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/--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
247 <tag><tt>-t target, --target target</tt></tag>
249 This option is used to set the target system. The target system
250 determines things like the character set that is used for strings and
251 character constants. The following target systems are supported:
259 <item>c16 (works also for the c116 with memory up to 32K)
262 <item>cbm510 (CBM-II series with 40 column video)
263 <item>cbm610 (all CBM-II II computers with 80 column video)
268 <item>pet (all CBM PET systems except the 2001)
274 <tag><tt>-v, --verbose</tt></tag>
276 Using this option, the compiler will be somewhat more verbose if errors
277 or warnings are encountered.
280 <tag><tt>--writable-strings</tt></tag>
282 Make string literals writable by placing them into the data segment instead
283 of the rodata segment.
286 <tag><tt>-Cl, --static-locals</tt></tag>
288 Use static storage for local variables instead of storage on the stack.
289 Since the stack is emulated in software, this gives shorter and usually
290 faster code, but the code is no longer reentrant. The difference between
291 <tt/-Cl/ and declaring local variables as static yourself is, that
292 initializer code is executed each time, the function is entered. So when
303 the variable <tt/a/ will always have the value <tt/1/ when entering the
304 function and using <tt/-Cl/, while in
309 static unsigned a = 1;
314 the variable <tt/a/ will have the value <tt/1/ only the first time that the
315 function is entered, and will keep the old value from one call of the
316 function to the next.
318 You may also use <tt><ref id="pragma-staticlocals"
319 name="#pragma staticlocals"></tt> to change this setting in your
323 <tag><tt>-I dir, --include-dir dir</tt></tag>
325 Set a directory where the compiler searches for include files. You may
326 use this option multiple times to add more than one directory to the
330 <label id="option-O">
331 <tag><tt>-O, -Oi, -Or, -Os</tt></tag>
333 Enable an optimizer run over the produced code.
335 Using <tt/-Oi/, the code generator will inline some code where otherwise a
336 runtime functions would have been called, even if the generated code is
337 larger. This will not only remove the overhead for a function call, but will
338 make the code visible for the optimizer. <tt/-Oi/ is an alias for
339 <tt/--codesize 200/.
341 <tt/-Or/ will make the compiler honor the <tt/register/ keyword. Local
342 variables may be placed in registers (which are actually zero page
343 locations). There is some overhead involved with register variables, since
344 the old contents of the registers must be saved and restored. In addition,
345 the current implementation does not make good use of register variables, so
346 using <tt/-Or/ may make your program even slower and larger. Use with care!
348 Using <tt/-Os/ will force the compiler to inline some known functions from
349 the C library like strlen. Note: This has two consequences:
352 <item>You may not use names of standard C functions in your own code. If you
353 do that, your program is not standard compliant anyway, but using
354 <tt/-Os/ will actually break things.
356 <item>The inlined string and memory functions will not handle strings or
357 memory areas larger than 255 bytes. Similarly, the inlined <tt/is..()/
358 functions will not work with values outside the char. range (such as
363 It is possible to concatenate the modifiers for <tt/-O/. For example, to
364 enable register variables and inlining of known functions, you may use
368 <tag><tt>-T, --add-source</tt></tag>
370 This include the source code as comments in the generated code. This is
374 <tag><tt>-V, --version</tt></tag>
376 Print the version number of the compiler. When submitting a bug report,
377 please include the operating system you're using, and the compiler
381 <label id="option-W">
382 <tag><tt>-W</tt></tag>
384 This option will suppress any warnings generated by the compiler. Since
385 any source file may be written in a manner that it will not produce
386 compiler warnings, using this option is usually not a good idea.
391 <sect>Input and output<p>
393 The compiler will accept one C file per invocation and create a file with
394 the same base name, but with the extension replaced by ".s". The output
395 file contains assembler code suitable for the use with the ca65 macro
398 In addition to the paths named in the <tt/-I/ option on the command line, the
399 directory named in the environment variable <tt/CC65_INC/ is added to the
400 search path for include files on startup.
