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>03.09.2000, 02.10.2001, 2005-8-1
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. In fact, I'm
27 planning a complete rewrite (that is, a complete new compiler) for the
28 next release, since there are too many limitations in the current code,
29 and removing these limitations would mean a rewrite of many more parts of
32 There are separate documents named <url url="library.html"> and <url
33 url="funcref.html"> that cover the library that is available for the compiler.
34 If you know C, and are interested in doing actual programming, the library
35 documentation is probably of much more use than this document.
37 If you need some hints for getting the best code out of the compiler, you
38 may have a look at <url url="coding.html"> which covers some code generation
45 The compiler translates C files into files containing assembly code that
46 may be translated by the ca65 macroassembler (for more information about
47 the assembler, have a look at <url url="ca65.html">).
50 <sect1>Command line option overview<p>
52 The compiler may be called as follows:
55 ---------------------------------------------------------------------------
56 Usage: cc65 [options] file
58 -Cl Make local variables static
59 -Dsym[=defn] Define a symbol
60 -I dir Set an include directory search path
62 -Oi Optimize code, inline more code
63 -Or Enable register variables
64 -Os Inline some known functions
65 -T Include source as comment
66 -V Print the compiler version number
69 -g Add debug info to object file
71 -j Default characters are signed
72 -o name Name the output file
73 -r Enable register variables
74 -t sys Set the target system
78 --add-source Include source as comment
79 --bss-name seg Set the name of the BSS segment
80 --check-stack Generate stack overflow checks
81 --code-name seg Set the name of the CODE segment
82 --codesize x Accept larger code by factor x
83 --cpu type Set cpu type
84 --create-dep Create a make dependency file
85 --data-name seg Set the name of the DATA segment
87 --debug-info Add debug info to object file
88 --forget-inc-paths Forget include search paths
89 --help Help (this text)
90 --include-dir dir Set an include directory search path
91 --register-space b Set space available for register variables
92 --register-vars Enable register variables
93 --rodata-name seg Set the name of the RODATA segment
94 --signed-chars Default characters are signed
95 --standard std Language standard (c89, c99, cc65)
96 --static-locals Make local variables static
97 --target sys Set the target system
98 --verbose Increase verbosity
99 --version Print the compiler version number
100 --writable-strings Make string literals writable
101 ---------------------------------------------------------------------------
105 <sect1>Command line options in detail<p>
107 Here is a description of all the command line options:
111 <tag><tt>--bss-name seg</tt></tag>
113 Set the name of the bss segment.
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-checkstack" name="#pragma checkstack"></tt> for an
120 explanation of this feature.
123 <tag><tt>--code-name seg</tt></tag>
125 Set the name of the code segment.
128 <label id="option-codesize">
129 <tag><tt>--codesize x</tt></tag>
131 This options allows finer control about speed vs. size decisions in the code
132 generation and optimization phases. It gives the allowed size increase
133 factor (in percent). The default is 100 when not using <tt/-Oi/ and 200 when
134 using <tt/-Oi/ (<tt/-Oi/ is the same as <tt/-O --codesize 200/).
137 <tag><tt>--cpu CPU</tt></tag>
139 A new, still experimental option. You may specify "6502" or "65C02" as
140 the CPU. 6502 is the default, so this will not change anything.
141 Specifying 65C02 will use a few 65C02 instructions when generating code.
142 Don't expect too much from this option: It is still new (and may have
143 bugs), and the additional instructions for the 65C02 are not that
147 <tag><tt>--create-dep</tt></tag>
149 Tells the compiler to generate a file containing the dependency list for
150 the compiled module in makefile syntax. The file is named as the C input
151 file with the extension replaced by <tt/.u/.
154 <tag><tt>-d, --debug</tt></tag>
156 Enables debug mode, something that should not be needed for mere
160 <tag><tt>-D sym[=definition]</tt></tag>
162 Define a macro on the command line. If no definition is given, the macro
163 is defined to the value "1".
166 <tag><tt>--forget-inc-paths</tt></tag>
168 Forget the builtin include paths. This is most useful when building
169 customized C or runtime libraries, in which case the standard header
170 files should be ignored.
