1 <!doctype linuxdoc system>
4 <title>cc65 Users Guide
5 <author><url url="mailto:uz@cc65.org" name="Ullrich von Bassewitz">,<newline>
6 <url url="mailto:gregdk@users.sf.net" name="Greg King">
10 cc65 is a C compiler for 6502 targets. It supports several 6502 based home
11 computers like the Commodore and Atari machines, but it is easily retargetable.
14 <!-- Table of contents -->
17 <!-- 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.
28 There are separate documents named <url url="library.html"> and <url
29 url="funcref.html"> that cover the library that is available for the compiler.
30 If you know C, and are interested in doing actual programming, the library
31 documentation is probably of much more use than this document.
33 If you need some hints for getting the best code out of the compiler, you
34 may have a look at <url url="coding.html"> which covers some code generation
41 The compiler translates C files into files containing assembly code that
42 may be translated by the ca65 macroassembler (for more information about
43 the assembler, have a look at <url url="ca65.html">).
46 <sect1>Command line option overview<p>
48 The compiler may be called as follows:
51 ---------------------------------------------------------------------------
52 Usage: cc65 [options] file
54 -Cl Make local variables static
55 -Dsym[=defn] Define a symbol
56 -E Stop after the preprocessing stage
57 -I dir Set an include directory search path
59 -Oi Optimize code, inline more code
60 -Or Enable register variables
61 -Os Inline some known functions
62 -T Include source as comment
63 -V Print the compiler version number
64 -W warning[,...] Suppress warnings
66 -g Add debug info to object file
68 -j Default characters are signed
69 -mm model Set the memory model
70 -o name Name the output file
71 -r Enable register variables
72 -t sys Set the target system
76 --add-source Include source as comment
77 --all-cdecl Make functions default to __cdecl__
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 (6502, 65c02)
83 --create-dep name Create a make dependency file
84 --create-full-dep name Create a full make dependency file
85 --data-name seg Set the name of the DATA segment
87 --debug-info Add debug info to object file
88 --debug-opt name Debug optimization steps
89 --dep-target target Use this dependency target
90 --disable-opt name Disable an optimization step
91 --enable-opt name Enable an optimization step
92 --help Help (this text)
93 --include-dir dir Set an include directory search path
94 --list-opt-steps List all optimizer steps and exit
95 --list-warnings List available warning types for -W
96 --local-strings Emit string literals immediately
97 --memory-model model Set the memory model
98 --register-space b Set space available for register variables
99 --register-vars Enable register variables
100 --rodata-name seg Set the name of the RODATA segment
101 --signed-chars Default characters are signed
102 --standard std Language standard (c89, c99, cc65)
103 --static-locals Make local variables static
104 --target sys Set the target system
105 --verbose Increase verbosity
106 --version Print the compiler version number
107 --writable-strings Make string literals writable
108 ---------------------------------------------------------------------------
112 <sect1>Command line options in detail<p>
114 Here is a description of all the command line options:
118 <tag><tt>--all-cdecl</tt></tag>
120 Tells the compiler that functions which aren't declared explicitly with
121 either the <tt/__cdecl__/ or <tt/__fastcall__/ calling conventions should
122 have the cdecl convention. (Normally, functions that aren't variadic are
126 <label id="option-bss-name">
127 <tag><tt>--bss-name seg</tt></tag>
129 Set the name of the bss segment. See also <tt/<ref id="pragma-bss-name"
130 name="#pragma bss-name">/.
133 <label id="option-check-stack">
134 <tag><tt>--check-stack</tt></tag>
136 Tells the compiler to generate code that checks for stack overflows. See
137 <tt/<ref id="pragma-check-stack" name="#pragma check-stack">/ for an
138 explanation of this feature.
141 <label id="option-code-name">
142 <tag><tt>--code-name seg</tt></tag>
144 Set the name of the code segment. See also <tt/<ref id="pragma-code-name"
145 name="#pragma code-name">/
148 <label id="option-codesize">
149 <tag><tt>--codesize x</tt></tag>
151 This options allows finer control about speed vs. size decisions in the code
152 generation and optimization phases. It gives the allowed size increase
153 factor (in percent). The default is 100 when not using <tt/-Oi/ and 200 when
154 using <tt/-Oi/ (<tt/-Oi/ is the same as <tt/-O --codesize 200/).
