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 Include files in single quotes are searched in the following places:
404 <item>The current directory.
405 <item>The value of the environment variable <tt/CC65_INC/ if it is defined.
406 <item>Any directory added with the <tt/-I/ option on the command line.
409 Include files in angle brackets are searched in the following places:
411 <item>A compiled in directory which is often <tt>/usr/lib/cc65/include</tt> on
413 <item>The value of the environment variable <tt/CC65_INC/ if it is defined.
414 <item>A subdirectory named <tt/include/ of the directory defined in the
415 environment variable <tt/CC65_HOME/, if it is defined.
416 <item>Any directory added with the <tt/-I/ option on the command line.
421 <sect>Differences to the ISO standard<p>
423 Apart from the things listed below, the compiler does support additional
424 keywords, has several functions in the standard headers with names outside the
425 reserved namespace and a few syntax extensions. All these can be disabled with
426 the <tt><ref id="option--standard" name="--standard"></tt> command line
427 option. Its use for maximum standards compatibility is advised.
429 Here is a list of differences between the language, the compiler accepts,
430 and the one defined by the ISO standard:
434 <item> The datatypes "float" and "double" are not available.
436 <item> C Functions may not return structs (or unions), and structs may not
437 be passed as parameters by value. However, struct assignment *is*
440 <item> Part of the C library is available only with fastcall calling
441 conventions (see below). It means that you must not mix pointers to
442 those functions with pointers to user-written, not-fastcall functions.
444 <item> The <tt/volatile/ keyword doesn't have an effect. This is not as bad
445 as it sounds, since the 6502 has so few registers that it isn't
446 possible to keep values in registers anyway.
450 There may be some more minor differences I'm currently not aware of. The
451 biggest problem is the missing float data type. With this limitation in
452 mind, you should be able to write fairly portable code.
458 This cc65 version has some extensions to the ISO C standard.
462 <item> The compiler allows to insert assembler statements into the output
466 asm (<string literal>[, optional parameters]) ;
470 __asm__ (<string literal>[, optional parameters]) ;
473 The first form is in the user namespace and is disabled if the <tt/-A/
476 There is a whole section covering inline assembler statements,
477 <ref id="inline-asm" name="see there">.
480 <item> There is a special calling convention named "fastcall".
481 The syntax for a function declaration using fastcall is
484 <return type> fastcall <function name> (<parameter list>)
488 <return type> __fastcall__ <function name> (<parameter list>)
492 void __fastcall__ f (unsigned char c)
494 The first form of the fastcall keyword is in the user namespace and can
495 therefore be disabled with the <tt><ref id="option--standard"
496 name="--standard"></tt> command line option.
498 For functions declared as <tt/fastcall/, the rightmost parameter is not
499 pushed on the stack but left in the primary register when the function
500 is called. This will reduce the cost when calling assembler functions
501 significantly, especially when the function itself is rather small.
504 <item> There are two pseudo variables named <tt/__AX__/ and <tt/__EAX__/.
505 Both refer to the primary register that is used by the compiler to
506 evaluate expressions or return function results. <tt/__AX__/ is of
507 type <tt/unsigned int/ and <tt/__EAX__/ of type <tt/long unsigned int/
508 respectively. The pseudo variables may be used as lvalue and rvalue as
509 every other variable. They are most useful together with short
510 sequences of assembler code. For example, the macro
520 will give the high byte of any unsigned value.
523 <item> Inside a function, the identifier <tt/__func__/ gives the name of the
524 current function as a string. Outside of functions, <tt/__func__/ is
529 #define PRINT_DEBUG(s) printf ("%s: %s\n", __func__, s);
532 The macro will print the name of the current function plus a given
536 <item> cc65 allows the initialization of <tt/void/ variables. This may be
537 used to create variable structures that are more compatible with
538 interfaces written for assembler languages. Here is an example:
541 void GCmd = { (char)3, (unsigned)0x2000, (unsigned)0x3000 };
544 This will be translated as follows:
553 Since the variable is of type <tt/void/ you may not use it as is.
554 However, taking the address of the variable results in a <tt/void*/
555 which may be passed to any function expecting a pointer.