173 <tag><tt>-g, --debug-info</tt></tag>
175 This will cause the compiler to insert a <tt/.DEBUGINFO/ command into the
176 generated assembler code. This will cause the assembler to include all
177 symbols in a special section in the object file.
180 <tag><tt>-h, --help</tt></tag>
182 Print the short option summary shown above.
185 <tag><tt>-o name</tt></tag>
187 Specify the name of the output file. If you don't specify a name, the
188 name of the C input file is used, with the extension replaced by ".s".
191 <tag><tt>-r, --register-vars</tt></tag>
193 <tt/-r/ will make the compiler honor the <tt/register/ keyword. Local
194 variables may be placed in registers (which are actually zero page
195 locations). There is some overhead involved with register variables, since
196 the old contents of the registers must be saved and restored. Since register
197 variables are of limited use without the optimizer, there is also a combined
198 switch: <tt/-Or/ will enable both, the optimizer and register variables.
200 For more information about register variables see <ref id="regvars"
201 name="register variables">.
203 The compiler setting can also be changed within the source file by using
204 <tt><ref id="pragma-regvars" name="#pragma regvars"></tt>.
207 <tag><tt>--register-space</tt></tag>
209 This option takes a numeric parameter and is used to specify, how much
210 zero page register space is available. Please note that just giving this
211 option will not increase or decrease by itself, it will just tell the
212 compiler about the available space. You will have to allocate that space
213 yourself using an assembler module with the necessary allocations, and a
214 linker configuration that matches the assembler module. The default value
215 for this option is 6 (bytes).
217 If you don't know what all this means, please don't use this option.
220 <tag><tt>--rodata-name seg</tt></tag>
222 Set the name of the rodata segment (the segment used for readonly data).
225 <tag><tt>-j, --signed-chars</tt></tag>
227 Using this option, you can make the default characters signed. Since the
228 6502 has no provisions for sign extending characters (which is needed on
229 almost any load operation), this will make the code larger and slower. A
230 better way is to declare characters explicitly as "signed" if needed. You
231 can also use <tt><ref id="pragma-signedchars"
232 name="#pragma signedchars"></tt> for better control of this option.
235 <label id="option--standard">
236 <tag><tt>--standard std</tt></tag>
238 This option allows to set the language standard supported. The argument is
246 Please note that the compiler does not support the c99 standard and never
247 will. c99 mode is actually c89 mode with a few selected c99 extensions
248 (// comments for example).
251 <tag><tt>-t target, --target target</tt></tag>
253 This option is used to set the target system. The target system
254 determines things like the character set that is used for strings and
255 character constants. The following target systems are supported:
263 <item>c16 (works also for the c116 with memory up to 32K)
266 <item>cbm510 (CBM-II series with 40 column video)
267 <item>cbm610 (all CBM-II II computers with 80 column video)
272 <item>pet (all CBM PET systems except the 2001)
278 <tag><tt>-v, --verbose</tt></tag>
280 Using this option, the compiler will be somewhat more verbose if errors
281 or warnings are encountered.
284 <tag><tt>--writable-strings</tt></tag>
286 Make string literals writable by placing them into the data segment instead
287 of the rodata segment.
290 <tag><tt>-Cl, --static-locals</tt></tag>
292 Use static storage for local variables instead of storage on the stack.
293 Since the stack is emulated in software, this gives shorter and usually
294 faster code, but the code is no longer reentrant. The difference between
295 <tt/-Cl/ and declaring local variables as static yourself is, that
296 initializer code is executed each time, the function is entered. So when
307 the variable <tt/a/ will always have the value <tt/1/ when entering the
308 function and using <tt/-Cl/, while in
313 static unsigned a = 1;
318 the variable <tt/a/ will have the value <tt/1/ only the first time that the
319 function is entered, and will keep the old value from one call of the
320 function to the next.
322 You may also use <tt><ref id="pragma-staticlocals"
323 name="#pragma staticlocals"></tt> to change this setting in your
327 <tag><tt>-I dir, --include-dir dir</tt></tag>
329 Set a directory where the compiler searches for include files. You may
330 use this option multiple times to add more than one directory to the
334 <label id="option-O">
335 <tag><tt>-O, -Oi, -Or, -Os</tt></tag>
337 Enable an optimizer run over the produced code.
339 Using <tt/-Oi/, the code generator will inline some code where otherwise a
340 runtime functions would have been called, even if the generated code is
341 larger. This will not only remove the overhead for a function call, but will
342 make the code visible for the optimizer. <tt/-Oi/ is an alias for
343 <tt/-O --codesize 200/.
