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 optmizer 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)
266 <item>pet (all CBM PET systems except the 2001)
271 <tag><tt>-v, --verbose</tt></tag>
273 Using this option, the compiler will be somewhat more verbose if errors
274 or warnings are encountered.
277 <tag><tt>--writable-strings</tt></tag>
279 Make string literals writable by placing them into the data segment instead
280 of the rodata segment.
283 <tag><tt>-Cl, --static-locals</tt></tag>
285 Use static storage for local variables instead of storage on the stack.
286 Since the stack is emulated in software, this gives shorter and usually
287 faster code, but the code is no longer reentrant. The difference between
288 <tt/-Cl/ and declaring local variables as static yourself is, that
289 initializer code is executed each time, the function is entered. So when
300 the variable a will always have the value 1 when entering the function
301 and using <tt/-Cl/, while in
306 static unsigned a = 1;
311 the variable a will have the value 1 only the first time, the function
312 is entered, and will keep the old value from one call of the function to
315 You may also use <tt><ref id="pragma-staticlocals" name="#pragma
316 staticlocals"></tt> to change this setting in your sources.
319 <tag><tt>-I dir, --include-dir dir</tt></tag>
321 Set a directory where the compiler searches for include files. You may
322 use this option multiple times to add more than one directory to the
326 <label id="option-O">
327 <tag><tt>-O, -Oi, -Or, -Os</tt></tag>
329 Enable an optimizer run over the produced code.
331 Using <tt/-Oi/, the code generator will inline some code where otherwise a
332 runtime functions would have been called, even if the generated code is
333 larger. This will not only remove the overhead for a function call, but will
334 make the code visible for the optimizer. <tt/-Oi/ is an alias for
337 <tt/-Or/ will make the compiler honor the <tt/register/ keyword. Local
338 variables may be placed in registers (which are actually zero page
339 locations). There is some overhead involved with register variables, since
340 the old contents of the registers must be saved and restored. In addition,
341 the current implementation does not make good use of register variables, so
342 using <tt/-Or/ may make your program even slower and larger. Use with care!
344 Using <tt/-Os/ will force the compiler to inline some known functions from
345 the C library like strlen. Note: This has two consequences:
348 <item>You may not use names of standard C functions in your own code. If you
349 do that, your program is not standard compliant anyway, but using
350 <tt/-Os/ will actually break things.
352 <item>The inlined string and memory functions will not handle strings or
353 memory areas larger than 255 bytes. Similar, the inlined <tt/is..()/
354 functions will not work with values outside char range.
358 It is possible to concatenate the modifiers for <tt/-O/. For example, to
359 enable register variables and inlining of known functions, you may use
363 <tag><tt>-T, --add-source</tt></tag>
365 This include the source code as comments in the generated code. This is
369 <tag><tt>-V, --version</tt></tag>
371 Print the version number of the compiler. When submitting a bug report,
372 please include the operating system you're using, and the compiler
376 <label id="option-W">
377 <tag><tt>-W</tt></tag>
379 This option will suppress any warnings generated by the compiler. Since
380 any source file may be written in a manner that it will not produce
381 compiler warnings, using this option is usually not a good idea.
386 <sect>Input and output<p>
388 The compiler will accept one C file per invocation and create a file with
389 the same base name, but with the extension replaced by ".s". The output
390 file contains assembler code suitable for the use with the ca65 macro
393 In addition to the paths named in the <tt/-I/ option on the command line, the
394 directory named in the environment variable <tt/CC65_INC/ is added to the
395 search path for include files on startup.
399 <sect>Differences to the ISO standard<p>
401 Here is a list of differences between the language, the compiler accepts,
402 and the one defined by the ISO standard:
406 <item> The compiler allows unnamed parameters in parameter lists. The
407 compiler will not issue warnings about unused parameters that don't
408 have a name. This feature can be disabled with the <tt><ref
409 id="option--standard" name="--standard"></tt> command line option.
411 <item> The compiler has some additional keywords:
417 <item><tt/__fastcall__/
421 <item><tt/__attribute__/
424 The keywords without the underlines can be disabled with the
425 <tt><ref id="option--standard" name="--standard"></tt> command line
428 <item> The datatypes "float" and "double" are not available.
430 <item> The compiler does not support bit fields.
