>-o name</tt></tag>
212 Specify the name of the output file. If you don't specify a name, the
213 name of the C input file is used, with the extension replaced by ".s".
216 <label id="option-register-vars">
217 <tag><tt>-r, --register-vars</tt></tag>
219 <tt/-r/ will make the compiler honor the <tt/register/ keyword. Local
220 variables may be placed in registers (which are actually zero page
221 locations). There is some overhead involved with register variables, since
222 the old contents of the registers must be saved and restored. Since register
223 variables are of limited use without the optimizer, there is also a combined
224 switch: <tt/-Or/ will enable both, the optimizer and register variables.
226 For more information about register variables see <ref id="register-vars"
227 name="register variables">.
229 The compiler setting can also be changed within the source file by using
230 <tt/<ref id="pragma-register-vars" name="#pragma register-vars">/.
233 <label id="option-register-space">
234 <tag><tt>--register-space</tt></tag>
236 This option takes a numeric parameter and is used to specify, how much
237 zero page register space is available. Please note that just giving this
238 option will not increase or decrease by itself, it will just tell the
239 compiler about the available space. You will have to allocate that space
240 yourself using an assembler module with the necessary allocations, and a
241 linker configuration that matches the assembler module. The default value
242 for this option is 6 (bytes).
244 If you don't know what all this means, please don't use this option.
247 <label id="option-rodata-name">
248 <tag><tt>--rodata-name seg</tt></tag>
250 Set the name of the rodata segment (the segment used for readonly data).
251 See also <tt/<ref id="pragma-rodata-name" name="#pragma rodata-name">/
253 <label id="option-signed-chars">
254 <tag><tt>-j, --signed-chars</tt></tag>
256 Using this option, you can make the default characters signed. Since the
257 6502 has no provisions for sign extending characters (which is needed on
258 almost any load operation), this will make the code larger and slower. A
259 better way is to declare characters explicitly as "signed" if needed. You
260 can also use <tt><ref id="pragma-signed-chars"
261 name="#pragma signed-chars"></tt> for better control of this option.
264 <label id="option--standard">
265 <tag><tt>--standard std</tt></tag>
267 This option allows to set the language standard supported. The argument is
275 Please note that the compiler does not support the c99 standard and never
276 will. c99 mode is actually c89 mode with a few selected c99 extensions
277 (// comments for example).
280 <label id="option-standard">
281 <tag><tt>-t target, --target target</tt></tag>
283 This option is used to set the target system. The target system
284 determines things like the character set that is used for strings and
285 character constants. The following target systems are supported:
293 <item>c16 (works also for the c116 with memory up to 32K)
296 <item>cbm510 (CBM-II series with 40 column video)
297 <item>cbm610 (all CBM-II II computers with 80 column video)
302 <item>pet (all CBM PET systems except the 2001)
308 <tag><tt>-v, --verbose</tt></tag>
310 Using this option, the compiler will be somewhat more verbose if errors
311 or warnings are encountered.
314 <label id="option-writable-strings">
315 <tag><tt>--writable-strings</tt></tag>
317 Make string literals writable by placing them into the data segment instead
318 of the rodata segment. You can also use <tt><ref id="pragma-writable-strings"
319 name="#pragma writable-strings"></tt> to control this option from within
323 <label id="option-static-locals">
324 <tag><tt>-Cl, --static-locals</tt></tag>
326 Use static storage for local variables instead of storage on the stack.
327 Since the stack is emulated in software, this gives shorter and usually
328 faster code, but the code is no longer reentrant. The difference between
329 <tt/-Cl/ and declaring local variables as static yourself is, that
330 initializer code is executed each time, the function is entered. So when
341 the variable <tt/a/ will always have the value <tt/1/ when entering the
342 function and using <tt/-Cl/, while in
347 static unsigned a = 1;
352 the variable <tt/a/ will have the value <tt/1/ only the first time that the
353 function is entered, and will keep the old value from one call of the
354 function to the next.