404 <sect>Differences to the ISO standard<p>
406 Here is a list of differences between the language, the compiler accepts,
407 and the one defined by the ISO standard:
411 <item> The compiler allows unnamed parameters in parameter lists. The
412 compiler will not issue warnings about unused parameters that don't
413 have a name. This feature can be disabled with the <tt><ref
414 id="option--standard" name="--standard"></tt> command line option.
416 <item> The compiler has some additional keywords:
422 <item><tt/__fastcall__/
426 <item><tt/__attribute__/
429 The keywords without the underlines can be disabled with the
430 <tt><ref id="option--standard" name="--standard"></tt> command line
433 <item> The datatypes "float" and "double" are not available.
435 <item> The compiler does not support bit fields.
437 <item> C Functions may not return structs (or unions), and structs may not
438 be passed as parameters by value. However, struct assignment *is*
441 <item> Part of the C library is available only with fastcall calling
442 conventions (see below). It means that you must not mix pointers to
443 those functions with pointers to user-written, not-fastcall functions.
447 There may be some more minor differences I'm currently not aware of. The
448 biggest problem is the missing float data type. With this limitation in
449 mind, you should be able to write fairly portable code.
455 This cc65 version has some extensions to the ISO C standard.
459 <item> The compiler allows to insert assembler statements into the output
463 asm (<string literal>[, optional parameters]) ;
467 __asm__ (<string literal>[, optional parameters]) ;
470 The first form is in the user namespace and is disabled if the <tt/-A/
473 There is a whole section covering inline assembler statements,
474 <ref id="inline-asm" name="see there">.
477 <item> There is a special calling convention named "fastcall".
478 The syntax for a function declaration using fastcall is
481 <return type> fastcall <function name> (<parameter list>)
485 <return type> __fastcall__ <function name> (<parameter list>)
489 void __fastcall__ f (unsigned char c)
491 The first form of the fastcall keyword is in the user namespace and can
492 therefore be disabled with the <tt><ref id="option--standard"
493 name="--standard"></tt> command line option.
495 For functions declared as <tt/fastcall/, the rightmost parameter is not
496 pushed on the stack but left in the primary register when the function
497 is called. This will reduce the cost when calling assembler functions
498 significantly, especially when the function itself is rather small.
501 <item> There are two pseudo variables named <tt/__AX__/ and <tt/__EAX__/.
502 Both refer to the primary register that is used by the compiler to
503 evaluate expressions or return function results. <tt/__AX__/ is of
504 type <tt/unsigned int/ and <tt/__EAX__/ of type <tt/long unsigned int/
505 respectively. The pseudo variables may be used as lvalue and rvalue as
506 every other variable. They are most useful together with short
507 sequences of assembler code. For example, the macro
517 will give the high byte of any unsigned value.
520 <item> Inside a function, the identifier <tt/__func__/ gives the name of the
521 current function as a string. Outside of functions, <tt/__func__/ is
526 #define PRINT_DEBUG(s) printf ("%s: %s\n", __func__, s);
529 The macro will print the name of the current function plus a given
533 <item> cc65 allows the initialization of <tt/void/ variables. This may be
534 used to create variable structures that are more compatible with
535 interfaces written for assembler languages. Here is an example:
538 void GCmd = { (char)3, (unsigned)0x2000, (unsigned)0x3000 };
541 This will be translated as follows:
550 Since the variable is of type <tt/void/ you may not use it as is.
551 However, taking the address of the variable results in a <tt/void*/
552 which may be passed to any function expecting a pointer.
554 See the <url url="geos.html" name="GEOS library document"> for examples
555 on how to use this feature.
558 <item> cc65 implements flexible array struct members as defined in the C99 ISO
559 standard. As an extension, these fields may be initialized. There are
560 several exceptions, however (which is probably the reason why the
561 standard does not define this feature, because it is highly
562 unorthogonal). Flexible array members cannot be initialized ...