345 <tt/-Or/ will make the compiler honor the <tt/register/ keyword. Local
346 variables may be placed in registers (which are actually zero page
347 locations). There is some overhead involved with register variables, since
348 the old contents of the registers must be saved and restored. In addition,
349 the current implementation does not make good use of register variables, so
350 using <tt/-Or/ may make your program even slower and larger. Use with care!
352 Using <tt/-Os/ will force the compiler to inline some known functions from
353 the C library like strlen. Note: This has two consequences:
356 <item>You may not use names of standard C functions in your own code. If you
357 do that, your program is not standard compliant anyway, but using
358 <tt/-Os/ will actually break things.
360 <item>The inlined string and memory functions will not handle strings or
361 memory areas larger than 255 bytes. Similarly, the inlined <tt/is..()/
362 functions will not work with values outside the char. range (such as
367 It is possible to concatenate the modifiers for <tt/-O/. For example, to
368 enable register variables and inlining of known functions, you may use
372 <tag><tt>-T, --add-source</tt></tag>
374 This include the source code as comments in the generated code. This is
378 <tag><tt>-V, --version</tt></tag>
380 Print the version number of the compiler. When submitting a bug report,
381 please include the operating system you're using, and the compiler
385 <label id="option-W">
386 <tag><tt>-W</tt></tag>
388 This option will suppress any warnings generated by the compiler. Since
389 any source file may be written in a manner that it will not produce
390 compiler warnings, using this option is usually not a good idea.
395 <sect>Input and output<p>
397 The compiler will accept one C file per invocation and create a file with
398 the same base name, but with the extension replaced by ".s". The output
399 file contains assembler code suitable for the use with the ca65 macro
402 In addition to the paths named in the <tt/-I/ option on the command line, the
403 directory named in the environment variable <tt/CC65_INC/ is added to the
404 search path for include files on startup.
408 <sect>Differences to the ISO standard<p>
410 Apart from the things listed below, the compiler does support additional
411 keywords, has several functions in the standard headers with names outside the
412 reserved namespace and a few syntax extensions. All these can be disabled with
413 the <tt><ref id="option--standard" name="--standard"></tt> command line
414 option. Its use for maximum standards compatibility is advised.
416 Here is a list of differences between the language, the compiler accepts,
417 and the one defined by the ISO standard:
421 <item> The datatypes "float" and "double" are not available.
423 <item> C Functions may not return structs (or unions), and structs may not
424 be passed as parameters by value. However, struct assignment *is*
427 <item> Part of the C library is available only with fastcall calling
428 conventions (see below). It means that you must not mix pointers to
429 those functions with pointers to user-written, not-fastcall functions.
431 <item> The <tt/volatile/ keyword doesn't have an effect. This is not as bad
432 as it sounds, since the 6502 has so few registers that it isn't
433 possible to keep values in registers anyway.
437 There may be some more minor differences I'm currently not aware of. The
438 biggest problem is the missing float data type. With this limitation in
439 mind, you should be able to write fairly portable code.
445 This cc65 version has some extensions to the ISO C standard.
449 <item> The compiler allows to insert assembler statements into the output
453 asm (<string literal>[, optional parameters]) ;
457 __asm__ (<string literal>[, optional parameters]) ;
460 The first form is in the user namespace and is disabled if the <tt/-A/
463 There is a whole section covering inline assembler statements,
464 <ref id="inline-asm" name="see there">.
467 <item> There is a special calling convention named "fastcall".
468 The syntax for a function declaration using fastcall is
471 <return type> fastcall <function name> (<parameter list>)
475 <return type> __fastcall__ <function name> (<parameter list>)
479 void __fastcall__ f (unsigned char c)
481 The first form of the fastcall keyword is in the user namespace and can
482 therefore be disabled with the <tt><ref id="option--standard"
483 name="--standard"></tt> command line option.
485 For functions declared as <tt/fastcall/, the rightmost parameter is not
486 pushed on the stack but left in the primary register when the function
487 is called. This will reduce the cost when calling assembler functions
488 significantly, especially when the function itself is rather small.