557 See the <url url="geos.html" name="GEOS library document"> for examples
558 on how to use this feature.
561 <item> cc65 implements flexible array struct members as defined in the C99 ISO
562 standard. As an extension, these fields may be initialized. There are
563 several exceptions, however (which is probably the reason why the
564 standard does not define this feature, because it is highly
565 unorthogonal). Flexible array members cannot be initialized ...
568 <item>... when defining an array of structs with flexible
570 <item>... if such a struct is a member field of another struct
571 which is not the last field.
572 <item>... if the struct which contains a flexible array member is
573 declared as <tt/register/, and the size and compiler settings
574 do allow the compiler actually to place the struct into the
575 register bank in the zero page.
578 Please note that -- as defined in the ISO C standard -- the <tt/sizeof/
579 operator returns the struct size with the flexible array member having
580 size zero, even if it is initialized.
587 <sect>Predefined macros<p>
589 The compiler defines several macros at startup:
593 <tag><tt>__CC65__</tt></tag>
595 This macro is always defined. Its value is the version number of the
596 compiler in hex. For example, version 2.10.1 of the compiler has this macro
597 defined as <tt/0x02A1/.
599 <tag><tt>__APPLE2__</tt></tag>
601 This macro is defined if the target is the Apple ][ (-t apple2).
603 <tag><tt>__APPLE2ENH__</tt></tag>
605 This macro is defined if the target is the enhanced Apple //e (-t apple2enh).
607 <tag><tt>__ATARI__</tt></tag>
609 This macro is defined if the target is one of the Atari computers
610 (400/800/130XL/800XL).
612 <tag><tt>__ATMOS__</tt></tag>
614 This macro is defined if the target is the Oric Atmos (-t atmos).
616 <tag><tt>__CBM__</tt></tag>
618 This macro is defined if the target system is one of the CBM targets.
620 <tag><tt>__C16__</tt></tag>
622 This macro is defined if the target is the c16 (-t c16).
624 <tag><tt>__C64__</tt></tag>
626 This macro is defined if the target is the c64 (-t c64).
628 <tag><tt>__C128__</tt></tag>
630 This macro is defined if the target is the c128 (-t c128).
632 <tag><tt>__CBM510__</tt></tag>
634 This macro is defined if the target is the CBM 500 series of computers.
636 <tag><tt>__CBM610__</tt></tag>
638 This macro is defined if the target is one of the CBM 600/700 family of
639 computers (called B series in the US).
641 <tag><tt>__GEOS__</tt></tag>
643 This macro is defined if you are compiling for the GEOS system (-t geos).
645 <tag><tt>__LUNIX__</tt></tag>
647 This macro is defined if you are compiling for the LUnix system (-t lunix).
649 <tag><tt>__LYNX__</tt></tag>
651 This macro is defined if the target is the Atari Lynx (-t lynx).
653 <tag><tt>__NES__</tt></tag>
655 This macro is defined if the target is the NES (-t nes).
657 <tag><tt>__PET__</tt></tag>
659 This macro is defined if the target is the PET family of computers (-t pet).
661 <tag><tt>__PLUS4__</tt></tag>
663 This macro is defined if the target is the plus/4 (-t plus4).
665 <tag><tt>__SUPERVISION__</tt></tag>
667 This macro is defined if the target is the supervision (-t supervision).
669 <tag><tt>__VIC20__</tt></tag>
671 This macro is defined if the target is the vic20 (-t vic20).
673 <tag><tt>__FILE__</tt></tag>
675 This macro expands to a string containing the name of the C source file.
677 <tag><tt>__LINE__</tt></tag>
679 This macro expands to the current line number.
681 <tag><tt>__CC65_STD__</tt></tag>
683 This macro is defined to one of the following depending on the <tt><ref
684 id="option--standard" name="--standard"></tt> command line option:
686 <item><tt/__CC65_STD_C89__/
687 <item><tt/__CC65_STD_C99__/
688 <item><tt/__CC65_STD_CC65__/
691 <tag><tt>__OPT__</tt></tag>
693 Is defined if the compiler was called with the <tt/-O/ command line option.
695 <tag><tt>__OPT_i__</tt></tag>
697 Is defined if the compiler was called with the <tt/-Oi/ command line option.
699 <tag><tt>__OPT_r__</tt></tag>
701 Is defined if the compiler was called with the <tt/-Or/ command line option.
703 <tag><tt>__OPT_s__</tt></tag>
705 Is defined if the compiler was called with the <tt/-Os/ command line option.
710 <sect>#pragmas<label id="pragmas"><p>
712 The compiler understands some pragmas that may be used to change code
713 generation and other stuff. Some of these pragmas understand a special form:
714 If the first parameter is <tt/push/, the old value is saved onto a stack
715 before changing it. The value may later be restored by using the <tt/pop/
716 parameter with the <tt/#pragma/.
718 <sect1><tt>#pragma bssseg ([push,]<name>)</tt><p>
720 This pragma changes the name used for the BSS segment (the BSS segment
721 is used to store uninitialized data). The argument is a string enclosed
724 Note: The default linker configuration file does only map the standard
725 segments. If you use other segments, you have to create a new linker
728 Beware: The startup code will zero only the default BSS segment. If you
729 use another BSS segment, you have to do that yourself, otherwise
730 uninitialized variables do not have the value zero.
732 The <tt/#pragma/ understands the push and pop parameters as explained above.
736 #pragma bssseg ("MyBSS")
740 <sect1><tt>#pragma charmap (<index>, <code>)</tt><p>
742 Each literal string and each literal character in the source is translated
743 by use of a translation table. This translation table is preset when the
744 compiler is started depending on the target system, for example to map
745 ISO-8859-1 characters into PETSCII if the target is a commodore machine.
747 This pragma allows to change entries in the translation table, so the
748 translation for individual characters, or even the complete table may be
751 Both arguments are assumed to be unsigned characters with a valid range of
754 Beware of two pitfalls:
757 <item>The character index is actually the code of the character in the
758 C source, so character mappings do always depend on the source
759 character set. This means that <tt/#pragma charmap/ is not
760 portable -- it depends on the build environment.
761 <item>While it is possible to use character literals as indices, the
762 result may be somewhat unexpected, since character literals are
763 itself translated. For this reason I would suggest to avoid
764 character literals and use numeric character codes instead.
769 /* Use a space wherever an 'a' occurs in ISO-8859-1 source */
770 #pragma charmap (0x61, 0x20);
774 <sect1><tt>#pragma checkstack ([push,]on|off)</tt><label id="pragma-checkstack"><p>
776 Tells the compiler to insert calls to a stack checking subroutine to detect
777 stack overflows. The stack checking code will lead to somewhat larger and
778 slower programs, so you may want to use this pragma when debugging your
779 program and switch it off for the release version. If a stack overflow is
780 detected, the program is aborted.
782 If the argument is "off", stack checks are disabled (the default), otherwise
785 The <tt/#pragma/ understands the push and pop parameters as explained above.
787 <sect1><tt>#pragma codeseg ([push,]<name>)</tt><p>
789 This pragma changes the name used for the CODE segment (the CODE segment
790 is used to store executable code). The argument is a string enclosed in
793 Note: The default linker configuration file does only map the standard
794 segments. If you use other segments, you have to create a new linker
797 The <tt/#pragma/ understands the push and pop parameters as explained above.
801 #pragma codeseg ("MyCODE")
805 <sect1><tt>#pragma codesize ([push,]<int>)</tt><label id="pragma-codesize"><p>
807 This pragma allows finer control about speed vs. size decisions in the code
808 generation and optimization phase. It gives the allowed size increase factor
809 (in percent). The default is can be changed by use of the <tt/<ref
810 id="option-codesize" name="--codesize">/ compiler option.