565 <item>... when defining an array of structs with flexible
567 <item>... if such a struct is a member field of another struct
568 which is not the last field.
569 <item>... if the struct which contains a flexible array member is
570 declared as <tt/register/, and the size and compiler settings
571 do allow the compiler actually to place the struct into the
572 register bank in the zero page.
575 Please note that -- as defined in the ISO C standard -- the <tt/sizeof/
576 operator returns the struct size with the flexible array member having
577 size zero, even if it is initialized.
584 <sect>Predefined macros<p>
586 The compiler defines several macros at startup:
590 <tag><tt>__CC65__</tt></tag>
592 This macro is always defined. Its value is the version number of the
593 compiler in hex. For example, version 2.10.1 of the compiler has this macro
594 defined as <tt/0x02A1/.
596 <tag><tt>__APPLE2__</tt></tag>
598 This macro is defined if the target is the Apple ][ (-t apple2).
600 <tag><tt>__APPLE2ENH__</tt></tag>
602 This macro is defined if the target is the enhanced Apple // (-t apple2enh).
604 <tag><tt>__ATARI__</tt></tag>
606 This macro is defined if the target is one of the Atari computers
607 (400/800/130XL/800XL).
609 <tag><tt>__ATMOS__</tt></tag>
611 This macro is defined if the target is the Oric Atmos (-t atmos).
613 <tag><tt>__CBM__</tt></tag>
615 This macro is defined if the target system is one of the CBM targets.
617 <tag><tt>__C16__</tt></tag>
619 This macro is defined if the target is the c16 (-t c16).
621 <tag><tt>__C64__</tt></tag>
623 This macro is defined if the target is the c64 (-t c64).
625 <tag><tt>__C128__</tt></tag>
627 This macro is defined if the target is the c128 (-t c128).
629 <tag><tt>__CBM510__</tt></tag>
631 This macro is defined if the target is the CBM 500 series of computers.
633 <tag><tt>__CBM610__</tt></tag>
635 This macro is defined if the target is one of the CBM 600/700 family of
636 computers (called B series in the US).
638 <tag><tt>__GEOS__</tt></tag>
640 This macro is defined if you are compiling for the GEOS system (-t geos).
642 <tag><tt>__LUNIX__</tt></tag>
644 This macro is defined if you are compiling for the LUnix system (-t lunix).
646 <tag><tt>__LYNX__</tt></tag>
648 This macro is defined if the target is the Atari Lynx (-t lynx).
650 <tag><tt>__NES__</tt></tag>
652 This macro is defined if the target is the NES (-t nes).
654 <tag><tt>__PET__</tt></tag>
656 This macro is defined if the target is the PET family of computers (-t pet).
658 <tag><tt>__PLUS4__</tt></tag>
660 This macro is defined if the target is the plus/4 (-t plus4).
662 <tag><tt>__SUPERVISION__</tt></tag>
664 This macro is defined if the target is the supervision (-t supervision).
666 <tag><tt>__VIC20__</tt></tag>
668 This macro is defined if the target is the vic20 (-t vic20).
670 <tag><tt>__FILE__</tt></tag>
672 This macro expands to a string containing the name of the C source file.
674 <tag><tt>__LINE__</tt></tag>
676 This macro expands to the current line number.
678 <tag><tt>__CC65_STD__</tt></tag>
680 This macro is defined to one of the following depending on the <tt><ref
681 id="option--standard" name="--standard"></tt> command line option:
683 <item><tt/__CC65_STD_C89__/
684 <item><tt/__CC65_STD_C99__/
685 <item><tt/__CC65_STD_CC65__/
688 <tag><tt>__OPT__</tt></tag>
690 Is defined if the compiler was called with the <tt/-O/ command line option.
692 <tag><tt>__OPT_i__</tt></tag>
694 Is defined if the compiler was called with the <tt/-Oi/ command line option.
696 <tag><tt>__OPT_r__</tt></tag>
698 Is defined if the compiler was called with the <tt/-Or/ command line option.
700 <tag><tt>__OPT_s__</tt></tag>
702 Is defined if the compiler was called with the <tt/-Os/ command line option.
707 <sect>#pragmas<label id="pragmas"><p>
709 The compiler understands some pragmas that may be used to change code
710 generation and other stuff. Some of these pragmas understand a special form:
711 If the first parameter is <tt/push/, the old value is saved onto a stack
712 before changing it. The value may later be restored by using the <tt/pop/
713 parameter with the <tt/#pragma/.
715 <sect1><tt>#pragma bssseg ([push,]<name>)</tt><p>
717 This pragma changes the name used for the BSS segment (the BSS segment
718 is used to store uninitialized data). The argument is a string enclosed
721 Note: The default linker configuration file does only map the standard
722 segments. If you use other segments, you have to create a new linker
725 Beware: The startup code will zero only the default BSS segment. If you
726 use another BSS segment, you have to do that yourself, otherwise
727 uninitialized variables do not have the value zero.
729 The <tt/#pragma/ understands the push and pop parameters as explained above.
733 #pragma bssseg ("MyBSS")
737 <sect1><tt>#pragma charmap (<index>, <code>)</tt><p>
739 Each literal string and each literal character in the source is translated
740 by use of a translation table. This translation table is preset when the
741 compiler is started depending on the target system, for example to map
742 ISO-8859-1 characters into PETSCII if the target is a commodore machine.
744 This pragma allows to change entries in the translation table, so the
745 translation for individual characters, or even the complete table may be
748 Both arguments are assumed to be unsigned characters with a valid range of
751 Beware of two pitfalls:
754 <item>The character index is actually the code of the character in the
755 C source, so character mappings do always depend on the source
756 character set. This means that <tt/#pragma charmap/ is not
757 portable -- it depends on the build environment.
758 <item>While it is possible to use character literals as indices, the
759 result may be somewhat unexpected, since character literals are
760 itself translated. For this reason I would suggest to avoid
761 character literals and use numeric character codes instead.
766 /* Use a space wherever an 'a' occurs in ISO-8859-1 source */
767 #pragma charmap (0x61, 0x20);
771 <sect1><tt>#pragma checkstack ([push,]on|off)</tt><label id="pragma-checkstack"><p>
773 Tells the compiler to insert calls to a stack checking subroutine to detect
774 stack overflows. The stack checking code will lead to somewhat larger and
775 slower programs, so you may want to use this pragma when debugging your
776 program and switch it off for the release version. If a stack overflow is
777 detected, the program is aborted.
779 If the argument is "off", stack checks are disabled (the default), otherwise
782 The <tt/#pragma/ understands the push and pop parameters as explained above.
784 <sect1><tt>#pragma codeseg ([push,]<name>)</tt><p>
786 This pragma changes the name used for the CODE segment (the CODE segment
787 is used to store executable code). The argument is a string enclosed in
790 Note: The default linker configuration file does only map the standard
791 segments. If you use other segments, you have to create a new linker
794 The <tt/#pragma/ understands the push and pop parameters as explained above.
798 #pragma codeseg ("MyCODE")
802 <sect1><tt>#pragma codesize ([push,]<int>)</tt><label id="pragma-codesize"><p>
804 This pragma allows finer control about speed vs. size decisions in the code
805 generation and optimization phase. It gives the allowed size increase factor
806 (in percent). The default is can be changed by use of the <tt/<ref
807 id="option-codesize" name="--codesize">/ compiler option.