157 <label id="option--cpu">
158 <tag><tt>--cpu CPU</tt></tag>
160 Set the CPU, the compiler generates code for. You may specify "6502" or
161 "65C02" as the CPU. The default depends on the selected target (see option
162 <tt/<ref id="option-t" name="-t">/). It is the 6502 CPU for most targets or
163 if no target has been set. Specifying 65C02 will use a few 65C02
164 instructions when generating code. Don't expect too much from this option:
165 In most cases the difference in size and speed is just 1-2%.
168 <label id="option-create-dep">
169 <tag><tt>--create-dep name</tt></tag>
171 Tells the compiler to generate a file containing the dependency list for the
172 compiled module in makefile syntax. The output is written to a file with the
173 given name. The output does not include system include files (in angle
177 <label id="option-create-full-dep">
178 <tag><tt>--create-full-dep name</tt></tag>
180 Tells the compiler to generate a file containing the dependency list for the
181 compiled module in makefile syntax. The output is written to a file with the
182 given name. The output does include system include files (in angle
186 <label id="option-data-name">
187 <tag><tt>--data-name seg</tt></tag>
189 Set the name of the data segment. See also <tt/<ref id="pragma-data-name"
190 name="#pragma data-name">/
193 <tag><tt>-d, --debug</tt></tag>
195 Enables debug mode, something that should not be needed for mere
199 <label id="option-dep-target">
200 <tag><tt>--dep-target target</tt></tag>
202 When generating a dependency file, don't use the actual output file as the
203 target of the dependency, but the file specified with this option. The
204 option has no effect if neither <tt/<ref id="option-create-dep"
205 name="--create-dep">/ nor <tt/<ref id="option-create-full-dep"
206 name="--create-full-dep">/ is specified.
209 <tag><tt>-D sym[=definition]</tt></tag>
211 Define a macro on the command line. If no definition is given, the macro
212 is defined to the value "1".
215 <tag><tt>-g, --debug-info</tt></tag>
217 This will cause the compiler to insert a <tt/.DEBUGINFO/ command into the
218 generated assembler code. This will cause the assembler to include all
219 symbols in a special section in the object file.
222 <tag><tt>-h, --help</tt></tag>
224 Print the short option summary shown above.
227 <label id="option-list-warnings">
228 <tag><tt>--list-warnings</tt></tag>
230 List the names of warning types available for use with <tt><ref
231 id="option-W" name="-W"></tt>.
234 <label id="option-local-strings">
235 <tag><tt>--local-strings</tt></tag>
237 Emit string literals into the rodata segment as soon as they're encountered
238 in the source (even if you do nothing but get the sizeof those strings). The
239 default is to keep string literals until end of assembly, merge read only
240 literals if possible, and then output the literals into the data or rodata
241 segment that is active at that point. Use of this option prevents merging of
242 duplicate strings, but the options that change the name of one of the data
245 You can also use <tt><ref id="pragma-local-strings"
246 name="#pragma local-strings"></tt> for fine grained control.
249 <tag><tt>-o name</tt></tag>
251 Specify the name of the output file. If you don't specify a name, the
252 name of the C input file is used, with the extension replaced by ".s".
255 <label id="option-register-vars">
256 <tag><tt>-r, --register-vars</tt></tag>
258 <tt/-r/ will make the compiler honor the <tt/register/ keyword. Local
259 variables may be placed in registers (which are actually zero page
260 locations). There is some overhead involved with register variables, since
261 the old contents of the registers must be saved and restored. Since register
262 variables are of limited use without the optimizer, there is also a combined
263 switch: <tt/-Or/ will enable both, the optimizer and register variables.
265 For more information about register variables see <ref id="register-vars"
266 name="register variables">.
268 The compiler setting can also be changed within the source file by using
269 <tt/<ref id="pragma-register-vars" name="#pragma register-vars">/.
272 <label id="option-register-space">
273 <tag><tt>--register-space</tt></tag>
275 This option takes a numeric parameter and is used to specify, how much
276 zero page register space is available. Please note that just giving this
277 option will not increase or decrease by itself, it will just tell the
278 compiler about the available space. You will have to allocate that space
279 yourself using an assembler module with the necessary allocations, and a
280 linker configuration that matches the assembler module. The default value
281 for this option is 6 (bytes).