812 The <tt/#pragma/ understands the push and pop parameters as explained above.
815 <sect1><tt>#pragma dataseg ([push,]<name>)</tt><p>
817 This pragma changes the name used for the DATA segment (the DATA segment
818 is used to store initialized data). The argument is a string enclosed in
821 Note: The default linker configuration file does only map the standard
822 segments. If you use other segments, you have to create a new linker
825 The <tt/#pragma/ understands the push and pop parameters as explained above.
829 #pragma dataseg ("MyDATA")
833 <sect1><tt>#pragma optimize ([push,]on|off)</tt><label id="pragma-optimize"><p>
835 Switch optimization on or off. If the argument is "off", optimization is
836 disabled, otherwise it is enabled. Please note that this pragma only effects
837 whole functions. The setting in effect when the function is encountered will
838 determine if the generated code is optimized or not.
840 Optimization and code generation is also controlled by the <ref
841 id="pragma-codesize" name="codesize pragma">.
843 The default is "off", but may be changed with the <tt/<ref name="-O"
844 id="option-O">/ compiler option.
846 The <tt/#pragma/ understands the push and pop parameters as explained above.
849 <sect1><tt>#pragma rodataseg ([push,]<name>)</tt><p>
851 This pragma changes the name used for the RODATA segment (the RODATA
852 segment is used to store readonly data). The argument is a string
853 enclosed in double quotes.
855 Note: The default linker configuration file does only map the standard
856 segments. If you use other segments, you have to create a new linker
859 The <tt/#pragma/ understands the push and pop parameters as explained above.
863 #pragma rodataseg ("MyRODATA")
867 <sect1><tt>#pragma regvaraddr ([push,]on|off)</tt><p>
869 The compiler does not allow to take the address of register variables.
870 The regvaraddr pragma changes this. Taking the address of a register
871 variable is allowed after using this pragma with "on" as argument.
872 Using "off" as an argument switches back to the default behaviour.
874 Beware: The C standard does not allow taking the address of a variable
875 declared as register. So your programs become non-portable if you use
876 this pragma. In addition, your program may not work. This is usually the
877 case if a subroutine is called with the address of a register variable,
878 and this subroutine (or a subroutine called from there) uses
879 register variables. So be careful with this #pragma.
881 The <tt/#pragma/ understands the push and pop parameters as explained above.
885 #pragma regvaraddr(on) /* Allow taking the address
886 * of register variables
891 <sect1><tt>#pragma regvars ([push,]on|off)</tt><label id="pragma-regvars"><p>
893 Enables or disables use of register variables. If register variables are
894 disabled (the default), the <tt/register/ keyword is ignored. Register
895 variables are explained in more detail in <ref id="regvars" name="a separate
898 The <tt/#pragma/ understands the push and pop parameters as explained above.
901 <sect1><tt>#pragma signedchars ([push,]on|off)</tt><label id="pragma-signedchars"><p>
903 Changes the signedness of the default character type. If the argument is
904 "on", default characters are signed, otherwise characters are unsigned.
905 The compiler default is to make characters unsigned since this creates a
906 lot better code. This default may be overridden by the <tt/--signed-chars/
909 The <tt/#pragma/ understands the push and pop parameters as explained above.
912 <sect1><tt>#pragma staticlocals ([push,]on|off)</tt><label id="pragma-staticlocals"<p>
914 Use variables in the bss segment instead of variables on the stack. This
915 pragma changes the default set by the compiler option <tt/-Cl/. If the
916 argument is "on", local variables are allocated in the BSS segment,
917 leading to shorter and in most cases faster, but non-reentrant code.
919 The <tt/#pragma/ understands the push and pop parameters as explained above.
922 <sect1><tt>#pragma warn ([push,]on|off)</tt><label id="pragma-warn"><p>
924 Switch compiler warnings on or off. If the argument is "off", warnings are
925 disabled, otherwise they're enabled. The default is "on", but may be changed
926 with the <tt/<ref name="-W" id="option-W">/ compiler option.