356 You may also use <tt><ref id="pragma-static-locals"
357 name="#pragma static-locals"></tt> to change this setting in your
361 <label id="option-include-dir">
362 <tag><tt>-I dir, --include-dir dir</tt></tag>
364 Set a directory where the compiler searches for include files. You may
365 use this option multiple times to add more than one directory to the
369 <label id="option-O">
370 <tag><tt>-O, -Oi, -Or, -Os</tt></tag>
372 Enable an optimizer run over the produced code.
374 Using <tt/-Oi/, the code generator will inline some code where otherwise a
375 runtime functions would have been called, even if the generated code is
376 larger. This will not only remove the overhead for a function call, but will
377 make the code visible for the optimizer. <tt/-Oi/ is an alias for
378 <tt/-O --codesize 200/.
380 <tt/-Or/ will make the compiler honor the <tt/register/ keyword. Local
381 variables may be placed in registers (which are actually zero page
382 locations). See also the <tt/<ref id="option-register-vars"
383 name="--register-vars">/ command line option, and the <ref
384 id="register-vars" name="discussion of register variables"> below.
386 Using <tt/-Os/ will force the compiler to inline some known functions from
387 the C library like strlen. Note: This has two consequences:
390 <item>You may not use names of standard C functions in your own code. If you
391 do that, your program is not standard compliant anyway, but using
392 <tt/-Os/ will actually break things.
394 <item>The inlined string and memory functions will not handle strings or
395 memory areas larger than 255 bytes. Similarly, the inlined <tt/is..()/
396 functions will not work with values outside the char. range (such as
401 It is possible to concatenate the modifiers for <tt/-O/. For example, to
402 enable register variables and inlining of known functions, you may use
406 <tag><tt>-T, --add-source</tt></tag>
408 This include the source code as comments in the generated code. This is
412 <tag><tt>-V, --version</tt></tag>
414 Print the version number of the compiler. When submitting a bug report,
415 please include the operating system you're using, and the compiler
419 <label id="option-W">
420 <tag><tt>-W name[,name]</tt></tag>
422 This option allows to control warnings generated by the compiler. It is
423 followed by a comma separated list of warnings that should be enabled or
424 disabled. To disable a warning, its name is prefixed by a minus sign. If
425 no such prefix exists, or the name is prefixed by a plus sign, the warning
428 The following warning names are currently recognized:
430 <tag><tt/error/</tag>
431 Treat all warnings as errors.
432 <tag><tt/unknown-pragma/</tag>
433 Warn about known #pragmas.
434 <tag><tt/unused-label/</tag>
435 Warn about unused labels.
436 <tag><tt/unused-param/</tag>
437 Warn about unused function parameters.
438 <tag><tt/unused-var/</tag>
439 Warn about unused variables.
442 You may also use <tt><ref id="pragma-warn" name="#pragma warn"></tt> to
443 control this setting for smaller pieces of code from within your code.
448 <sect>Input and output<p>
450 The compiler will accept one C file per invocation and create a file with
451 the same base name, but with the extension replaced by ".s". The output
452 file contains assembler code suitable for the use with the ca65 macro
455 Include files in single quotes are searched in the following places:
457 <item>The current directory.
458 <item>The value of the environment variable <tt/CC65_INC/ if it is defined.
459 <item>Any directory added with the <tt/-I/ option on the command line.
462 Include files in angle brackets are searched in the following places:
464 <item>A compiled in directory which is often <tt>/usr/lib/cc65/include</tt> on
466 <item>The value of the environment variable <tt/CC65_INC/ if it is defined.
467 <item>A subdirectory named <tt/include/ of the directory defined in the
468 environment variable <tt/CC65_HOME/, if it is defined.
469 <item>Any directory added with the <tt/-I/ option on the command line.
474 <sect>Differences to the ISO standard<p>
476 Apart from the things listed below, the compiler does support additional
477 keywords, has several functions in the standard headers with names outside the
478 reserved namespace and a few syntax extensions. All these can be disabled with
479 the <tt><ref id="option--standard" name="--standard"></tt> command line
480 option. Its use for maximum standards compatibility is advised.
482 Here is a list of differences between the language, the compiler accepts,
483 and the one defined by the ISO standard:
487 <item> The datatypes "float" and "double" are not available.