809 The <tt/#pragma/ understands the push and pop parameters as explained above.
812 <sect1><tt>#pragma dataseg ([push,]<name>)</tt><p>
814 This pragma changes the name used for the DATA segment (the DATA segment
815 is used to store initialized data). The argument is a string enclosed in
818 Note: The default linker configuration file does only map the standard
819 segments. If you use other segments, you have to create a new linker
822 The <tt/#pragma/ understands the push and pop parameters as explained above.
826 #pragma dataseg ("MyDATA")
830 <sect1><tt>#pragma optimize ([push,]on|off)</tt><label id="pragma-optimize"><p>
832 Switch optimization on or off. If the argument is "off", optimization is
833 disabled, otherwise it is enabled. Please note that this pragma only effects
834 whole functions. The setting in effect when the function is encountered will
835 determine if the generated code is optimized or not.
837 Optimization and code generation is also controlled by the <ref
838 id="pragma-codesize" name="codesize pragma">.
840 The default is "off", but may be changed with the <tt/<ref name="-O"
841 id="option-O">/ compiler option.
843 The <tt/#pragma/ understands the push and pop parameters as explained above.
846 <sect1><tt>#pragma rodataseg ([push,]<name>)</tt><p>
848 This pragma changes the name used for the RODATA segment (the RODATA
849 segment is used to store readonly data). The argument is a string
850 enclosed in double quotes.
852 Note: The default linker configuration file does only map the standard
853 segments. If you use other segments, you have to create a new linker
856 The <tt/#pragma/ understands the push and pop parameters as explained above.
860 #pragma rodataseg ("MyRODATA")
864 <sect1><tt>#pragma regvaraddr ([push,]on|off)</tt><p>
866 The compiler does not allow to take the address of register variables.
867 The regvaraddr pragma changes this. Taking the address of a register
868 variable is allowed after using this pragma with "on" as argument.
869 Using "off" as an argument switches back to the default behaviour.
871 Beware: The C standard does not allow taking the address of a variable
872 declared as register. So your programs become non-portable if you use
873 this pragma. In addition, your program may not work. This is usually the
874 case if a subroutine is called with the address of a register variable,
875 and this subroutine (or a subroutine called from there) uses
876 register variables. So be careful with this #pragma.
878 The <tt/#pragma/ understands the push and pop parameters as explained above.
882 #pragma regvaraddr(on) /* Allow taking the address
883 * of register variables
888 <sect1><tt>#pragma regvars ([push,]on|off)</tt><label id="pragma-regvars"><p>
890 Enables or disables use of register variables. If register variables are
891 disabled (the default), the <tt/register/ keyword is ignored. Register
892 variables are explained in more detail in <ref id="regvars" name="a separate
895 The <tt/#pragma/ understands the push and pop parameters as explained above.
898 <sect1><tt>#pragma signedchars ([push,]on|off)</tt><label id="pragma-signedchars"><p>
900 Changes the signedness of the default character type. If the argument is
901 "on", default characters are signed, otherwise characters are unsigned.
902 The compiler default is to make characters unsigned since this creates a
903 lot better code. This default may be overridden by the <tt/--signed-chars/
906 The <tt/#pragma/ understands the push and pop parameters as explained above.
909 <sect1><tt>#pragma staticlocals ([push,]on|off)</tt><label id="pragma-staticlocals"<p>
911 Use variables in the bss segment instead of variables on the stack. This
912 pragma changes the default set by the compiler option <tt/-Cl/. If the
913 argument is "on", local variables are allocated in the BSS segment,
914 leading to shorter and in most cases faster, but non-reentrant code.
916 The <tt/#pragma/ understands the push and pop parameters as explained above.
919 <sect1><tt>#pragma warn ([push,]on|off)</tt><label id="pragma-warn"><p>
921 Switch compiler warnings on or off. If the argument is "off", warnings are
922 disabled, otherwise they're enabled. The default is "on", but may be changed
923 with the <tt/<ref name="-W" id="option-W">/ compiler option.