283 If you don't know what all this means, please don't use this option.
286 <label id="option-rodata-name">
287 <tag><tt>--rodata-name seg</tt></tag>
289 Set the name of the rodata segment (the segment used for readonly data).
290 See also <tt/<ref id="pragma-rodata-name" name="#pragma rodata-name">/
292 <label id="option-signed-chars">
293 <tag><tt>-j, --signed-chars</tt></tag>
295 Using this option, you can make the default characters signed. Since the
296 6502 has no provisions for sign extending characters (which is needed on
297 almost any load operation), this will make the code larger and slower. A
298 better way is to declare characters explicitly as "signed" if needed. You
299 can also use <tt><ref id="pragma-signed-chars"
300 name="#pragma signed-chars"></tt> for better control of this option.
303 <label id="option--standard">
304 <tag><tt>--standard std</tt></tag>
306 This option allows to set the language standard supported. The argument is
310 This disables anything that is illegal in C89/C90. Among those things
311 are <tt>//</tt> comments and the non-standard keywords without
312 underscores. Please note that cc65 is not a fully C89 compliant compiler
313 despite this option. A few more things (like floats) are missing.
316 This enables a few features from the C99 standard. With this option,
317 <tt>//</tt> comments are allowed. It will also cause warnings and even
318 errors in a few situations that are allowed with <tt/--standard c89/.
319 For example, a call to a function without a prototype is an error in
323 This is the default mode. It is like c99 mode, but additional features
324 are enabled. Among these are "void data", non-standard keywords without
325 the underlines, unnamed function parameters and the requirement for
326 main() to return an int.
329 Please note that the compiler does not support the C99 standard and never
330 will. c99 mode is actually c89 mode with a few selected C99 extensions.
333 <label id="option-t">
334 <tag><tt>-t target, --target target</tt></tag>
336 This option is used to set the target system. The target system determines
337 the character set that is used for strings and character constants and the
338 default CPU. The CPU setting can be overriden by use of the <tt/<ref
339 id="option--cpu" name="--cpu">/ option.
341 The following target systems are supported:
350 <item>c16 (works also for the c116 with memory up to 32K)
353 <item>cbm510 (CBM-II series with 40 column video)
354 <item>cbm610 (all CBM-II II computers with 80 column video)
361 <item>pet (all CBM PET systems except the 2001)
369 <tag><tt>-v, --verbose</tt></tag>
371 Using this option, the compiler will be somewhat more verbose if errors
372 or warnings are encountered.
375 <label id="option-writable-strings">
376 <tag><tt>--writable-strings</tt></tag>
378 Make string literals writable by placing them into the data segment instead
379 of the rodata segment. You can also use <tt><ref id="pragma-writable-strings"
380 name="#pragma writable-strings"></tt> to control this option from within
384 <label id="option-static-locals">
385 <tag><tt>-Cl, --static-locals</tt></tag>
387 Use static storage for local variables instead of storage on the stack.
388 Since the stack is emulated in software, this gives shorter and usually
389 faster code, but the code is no longer reentrant. The difference between
390 <tt/-Cl/ and declaring local variables as static yourself is, that
391 initializer code is executed each time, the function is entered. So when
402 the variable <tt/a/ will always have the value <tt/1/ when entering the
403 function and using <tt/-Cl/, while in
408 static unsigned a = 1;
413 the variable <tt/a/ will have the value <tt/1/ only the first time that the
414 function is entered, and will keep the old value from one call of the
415 function to the next.
417 You may also use <tt><ref id="pragma-static-locals"
418 name="#pragma static-locals"></tt> to change this setting in your
422 <label id="option-include-dir">
423 <tag><tt>-I dir, --include-dir dir</tt></tag>
425 Set a directory where the compiler searches for include files. You may
426 use this option multiple times to add more than one directory to the
430 <label id="option-O">
431 <tag><tt>-O, -Oi, -Or, -Os</tt></tag>
433 Enable an optimizer run over the produced code.
435 Using <tt/-Oi/, the code generator will inline some code where otherwise a
436 runtime functions would have been called, even if the generated code is
437 larger. This will not only remove the overhead for a function call, but will
438 make the code visible for the optimizer. <tt/-Oi/ is an alias for
439 <tt/-O --codesize 200/.
441 <tt/-Or/ will make the compiler honor the <tt/register/ keyword. Local
442 variables may be placed in registers (which are actually zero page
443 locations). See also the <tt/<ref id="option-register-vars"
444 name="--register-vars">/ command line option, and the <ref
445 id="register-vars" name="discussion of register variables"> below.
