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
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 is a separate document named "library.txt" that covers the library
33 available for the compiler. If you know C and are interested in doing
34 actual programming, the library documentation is probably of much more use
37 If you need some hints for getting the best code out of the compiler, you
38 may have a look at "coding.txt" which covers some code generation issues.
44 The compiler translates C files into files containing assembler code that
45 may be translated by the ca65 macroassembler (for more information about
46 the assembler, have a look at ca65.txt).
49 <sect1>Command line option overview<p>
51 The compiler may be called as follows:
54 ---------------------------------------------------------------------------
55 Usage: cc65 [options] file
57 -Cl Make local variables static
58 -Dsym[=defn] Define a symbol
59 -I dir Set an include directory search path
61 -Oi Optimize code, inline more code
62 -Or Enable register variables
63 -Os Inline some known functions
64 -T Include source as comment
65 -V Print the compiler version number
68 -g Add debug info to object file
70 -j Default characters are signed
71 -o name Name the output file
72 -r Enable register variables
73 -t sys Set the target system
77 --add-source Include source as comment
78 --bss-name seg Set the name of the BSS segment
79 --check-stack Generate stack overflow checks
80 --code-name seg Set the name of the CODE segment
81 --codesize x Accept larger code by factor x
82 --cpu type Set cpu type
83 --create-dep Create a make dependency file
84 --data-name seg Set the name of the DATA segment
86 --debug-info Add debug info to object file
87 --forget-inc-paths Forget include search paths
88 --help Help (this text)
89 --include-dir dir Set an include directory search path
90 --register-space b Set space available for register variables
91 --register-vars Enable register variables
92 --rodata-name seg Set the name of the RODATA segment
93 --signed-chars Default characters are signed
94 --standard std Language standard (c89, c99, cc65)
95 --static-locals Make local variables static
96 --target sys Set the target system
97 --verbose Increase verbosity
98 --version Print the compiler version number
99 --writable-strings Make string literals writable
100 ---------------------------------------------------------------------------
104 <sect1>Command line options in detail<p>
106 Here is a description of all the command line options:
110 <tag><tt>--bss-name seg</tt></tag>
112 Set the name of the bss segment.
115 <tag><tt>--check-stack</tt></tag>
117 Tells the compiler to generate code that checks for stack overflows. See
118 <tt><ref id="pragma-checkstack" name="#pragma checkstack"></tt> for an
119 explanation of this feature.
122 <tag><tt>--code-name seg</tt></tag>
124 Set the name of the code segment.
127 <label id="option-codesize">
128 <tag><tt>--codesize x</tt></tag>
130 This options allows finer control about speed vs. size decisions in the code
131 generation and optimization phases. It gives the allowed size increase
132 factor (in percent). The default is 100 when not using <tt/-Oi/ and 200 when
133 using <tt/-Oi/ (<tt/-Oi/ is the same as <tt/--codesize 200/).
136 <tag><tt>--cpu CPU</tt></tag>
138 A new, still experimental option. You may specify "6502" or "65C02" as
139 the CPU. 6502 is the default, so this will not change anything.
140 Specifying 65C02 will use a few 65C02 instructions when generating code.
141 Don't expect too much from this option: It is still new (and may have
142 bugs), and the additional instructions for the 65C02 are not that
146 <tag><tt>--create-dep</tt></tag>
148 Tells the compiler to generate a file containing the dependency list for
149 the compiled module in makefile syntax. The file is named as the C input
150 file with the extension replaced by <tt/.u/.
153 <tag><tt>-d, --debug</tt></tag>
155 Enables debug mode, something that should not be needed for mere
159 <tag><tt>-D sym[=definition]</tt></tag>
161 Define a macro on the command line. If no definition is given, the macro
162 is defined to the value "1".
165 <tag><tt>--forget-inc-paths</tt></tag>
167 Forget the builtin include paths. This is most useful when building
168 customized C or runtime libraries, in which case the standard header
169 files should be ignored.
172 <tag><tt>-g, --debug-info</tt></tag>
174 This will cause the compiler to insert a <tt/.DEBUGINFO/ command into the
175 generated assembler code. This will cause the assembler to include all
176 symbols in a special section in the object file.