491 <item> There are two pseudo variables named <tt/__AX__/ and <tt/__EAX__/.
492 Both refer to the primary register that is used by the compiler to
493 evaluate expressions or return function results. <tt/__AX__/ is of
494 type <tt/unsigned int/ and <tt/__EAX__/ of type <tt/long unsigned int/
495 respectively. The pseudo variables may be used as lvalue and rvalue as
496 every other variable. They are most useful together with short
497 sequences of assembler code. For example, the macro
507 will give the high byte of any unsigned value.
510 <item> Inside a function, the identifier <tt/__func__/ gives the name of the
511 current function as a string. Outside of functions, <tt/__func__/ is
516 #define PRINT_DEBUG(s) printf ("%s: %s\n", __func__, s);
519 The macro will print the name of the current function plus a given
523 <item> cc65 allows the initialization of <tt/void/ variables. This may be
524 used to create variable structures that are more compatible with
525 interfaces written for assembler languages. Here is an example:
528 void GCmd = { (char)3, (unsigned)0x2000, (unsigned)0x3000 };
531 This will be translated as follows:
540 Since the variable is of type <tt/void/ you may not use it as is.
541 However, taking the address of the variable results in a <tt/void*/
542 which may be passed to any function expecting a pointer.
544 See the <url url="geos.html" name="GEOS library document"> for examples
545 on how to use this feature.
548 <item> cc65 implements flexible array struct members as defined in the C99 ISO
549 standard. As an extension, these fields may be initialized. There are
550 several exceptions, however (which is probably the reason why the
551 standard does not define this feature, because it is highly
552 unorthogonal). Flexible array members cannot be initialized ...
555 <item>... when defining an array of structs with flexible
557 <item>... if such a struct is a member field of another struct
558 which is not the last field.
559 <item>... if the struct which contains a flexible array member is
560 declared as <tt/register/, and the size and compiler settings
561 do allow the compiler actually to place the struct into the
562 register bank in the zero page.
565 Please note that -- as defined in the ISO C standard -- the <tt/sizeof/
566 operator returns the struct size with the flexible array member having
567 size zero, even if it is initialized.
574 <sect>Predefined macros<p>
576 The compiler defines several macros at startup:
580 <tag><tt>__CC65__</tt></tag>
582 This macro is always defined. Its value is the version number of the
583 compiler in hex. For example, version 2.10.1 of the compiler has this macro
584 defined as <tt/0x02A1/.
586 <tag><tt>__APPLE2__</tt></tag>
588 This macro is defined if the target is the Apple ][ (-t apple2).
590 <tag><tt>__APPLE2ENH__</tt></tag>
592 This macro is defined if the target is the enhanced Apple //e (-t apple2enh).
594 <tag><tt>__ATARI__</tt></tag>
596 This macro is defined if the target is one of the Atari computers
597 (400/800/130XL/800XL).
599 <tag><tt>__ATMOS__</tt></tag>
601 This macro is defined if the target is the Oric Atmos (-t atmos).
603 <tag><tt>__CBM__</tt></tag>
605 This macro is defined if the target system is one of the CBM targets.
607 <tag><tt>__C16__</tt></tag>
609 This macro is defined if the target is the c16 (-t c16).
611 <tag><tt>__C64__</tt></tag>
613 This macro is defined if the target is the c64 (-t c64).
615 <tag><tt>__C128__</tt></tag>
617 This macro is defined if the target is the c128 (-t c128).
619 <tag><tt>__CBM510__</tt></tag>
621 This macro is defined if the target is the CBM 500 series of computers.
623 <tag><tt>__CBM610__</tt></tag>
625 This macro is defined if the target is one of the CBM 600/700 family of
626 computers (called B series in the US).