432 <item> C Functions may not return structs (or unions), and structs may not
433 be passed as parameters by value. However, struct assignment *is*
436 <item> Part of the C library is available only with fastcall calling
437 conventions (see below). This means, that you may not mix pointers to
438 those functions with pointers to user written functions.
442 There may be some more minor differences, I'm currently not aware off. The
443 biggest problem is the missing float data type. With this limitation in
444 mind, you should be able to write fairly portable code.
450 This cc65 version has some extensions to the ISO C standard.
454 <item> The compiler allows to insert assembler statements into the output
458 asm (<string literal>[, optional parameters]) ;
462 __asm__ (<string literal>[, optional parameters]) ;
465 The first form is in the user namespace and is disabled if the <tt/-A/
468 There is a whole section covering inline assembler statements,
469 <ref id="inline-asm" name="see there">.
472 <item> There is a special calling convention named "fastcall". This calling
473 convention is currently only usable for functions written in
474 assembler. The syntax for a function declaration using fastcall is
477 <return type> fastcall <function name> (<parameter list>)
481 <return type> __fastcall__ <function name> (<parameter list>)
485 void __fastcall__ f (unsigned char c)
487 The first form of the fastcall keyword is in the user namespace and can
488 therefore be disabled with the <tt><ref id="option--standard"
489 name="--standard"></tt> command line option.
491 For functions declared as <tt/fastcall/, the rightmost parameter is not
492 pushed on the stack but left in the primary register when the function
493 is called. This will reduce the cost when calling assembler functions
494 significantly, especially when the function itself is rather small.
497 <item> There are two pseudo variables named <tt/__AX__/ and <tt/__EAX__/.
498 Both refer to the primary register that is used by the compiler to
499 evaluate expressions or return function results. <tt/__AX__/ is of
500 type <tt/unsigned int/ and <tt/__EAX__/ of type <tt/long unsigned int/
501 respectively. The pseudo variables may be used as lvalue and rvalue as
502 every other variable. They are most useful together with short
503 sequences of assembler code. For example, the macro
513 will give the high byte of any unsigned value.
516 <item> Inside a function, the identifier <tt/__func__/ gives the name of the
517 current function as a string. Outside of functions, <tt/__func__/ is
522 #define PRINT_DEBUG(s) printf ("%s: %s\n", __func__, s);
525 The macro will print the name of the current function plus a given
529 <item> cc65 allows the initialization of <tt/void/ variables. This may be
530 used to create variable structures that are more compatible with
531 interfaces written for assembler languages. Here is an example:
534 void GCmd = { (char)3, (unsigned)0x2000, (unsigned)0x3000 };
537 This will be translated as follows:
546 Since the variable is of type <tt/void/ you may not use it as is.
547 However, taking the address of the variable results in a <tt/void*/
548 which may be passed to any function expecting a pointer.
550 See the <htmlurl url="geos.html" name="GEOS library"> for examples on
551 how to use this feature.
554 <item> cc65 implements flexible array struct members as defined in the C99 ISO
555 standard. As an extension, these fields may be initialized. There are
556 several exceptions, however (which is probably the reason why the
557 standard does not define this feature, because it is highly
558 unorthogonal). Flexible array members cannot be initialized...
561 <item> ...when defining an array of structs with flexible members.
562 <item> ...if such a struct is a member field of another struct which
563 is not the last field.
564 <item> If the struct which contains a flexible array member is
565 declared as <tt/register/ and the size and compiler settings
566 do allow the compiler to actually place the struct into the
567 register bank in the zero page.
570 Please note that - as defined in the ISO C standard - the <tt/sizeof/
571 operator returns the struct size with the flexible array member having
572 size zero, even if it is initialized.
579 <sect>Predefined macros<p>
581 The compiler defines several macros at startup:
585 <tag><tt>__CC65__</tt></tag>
587 This macro is always defined. Its value is the version number of the
588 compiler in hex. Version 2.0.1 of the compiler will have this macro defined
591 <tag><tt>__APPLE2__</tt></tag>
593 This macro is defined if the target is the Apple ][ (-t apple2).
595 <tag><tt>__ATARI__</tt></tag>
597 This macro is defined if the target is one of the Atari computers
598 (400/800/130XL/800XL).