179 <tag><tt>-h, --help</tt></tag>
181 Print the short option summary shown above.
184 <tag><tt>-o name</tt></tag>
186 Specify the name of the output file. If you don't specify a name, the
187 name of the C input file is used, with the extension replaced by ".s".
190 <tag><tt>-r, --register-vars</tt></tag>
192 <tt/-r/ will make the compiler honor the <tt/register/ keyword. Local
193 variables may be placed in registers (which are actually zero page
194 locations). There is some overhead involved with register variables, since
195 the old contents of the registers must be saved and restored. Since register
196 variables are of limited use without the optimizer, there is also a combined
197 switch: <tt/-Or/ will enable both, the optimizer and register variables.
199 For more information about register variables see <ref id="regvars"
200 name="register variables">.
202 The compiler setting can also be changed within the source file by using
203 <tt><ref id="pragma-regvars" name="#pragma regvars"></tt>.
206 <tag><tt>--register-space</tt></tag>
208 This option takes a numeric parameter and is used to specify, how much
209 zero page register space is available. Please note that just giving this
210 option will not increase or decrease by itself, it will just tell the
211 compiler about the available space. You will have to allocate that space
212 yourself using an assembler module with the necessary allocations, and a
213 linker configuration that matches the assembler module. The default value
214 for this option is 6 (bytes).
216 If you don't know what all this means, please don't use this option.
219 <tag><tt>--rodata-name seg</tt></tag>
221 Set the name of the rodata segment (the segment used for readonly data).
224 <tag><tt>-j, --signed-chars</tt></tag>
226 Using this option, you can make the default characters signed. Since the
227 6502 has no provisions for sign extending characters (which is needed on
228 almost any load operation), this will make the code larger and slower. A
229 better way is to declare characters explicitly as "signed" if needed. You
230 can also use <tt><ref id="pragma-signedchars" name="#pragma
231 signedchars"></tt> for better control of this option.
234 <label id="option--standard">
235 <tag><tt>--standard std</tt></tag>
237 This option allows to set the language standard supported. The argument is
246 <tag><tt>-t target, --target target</tt></tag>
248 This option is used to set the target system. The target system
249 determines things like the character set that is used for strings and
250 character constants. The following target systems are supported:
258 <item>c16 (works also for the c116 with memory up to 32K)
261 <item>cbm510 (CBM-II series with 40 column video)
262 <item>cbm610 (all CBM-II II computers with 80 column video)
267 <item>pet (all CBM PET systems except the 2001)
273 <tag><tt>-v, --verbose</tt></tag>
275 Using this option, the compiler will be somewhat more verbose if errors
276 or warnings are encountered.
279 <tag><tt>--writable-strings</tt></tag>
281 Make string literals writable by placing them into the data segment instead
282 of the rodata segment.
285 <tag><tt>-Cl, --static-locals</tt></tag>
287 Use static storage for local variables instead of storage on the stack.
288 Since the stack is emulated in software, this gives shorter and usually
289 faster code, but the code is no longer reentrant. The difference between
290 <tt/-Cl/ and declaring local variables as static yourself is, that
291 initializer code is executed each time, the function is entered. So when
302 the variable a will always have the value 1 when entering the function
303 and using <tt/-Cl/, while in
308 static unsigned a = 1;
313 the variable a will have the value 1 only the first time, the function
314 is entered, and will keep the old value from one call of the function to
317 You may also use <tt><ref id="pragma-staticlocals" name="#pragma
318 staticlocals"></tt> to change this setting in your sources.
321 <tag><tt>-I dir, --include-dir dir</tt></tag>
323 Set a directory where the compiler searches for include files. You may
324 use this option multiple times to add more than one directory to the
328 <label id="option-O">
329 <tag><tt>-O, -Oi, -Or, -Os</tt></tag>
331 Enable an optimizer run over the produced code.
333 Using <tt/-Oi/, the code generator will inline some code where otherwise a
334 runtime functions would have been called, even if the generated code is
335 larger. This will not only remove the overhead for a function call, but will
336 make the code visible for the optimizer. <tt/-Oi/ is an alias for
339 <tt/-Or/ will make the compiler honor the <tt/register/ keyword. Local
340 variables may be placed in registers (which are actually zero page
341 locations). There is some overhead involved with register variables, since
342 the old contents of the registers must be saved and restored. In addition,
343 the current implementation does not make good use of register variables, so
344 using <tt/-Or/ may make your program even slower and larger. Use with care!