447 Using <tt/-Os/ will force the compiler to inline some known functions from
448 the C library like strlen. Note: This has two consequences:
451 <item>You may not use names of standard C functions in your own code. If you
452 do that, your program is not standard compliant anyway, but using
453 <tt/-Os/ will actually break things.
455 <item>The inlined string and memory functions will not handle strings or
456 memory areas larger than 255 bytes. Similarly, the inlined <tt/is..()/
457 functions will not work with values outside the char. range (such as
462 It is possible to concatenate the modifiers for <tt/-O/. For example, to
463 enable register variables and inlining of known functions, you may use
467 <tag><tt>-T, --add-source</tt></tag>
469 This include the source code as comments in the generated code. This is
473 <tag><tt>-V, --version</tt></tag>
475 Print the version number of the compiler. When submitting a bug report,
476 please include the operating system you're using, and the compiler
480 <label id="option-W">
481 <tag><tt>-W name[,name]</tt></tag>
483 This option allows to control warnings generated by the compiler. It is
484 followed by a comma separated list of warnings that should be enabled or
485 disabled. To disable a warning, its name is prefixed by a minus sign. If
486 no such prefix exists, or the name is prefixed by a plus sign, the warning
489 The following warning names are currently recognized:
491 <tag><tt/const-comparison/</tag>
492 Warn if the result of a comparison is constant.
493 <tag><tt/error/</tag>
494 Treat all warnings as errors.
495 <tag><tt/no-effect/</tag>
496 Warn about statements that don't have an effect.
497 <tag><tt/struct-param/</tag>
498 Warn when passing structs by value.
499 <tag><tt/unknown-pragma/</tag>
500 Warn about known #pragmas.
501 <tag><tt/unused-label/</tag>
502 Warn about unused labels.
503 <tag><tt/unused-param/</tag>
504 Warn about unused function parameters.
505 <tag><tt/unused-var/</tag>
506 Warn about unused variables.
509 The full list of available warning names may be retrieved by using the
510 option <tt><ref id="option-list-warnings" name="--list-warnings"></tt>.
512 You may also use <tt><ref id="pragma-warn" name="#pragma warn"></tt> to
513 control this setting for smaller pieces of code from within your code.
518 <sect>Input and output<p>
520 The compiler will accept one C file per invocation and create a file with
521 the same base name, but with the extension replaced by ".s". The output
522 file contains assembler code suitable for use with the ca65 macro
525 Include files in quotes are searched in the following places:
527 <item>The current file's directory.
528 <item>Any directory added with the <tt/-I/ option on the command line.
529 <item>The value of the environment variable <tt/CC65_INC/ if it is defined.
532 Include files in angle brackets are searched in the following places:
534 <item>Any directory added with the <tt/-I/ option on the command line.
535 <item>The value of the environment variable <tt/CC65_INC/ if it is defined.
536 <item>A subdirectory named <tt/include/ of the directory defined in the
537 environment variable <tt/CC65_HOME/, if it is defined.
538 <item>An optionally compiled-in directory.
543 <sect>Differences to the ISO standard<p>
545 Apart from the things listed below, the compiler does support additional
546 keywords, has several functions in the standard headers with names outside the
547 reserved namespace and a few syntax extensions. All these can be disabled with
548 the <tt><ref id="option--standard" name="--standard"></tt> command line
549 option. Its use for maximum standards compatibility is advised.
551 Here is a list of differences between the language, the compiler accepts,
552 and the one defined by the ISO standard:
556 <item> The datatypes "float" and "double" are not available.
558 <item> C Functions may not return structs (or unions), and structs may not
559 be passed as parameters by value. However, struct assignment *is*
562 <item> Most of the C library is available with only the fastcall calling
563 convention (<ref id="extension-fastcall" name="see below">). It means
564 that you must not mix pointers to those functions with pointers to
565 user-written, cdecl functions (the calling conventions are incompatible).
567 <item> The <tt/volatile/ keyword has almost no effect. That is not as bad
568 as it sounds, since the 6502 has so few registers that it isn't
569 possible to keep values in registers anyway.
573 There may be some more minor differences I'm currently not aware of. The
574 biggest problem is the missing float data type. With this limitation in
575 mind, you should be able to write fairly portable code.