600 <tag><tt>__ATMOS__</tt></tag>
602 This macro is defined if the target is the Oric Atmos (-t atmos).
604 <tag><tt>__CBM__</tt></tag>
606 This macro is defined if the target system is one of the CBM targets.
608 <tag><tt>__C16__</tt></tag>
610 This macro is defined if the target is the c16 (-t c16).
612 <tag><tt>__C64__</tt></tag>
614 This macro is defined if the target is the c64 (-t c64).
616 <tag><tt>__C128__</tt></tag>
618 This macro is defined if the target is the c128 (-t c128).
620 <tag><tt>__CBM510__</tt></tag>
622 This macro is defined if the target is the CBM 500 series of computers.
624 <tag><tt>__CBM610__</tt></tag>
626 This macro is defined if the target is one of the CBM 600/700 family of
627 computers (called B series in the US).
629 <tag><tt>__GEOS__</tt></tag>
631 This macro is defined if you are compiling for the GEOS system (-t geos).
633 <tag><tt>__PET__</tt></tag>
635 This macro is defined if the target is the PET family of computers (-t pet).
637 <tag><tt>__PLUS4__</tt></tag>
639 This macro is defined if the target is the plus/4 (-t plus4).
641 <tag><tt>__VIC20__</tt></tag>
643 This macro is defined if the target is the vic20 (-t vic20).
645 <tag><tt>__FILE__</tt></tag>
647 This macro expands to a string containing the name of the C source file.
649 <tag><tt>__LINE__</tt></tag>
651 This macro expands to the current line number.
653 <tag><tt>__CC65_STD__</tt></tag>
655 This macro is defined to one of the following depending on the <tt><ref
656 id="option--standard" name="--standard"></tt> command line option:
658 <item><tt/__CC65_STD_C89__/
659 <item><tt/__CC65_STD_C99__/
660 <item><tt/__CC65_STD_CCC65__/
663 <tag><tt>__OPT__</tt></tag>
665 Is defined if the compiler was called with the <tt/-O/ command line option.
667 <tag><tt>__OPT_i__</tt></tag>
669 Is defined if the compiler was called with the <tt/-Oi/ command line option.
671 <tag><tt>__OPT_r__</tt></tag>
673 Is defined if the compiler was called with the <tt/-Or/ command line option.
675 <tag><tt>__OPT_s__</tt></tag>
677 Is defined if the compiler was called with the <tt/-Os/ command line option.
682 <sect>#pragmas<label id="pragmas"><p>
684 The compiler understands some pragmas that may be used to change code
685 generation and other stuff. Some of these pragmas understand a special form:
686 If the first parameter is <tt/push/, the old value is saved onto a stack
687 before changing it. The value may later be restored by using the <tt/pop/
688 parameter with the <tt/#pragma/.
690 <sect1><tt>#pragma bssseg (<name>)</tt><p>
692 This pragma changes the name used for the BSS segment (the BSS segment
693 is used to store uninitialized data). The argument is a string enclosed
696 Note: The default linker configuration file does only map the standard
697 segments. If you use other segments, you have to create a new linker
700 Beware: The startup code will zero only the default BSS segment. If you
701 use another BSS segment, you have to do that yourself, otherwise
702 uninitialized variables do not have the value zero.
704 The <tt/#pragma/ understands the push and pop parameters as explained above.
708 #pragma bssseg ("MyBSS")
712 <sect1><tt>#pragma charmap (<index>, <code>)</tt><p>
714 Each literal string and each literal character in the source is translated
715 by use of a translation table. This translation table is preset when the
716 compiler is started depending on the target system, for example to map
717 ISO-8859-1 characters into PETSCII if the target is a commodore machine.
719 This pragma allows to change entries in the translation table, so the
720 translation for individual characters, or even the complete table may be
723 Both arguments are assumed to be unsigned characters with a valid range of
726 Beware of two pitfalls:
729 <item>The character index is actually the code of the character in the
730 C source, so character mappings do always depend on the source
731 character set. This means that <tt/#pragma charmap/ is not portable
732 - it depends on the build environment.
733 <item>While it is possible to use character literals as indices, the
734 result may be somewhat unexpected, since character literals are
735 itself translated. For this reason I would suggest to avoid
736 character literals and use numeric character codes instead.