489 <item> C Functions may not return structs (or unions), and structs may not
490 be passed as parameters by value. However, struct assignment *is*
493 <item> Part of the C library is available only with fastcall calling
494 conventions (see below). It means that you must not mix pointers to
495 those functions with pointers to user-written, not-fastcall functions.
497 <item> The <tt/volatile/ keyword doesn't have an effect. This is not as bad
498 as it sounds, since the 6502 has so few registers that it isn't
499 possible to keep values in registers anyway.
503 There may be some more minor differences I'm currently not aware of. The
504 biggest problem is the missing float data type. With this limitation in
505 mind, you should be able to write fairly portable code.
511 This cc65 version has some extensions to the ISO C standard.
515 <item> The compiler allows to insert assembler statements into the output
519 asm (<string literal>[, optional parameters]) ;
523 __asm__ (<string literal>[, optional parameters]) ;
526 The first form is in the user namespace and is disabled if the <tt/-A/
529 There is a whole section covering inline assembler statements,
530 <ref id="inline-asm" name="see there">.
533 <item> There is a special calling convention named "fastcall".
534 The syntax for a function declaration using fastcall is
537 <return type> fastcall <function name> (<parameter list>)
541 <return type> __fastcall__ <function name> (<parameter list>)
545 void __fastcall__ f (unsigned char c)
547 The first form of the fastcall keyword is in the user namespace and can
548 therefore be disabled with the <tt><ref id="option--standard"
549 name="--standard"></tt> command line option.
551 For functions declared as <tt/fastcall/, the rightmost parameter is not
552 pushed on the stack but left in the primary register when the function
553 is called. This will reduce the cost when calling assembler functions
554 significantly, especially when the function itself is rather small.
557 <item> There are two pseudo variables named <tt/__AX__/ and <tt/__EAX__/.
558 Both refer to the primary register that is used by the compiler to
559 evaluate expressions or return function results. <tt/__AX__/ is of
560 type <tt/unsigned int/ and <tt/__EAX__/ of type <tt/long unsigned int/
561 respectively. The pseudo variables may be used as lvalue and rvalue as
562 every other variable. They are most useful together with short
563 sequences of assembler code. For example, the macro
573 will give the high byte of any unsigned value.
576 <item> Inside a function, the identifier <tt/__func__/ gives the name of the
577 current function as a string. Outside of functions, <tt/__func__/ is
582 #define PRINT_DEBUG(s) printf ("%s: %s\n", __func__, s);
585 The macro will print the name of the current function plus a given
589 <item> cc65 allows the initialization of <tt/void/ variables. This may be
590 used to create variable structures that are more compatible with
591 interfaces written for assembler languages. Here is an example:
594 void GCmd = { (char)3, (unsigned)0x2000, (unsigned)0x3000 };
597 This will be translated as follows:
606 Since the variable is of type <tt/void/ you may not use it as is.
607 However, taking the address of the variable results in a <tt/void*/
608 which may be passed to any function expecting a pointer.
610 See the <url url="geos.html" name="GEOS library document"> for examples
611 on how to use this feature.
614 <item> cc65 implements flexible array struct members as defined in the C99 ISO
615 standard. As an extension, these fields may be initialized. There are
616 several exceptions, however (which is probably the reason why the
617 standard does not define this feature, because it is highly
618 unorthogonal). Flexible array members cannot be initialized ...
621 <item>... when defining an array of structs with flexible
623 <item>... if such a struct is a member field of another struct
624 which is not the last field.
625 <item>... if the struct which contains a flexible array member is
626 declared as <tt/register/, and the size and compiler settings
627 do allow the compiler actually to place the struct into the
628 register bank in the zero page.
631 Please note that -- as defined in the ISO C standard -- the <tt/sizeof/
632 operator returns the struct size with the flexible array member having
633 size zero, even if it is initialized.
640 <sect>Predefined macros<p>
642 The compiler defines several macros at startup:
646 <tag><tt>__CC65__</tt></tag>
648 This macro is always defined. Its value is the version number of the
649 compiler in hex. For example, version 2.10.1 of the compiler has this macro
650 defined as <tt/0x02A1/.