928 The <tt/#pragma/ understands the push and pop parameters as explained above.
931 <sect1><tt>#pragma zpsym (<name>)</tt><p>
933 Tell the compiler that the -- previously as external declared -- symbol with
934 the given name is a zero page symbol (usually from an assembler file).
935 The compiler will create a matching import declaration for the assembler.
940 #pragma zpsym ("foo"); /* foo is in the zeropage */
946 <sect>Register variables<label id="regvars"><p>
948 The runtime for all supported platforms has 6 bytes of zero page space
949 available for register variables (this could be increased, but I think it's a
950 good value). So you can declare register variables up to a total size of 6 per
951 function. The compiler will allocate register space on a "first come, first
952 served" base and convert any <tt/register/ declarations that exceed the
953 available register space silently to <tt/auto/. Parameters can also be
954 declared as <tt/register/, this will in fact give slightly shorter code than
955 using a register variable.
957 Since a function must save the current values of the registers on entry and
958 restore them on exit, there is an overhead associated with register variables,
959 and this overhead is quite high (about 20 bytes per variable). This means that
960 just declaring anything as <tt/register/ is not a good idea.
962 The best use for register variables are pointers, especially those that point
963 to structures. The magic number here is about 3 uses of a struct field: If the
964 function contains this number or even more, the generated code will be usually
965 shorter and faster when using a register variable for the struct pointer. The
966 reason for this is that the register variable can in many cases be used as a
967 pointer directly. Having a pointer in an auto variable means that this pointer
968 must first be copied into a zero page location, before it can be dereferenced.
970 Second best use for register variables are counters. However, there is not
971 much difference in the code generated for counters, so you will need at least
972 100 operations on this variable (for example in a loop) to make it worth the
973 trouble. The only savings you get here are by the use of a zero page variable
974 instead of one on the stack or in the data segment.
976 Register variables must be explicitly enabled by using <tt/-Or/ or <tt/-r/ on
977 the command line. Register variables are only accepted on function top level,
978 register variables declared in interior blocks are silently converted to
979 <tt/auto/. With register variables disabled, all variables declared as
980 <tt/register/ are actually auto variables.
982 Please take care when using register variables: While they are helpful and can
983 lead to a tremendous speedup when used correctly, improper usage will cause
984 bloated code and a slowdown.
988 <sect>Inline assembler<label id="inline-asm"><p>
990 The compiler allows to insert assembler statements into the output file. The
994 asm (<string literal>[, optional parameters]) ;
998 __asm__ (<string literal>[, optional parameters]) ;
1002 The first form is in the user namespace and is disabled by <tt><ref
1003 id="option--standard" name="--standard"></tt> if the argument is not <tt/cc65/.
1005 The asm statement may be used inside a function and on global file level. An
1006 inline assembler statement is a primary expression, so it may also be used as
1007 part of an expression. Please note however that the result of an expression
1008 containing just an inline assembler statement is always of type <tt/void/.
1010 The contents of the string literal are preparsed by the compiler and inserted
1011 into the generated assembly output, so that the can be further processed by
1012 the backend and especially the optimizer. For this reason, the compiler does
1013 only allow regular 6502 opcodes to be used with the inline assembler. Pseudo
1014 instructions (like <tt/.import/, <tt/.byte/ and so on) are <em/not/ allowed,
1015 even if the ca65 assembler (which is used to translate the generated assembler
1016 code) would accept them. The builtin inline assembler is not a replacement for
1017 the full blown macro assembler which comes with the compiler.
1019 Note: Inline assembler statements are subject to all optimizations done by the
1020 compiler. There is currently no way to protect an inline assembler statement
1021 from being moved or removed completely by the optimizer. If in doubt, check
1022 the generated assembler output, or disable optimizations.
1024 The string literal may contain format specifiers from the following list. For
1025 each format specifier, an argument is expected which is inserted instead of
1026 the format specifier before passing the assembly code line to the backend.