741 /* Use a space wherever an 'a' occurs in ISO-8859-1 source */
742 #pragma charmap (0x61, 0x20);
746 <sect1><tt>#pragma checkstack ([push,]on|off)</tt><label id="pragma-checkstack"><p>
748 Tells the compiler to insert calls to a stack checking subroutine to detect
749 stack overflows. The stack checking code will lead to somewhat larger and
750 slower programs, so you may want to use this pragma when debugging your
751 program and switch it off for the release version. If a stack overflow is
752 detected, the program is aborted.
754 If the argument is "off", stack checks are disabled (the default), otherwise
757 The <tt/#pragma/ understands the push and pop parameters as explained above.
759 <sect1><tt>#pragma codeseg ([push,]<name>)</tt><p>
761 This pragma changes the name used for the CODE segment (the CODE segment
762 is used to store executable code). The argument is a string enclosed in
765 Note: The default linker configuration file does only map the standard
766 segments. If you use other segments, you have to create a new linker
769 The <tt/#pragma/ understands the push and pop parameters as explained above.
773 #pragma codeseg ("MyCODE")
777 <sect1><tt>#pragma codesize ([push,]<int>)</tt><label id="pragma-codesize"><p>
779 This pragma allows finer control about speed vs. size decisions in the code
780 generation and optimization phase. It gives the allowed size increase factor
781 (in percent). The default is can be changed by use of the <tt/<ref
782 id="option-codesize" name="--codesize">/ compiler option.
784 The <tt/#pragma/ understands the push and pop parameters as explained above.
787 <sect1><tt>#pragma dataseg ([push,]<name>)</tt><p>
789 This pragma changes the name used for the DATA segment (the DATA segment
790 is used to store initialized data). 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 dataseg ("MyDATA")
805 <sect1><tt>#pragma optimize ([push,]on|off)</tt><label id="pragma-optimize"><p>
807 Switch optimization on or off. If the argument is "off", optimization is
808 disabled, otherwise it is enabled. Please note that this pragma only effects
809 whole functions. The setting in effect when the function is encountered will
810 determine if the generated code is optimized or not.
812 Optimization and code generation is also controlled by the <ref
813 id="pragma-codesize" name="codesize pragma">.
815 The default is "off", but may be changed with the <tt/<ref name="-O"
816 id="option-O">/ compiler option.
818 The <tt/#pragma/ understands the push and pop parameters as explained above.
821 <sect1><tt>#pragma rodataseg ([push,]<name>)</tt><p>
823 This pragma changes the name used for the RODATA segment (the RODATA
824 segment is used to store readonly data). The argument is a string
825 enclosed in double quotes.
827 Note: The default linker configuration file does only map the standard
828 segments. If you use other segments, you have to create a new linker
831 The <tt/#pragma/ understands the push and pop parameters as explained above.
835 #pragma rodataseg ("MyRODATA")
839 <sect1><tt>#pragma regvaraddr ([push,]on|off)</tt><p>
841 The compiler does not allow to take the address of register variables.
842 The regvaraddr pragma changes this. Taking the address of a register
843 variable is allowed after using this pragma with "on" as argument.
844 Using "off" as an argument switches back to the default behaviour.
846 Beware: The C standard does not allow taking the address of a variable
847 declared as register. So your programs become non-portable if you use
848 this pragma. In addition, your program may not work. This is usually the
849 case if a subroutine is called with the address of a register variable,
850 and this subroutine (or a subroutine called from there) uses itself
851 register variables. So be careful with this #pragma.
853 The <tt/#pragma/ understands the push and pop parameters as explained above.
857 #pragma regvaraddr(on) /* Allow taking the address
858 * of register variables
863 <sect1><tt>#pragma regvars ([push,]on|off)</tt><label id="pragma-regvars"><p>
865 Enables or disables use of register variables. If register variables are
866 disabled (the default), the <tt/register/ keyword is ignored. Register
867 variables are explained in more detail in <ref id="regvars" name="a separate
870 The <tt/#pragma/ understands the push and pop parameters as explained above.
873 <sect1><tt>#pragma signedchars ([push,]on|off)</tt><label id="pragma-signedchars"><p>
875 Changes the signedness of the default character type. If the argument is
876 "on", default characters are signed, otherwise characters are unsigned.