925 The <tt/#pragma/ understands the push and pop parameters as explained above.
928 <sect1><tt>#pragma zpsym (<name>)</tt><p>
930 Tell the compiler that the -- previously as external declared -- symbol with
931 the given name is a zero page symbol (usually from an assembler file).
932 The compiler will create a matching import declaration for the assembler.
937 #pragma zpsym ("foo"); /* foo is in the zeropage */
943 <sect>Register variables<label id="regvars"><p>
945 The runtime for all supported platforms has 6 bytes of zero page space
946 available for register variables (this could be increased, but I think it's a
947 good value). So you can declare register variables up to a total size of 6 per
948 function. The compiler will allocate register space on a "first come, first
949 served" base and convert any <tt/register/ declarations that exceed the
950 available register space silently to <tt/auto/. Parameters can also be
951 declared as <tt/register/, this will in fact give slightly shorter code than
952 using a register variable.
954 Since a function must save the current values of the registers on entry and
955 restore them on exit, there is an overhead associated with register variables,
956 and this overhead is quite high (about 20 bytes per variable). This means that
957 just declaring anything as <tt/register/ is not a good idea.
959 The best use for register variables are pointers, especially those that point
960 to structures. The magic number here is about 3 uses of a struct field: If the
961 function contains this number or even more, the generated code will be usually
962 shorter and faster when using a register variable for the struct pointer. The
963 reason for this is that the register variable can in many cases be used as a
964 pointer directly. Having a pointer in an auto variable means that this pointer
965 must first be copied into a zero page location, before it can be dereferenced.
967 Second best use for register variables are counters. However, there is not
968 much difference in the code generated for counters, so you will need at least
969 100 operations on this variable (for example in a loop) to make it worth the
970 trouble. The only savings you get here are by the use of a zero page variable
971 instead of one on the stack or in the data segment.
973 Register variables must be explicitly enabled by using <tt/-Or/ or <tt/-r/ on
974 the command line. Register variables are only accepted on function top level,
975 register variables declared in interior blocks are silently converted to
976 <tt/auto/. With register variables disabled, all variables declared as
977 <tt/register/ are actually auto variables.
979 Please take care when using register variables: While they are helpful and can
980 lead to a tremendous speedup when used correctly, improper usage will cause
981 bloated code and a slowdown.
985 <sect>Inline assembler<label id="inline-asm"><p>
987 The compiler allows to insert assembler statements into the output file. The
991 asm (<string literal>[, optional parameters]) ;
995 __asm__ (<string literal>[, optional parameters]) ;
999 The first form is in the user namespace and is disabled by <tt><ref
1000 id="option--standard" name="--standard"></tt> if the argument is not <tt/cc65/.
1002 The asm statement may be used inside a function and on global file level. An
1003 inline assembler statement is a primary expression, so it may also be used as
1004 part of an expression. Please note however that the result of an expression
1005 containing just an inline assembler statement is always of type <tt/void/.
1007 The contents of the string literal are preparsed by the compiler and inserted
1008 into the generated assembly output, so that the can be further processed by
1009 the backend and especially the optimizer. For this reason, the compiler does
1010 only allow regular 6502 opcodes to be used with the inline assembler. Pseudo
1011 instructions (like <tt/.import/, <tt/.byte/ and so on) are <em/not/ allowed,
1012 even if the ca65 assembler (which is used to translate the generated assembler
1013 code) would accept them. The builtin inline assembler is not a replacement for
1014 the full blown macro assembler which comes with the compiler.
1016 Note: Inline assembler statements are subject to all optimizations done by the
1017 compiler. There is currently no way to protect an inline assembler statement
1018 from being moved or removed completely by the optimizer. If in doubt, check
1019 the generated assembler output, or disable optimizations.
1021 The string literal may contain format specifiers from the following list. For
1022 each format specifier, an argument is expected which is inserted instead of
1023 the format specifier before passing the assembly code line to the backend.