628 <tag><tt>__GEOS__</tt></tag>
630 This macro is defined if you are compiling for the GEOS system (-t geos).
632 <tag><tt>__LUNIX__</tt></tag>
634 This macro is defined if you are compiling for the LUnix system (-t lunix).
636 <tag><tt>__LYNX__</tt></tag>
638 This macro is defined if the target is the Atari Lynx (-t lynx).
640 <tag><tt>__NES__</tt></tag>
642 This macro is defined if the target is the NES (-t nes).
644 <tag><tt>__PET__</tt></tag>
646 This macro is defined if the target is the PET family of computers (-t pet).
648 <tag><tt>__PLUS4__</tt></tag>
650 This macro is defined if the target is the plus/4 (-t plus4).
652 <tag><tt>__SUPERVISION__</tt></tag>
654 This macro is defined if the target is the supervision (-t supervision).
656 <tag><tt>__VIC20__</tt></tag>
658 This macro is defined if the target is the vic20 (-t vic20).
660 <tag><tt>__FILE__</tt></tag>
662 This macro expands to a string containing the name of the C source file.
664 <tag><tt>__LINE__</tt></tag>
666 This macro expands to the current line number.
668 <tag><tt>__CC65_STD__</tt></tag>
670 This macro is defined to one of the following depending on the <tt><ref
671 id="option--standard" name="--standard"></tt> command line option:
673 <item><tt/__CC65_STD_C89__/
674 <item><tt/__CC65_STD_C99__/
675 <item><tt/__CC65_STD_CC65__/
678 <tag><tt>__OPT__</tt></tag>
680 Is defined if the compiler was called with the <tt/-O/ command line option.
682 <tag><tt>__OPT_i__</tt></tag>
684 Is defined if the compiler was called with the <tt/-Oi/ command line option.
686 <tag><tt>__OPT_r__</tt></tag>
688 Is defined if the compiler was called with the <tt/-Or/ command line option.
690 <tag><tt>__OPT_s__</tt></tag>
692 Is defined if the compiler was called with the <tt/-Os/ command line option.
697 <sect>#pragmas<label id="pragmas"><p>
699 The compiler understands some pragmas that may be used to change code
700 generation and other stuff. Some of these pragmas understand a special form:
701 If the first parameter is <tt/push/, the old value is saved onto a stack
702 before changing it. The value may later be restored by using the <tt/pop/
703 parameter with the <tt/#pragma/.
705 <sect1><tt>#pragma bssseg ([push,]<name>)</tt><p>
707 This pragma changes the name used for the BSS segment (the BSS segment
708 is used to store uninitialized data). The argument is a string enclosed
711 Note: The default linker configuration file does only map the standard
712 segments. If you use other segments, you have to create a new linker
715 Beware: The startup code will zero only the default BSS segment. If you
716 use another BSS segment, you have to do that yourself, otherwise
717 uninitialized variables do not have the value zero.
719 The <tt/#pragma/ understands the push and pop parameters as explained above.
723 #pragma bssseg ("MyBSS")
727 <sect1><tt>#pragma charmap (<index>, <code>)</tt><p>
729 Each literal string and each literal character in the source is translated
730 by use of a translation table. This translation table is preset when the
731 compiler is started depending on the target system, for example to map
732 ISO-8859-1 characters into PETSCII if the target is a commodore machine.
734 This pragma allows to change entries in the translation table, so the
735 translation for individual characters, or even the complete table may be
738 Both arguments are assumed to be unsigned characters with a valid range of
741 Beware of two pitfalls:
744 <item>The character index is actually the code of the character in the
745 C source, so character mappings do always depend on the source
746 character set. This means that <tt/#pragma charmap/ is not
747 portable -- it depends on the build environment.
748 <item>While it is possible to use character literals as indices, the
749 result may be somewhat unexpected, since character literals are
750 itself translated. For this reason I would suggest to avoid
751 character literals and use numeric character codes instead.
756 /* Use a space wherever an 'a' occurs in ISO-8859-1 source */
757 #pragma charmap (0x61, 0x20);
761 <sect1><tt>#pragma checkstack ([push,]on|off)</tt><label id="pragma-checkstack"><p>
763 Tells the compiler to insert calls to a stack checking subroutine to detect
764 stack overflows. The stack checking code will lead to somewhat larger and
765 slower programs, so you may want to use this pragma when debugging your
766 program and switch it off for the release version. If a stack overflow is
767 detected, the program is aborted.