877 The compiler default is to make characters unsigned since this creates a
878 lot better code. This default may be overridden by the <tt/--signed-chars/
881 The <tt/#pragma/ understands the push and pop parameters as explained above.
884 <sect1><tt>#pragma staticlocals ([push,]on|off)</tt><label id="pragma-staticlocals"<p>
886 Use variables in the bss segment instead of variables on the stack. This
887 pragma changes the default set by the compiler option <tt/-Cl/. If the
888 argument is "on", local variables are allocated in the BSS segment,
889 leading to shorter and in most cases faster, but non-reentrant code.
891 The <tt/#pragma/ understands the push and pop parameters as explained above.
894 <sect1><tt>#pragma warn ([push,]on|off)</tt><label id="pragma-warn"><p>
896 Switch compiler warnings on or off. If the argument is "off", warnings are
897 disabled, otherwise they're enabled. The default is "on", but may be changed
898 with the <tt/<ref name="-W" id="option-W">/ compiler option.
900 The <tt/#pragma/ understands the push and pop parameters as explained above.
903 <sect1><tt>#pragma zpsym (<name>)</tt><p>
905 Tell the compiler that the - previously as external declared - symbol with
906 the given name is a zero page symbol (usually from an assembler file).
907 The compiler will create a matching import declaration for the assembler.
912 #pragma zpsym ("foo"); /* foo is in the zeropage */
918 <sect>Register variables<label id="regvars"><p>
920 The runtime for all supported platforms has 6 bytes of zero page space
921 available for register variables (this could be increased, but I think it's a
922 good value). So you can declare register variables up to a total size of 6 per
923 function. The compiler will allocate register space on a "first come, first
924 served" base and convert any <tt/register/ declarations that exceed the
925 available register space silently to <tt/auto/. Parameters can also be
926 declared as <tt/register/, this will in fact give slightly shorter code than
927 using a register variable.
929 Since a function must save the current values of the registers on entry and
930 restore them on exit, there is an overhead associated with register variables,
931 and this overhead is quite high (about 20 bytes per variable). This means that
932 just declaring anything as <tt/register/ is not a good idea.
934 The best use for register variables are pointers, especially those that point
935 to structures. The magic number here is about 3 uses of a struct field: If the
936 function contains this number or even more, the generated code will be usually
937 shorter and faster when using a register variable for the struct pointer. The
938 reason for this is that the register variable can in many cases be used as a
939 pointer directly. Having a pointer in an auto variable means that this pointer
940 must first be copied into a zero page location, before it can be dereferenced.
942 Second best use for register variables are counters. However, there is not
943 much difference in the code generated for counters, so you will need at least
944 100 operations on this variable (for example in a loop) to make it worth the
945 trouble. The only savings you get here are by the use of a zero page variable
946 instead of one on the stack or in the data segment.
948 Register variables must be explicitly enabled by using <tt/-Or/ or <tt/-r/ on
949 the command line. Register variables are only accepted on function top level,
950 register variables declared in interior blocks are silently converted to
951 <tt/auto/. With register variables disabled, all variables declared as
952 <tt/register/ are actually auto variables.
954 Please take care when using register variables: While they are helpful and can
955 lead to a tremendous speedup when used correctly, improper usage will cause
956 bloated code and a slowdown.
960 <sect>Inline assembler<label id="inline-asm"><p>
962 The compiler allows to insert assembler statements into the output file. The
966 asm (<string literal>[, optional parameters]) ;
970 __asm__ (<string literal>[, optional parameters]) ;
974 The first form is in the user namespace and is disabled by <tt><ref
975 id="option--standard" name="--standard"></tt> if the argument is not <tt/cc65/.
977 The asm statement may be used inside a function and on global file level. An
978 inline assembler statement is a primary expression, so it may also be used as
979 part of an expression. Please note however that the result of an expression
980 containing just an inline assembler statement is always of type <tt/void/.
982 The contents of the string literal are preparsed by the compiler and inserted
983 into the generated assembly output, so that the can be further processed by
984 the backend and especially the optimizer. For this reason, the compiler does
985 only allow regular 6502 opcodes to be used with the inline assembler. Pseudo
986 instructions (like <tt/.import/, <tt/.byte/ and so on) are <em/not/ allowed,
987 even if the ca65 assembler (which is used to translate the generated assembler
988 code) would accept them. The builtin inline assembler is not a replacement for
989 the full blown macro assembler which comes with the compiler.