1029 <item><tt/%b/ - Numerical 8-bit value
1030 <item><tt/%w/ - Numerical 16-bit value
1031 <item><tt/%l/ - Numerical 32-bit value
1032 <item><tt/%v/ - Assembler name of a (global) variable or function
1033 <item><tt/%o/ - Stack offset of a (local) variable
1034 <item><tt/%g/ - Assembler name of a C label
1035 <item><tt/%s/ - The argument is converted to a string
1036 <item><tt/%%/ - The % sign itself
1039 Using these format specifiers, you can access C <tt/#defines/, variables or
1040 similar stuff from the inline assembler. For example, to load the value of
1041 a C <tt/#define/ into the Y register, one would use
1045 __asm__ ("ldy #%b", OFFS);
1048 Or, to access a struct member of a static variable:
1054 unsigned char color;
1056 static pixel_t pixel;
1057 __asm__ ("ldy #%b", offsetof(pixel_t, color));
1058 __asm__ ("lda %v,y", pixel);
1062 Note: Do not embed the assembler labels that are used as names of global
1063 variables or functions into your asm statements. Code like this
1067 int bar () { return 1; }
1068 __asm__ ("lda _foo"); /* DON'T DO THAT! */
1070 __asm__ ("jsr _bar"); /* DON'T DO THAT EITHER! */
1074 may stop working if the way, the compiler generates these names is changed in
1075 a future version. Instead use the format specifiers from the table above:
1078 __asm__ ("lda %v", foo); /* OK */
1080 __asm__ ("jsr %v", bar); /* OK */
1085 <sect>Implementation-defined behavior<p>
1087 This section describes the behavior of cc65 when the standard describes the
1088 behavior as implementation-defined.
1092 <sect>Bugs/Feedback<p>
1094 If you have problems using the compiler, if you find any bugs, or if you're
1095 doing something interesting with it, I would be glad to hear from you. Feel
1096 free to contact me by email (<htmlurl url="mailto:uz@cc65.org"
1097 name="uz@cc65.org">).
1103 This is the original compiler copyright:
1106 --------------------------------------------------------------------------
1109 This is the copyright notice for RA65, LINK65, LIBR65, and other
1110 Atari 8-bit programs. Said programs are Copyright 1989, by John R.
1111 Dunning. All rights reserved, with the following exceptions:
1113 Anyone may copy or redistribute these programs, provided that:
1115 1: You don't charge anything for the copy. It is permissable to
1116 charge a nominal fee for media, etc.
1118 2: All source code and documentation for the programs is made
1119 available as part of the distribution.
1121 3: This copyright notice is preserved verbatim, and included in
1124 You are allowed to modify these programs, and redistribute the
1125 modified versions, provided that the modifications are clearly noted.
1127 There is NO WARRANTY with this software, it comes as is, and is
1128 distributed in the hope that it may be useful.
1130 This copyright notice applies to any program which contains
1131 this text, or the refers to this file.
1133 This copyright notice is based on the one published by the Free
1134 Software Foundation, sometimes known as the GNU project. The idea
1135 is the same as theirs, ie the software is free, and is intended to
1136 stay that way. Everybody has the right to copy, modify, and re-
1137 distribute this software. Nobody has the right to prevent anyone
1138 else from copying, modifying or redistributing it.
1140 --------------------------------------------------------------------------
1143 Small parts of the compiler (parts of the preprocessor and main parser) are
1144 still covered by this copyright. The main portion is covered by the usual
1145 cc65 license, which reads:
1147 This software is provided 'as-is', without any expressed or implied
1148 warranty. In no event will the authors be held liable for any damages
1149 arising from the use of this software.
1151 Permission is granted to anyone to use this software for any purpose,
1152 including commercial applications, and to alter it and redistribute it
1153 freely, subject to the following restrictions:
1156 <item> The origin of this software must not be misrepresented; you must not
1157 claim that you wrote the original software. If you use this software
1158 in a product, an acknowledgment in the product documentation would be
1159 appreciated but is not required.
1160 <item> Altered source versions must be plainly marked as such, and must not
1161 be misrepresented as being the original software.
1162 <item> This notice may not be removed or altered from any source