346 Using <tt/-Os/ will force the compiler to inline some known functions from
347 the C library like strlen. Note: This has two consequences:
350 <item>You may not use names of standard C functions in your own code. If you
351 do that, your program is not standard compliant anyway, but using
352 <tt/-Os/ will actually break things.
354 <item>The inlined string and memory functions will not handle strings or
355 memory areas larger than 255 bytes. Similar, the inlined <tt/is..()/
356 functions will not work with values outside char range.
360 It is possible to concatenate the modifiers for <tt/-O/. For example, to
361 enable register variables and inlining of known functions, you may use
365 <tag><tt>-T, --add-source</tt></tag>
367 This include the source code as comments in the generated code. This is
371 <tag><tt>-V, --version</tt></tag>
373 Print the version number of the compiler. When submitting a bug report,
374 please include the operating system you're using, and the compiler
378 <label id="option-W">
379 <tag><tt>-W</tt></tag>
381 This option will suppress any warnings generated by the compiler. Since
382 any source file may be written in a manner that it will not produce
383 compiler warnings, using this option is usually not a good idea.
388 <sect>Input and output<p>
390 The compiler will accept one C file per invocation and create a file with
391 the same base name, but with the extension replaced by ".s". The output
392 file contains assembler code suitable for the use with the ca65 macro
395 In addition to the paths named in the <tt/-I/ option on the command line, the
396 directory named in the environment variable <tt/CC65_INC/ is added to the
397 search path for include files on startup.
401 <sect>Differences to the ISO standard<p>
403 Here is a list of differences between the language, the compiler accepts,
404 and the one defined by the ISO standard:
408 <item> The compiler allows unnamed parameters in parameter lists. The
409 compiler will not issue warnings about unused parameters that don't
410 have a name. This feature can be disabled with the <tt><ref
411 id="option--standard" name="--standard"></tt> command line option.
413 <item> The compiler has some additional keywords:
419 <item><tt/__fastcall__/
423 <item><tt/__attribute__/
426 The keywords without the underlines can be disabled with the
427 <tt><ref id="option--standard" name="--standard"></tt> command line
430 <item> The datatypes "float" and "double" are not available.
432 <item> The compiler does not support bit fields.
434 <item> C Functions may not return structs (or unions), and structs may not
435 be passed as parameters by value. However, struct assignment *is*
438 <item> Part of the C library is available only with fastcall calling
439 conventions (see below). This means, that you may not mix pointers to
440 those functions with pointers to user written functions.
444 There may be some more minor differences, I'm currently not aware off. The
445 biggest problem is the missing float data type. With this limitation in
446 mind, you should be able to write fairly portable code.
452 This cc65 version has some extensions to the ISO C standard.
456 <item> The compiler allows to insert assembler statements into the output
460 asm (<string literal>[, optional parameters]) ;
464 __asm__ (<string literal>[, optional parameters]) ;
467 The first form is in the user namespace and is disabled if the <tt/-A/
470 There is a whole section covering inline assembler statements,
471 <ref id="inline-asm" name="see there">.
474 <item> There is a special calling convention named "fastcall". This calling
475 convention is currently only usable for functions written in
476 assembler. The syntax for a function declaration using fastcall is
479 <return type> fastcall <function name> (<parameter list>)
483 <return type> __fastcall__ <function name> (<parameter list>)
487 void __fastcall__ f (unsigned char c)
489 The first form of the fastcall keyword is in the user namespace and can
490 therefore be disabled with the <tt><ref id="option--standard"
491 name="--standard"></tt> command line option.
493 For functions declared as <tt/fastcall/, the rightmost parameter is not
494 pushed on the stack but left in the primary register when the function
495 is called. This will reduce the cost when calling assembler functions
496 significantly, especially when the function itself is rather small.
499 <item> There are two pseudo variables named <tt/__AX__/ and <tt/__EAX__/.