581 This cc65 version has some extensions to the ISO C standard.
585 <item> The compiler allows to insert assembler statements into the output
589 asm [optional volatile] (<string literal>[, optional parameters]) ;
593 __asm__ [optional volatile] (<string literal>[, optional parameters]) ;
596 The first form is in the user namespace; and, is disabled if the <tt/-A/
599 There is a whole section covering inline assembler statements,
600 <ref id="inline-asm" name="see there">.
603 <label id="extension-fastcall">
604 <item> The normal calling convention -- for non-variadic functions -- is
605 named "fastcall". The syntax for a function declaration that
606 <em/explicitly/ uses fastcall is
609 <return type> fastcall <function name> (<parameter list>)
613 <return type> __fastcall__ <function name> (<parameter list>)
617 void __fastcall__ f (unsigned char c)
619 The first form of the fastcall keyword is in the user namespace and can
620 therefore be disabled with the <tt><ref id="option--standard"
621 name="--standard"></tt> command line option.
623 For functions that are <tt/fastcall/, the rightmost parameter is not
624 pushed on the stack but left in the primary register when the function
625 is called. That significantly reduces the cost of calling those functions.
629 <item> There is another calling convention named "cdecl". Variadic functions
630 (their prototypes have an ellipsis [<tt/.../]) always use that
631 convention. The syntax for a function declaration using cdecl is
634 <return type> cdecl <function name> (<parameter list>)
638 <return type> __cdecl__ <function name> (<parameter list>)
642 int* __cdecl__ f (unsigned char c)
645 The first form of the cdecl keyword is in the user namespace;
646 and therefore, can be disabled with the <tt/<ref id="option--standard"
647 name="--standard">/ command-line option.
649 For functions that are <tt/cdecl/, the rightmost parameter is pushed
650 onto the stack before the function is called. That increases the cost
651 of calling those functions, especially when they are called from many
652 places.<newline><newline>
655 <item> There are two pseudo variables named <tt/__AX__/ and <tt/__EAX__/.
656 Both refer to the primary register that is used by the compiler to
657 evaluate expressions or return function results. <tt/__AX__/ is of
658 type <tt/unsigned int/ and <tt/__EAX__/ of type <tt/long unsigned int/
659 respectively. The pseudo variables may be used as lvalue and rvalue as
660 every other variable. They are most useful together with short
661 sequences of assembler code. For example, the macro
671 will give the high byte of any unsigned value.
674 <item> Inside a function, the identifier <tt/__func__/ gives the name of the
675 current function as a string. Outside of functions, <tt/__func__/ is
680 #define PRINT_DEBUG(s) printf ("%s: %s\n", __func__, s);
683 The macro will print the name of the current function plus a given
687 <item> cc65 allows the initialization of <tt/void/ variables. This may be
688 used to create variable structures that are more compatible with
689 interfaces written for assembler languages. Here is an example:
692 void GCmd = { (char)3, (unsigned)0x2000, (unsigned)0x3000 };
695 This will be translated as follows:
704 Since the variable is of type <tt/void/ you may not use it as is.
705 However, taking the address of the variable results in a <tt/void*/
706 which may be passed to any function expecting a pointer.
708 See the <url url="geos.html" name="GEOS library document"> for examples
709 on how to use this feature.
712 <item> cc65 implements flexible array struct members as defined in the C99 ISO
713 standard. As an extension, these fields may be initialized. There are
714 several exceptions, however (which is probably the reason why the
715 standard does not define this feature, because it is highly
716 unorthogonal). Flexible array members cannot be initialized ...
719 <item>... when defining an array of structs with flexible
721 <item>... if such a struct is a member field of another struct
722 which is not the last field.
723 <item>... if the struct which contains a flexible array member is
724 declared as <tt/register/, and the size and compiler settings
725 do allow the compiler actually to place the struct into the
726 register bank in the zero page.
729 Please note that -- as defined in the ISO C standard -- the <tt/sizeof/
730 operator returns the struct size with the flexible array member having
731 size zero, even if it is initialized.