991 Note: Inline assembler statements are subject to all optimizations done by the
992 compiler. There is currently no way to protect an inline assembler statement
993 from being moved or removed completely by the optimizer. If in doubt, check
994 the generated assembler output, or disable optimizations.
996 The string literal may contain format specifiers from the following list. For
997 each format specifier, an argument is expected which is inserted instead of
998 the format specifier before passing the assembly code line to the backend.
1001 <item><tt/%b/ - Numerical 8 bit value
1002 <item><tt/%w/ - Numerical 16 bit value
1003 <item><tt/%l/ - Numerical 32 bit value
1004 <item><tt/%v/ - Assembler name of a (global) variable or function
1005 <item><tt/%o/ - Stack offset of a (local) variable
1006 <item><tt/%g/ - Assembler name of a C label
1007 <item><tt/%s/ - The argument is converted to a string
1008 <item><tt/%%/ - The % sign itself
1011 Using these format specifiers, you can access C <tt/#defines/, variables or
1012 similar stuff from the inline assembler. For example, to load the value of
1013 a C <tt/#define/ into the Y register, one would use
1017 __asm__ ("ldy #%b", OFFS);
1020 Or, to access a struct member of a static variable:
1026 unsigned char color;
1028 static pixel_t pixel;
1029 __asm__ ("ldy #%b", offsetof(pixel_t, color));
1030 __asm__ ("lda %v,y", pixel);
1034 Note: Do not embedd the assembler labels that are used as names of global
1035 variables or functions into your asm statements. Code like this
1039 int bar () { return 1; }
1040 __asm__ ("lda _foo"); /* DON'T DO THAT! */
1042 __asm__ ("jsr _bar"); /* DON'T DO THAT EITHER! */
1046 may stop working if the way, the compiler generates these names is changed in
1047 a future version. Instead use the format specifiers from the table above.
1051 <sect>Bugs/Feedback<p>
1053 If you have problems using the compiler, if you find any bugs, or if you're
1054 doing something interesting with it, I would be glad to hear from you. Feel
1055 free to contact me by email (<htmlurl url="mailto:uz@cc65.org" name="uz@cc65.org">).
1061 This is the original compiler copyright:
1064 --------------------------------------------------------------------------
1067 This is the copyright notice for RA65, LINK65, LIBR65, and other
1068 Atari 8-bit programs. Said programs are Copyright 1989, by John R.
1069 Dunning. All rights reserved, with the following exceptions:
1071 Anyone may copy or redistribute these programs, provided that:
1073 1: You don't charge anything for the copy. It is permissable to
1074 charge a nominal fee for media, etc.
1076 2: All source code and documentation for the programs is made
1077 available as part of the distribution.
1079 3: This copyright notice is preserved verbatim, and included in
1082 You are allowed to modify these programs, and redistribute the
1083 modified versions, provided that the modifications are clearly noted.
1085 There is NO WARRANTY with this software, it comes as is, and is
1086 distributed in the hope that it may be useful.
1088 This copyright notice applies to any program which contains
1089 this text, or the refers to this file.
1091 This copyright notice is based on the one published by the Free
1092 Software Foundation, sometimes known as the GNU project. The idea
1093 is the same as theirs, ie the software is free, and is intended to
1094 stay that way. Everybody has the right to copy, modify, and re-
1095 distribute this software. Nobody has the right to prevent anyone
1096 else from copying, modifying or redistributing it.
1098 --------------------------------------------------------------------------
1101 Small parts of the compiler (parts of the preprocessor and main parser) are
1102 still covered by this copyright. The main portion is covered by the usual
1103 cc65 license, which reads:
1105 This software is provided 'as-is', without any expressed or implied
1106 warranty. In no event will the authors be held liable for any damages
1107 arising from the use of this software.
1109 Permission is granted to anyone to use this software for any purpose,
1110 including commercial applications, and to alter it and redistribute it
1111 freely, subject to the following restrictions:
1114 <item> The origin of this software must not be misrepresented; you must not
1115 claim that you wrote the original software. If you use this software
1116 in a product, an acknowledgment in the product documentation would be
1117 appreciated but is not required.
1118 <item> Altered source versions must be plainly marked as such, and must not
1119 be misrepresented as being the original software.
1120 <item> This notice may not be removed or altered from any source