769 If the argument is "off", stack checks are disabled (the default), otherwise
772 The <tt/#pragma/ understands the push and pop parameters as explained above.
774 <sect1><tt>#pragma codeseg ([push,]<name>)</tt><p>
776 This pragma changes the name used for the CODE segment (the CODE segment
777 is used to store executable code). The argument is a string enclosed in
780 Note: The default linker configuration file does only map the standard
781 segments. If you use other segments, you have to create a new linker
784 The <tt/#pragma/ understands the push and pop parameters as explained above.
788 #pragma codeseg ("MyCODE")
792 <sect1><tt>#pragma codesize ([push,]<int>)</tt><label id="pragma-codesize"><p>
794 This pragma allows finer control about speed vs. size decisions in the code
795 generation and optimization phase. It gives the allowed size increase factor
796 (in percent). The default is can be changed by use of the <tt/<ref
797 id="option-codesize" name="--codesize">/ compiler option.
799 The <tt/#pragma/ understands the push and pop parameters as explained above.
802 <sect1><tt>#pragma dataseg ([push,]<name>)</tt><p>
804 This pragma changes the name used for the DATA segment (the DATA segment
805 is used to store initialized data). The argument is a string enclosed in
808 Note: The default linker configuration file does only map the standard
809 segments. If you use other segments, you have to create a new linker
812 The <tt/#pragma/ understands the push and pop parameters as explained above.
816 #pragma dataseg ("MyDATA")
820 <sect1><tt>#pragma optimize ([push,]on|off)</tt><label id="pragma-optimize"><p>
822 Switch optimization on or off. If the argument is "off", optimization is
823 disabled, otherwise it is enabled. Please note that this pragma only effects
824 whole functions. The setting in effect when the function is encountered will
825 determine if the generated code is optimized or not.
827 Optimization and code generation is also controlled by the <ref
828 id="pragma-codesize" name="codesize pragma">.
830 The default is "off", but may be changed with the <tt/<ref name="-O"
831 id="option-O">/ compiler option.
833 The <tt/#pragma/ understands the push and pop parameters as explained above.
836 <sect1><tt>#pragma rodataseg ([push,]<name>)</tt><p>
838 This pragma changes the name used for the RODATA segment (the RODATA
839 segment is used to store readonly data). The argument is a string
840 enclosed in double quotes.
842 Note: The default linker configuration file does only map the standard
843 segments. If you use other segments, you have to create a new linker
846 The <tt/#pragma/ understands the push and pop parameters as explained above.
850 #pragma rodataseg ("MyRODATA")
854 <sect1><tt>#pragma regvaraddr ([push,]on|off)</tt><p>
856 The compiler does not allow to take the address of register variables.
857 The regvaraddr pragma changes this. Taking the address of a register
858 variable is allowed after using this pragma with "on" as argument.
859 Using "off" as an argument switches back to the default behaviour.
861 Beware: The C standard does not allow taking the address of a variable
862 declared as register. So your programs become non-portable if you use
863 this pragma. In addition, your program may not work. This is usually the
864 case if a subroutine is called with the address of a register variable,
865 and this subroutine (or a subroutine called from there) uses
866 register variables. So be careful with this #pragma.
868 The <tt/#pragma/ understands the push and pop parameters as explained above.
872 #pragma regvaraddr(on) /* Allow taking the address
873 * of register variables
878 <sect1><tt>#pragma regvars ([push,]on|off)</tt><label id="pragma-regvars"><p>
880 Enables or disables use of register variables. If register variables are
881 disabled (the default), the <tt/register/ keyword is ignored. Register
882 variables are explained in more detail in <ref id="regvars" name="a separate
885 The <tt/#pragma/ understands the push and pop parameters as explained above.
888 <sect1><tt>#pragma signedchars ([push,]on|off)</tt><label id="pragma-signedchars"><p>
890 Changes the signedness of the default character type. If the argument is
891 "on", default characters are signed, otherwise characters are unsigned.
892 The compiler default is to make characters unsigned since this creates a
893 lot better code. This default may be overridden by the <tt/--signed-chars/
896 The <tt/#pragma/ understands the push and pop parameters as explained above.
899 <sect1><tt>#pragma staticlocals ([push,]on|off)</tt><label id="pragma-staticlocals"<p>
901 Use variables in the bss segment instead of variables on the stack. This
902 pragma changes the default set by the compiler option <tt/-Cl/. If the
903 argument is "on", local variables are allocated in the BSS segment,
904 leading to shorter and in most cases faster, but non-reentrant code.