500 Both refer to the primary register that is used by the compiler to
501 evaluate expressions or return function results. <tt/__AX__/ is of
502 type <tt/unsigned int/ and <tt/__EAX__/ of type <tt/long unsigned int/
503 respectively. The pseudo variables may be used as lvalue and rvalue as
504 every other variable. They are most useful together with short
505 sequences of assembler code. For example, the macro
515 will give the high byte of any unsigned value.
518 <item> Inside a function, the identifier <tt/__func__/ gives the name of the
519 current function as a string. Outside of functions, <tt/__func__/ is
524 #define PRINT_DEBUG(s) printf ("%s: %s\n", __func__, s);
527 The macro will print the name of the current function plus a given
531 <item> cc65 allows the initialization of <tt/void/ variables. This may be
532 used to create variable structures that are more compatible with
533 interfaces written for assembler languages. Here is an example:
536 void GCmd = { (char)3, (unsigned)0x2000, (unsigned)0x3000 };
539 This will be translated as follows:
548 Since the variable is of type <tt/void/ you may not use it as is.
549 However, taking the address of the variable results in a <tt/void*/
550 which may be passed to any function expecting a pointer.
552 See the <htmlurl url="geos.html" name="GEOS library"> for examples on
553 how to use this feature.
556 <item> cc65 implements flexible array struct members as defined in the C99 ISO
557 standard. As an extension, these fields may be initialized. There are
558 several exceptions, however (which is probably the reason why the
559 standard does not define this feature, because it is highly
560 unorthogonal). Flexible array members cannot be initialized...
563 + <!-- add to get rid of "..when undefined" message on Debian Woody -->
564 <item> ...when defining an array of structs with flexible
566 <item> ...if such a struct is a member field of another struct
567 which is not the last field.
568 <item> If the struct which contains a flexible array member is
569 declared as <tt/register/ and the size and compiler settings
570 do allow the compiler to actually place the struct into the
571 register bank in the zero page.
574 Please note that - as defined in the ISO C standard - the <tt/sizeof/
575 operator returns the struct size with the flexible array member having
576 size zero, even if it is initialized.
583 <sect>Predefined macros<p>
585 The compiler defines several macros at startup:
589 <tag><tt>__CC65__</tt></tag>
591 This macro is always defined. Its value is the version number of the
592 compiler in hex. Version 2.0.1 of the compiler will have this macro defined
595 <tag><tt>__APPLE2__</tt></tag>
597 This macro is defined if the target is the Apple ][ (-t apple2).
599 <tag><tt>__APPLE2ENH__</tt></tag>
601 This macro is defined if the target is the enhanced Apple // (-t apple2enh).
603 <tag><tt>__ATARI__</tt></tag>
605 This macro is defined if the target is one of the Atari computers
606 (400/800/130XL/800XL).
608 <tag><tt>__ATMOS__</tt></tag>
610 This macro is defined if the target is the Oric Atmos (-t atmos).
612 <tag><tt>__CBM__</tt></tag>
614 This macro is defined if the target system is one of the CBM targets.
616 <tag><tt>__C16__</tt></tag>
618 This macro is defined if the target is the c16 (-t c16).
620 <tag><tt>__C64__</tt></tag>
622 This macro is defined if the target is the c64 (-t c64).
624 <tag><tt>__C128__</tt></tag>
626 This macro is defined if the target is the c128 (-t c128).
628 <tag><tt>__CBM510__</tt></tag>
630 This macro is defined if the target is the CBM 500 series of computers.
632 <tag><tt>__CBM610__</tt></tag>
634 This macro is defined if the target is one of the CBM 600/700 family of
635 computers (called B series in the US).