652 <tag><tt>__APPLE2__</tt></tag>
654 This macro is defined if the target is the Apple ][ (-t apple2).
656 <tag><tt>__APPLE2ENH__</tt></tag>
658 This macro is defined if the target is the enhanced Apple //e (-t apple2enh).
660 <tag><tt>__ATARI__</tt></tag>
662 This macro is defined if the target is one of the Atari computers
663 (400/800/130XL/800XL).
665 <tag><tt>__ATMOS__</tt></tag>
667 This macro is defined if the target is the Oric Atmos (-t atmos).
669 <tag><tt>__CBM__</tt></tag>
671 This macro is defined if the target system is one of the CBM targets.
673 <tag><tt>__C16__</tt></tag>
675 This macro is defined if the target is the c16 (-t c16).
677 <tag><tt>__C64__</tt></tag>
679 This macro is defined if the target is the c64 (-t c64).
681 <tag><tt>__C128__</tt></tag>
683 This macro is defined if the target is the c128 (-t c128).
685 <tag><tt>__CBM510__</tt></tag>
687 This macro is defined if the target is the CBM 500 series of computers.
689 <tag><tt>__CBM610__</tt></tag>
691 This macro is defined if the target is one of the CBM 600/700 family of
692 computers (called B series in the US).
694 <tag><tt>__GEOS__</tt></tag>
696 This macro is defined if you are compiling for the GEOS system (-t geos).
698 <tag><tt>__LUNIX__</tt></tag>
700 This macro is defined if you are compiling for the LUnix system (-t lunix).
702 <tag><tt>__LYNX__</tt></tag>
704 This macro is defined if the target is the Atari Lynx (-t lynx).
706 <tag><tt>__NES__</tt></tag>
708 This macro is defined if the target is the NES (-t nes).
710 <tag><tt>__PET__</tt></tag>
712 This macro is defined if the target is the PET family of computers (-t pet).
714 <tag><tt>__PLUS4__</tt></tag>
716 This macro is defined if the target is the plus/4 (-t plus4).
718 <tag><tt>__SUPERVISION__</tt></tag>
720 This macro is defined if the target is the supervision (-t supervision).
722 <tag><tt>__VIC20__</tt></tag>
724 This macro is defined if the target is the vic20 (-t vic20).
726 <tag><tt>__FILE__</tt></tag>
728 This macro expands to a string containing the name of the C source file.
730 <tag><tt>__LINE__</tt></tag>
732 This macro expands to the current line number.
734 <tag><tt>__CC65_STD__</tt></tag>
736 This macro is defined to one of the following depending on the <tt><ref
737 id="option--standard" name="--standard"></tt> command line option:
739 <item><tt/__CC65_STD_C89__/
740 <item><tt/__CC65_STD_C99__/
741 <item><tt/__CC65_STD_CC65__/
744 <tag><tt>__OPT__</tt></tag>
746 Is defined if the compiler was called with the <tt/-O/ command line option.
748 <tag><tt>__OPT_i__</tt></tag>
750 Is defined if the compiler was called with the <tt/-Oi/ command line option.
752 <tag><tt>__OPT_r__</tt></tag>
754 Is defined if the compiler was called with the <tt/-Or/ command line option.
756 <tag><tt>__OPT_s__</tt></tag>
758 Is defined if the compiler was called with the <tt/-Os/ command line option.
763 <sect>#pragmas<label id="pragmas"><p>
765 The compiler understands some pragmas that may be used to change code
766 generation and other stuff. Some of these pragmas understand a special form:
767 If the first parameter is <tt/push/, the old value is saved onto a stack
768 before changing it. The value may later be restored by using the <tt/pop/
769 parameter with the <tt/#pragma/.
771 <sect1><tt>#pragma bss-name ([push,] <name>)</tt><label id="pragma-bss-name"><p>
773 This pragma changes the name used for the BSS segment (the BSS segment
774 is used to store uninitialized data). The argument is a string enclosed
777 Note: The default linker configuration file does only map the standard
778 segments. If you use other segments, you have to create a new linker
781 Beware: The startup code will zero only the default BSS segment. If you
782 use another BSS segment, you have to do that yourself, otherwise
783 uninitialized variables do not have the value zero.