906 The <tt/#pragma/ understands the push and pop parameters as explained above.
909 <sect1><tt>#pragma warn ([push,]on|off)</tt><label id="pragma-warn"><p>
911 Switch compiler warnings on or off. If the argument is "off", warnings are
912 disabled, otherwise they're enabled. The default is "on", but may be changed
913 with the <tt/<ref name="-W" id="option-W">/ compiler option.
915 The <tt/#pragma/ understands the push and pop parameters as explained above.
918 <sect1><tt>#pragma zpsym (<name>)</tt><p>
920 Tell the compiler that the -- previously as external declared -- symbol with
921 the given name is a zero page symbol (usually from an assembler file).
922 The compiler will create a matching import declaration for the assembler.
927 #pragma zpsym ("foo"); /* foo is in the zeropage */
933 <sect>Register variables<label id="regvars"><p>
935 The runtime for all supported platforms has 6 bytes of zero page space
936 available for register variables (this could be increased, but I think it's a
937 good value). So you can declare register variables up to a total size of 6 per
938 function. The compiler will allocate register space on a "first come, first
939 served" base and convert any <tt/register/ declarations that exceed the
940 available register space silently to <tt/auto/. Parameters can also be
941 declared as <tt/register/, this will in fact give slightly shorter code than
942 using a register variable.
944 Since a function must save the current values of the registers on entry and
945 restore them on exit, there is an overhead associated with register variables,
946 and this overhead is quite high (about 20 bytes per variable). This means that
947 just declaring anything as <tt/register/ is not a good idea.
949 The best use for register variables are pointers, especially those that point
950 to structures. The magic number here is about 3 uses of a struct field: If the
951 function contains this number or even more, the generated code will be usually
952 shorter and faster when using a register variable for the struct pointer. The
953 reason for this is that the register variable can in many cases be used as a
954 pointer directly. Having a pointer in an auto variable means that this pointer
955 must first be copied into a zero page location, before it can be dereferenced.
957 Second best use for register variables are counters. However, there is not
958 much difference in the code generated for counters, so you will need at least
959 100 operations on this variable (for example in a loop) to make it worth the
960 trouble. The only savings you get here are by the use of a zero page variable
961 instead of one on the stack or in the data segment.
963 Register variables must be explicitly enabled by using <tt/-Or/ or <tt/-r/ on
964 the command line. Register variables are only accepted on function top level,
965 register variables declared in interior blocks are silently converted to
966 <tt/auto/. With register variables disabled, all variables declared as
967 <tt/register/ are actually auto variables.
969 Please take care when using register variables: While they are helpful and can
970 lead to a tremendous speedup when used correctly, improper usage will cause
971 bloated code and a slowdown.
975 <sect>Inline assembler<label id="inline-asm"><p>
977 The compiler allows to insert assembler statements into the output file. The
981 asm (<string literal>[, optional parameters]) ;
985 __asm__ (<string literal>[, optional parameters]) ;
989 The first form is in the user namespace and is disabled by <tt><ref
990 id="option--standard" name="--standard"></tt> if the argument is not <tt/cc65/.
992 The asm statement may be used inside a function and on global file level. An
993 inline assembler statement is a primary expression, so it may also be used as
994 part of an expression. Please note however that the result of an expression
995 containing just an inline assembler statement is always of type <tt/void/.
997 The contents of the string literal are preparsed by the compiler and inserted
998 into the generated assembly output, so that the can be further processed by
999 the backend and especially the optimizer. For this reason, the compiler does
1000 only allow regular 6502 opcodes to be used with the inline assembler. Pseudo
1001 instructions (like <tt/.import/, <tt/.byte/ and so on) are <em/not/ allowed,
1002 even if the ca65 assembler (which is used to translate the generated assembler
1003 code) would accept them. The builtin inline assembler is not a replacement for
1004 the full blown macro assembler which comes with the compiler.
1006 Note: Inline assembler statements are subject to all optimizations done by the
1007 compiler. There is currently no way to protect an inline assembler statement
1008 from being moved or removed completely by the optimizer. If in doubt, check
1009 the generated assembler output, or disable optimizations.
1011 The string literal may contain format specifiers from the following list. For
1012 each format specifier, an argument is expected which is inserted instead of
1013 the format specifier before passing the assembly code line to the backend.