1026 <item><tt/%b/ - Numerical 8-bit value
1027 <item><tt/%w/ - Numerical 16-bit value
1028 <item><tt/%l/ - Numerical 32-bit value
1029 <item><tt/%v/ - Assembler name of a (global) variable or function
1030 <item><tt/%o/ - Stack offset of a (local) variable
1031 <item><tt/%g/ - Assembler name of a C label
1032 <item><tt/%s/ - The argument is converted to a string
1033 <item><tt/%%/ - The % sign itself
1036 Using these format specifiers, you can access C <tt/#defines/, variables or
1037 similar stuff from the inline assembler. For example, to load the value of
1038 a C <tt/#define/ into the Y register, one would use
1042 __asm__ ("ldy #%b", OFFS);
1045 Or, to access a struct member of a static variable:
1051 unsigned char color;
1053 static pixel_t pixel;
1054 __asm__ ("ldy #%b", offsetof(pixel_t, color));
1055 __asm__ ("lda %v,y", pixel);
1059 Note: Do not embed the assembler labels that are used as names of global
1060 variables or functions into your asm statements. Code like this
1064 int bar () { return 1; }
1065 __asm__ ("lda _foo"); /* DON'T DO THAT! */
1067 __asm__ ("jsr _bar"); /* DON'T DO THAT EITHER! */
1071 may stop working if the way, the compiler generates these names is changed in
1072 a future version. Instead use the format specifiers from the table above:
1075 __asm__ ("lda %v", foo); /* OK */
1077 __asm__ ("jsr %v", bar); /* OK */
1082 <sect>Bugs/Feedback<p>
1084 If you have problems using the compiler, if you find any bugs, or if you're
1085 doing something interesting with it, I would be glad to hear from you. Feel
1086 free to contact me by email (<htmlurl url="mailto:uz@cc65.org"
1087 name="uz@cc65.org">).
1093 This is the original compiler copyright:
1096 --------------------------------------------------------------------------
1099 This is the copyright notice for RA65, LINK65, LIBR65, and other
1100 Atari 8-bit programs. Said programs are Copyright 1989, by John R.
1101 Dunning. All rights reserved, with the following exceptions:
1103 Anyone may copy or redistribute these programs, provided that:
1105 1: You don't charge anything for the copy. It is permissable to
1106 charge a nominal fee for media, etc.
1108 2: All source code and documentation for the programs is made
1109 available as part of the distribution.
1111 3: This copyright notice is preserved verbatim, and included in
1114 You are allowed to modify these programs, and redistribute the
1115 modified versions, provided that the modifications are clearly noted.
1117 There is NO WARRANTY with this software, it comes as is, and is
1118 distributed in the hope that it may be useful.
1120 This copyright notice applies to any program which contains
1121 this text, or the refers to this file.
1123 This copyright notice is based on the one published by the Free
1124 Software Foundation, sometimes known as the GNU project. The idea
1125 is the same as theirs, ie the software is free, and is intended to
1126 stay that way. Everybody has the right to copy, modify, and re-
1127 distribute this software. Nobody has the right to prevent anyone
1128 else from copying, modifying or redistributing it.
1130 --------------------------------------------------------------------------
1133 Small parts of the compiler (parts of the preprocessor and main parser) are
1134 still covered by this copyright. The main portion is covered by the usual
1135 cc65 license, which reads:
1137 This software is provided 'as-is', without any expressed or implied
1138 warranty. In no event will the authors be held liable for any damages
1139 arising from the use of this software.
1141 Permission is granted to anyone to use this software for any purpose,
1142 including commercial applications, and to alter it and redistribute it
1143 freely, subject to the following restrictions:
1146 <item> The origin of this software must not be misrepresented; you must not
1147 claim that you wrote the original software. If you use this software
1148 in a product, an acknowledgment in the product documentation would be
1149 appreciated but is not required.
1150 <item> Altered source versions must be plainly marked as such, and must not
1151 be misrepresented as being the original software.
1152 <item> This notice may not be removed or altered from any source