739 <sect>Predefined macros<p>
741 The compiler defines several macros at startup:
744 <tag><tt>__APPLE2__</tt></tag>
746 This macro is defined if the target is the Apple ][ (-t apple2) or the enhanced Apple //e (-t apple2enh).
748 <tag><tt>__APPLE2ENH__</tt></tag>
750 This macro is defined if the target is the enhanced Apple //e (-t apple2enh).
752 <tag><tt>__ATARI5200__</tt></tag>
754 This macro is defined if the target is the Atari 5200 game console.
756 <tag><tt>__ATARI__</tt></tag>
758 This macro is defined if the target is the Atari 400/800 (-t atari) or the Atari 800XL/130XE (-t atarixl).
760 <tag><tt>__ATARIXL__</tt></tag>
762 This macro is defined if the target is the Atari 800XL/130XE (-t atarixl).
764 <tag><tt>__ATMOS__</tt></tag>
766 This macro is defined if the target is the Oric Atmos (-t atmos).
768 <tag><tt>__C128__</tt></tag>
770 This macro is defined if the target is the Commodore 128 (-t c128).
772 <tag><tt>__C16__</tt></tag>
774 This macro is defined if the target is the Commodore 16/116 (-t c16) or the Commodore Plus/4 (-t plus4).
776 <tag><tt>__C64__</tt></tag>
778 This macro is defined if the target is the Commodore 64 (-t c64).
780 <tag><tt>__CBM__</tt></tag>
782 This macro is defined if the target system is one of the CBM targets.
784 <tag><tt>__CBM510__</tt></tag>
786 This macro is defined if the target is the CBM 500 series of computers.
788 <tag><tt>__CBM610__</tt></tag>
790 This macro is defined if the target is one of the CBM 600/700 family of
791 computers (called B series in the US).
793 <tag><tt>__CC65__</tt></tag>
795 This macro is always defined. Its value is the version number of the
796 compiler in hex. For example, version 2.14 of the compiler has this macro
797 defined as <tt/0x02E0/.
799 <tag><tt>__CC65_STD__</tt></tag>
801 This macro is defined to one of the following depending on the <tt><ref
802 id="option--standard" name="--standard"></tt> command line option:
804 <item><tt/__CC65_STD_C89__/
805 <item><tt/__CC65_STD_C99__/
806 <item><tt/__CC65_STD_CC65__/
809 <tag><tt>__DATE__</tt></tag>
811 This macro expands to the date of translation of the preprocessing
812 translation unit in the form "Mmm dd yyyy".
814 <tag><tt>__FILE__</tt></tag>
816 This macro expands to a string containing the name of the C source file.
818 <tag><tt>__GEOS__</tt></tag>
820 This macro is defined if you are compiling for one of the GEOS systems.
822 <tag><tt>__GEOS_APPLE__</tt></tag>
824 This macro is defined if you are compiling for the Apple GEOS system (-t geos-apple).
826 <tag><tt>__GEOS_CBM__</tt></tag>
828 This macro is defined if you are compiling for the GEOS 64/128 system (-t geos-cbm).
830 <tag><tt>__LINE__</tt></tag>
832 This macro expands to the current line number.
834 <tag><tt>__LUNIX__</tt></tag>
836 This macro is defined if you are compiling for the LUnix system (-t lunix).
838 <tag><tt>__LYNX__</tt></tag>
840 This macro is defined if the target is the Atari Lynx (-t lynx).
842 <tag><tt>__NES__</tt></tag>
844 This macro is defined if the target is the Nintendo Entertainment System (-t nes).
846 <tag><tt>__OPT__</tt></tag>
848 Is defined if the compiler was called with the <tt/-O/ command line option.
850 <tag><tt>__OPT_i__</tt></tag>
852 Is defined if the compiler was called with the <tt/-Oi/ command line option.
854 <tag><tt>__OPT_r__</tt></tag>
856 Is defined if the compiler was called with the <tt/-Or/ command line option.
858 <tag><tt>__OPT_s__</tt></tag>
860 Is defined if the compiler was called with the <tt/-Os/ command line option.
862 <tag><tt>__OSIC1P__</tt></tag>
864 This macro is defined if the target is the Ohio Scientific Challenger 1P
867 <tag><tt>__PET__</tt></tag>
869 This macro is defined if the target is the PET family of computers (-t pet).
871 <tag><tt>__PLUS4__</tt></tag>
873 This macro is defined if the target is the Commodore Plus/4 (-t plus4).
875 <tag><tt>__STDC_HOSTED__</tt></tag>
877 This macro is expands to the integer constant 1.
879 <tag><tt>__SIM6502__</tt></tag>
881 This macro is defined if the target is sim65 in 6502 mode (-t sim6502).
883 <tag><tt>__SIM65C02__</tt></tag>
884 This macro is defined if the target is sim65 in 65C02 mode (-t sim65c02).
886 <tag><tt>__SUPERVISION__</tt></tag>
888 This macro is defined if the target is the Supervision (-t supervision).
890 <tag><tt>__TIME__</tt></tag>
892 This macro expands to the time of translation of the preprocessing
893 translation unit in the form "hh:mm:ss".