785 The <tt/#pragma/ understands the push and pop parameters as explained above.
789 #pragma bss-name ("MyBSS")
793 <sect1><tt>#pragma charmap (<index>, <code>)</tt><label id="pragma-charmap"><p>
795 Each literal string and each literal character in the source is translated
796 by use of a translation table. This translation table is preset when the
797 compiler is started depending on the target system, for example to map
798 ISO-8859-1 characters into PETSCII if the target is a commodore machine.
800 This pragma allows to change entries in the translation table, so the
801 translation for individual characters, or even the complete table may be
804 Both arguments are assumed to be unsigned characters with a valid range of
807 Beware of two pitfalls:
810 <item>The character index is actually the code of the character in the
811 C source, so character mappings do always depend on the source
812 character set. This means that <tt/#pragma charmap/ is not
813 portable -- it depends on the build environment.
814 <item>While it is possible to use character literals as indices, the
815 result may be somewhat unexpected, since character literals are
816 itself translated. For this reason I would suggest to avoid
817 character literals and use numeric character codes instead.
822 /* Use a space wherever an 'a' occurs in ISO-8859-1 source */
823 #pragma charmap (0x61, 0x20);
827 <sect1><tt>#pragma check-stack ([push,] on|off)</tt><label id="pragma-check-stack"><p>
829 Tells the compiler to insert calls to a stack checking subroutine to detect
830 stack overflows. The stack checking code will lead to somewhat larger and
831 slower programs, so you may want to use this pragma when debugging your
832 program and switch it off for the release version. If a stack overflow is
833 detected, the program is aborted.
835 If the argument is "off", stack checks are disabled (the default), otherwise
838 The <tt/#pragma/ understands the push and pop parameters as explained above.
840 <sect1><tt>#pragma code-name ([push,] <name>)</tt><label id="pragma-code-name"><p>
842 This pragma changes the name used for the CODE segment (the CODE segment
843 is used to store executable code). The argument is a string enclosed in
846 Note: The default linker configuration file does only map the standard
847 segments. If you use other segments, you have to create a new linker
850 The <tt/#pragma/ understands the push and pop parameters as explained above.
854 #pragma code-name ("MyCODE")
858 <sect1><tt>#pragma codesize ([push,] <int>)</tt><label id="pragma-codesize"><p>
860 This pragma allows finer control about speed vs. size decisions in the code
861 generation and optimization phase. It gives the allowed size increase factor
862 (in percent). The default is can be changed by use of the <tt/<ref
863 id="option-codesize" name="--codesize">/ compiler option.
865 The <tt/#pragma/ understands the push and pop parameters as explained above.
868 <sect1><tt>#pragma data-name ([push,] <name>)</tt><label id="pragma-data-name"><p>
870 This pragma changes the name used for the DATA segment (the DATA segment
871 is used to store initialized data). The argument is a string enclosed in
874 Note: The default linker configuration file does only map the standard
875 segments. If you use other segments, you have to create a new linker
878 The <tt/#pragma/ understands the push and pop parameters as explained above.
882 #pragma data-name ("MyDATA")
886 <sect1><tt>#pragma local-strings ([push,] on|off)</tt><label id="pragma-local-strings"><p>
888 When "on", emit string literals to the data segment when they're encountered
889 in the source. The default ("off") is to keep string literals until end of
890 assembly, merge read only literals if possible, and then output the literals
891 into the data or rodata segment that is active at that point.
893 Using this <tt/#pragma/ it is possible to control the behaviour from within
894 the source. When <tt/#pragma local-strings/ is active, string literals are
895 output immediately, which means that they go into the currently active data
896 or rodata segment, but cannot be merged. When inactive, string literals are
897 remembered and output as a whole when translation is finished.
900 <sect1><tt>#pragma optimize ([push,] on|off)</tt><label id="pragma-optimize"><p>
902 Switch optimization on or off. If the argument is "off", optimization is
903 disabled, otherwise it is enabled. Please note that this pragma only effects
904 whole functions. The setting in effect when the function is encountered will
905 determine if the generated code is optimized or not.
907 Optimization and code generation is also controlled by the <ref
908 id="pragma-codesize" name="codesize pragma">.