637 <tag><tt>__GEOS__</tt></tag>
639 This macro is defined if you are compiling for the GEOS system (-t geos).
641 <tag><tt>__LUNIX__</tt></tag>
643 This macro is defined if you are compiling for the LUnix system (-t lunix).
645 <tag><tt>__LYNX__</tt></tag>
647 This macro is defined if the target is the Atari Lynx (-t lynx).
649 <tag><tt>__NES__</tt></tag>
651 This macro is defined if the target is the NES (-t nes).
653 <tag><tt>__PET__</tt></tag>
655 This macro is defined if the target is the PET family of computers (-t pet).
657 <tag><tt>__PLUS4__</tt></tag>
659 This macro is defined if the target is the plus/4 (-t plus4).
661 <tag><tt>__SUPERVISION__</tt></tag>
663 This macro is defined if the target is the supervision (-t supervision).
665 <tag><tt>__VIC20__</tt></tag>
667 This macro is defined if the target is the vic20 (-t vic20).
669 <tag><tt>__FILE__</tt></tag>
671 This macro expands to a string containing the name of the C source file.
673 <tag><tt>__LINE__</tt></tag>
675 This macro expands to the current line number.
677 <tag><tt>__CC65_STD__</tt></tag>
679 This macro is defined to one of the following depending on the <tt><ref
680 id="option--standard" name="--standard"></tt> command line option:
682 <item><tt/__CC65_STD_C89__/
683 <item><tt/__CC65_STD_C99__/
684 <item><tt/__CC65_STD_CC65__/
687 <tag><tt>__OPT__</tt></tag>
689 Is defined if the compiler was called with the <tt/-O/ command line option.
691 <tag><tt>__OPT_i__</tt></tag>
693 Is defined if the compiler was called with the <tt/-Oi/ command line option.
695 <tag><tt>__OPT_r__</tt></tag>
697 Is defined if the compiler was called with the <tt/-Or/ command line option.
699 <tag><tt>__OPT_s__</tt></tag>
701 Is defined if the compiler was called with the <tt/-Os/ command line option.
706 <sect>#pragmas<label id="pragmas"><p>
708 The compiler understands some pragmas that may be used to change code
709 generation and other stuff. Some of these pragmas understand a special form:
710 If the first parameter is <tt/push/, the old value is saved onto a stack
711 before changing it. The value may later be restored by using the <tt/pop/
712 parameter with the <tt/#pragma/.
714 <sect1><tt>#pragma bssseg (<name>)</tt><p>
716 This pragma changes the name used for the BSS segment (the BSS segment
717 is used to store uninitialized data). The argument is a string enclosed
720 Note: The default linker configuration file does only map the standard
721 segments. If you use other segments, you have to create a new linker
724 Beware: The startup code will zero only the default BSS segment. If you
725 use another BSS segment, you have to do that yourself, otherwise
726 uninitialized variables do not have the value zero.
728 The <tt/#pragma/ understands the push and pop parameters as explained above.
732 #pragma bssseg ("MyBSS")
736 <sect1><tt>#pragma charmap (<index>, <code>)</tt><p>
738 Each literal string and each literal character in the source is translated
739 by use of a translation table. This translation table is preset when the
740 compiler is started depending on the target system, for example to map
741 ISO-8859-1 characters into PETSCII if the target is a commodore machine.
743 This pragma allows to change entries in the translation table, so the
744 translation for individual characters, or even the complete table may be
747 Both arguments are assumed to be unsigned characters with a valid range of
750 Beware of two pitfalls:
753 <item>The character index is actually the code of the character in the
754 C source, so character mappings do always depend on the source
755 character set. This means that <tt/#pragma charmap/ is not portable
756 - it depends on the build environment.
757 <item>While it is possible to use character literals as indices, the
758 result may be somewhat unexpected, since character literals are
759 itself translated. For this reason I would suggest to avoid
760 character literals and use numeric character codes instead.
765 /* Use a space wherever an 'a' occurs in ISO-8859-1 source */
766 #pragma charmap (0x61, 0x20);
770 <sect1><tt>#pragma checkstack ([push,]on|off)</tt><label id="pragma-checkstack"><p>
772 Tells the compiler to insert calls to a stack checking subroutine to detect
773 stack overflows. The stack checking code will lead to somewhat larger and
774 slower programs, so you may want to use this pragma when debugging your
775 program and switch it off for the release version. If a stack overflow is
776 detected, the program is aborted.