895 <tag><tt>__VIC20__</tt></tag>
897 This macro is defined if the target is the Commodore VIC20 (-t vic20).
901 <sect>#pragmas<label id="pragmas"><p>
903 The compiler understands some pragmas that may be used to change code
904 generation and other stuff. Some of these pragmas understand a special form:
905 If the first parameter is <tt/push/, the old value is saved onto a stack
906 before changing it. The value may later be restored by using the <tt/pop/
907 parameter with the <tt/#pragma/.
909 <sect1><tt>#pragma bss-name ([push,] <name>)</tt><label id="pragma-bss-name"><p>
911 This pragma changes the name used for the BSS segment (the BSS segment
912 is used to store uninitialized data). The argument is a string enclosed
915 Note: The default linker configuration file does only map the standard
916 segments. If you use other segments, you have to create a new linker
919 Beware: The startup code will zero only the default BSS segment. If you
920 use another BSS segment, you have to do that yourself, otherwise
921 uninitialized variables do not have the value zero.
923 The <tt/#pragma/ understands the push and pop parameters as explained above.
927 #pragma bss-name ("MyBSS")
931 <sect1><tt>#pragma charmap (<index>, <code>)</tt><label id="pragma-charmap"><p>
933 Each literal string and each literal character in the source is translated
934 by use of a translation table. This translation table is preset when the
935 compiler is started depending on the target system, for example to map
936 ISO-8859-1 characters into PETSCII if the target is a commodore machine.
938 This pragma allows to change entries in the translation table, so the
939 translation for individual characters, or even the complete table may be
942 Both arguments are assumed to be unsigned characters with a valid range of
945 Beware of two pitfalls:
948 <item>The character index is actually the code of the character in the
949 C source, so character mappings do always depend on the source
950 character set. This means that <tt/#pragma charmap/ is not
951 portable -- it depends on the build environment.
952 <item>While it is possible to use character literals as indices, the
953 result may be somewhat unexpected, since character literals are
954 itself translated. For this reason I would suggest to avoid
955 character literals and use numeric character codes instead.
960 /* Use a space wherever an 'a' occurs in ISO-8859-1 source */
961 #pragma charmap (0x61, 0x20);
965 <sect1><tt>#pragma check-stack ([push,] on|off)</tt><label id="pragma-check-stack"><p>
967 Tells the compiler to insert calls to a stack checking subroutine to detect
968 stack overflows. The stack checking code will lead to somewhat larger and
969 slower programs, so you may want to use this pragma when debugging your
970 program and switch it off for the release version. If a stack overflow is
971 detected, the program is aborted.
973 If the argument is "off", stack checks are disabled (the default), otherwise
976 The <tt/#pragma/ understands the push and pop parameters as explained above.
978 <sect1><tt>#pragma code-name ([push,] <name>)</tt><label id="pragma-code-name"><p>
980 This pragma changes the name used for the CODE segment (the CODE segment
981 is used to store executable code). The argument is a string enclosed in
984 Note: The default linker configuration file does only map the standard
985 segments. If you use other segments, you have to create a new linker
988 The <tt/#pragma/ understands the push and pop parameters as explained above.
992 #pragma code-name ("MyCODE")
996 <sect1><tt>#pragma codesize ([push,] <int>)</tt><label id="pragma-codesize"><p>
998 This pragma allows finer control about speed vs. size decisions in the code
999 generation and optimization phase. It gives the allowed size increase factor
1000 (in percent). The default is can be changed by use of the <tt/<ref
1001 id="option-codesize" name="--codesize">/ compiler option.
1003 The <tt/#pragma/ understands the push and pop parameters as explained above.
1006 <sect1><tt>#pragma data-name ([push,] <name>)</tt><label id="pragma-data-name"><p>
1008 This pragma changes the name used for the DATA segment (the DATA segment
1009 is used to store initialized data). The argument is a string enclosed in
1012 Note: The default linker configuration file does only map the standard
1013 segments. If you use other segments, you have to create a new linker
1016 The <tt/#pragma/ understands the push and pop parameters as explained above.
1020 #pragma data-name ("MyDATA")
1024 <sect1><tt>#pragma local-strings ([push,] on|off)</tt><label id="pragma-local-strings"><p>
1026 When "on", emit string literals to the data segment when they're encountered
1027 in the source. The default ("off") is to keep string literals until end of
1028 assembly, merge read only literals if possible, and then output the literals
1029 into the data or rodata segment that is active at that point.