910 The default is "off", but may be changed with the <tt/<ref name="-O"
911 id="option-O">/ compiler option.
913 The <tt/#pragma/ understands the push and pop parameters as explained above.
916 <sect1><tt>#pragma rodata-name ([push,] <name>)</tt><label id="pragma-rodata-name"><p>
918 This pragma changes the name used for the RODATA segment (the RODATA
919 segment is used to store readonly data). The argument is a string
920 enclosed in double quotes.
922 Note: The default linker configuration file does only map the standard
923 segments. If you use other segments, you have to create a new linker
926 The <tt/#pragma/ understands the push and pop parameters as explained above.
930 #pragma rodata-name ("MyRODATA")
934 <sect1><tt>#pragma regvaraddr ([push,] on|off)</tt><label id="pragma-regvaraddr"><p>
936 The compiler does not allow to take the address of register variables.
937 The regvaraddr pragma changes this. Taking the address of a register
938 variable is allowed after using this pragma with "on" as argument.
939 Using "off" as an argument switches back to the default behaviour.
941 Beware: The C standard does not allow taking the address of a variable
942 declared as register. So your programs become non-portable if you use
943 this pragma. In addition, your program may not work. This is usually the
944 case if a subroutine is called with the address of a register variable,
945 and this subroutine (or a subroutine called from there) uses
946 register variables. So be careful with this #pragma.
948 The <tt/#pragma/ understands the push and pop parameters as explained above.
952 #pragma regvaraddr(on) /* Allow taking the address
953 * of register variables
958 <sect1><tt>#pragma register-vars ([push,] on|off)</tt><label id="pragma-register-vars"><p>
960 Enables or disables use of register variables. If register variables are
961 disabled (the default), the <tt/register/ keyword is ignored. Register
962 variables are explained in more detail in <ref id="register-vars" name="a separate
965 The <tt/#pragma/ understands the push and pop parameters as explained above.
968 <sect1><tt>#pragma signed-chars ([push,] on|off)</tt><label id="pragma-signed-chars"><p>
970 Changes the signedness of the default character type. If the argument is
971 "on", default characters are signed, otherwise characters are unsigned. The
972 compiler default is to make characters unsigned since this creates a lot
973 better code. This default may be overridden by the <tt/<ref
974 name="--signed-chars" id="option-signed-chars">/ command line option.
976 The <tt/#pragma/ understands the push and pop parameters as explained above.
979 <sect1><tt>#pragma static-locals ([push,] on|off)</tt><label id="pragma-static-locals"<p>
981 Use variables in the bss segment instead of variables on the stack. This
982 pragma changes the default set by the compiler option <tt/<ref
983 name="--static-locals" id="option-static-locals">/. If the argument is "on",
984 local variables are allocated in the BSS segment, leading to shorter and in
985 most cases faster, but non-reentrant code.
987 The <tt/#pragma/ understands the push and pop parameters as explained above.
990 <sect1><tt>#pragma warn (name, [push,] on|off)</tt><label id="pragma-warn"><p>
992 Switch compiler warnings on or off. "name" is the name of a warning (see the
993 <tt/<ref name="-W" id="option-W">/ compiler option for a list). The name is
994 either followed by "pop", which restores the last pushed state, or by "on" or
995 "off", optionally preceeded by "push" to push the current state before
1000 /* Don't warn about the unused parameter in function func */
1001 #pragma warn (unused-param, push, off)
1002 static int func (int unused)
1006 #pragma warn (unused-param, pop)
1009 <sect1><tt>#pragma writable-strings ([push,] on|off)</tt><label id="pragma-writable-strings"><p>
1011 Changes the storage location of string literals. For historical reasons,
1012 the C standard defines that string literals are of type "char[]", but
1013 writing to such a literal causes undefined behaviour. Most compilers
1014 (including cc65) place string literals in the read-only data segment, which
1015 may cause problems with old C code that writes to string literals.
1017 Using this pragma (or the corresponding command line option <tt/<ref
1018 name="--writable-strings" id="option-writable-strings">/) causes the
1019 literals to be placed in the data segment so they can be written to without
1022 The <tt/#pragma/ understands the push and pop parameters as explained above.
1025 <sect1><tt>#pragma zpsym (<name>)</tt><p>
1027 Tell the compiler that the -- previously as external declared -- symbol with
1028 the given name is a zero page symbol (usually from an assembler file).