778 If the argument is "off", stack checks are disabled (the default), otherwise
781 The <tt/#pragma/ understands the push and pop parameters as explained above.
783 <sect1><tt>#pragma codeseg ([push,]<name>)</tt><p>
785 This pragma changes the name used for the CODE segment (the CODE segment
786 is used to store executable code). The argument is a string enclosed in
789 Note: The default linker configuration file does only map the standard
790 segments. If you use other segments, you have to create a new linker
793 The <tt/#pragma/ understands the push and pop parameters as explained above.
797 #pragma codeseg ("MyCODE")
801 <sect1><tt>#pragma codesize ([push,]<int>)</tt><label id="pragma-codesize"><p>
803 This pragma allows finer control about speed vs. size decisions in the code
804 generation and optimization phase. It gives the allowed size increase factor
805 (in percent). The default is can be changed by use of the <tt/<ref
806 id="option-codesize" name="--codesize">/ compiler option.
808 The <tt/#pragma/ understands the push and pop parameters as explained above.
811 <sect1><tt>#pragma dataseg ([push,]<name>)</tt><p>
813 This pragma changes the name used for the DATA segment (the DATA segment
814 is used to store initialized data). The argument is a string enclosed in
817 Note: The default linker configuration file does only map the standard
818 segments. If you use other segments, you have to create a new linker
821 The <tt/#pragma/ understands the push and pop parameters as explained above.
825 #pragma dataseg ("MyDATA")
829 <sect1><tt>#pragma optimize ([push,]on|off)</tt><label id="pragma-optimize"><p>
831 Switch optimization on or off. If the argument is "off", optimization is
832 disabled, otherwise it is enabled. Please note that this pragma only effects
833 whole functions. The setting in effect when the function is encountered will
834 determine if the generated code is optimized or not.
836 Optimization and code generation is also controlled by the <ref
837 id="pragma-codesize" name="codesize pragma">.
839 The default is "off", but may be changed with the <tt/<ref name="-O"
840 id="option-O">/ compiler option.
842 The <tt/#pragma/ understands the push and pop parameters as explained above.
845 <sect1><tt>#pragma rodataseg ([push,]<name>)</tt><p>
847 This pragma changes the name used for the RODATA segment (the RODATA
848 segment is used to store readonly data). The argument is a string
849 enclosed in double quotes.
851 Note: The default linker configuration file does only map the standard
852 segments. If you use other segments, you have to create a new linker
855 The <tt/#pragma/ understands the push and pop parameters as explained above.
859 #pragma rodataseg ("MyRODATA")
863 <sect1><tt>#pragma regvaraddr ([push,]on|off)</tt><p>
865 The compiler does not allow to take the address of register variables.
866 The regvaraddr pragma changes this. Taking the address of a register
867 variable is allowed after using this pragma with "on" as argument.
868 Using "off" as an argument switches back to the default behaviour.
870 Beware: The C standard does not allow taking the address of a variable
871 declared as register. So your programs become non-portable if you use
872 this pragma. In addition, your program may not work. This is usually the
873 case if a subroutine is called with the address of a register variable,
874 and this subroutine (or a subroutine called from there) uses itself
875 register variables. So be careful with this #pragma.
877 The <tt/#pragma/ understands the push and pop parameters as explained above.
881 #pragma regvaraddr(on) /* Allow taking the address
882 * of register variables
887 <sect1><tt>#pragma regvars ([push,]on|off)</tt><label id="pragma-regvars"><p>
889 Enables or disables use of register variables. If register variables are
890 disabled (the default), the <tt/register/ keyword is ignored. Register
891 variables are explained in more detail in <ref id="regvars" name="a separate
894 The <tt/#pragma/ understands the push and pop parameters as explained above.
897 <sect1><tt>#pragma signedchars ([push,]on|off)</tt><label id="pragma-signedchars"><p>
899 Changes the signedness of the default character type. If the argument is
900 "on", default characters are signed, otherwise characters are unsigned.
901 The compiler default is to make characters unsigned since this creates a
902 lot better code. This default may be overridden by the <tt/--signed-chars/
905 The <tt/#pragma/ understands the push and pop parameters as explained above.
908 <sect1><tt>#pragma staticlocals ([push,]on|off)</tt><label id="pragma-staticlocals"<p>
910 Use variables in the bss segment instead of variables on the stack. This
911 pragma changes the default set by the compiler option <tt/-Cl/. If the
912 argument is "on", local variables are allocated in the BSS segment,
913 leading to shorter and in most cases faster, but non-reentrant code.