1016 <item><tt/%b/ - Numerical 8-bit value
1017 <item><tt/%w/ - Numerical 16-bit value
1018 <item><tt/%l/ - Numerical 32-bit value
1019 <item><tt/%v/ - Assembler name of a (global) variable or function
1020 <item><tt/%o/ - Stack offset of a (local) variable
1021 <item><tt/%g/ - Assembler name of a C label
1022 <item><tt/%s/ - The argument is converted to a string
1023 <item><tt/%%/ - The % sign itself
1026 Using these format specifiers, you can access C <tt/#defines/, variables or
1027 similar stuff from the inline assembler. For example, to load the value of
1028 a C <tt/#define/ into the Y register, one would use
1032 __asm__ ("ldy #%b", OFFS);
1035 Or, to access a struct member of a static variable:
1041 unsigned char color;
1043 static pixel_t pixel;
1044 __asm__ ("ldy #%b", offsetof(pixel_t, color));
1045 __asm__ ("lda %v,y", pixel);
1049 Note: Do not embed the assembler labels that are used as names of global
1050 variables or functions into your asm statements. Code like this
1054 int bar () { return 1; }
1055 __asm__ ("lda _foo"); /* DON'T DO THAT! */
1057 __asm__ ("jsr _bar"); /* DON'T DO THAT EITHER! */
1061 may stop working if the way, the compiler generates these names is changed in
1062 a future version. Instead use the format specifiers from the table above:
1065 __asm__ ("lda %v", foo); /* OK */
1067 __asm__ ("jsr %v", bar); /* OK */
1072 <sect>Implementation-defined behavior<p>
1074 This section describes the behavior of cc65 when the standard describes the
1075 behavior as implementation-defined.
1079 <sect>Bugs/Feedback<p>
1081 If you have problems using the compiler, if you find any bugs, or if you're
1082 doing something interesting with it, I would be glad to hear from you. Feel
1083 free to contact me by email (<htmlurl url="mailto:uz@cc65.org"
1084 name="uz@cc65.org">).
1090 This is the original compiler copyright:
1093 --------------------------------------------------------------------------
1096 This is the copyright notice for RA65, LINK65, LIBR65, and other
1097 Atari 8-bit programs. Said programs are Copyright 1989, by John R.
1098 Dunning. All rights reserved, with the following exceptions:
1100 Anyone may copy or redistribute these programs, provided that:
1102 1: You don't charge anything for the copy. It is permissable to
1103 charge a nominal fee for media, etc.
1105 2: All source code and documentation for the programs is made
1106 available as part of the distribution.
1108 3: This copyright notice is preserved verbatim, and included in
1111 You are allowed to modify these programs, and redistribute the
1112 modified versions, provided that the modifications are clearly noted.
1114 There is NO WARRANTY with this software, it comes as is, and is
1115 distributed in the hope that it may be useful.
1117 This copyright notice applies to any program which contains
1118 this text, or the refers to this file.
1120 This copyright notice is based on the one published by the Free
1121 Software Foundation, sometimes known as the GNU project. The idea
1122 is the same as theirs, ie the software is free, and is intended to
1123 stay that way. Everybody has the right to copy, modify, and re-
1124 distribute this software. Nobody has the right to prevent anyone
1125 else from copying, modifying or redistributing it.
1127 --------------------------------------------------------------------------
1130 Small parts of the compiler (parts of the preprocessor and main parser) are
1131 still covered by this copyright. The main portion is covered by the usual
1132 cc65 license, which reads:
1134 This software is provided 'as-is', without any expressed or implied
1135 warranty. In no event will the authors be held liable for any damages
1136 arising from the use of this software.
1138 Permission is granted to anyone to use this software for any purpose,
1139 including commercial applications, and to alter it and redistribute it
1140 freely, subject to the following restrictions:
1143 <item> The origin of this software must not be misrepresented; you must not
1144 claim that you wrote the original software. If you use this software
1145 in a product, an acknowledgment in the product documentation would be
1146 appreciated but is not required.
1147 <item> Altered source versions must be plainly marked as such, and must not
1148 be misrepresented as being the original software.
1149 <item> This notice may not be removed or altered from any source