1029 The compiler will create a matching import declaration for the assembler.
1034 #pragma zpsym ("foo"); /* foo is in the zeropage */
1040 <sect>Register variables<label id="register-vars"><p>
1042 The runtime for all supported platforms has 6 bytes of zero page space
1043 available for register variables (this could be increased, but I think it's a
1044 good value). So you can declare register variables up to a total size of 6 per
1045 function. The compiler will allocate register space on a "first come, first
1046 served" base and convert any <tt/register/ declarations that exceed the
1047 available register space silently to <tt/auto/. Parameters can also be
1048 declared as <tt/register/, this will in fact give slightly shorter code than
1049 using a register variable.
1051 Since a function must save the current values of the registers on entry and
1052 restore them on exit, there is an overhead associated with register variables,
1053 and this overhead is quite high (about 20 bytes per variable). This means that
1054 just declaring anything as <tt/register/ is not a good idea.
1056 The best use for register variables are pointers, especially those that point
1057 to structures. The magic number here is about 3 uses of a struct field: If the
1058 function contains this number or even more, the generated code will be usually
1059 shorter and faster when using a register variable for the struct pointer. The
1060 reason for this is that the register variable can in many cases be used as a
1061 pointer directly. Having a pointer in an auto variable means that this pointer
1062 must first be copied into a zero page location, before it can be dereferenced.
1064 Second best use for register variables are counters. However, there is not
1065 much difference in the code generated for counters, so you will need at least
1066 100 operations on this variable (for example in a loop) to make it worth the
1067 trouble. The only savings you get here are by the use of a zero page variable
1068 instead of one on the stack or in the data segment.
1070 Register variables must be explicitly enabled, either by using <tt/<ref
1071 name="-Or" id="option-O">/ or <tt/<ref name="--register-vars"
1072 id="option-register-vars">/ on the command line or by use of <tt/<ref
1073 name="#pragma register-vars" id="pragma-register-vars">/. Register variables
1074 are only accepted on function top level, register variables declared in
1075 interior blocks are silently converted to <tt/auto/. With register variables
1076 disabled, all variables declared as <tt/register/ are actually auto variables.
1078 Please take care when using register variables: While they are helpful and can
1079 lead to a tremendous speedup when used correctly, improper usage will cause
1080 bloated code and a slowdown.
1084 <sect>Inline assembler<label id="inline-asm"><p>
1086 The compiler allows to insert assembler statements into the output file. The
1090 asm (<string literal>[, optional parameters]) ;
1094 __asm__ (<string literal>[, optional parameters]) ;
1098 The first form is in the user namespace and is disabled by <tt><ref
1099 id="option--standard" name="--standard"></tt> if the argument is not <tt/cc65/.
1101 The asm statement may be used inside a function and on global file level. An
1102 inline assembler statement is a primary expression, so it may also be used as
1103 part of an expression. Please note however that the result of an expression
1104 containing just an inline assembler statement is always of type <tt/void/.
1106 The contents of the string literal are preparsed by the compiler and inserted
1107 into the generated assembly output, so that the can be further processed by
1108 the backend and especially the optimizer. For this reason, the compiler does
1109 only allow regular 6502 opcodes to be used with the inline assembler. Pseudo
1110 instructions (like <tt/.import/, <tt/.byte/ and so on) are <em/not/ allowed,
1111 even if the ca65 assembler (which is used to translate the generated assembler
1112 code) would accept them. The builtin inline assembler is not a replacement for
1113 the full blown macro assembler which comes with the compiler.
1115 Note: Inline assembler statements are subject to all optimizations done by the
1116 compiler. There is currently no way to protect an inline assembler statement
1117 from being moved or removed completely by the optimizer. If in doubt, check
1118 the generated assembler output, or disable optimizations.
1120 The string literal may contain format specifiers from the following list. For
1121 each format specifier, an argument is expected which is inserted instead of
1122 the format specifier before passing the assembly code line to the backend.