915 The <tt/#pragma/ understands the push and pop parameters as explained above.
918 <sect1><tt>#pragma warn ([push,]on|off)</tt><label id="pragma-warn"><p>
920 Switch compiler warnings on or off. If the argument is "off", warnings are
921 disabled, otherwise they're enabled. The default is "on", but may be changed
922 with the <tt/<ref name="-W" id="option-W">/ compiler option.
924 The <tt/#pragma/ understands the push and pop parameters as explained above.
927 <sect1><tt>#pragma zpsym (<name>)</tt><p>
929 Tell the compiler that the - previously as external declared - symbol with
930 the given name is a zero page symbol (usually from an assembler file).
931 The compiler will create a matching import declaration for the assembler.
936 #pragma zpsym ("foo"); /* foo is in the zeropage */
942 <sect>Register variables<label id="regvars"><p>
944 The runtime for all supported platforms has 6 bytes of zero page space
945 available for register variables (this could be increased, but I think it's a
946 good value). So you can declare register variables up to a total size of 6 per
947 function. The compiler will allocate register space on a "first come, first
948 served" base and convert any <tt/register/ declarations that exceed the
949 available register space silently to <tt/auto/. Parameters can also be
950 declared as <tt/register/, this will in fact give slightly shorter code than
951 using a register variable.
953 Since a function must save the current values of the registers on entry and
954 restore them on exit, there is an overhead associated with register variables,
955 and this overhead is quite high (about 20 bytes per variable). This means that
956 just declaring anything as <tt/register/ is not a good idea.
958 The best use for register variables are pointers, especially those that point
959 to structures. The magic number here is about 3 uses of a struct field: If the
960 function contains this number or even more, the generated code will be usually
961 shorter and faster when using a register variable for the struct pointer. The
962 reason for this is that the register variable can in many cases be used as a
963 pointer directly. Having a pointer in an auto variable means that this pointer
964 must first be copied into a zero page location, before it can be dereferenced.
966 Second best use for register variables are counters. However, there is not
967 much difference in the code generated for counters, so you will need at least
968 100 operations on this variable (for example in a loop) to make it worth the
969 trouble. The only savings you get here are by the use of a zero page variable
970 instead of one on the stack or in the data segment.
972 Register variables must be explicitly enabled by using <tt/-Or/ or <tt/-r/ on
973 the command line. Register variables are only accepted on function top level,
974 register variables declared in interior blocks are silently converted to
975 <tt/auto/. With register variables disabled, all variables declared as
976 <tt/register/ are actually auto variables.
978 Please take care when using register variables: While they are helpful and can
979 lead to a tremendous speedup when used correctly, improper usage will cause
980 bloated code and a slowdown.
984 <sect>Inline assembler<label id="inline-asm"><p>
986 The compiler allows to insert assembler statements into the output file. The
990 asm (<string literal>[, optional parameters]) ;
994 __asm__ (<string literal>[, optional parameters]) ;
998 The first form is in the user namespace and is disabled by <tt><ref
999 id="option--standard" name="--standard"></tt> if the argument is not <tt/cc65/.
1001 The asm statement may be used inside a function and on global file level. An
1002 inline assembler statement is a primary expression, so it may also be used as
1003 part of an expression. Please note however that the result of an expression
1004 containing just an inline assembler statement is always of type <tt/void/.
1006 The contents of the string literal are preparsed by the compiler and inserted
1007 into the generated assembly output, so that the can be further processed by
1008 the backend and especially the optimizer. For this reason, the compiler does
1009 only allow regular 6502 opcodes to be used with the inline assembler. Pseudo
1010 instructions (like <tt/.import/, <tt/.byte/ and so on) are <em/not/ allowed,
1011 even if the ca65 assembler (which is used to translate the generated assembler
1012 code) would accept them. The builtin inline assembler is not a replacement for
1013 the full blown macro assembler which comes with the compiler.
1015 Note: Inline assembler statements are subject to all optimizations done by the
1016 compiler. There is currently no way to protect an inline assembler statement
1017 from being moved or removed completely by the optimizer. If in doubt, check
1018 the generated assembler output, or disable optimizations.
1020 The string literal may contain format specifiers from the following list. For
1021 each format specifier, an argument is expected which is inserted instead of
1022 the format specifier before passing the assembly code line to the backend.
1025 <item><tt/%b/ - Numerical 8 bit value
1026 <item><tt/%w/ - Numerical 16 bit value
1027 <item><tt/%l/ - Numerical 32 bit value
1028 <item><tt/%v/ - Assembler name of a (global) variable or function
1029 <item><tt/%o/ - Stack offset of a (local) variable
1030 <item><tt/%g/ - Assembler name of a C label
1031 <item><tt/%s/ - The argument is converted to a string
1032 <item><tt/%%/ - The % sign itself
1035 Using these format specifiers, you can access C <tt/#defines/, variables or
1036 similar stuff from the inline assembler. For example, to load the value of
1037 a C <tt/#define/ into the Y register, one would use
1041 __asm__ ("ldy #%b", OFFS);
1044 Or, to access a struct member of a static variable:
1050 unsigned char color;
1052 static pixel_t pixel;
1053 __asm__ ("ldy #%b", offsetof(pixel_t, color));
1054 __asm__ ("lda %v,y", pixel);
1058 Note: Do not embed the assembler labels that are used as names of global
1059 variables or functions into your asm statements. Code like this
1063 int bar () { return 1; }
1064 __asm__ ("lda _foo"); /* DON'T DO THAT! */
1066 __asm__ ("jsr _bar"); /* DON'T DO THAT EITHER! */
1070 may stop working if the way, the compiler generates these names is changed in
1071 a future version. Instead use the format specifiers from the table above:
1074 __asm__ ("lda %v", foo); /* OK */
1076 __asm__ ("jsr %v", bar); /* OK */
1081 <sect>Bugs/Feedback<p>
1083 If you have problems using the compiler, if you find any bugs, or if you're
1084 doing something interesting with it, I would be glad to hear from you. Feel
1085 free to contact me by email (<htmlurl url="mailto:uz@cc65.org" name="uz@cc65.org">).
1091 This is the original compiler copyright:
1094 --------------------------------------------------------------------------
1097 This is the copyright notice for RA65, LINK65, LIBR65, and other
1098 Atari 8-bit programs. Said programs are Copyright 1989, by John R.
1099 Dunning. All rights reserved, with the following exceptions:
1101 Anyone may copy or redistribute these programs, provided that:
1103 1: You don't charge anything for the copy. It is permissable to
1104 charge a nominal fee for media, etc.
1106 2: All source code and documentation for the programs is made
1107 available as part of the distribution.
1109 3: This copyright notice is preserved verbatim, and included in
1112 You are allowed to modify these programs, and redistribute the
1113 modified versions, provided that the modifications are clearly noted.
1115 There is NO WARRANTY with this software, it comes as is, and is
1116 distributed in the hope that it may be useful.
1118 This copyright notice applies to any program which contains
1119 this text, or the refers to this file.
1121 This copyright notice is based on the one published by the Free
1122 Software Foundation, sometimes known as the GNU project. The idea
1123 is the same as theirs, ie the software is free, and is intended to
1124 stay that way. Everybody has the right to copy, modify, and re-
1125 distribute this software. Nobody has the right to prevent anyone
1126 else from copying, modifying or redistributing it.
1128 --------------------------------------------------------------------------
1131 Small parts of the compiler (parts of the preprocessor and main parser) are
1132 still covered by this copyright. The main portion is covered by the usual
1133 cc65 license, which reads:
1135 This software is provided 'as-is', without any expressed or implied
1136 warranty. In no event will the authors be held liable for any damages
1137 arising from the use of this software.
1139 Permission is granted to anyone to use this software for any purpose,
1140 including commercial applications, and to alter it and redistribute it
1141 freely, subject to the following restrictions:
1144 <item> The origin of this software must not be misrepresented; you must not
1145 claim that you wrote the original software. If you use this software
1146 in a product, an acknowledgment in the product documentation would be
1147 appreciated but is not required.
1148 <item> Altered source versions must be plainly marked as such, and must not
1149 be misrepresented as being the original software.
1150 <item> This notice may not be removed or altered from any source