1125 <item><tt/%b/ - Numerical 8-bit value
1126 <item><tt/%w/ - Numerical 16-bit value
1127 <item><tt/%l/ - Numerical 32-bit value
1128 <item><tt/%v/ - Assembler name of a (global) variable or function
1129 <item><tt/%o/ - Stack offset of a (local) variable
1130 <item><tt/%g/ - Assembler name of a C label
1131 <item><tt/%s/ - The argument is converted to a string
1132 <item><tt/%%/ - The % sign itself
1135 Using these format specifiers, you can access C <tt/#defines/, variables or
1136 similar stuff from the inline assembler. For example, to load the value of
1137 a C <tt/#define/ into the Y register, one would use
1141 __asm__ ("ldy #%b", OFFS);
1144 Or, to access a struct member of a static variable:
1150 unsigned char color;
1152 static pixel_t pixel;
1153 __asm__ ("ldy #%b", offsetof(pixel_t, color));
1154 __asm__ ("lda %v,y", pixel);
1158 Note: Do not embed the assembler labels that are used as names of global
1159 variables or functions into your asm statements. Code like this
1163 int bar () { return 1; }
1164 __asm__ ("lda _foo"); /* DON'T DO THAT! */
1166 __asm__ ("jsr _bar"); /* DON'T DO THAT EITHER! */
1170 may stop working if the way, the compiler generates these names is changed in
1171 a future version. Instead use the format specifiers from the table above:
1174 __asm__ ("lda %v", foo); /* OK */
1176 __asm__ ("jsr %v", bar); /* OK */
1181 <sect>Implementation-defined behavior<p>
1183 This section describes the behavior of cc65 when the standard describes the
1184 behavior as implementation-defined.
1188 <sect>Bugs/Feedback<p>
1190 If you have problems using the compiler, if you find any bugs, or if you're
1191 doing something interesting with it, I would be glad to hear from you. Feel
1192 free to contact me by email (<htmlurl url="mailto:uz@cc65.org"
1193 name="uz@cc65.org">).
1199 This is the original compiler copyright:
1202 --------------------------------------------------------------------------
1205 This is the copyright notice for RA65, LINK65, LIBR65, and other
1206 Atari 8-bit programs. Said programs are Copyright 1989, by John R.
1207 Dunning. All rights reserved, with the following exceptions:
1209 Anyone may copy or redistribute these programs, provided that:
1211 1: You don't charge anything for the copy. It is permissable to
1212 charge a nominal fee for media, etc.
1214 2: All source code and documentation for the programs is made
1215 available as part of the distribution.
1217 3: This copyright notice is preserved verbatim, and included in
1220 You are allowed to modify these programs, and redistribute the
1221 modified versions, provided that the modifications are clearly noted.
1223 There is NO WARRANTY with this software, it comes as is, and is
1224 distributed in the hope that it may be useful.
1226 This copyright notice applies to any program which contains
1227 this text, or the refers to this file.
1229 This copyright notice is based on the one published by the Free
1230 Software Foundation, sometimes known as the GNU project. The idea
1231 is the same as theirs, ie the software is free, and is intended to
1232 stay that way. Everybody has the right to copy, modify, and re-
1233 distribute this software. Nobody has the right to prevent anyone
1234 else from copying, modifying or redistributing it.
1236 --------------------------------------------------------------------------
1239 Small parts of the compiler (parts of the preprocessor and main parser) are
1240 still covered by this copyright. The main portion is covered by the usual
1241 cc65 license, which reads:
1243 This software is provided 'as-is', without any expressed or implied
1244 warranty. In no event will the authors be held liable for any damages
1245 arising from the use of this software.
1247 Permission is granted to anyone to use this software for any purpose,
1248 including commercial applications, and to alter it and redistribute it
1249 freely, subject to the following restrictions:
1252 <item> The origin of this software must not be misrepresented; you must not
1253 claim that you wrote the original software. If you use this software
1254 in a product, an acknowledgment in the product documentation would be
1255 appreciated but is not required.
1256 <item> Altered source versions must be plainly marked as such, and must not
1257 be misrepresented as being the original software.
1258 <item> This notice may not be removed or altered from any source