1031 Using this <tt/#pragma/ it is possible to control the behaviour from within
1032 the source. When <tt/#pragma local-strings/ is active, string literals are
1033 output immediately, which means that they go into the currently active data
1034 or rodata segment, but cannot be merged. When inactive, string literals are
1035 remembered and output as a whole when translation is finished.
1038 <sect1><tt>#pragma optimize ([push,] on|off)</tt><label id="pragma-optimize"><p>
1040 Switch optimization on or off. If the argument is "off", optimization is
1041 disabled, otherwise it is enabled. Please note that this pragma only effects
1042 whole functions. The setting in effect when the function is encountered will
1043 determine if the generated code is optimized or not.
1045 Optimization and code generation is also controlled by the <ref
1046 id="pragma-codesize" name="codesize pragma">.
1048 The default is "off", but may be changed with the <tt/<ref name="-O"
1049 id="option-O">/ compiler option.
1051 The <tt/#pragma/ understands the push and pop parameters as explained above.
1054 <sect1><tt>#pragma rodata-name ([push,] <name>)</tt><label id="pragma-rodata-name"><p>
1056 This pragma changes the name used for the RODATA segment (the RODATA
1057 segment is used to store readonly data). The argument is a string
1058 enclosed in double quotes.
1060 Note: The default linker configuration file does only map the standard
1061 segments. If you use other segments, you have to create a new linker
1064 The <tt/#pragma/ understands the push and pop parameters as explained above.
1068 #pragma rodata-name ("MyRODATA")
1072 <sect1><tt>#pragma regvaraddr ([push,] on|off)</tt><label id="pragma-regvaraddr"><p>
1074 The compiler does not allow to take the address of register variables.
1075 The regvaraddr pragma changes this. Taking the address of a register
1076 variable is allowed after using this pragma with "on" as argument.
1077 Using "off" as an argument switches back to the default behaviour.
1079 Beware: The C standard does not allow taking the address of a variable
1080 declared as register. So your programs become non-portable if you use
1081 this pragma. In addition, your program may not work. This is usually the
1082 case if a subroutine is called with the address of a register variable,
1083 and this subroutine (or a subroutine called from there) uses
1084 register variables. So be careful with this #pragma.
1086 The <tt/#pragma/ understands the push and pop parameters as explained above.
1090 #pragma regvaraddr(on) /* Allow taking the address
1091 * of register variables
1096 <sect1><tt>#pragma register-vars ([push,] on|off)</tt><label id="pragma-register-vars"><p>
1098 Enables or disables use of register variables. If register variables are
1099 disabled (the default), the <tt/register/ keyword is ignored. Register
1100 variables are explained in more detail in <ref id="register-vars" name="a separate
1103 The <tt/#pragma/ understands the push and pop parameters as explained above.
1106 <sect1><tt>#pragma signed-chars ([push,] on|off)</tt><label id="pragma-signed-chars"><p>
1108 Changes the signedness of the default character type. If the argument is
1109 "on", default characters are signed, otherwise characters are unsigned. The
1110 compiler default is to make characters unsigned since this creates a lot
1111 better code. This default may be overridden by the <tt/<ref
1112 name="--signed-chars" id="option-signed-chars">/ command line option.
1114 The <tt/#pragma/ understands the push and pop parameters as explained above.
1117 <sect1><tt>#pragma static-locals ([push,] on|off)</tt><label id="pragma-static-locals"<p>
1119 Use variables in the bss segment instead of variables on the stack. This
1120 pragma changes the default set by the compiler option <tt/<ref
1121 name="--static-locals" id="option-static-locals">/. If the argument is "on",
1122 local variables are allocated in the BSS segment, leading to shorter and in
1123 most cases faster, but non-reentrant code.
1125 The <tt/#pragma/ understands the push and pop parameters as explained above.
1128 <sect1><tt>#pragma warn (name, [push,] on|off)</tt><label id="pragma-warn"><p>
1130 Switch compiler warnings on or off. "name" is the name of a warning (see the
1131 <tt/<ref name="-W" id="option-W">/ compiler option for a list). The name is
1132 either followed by "pop", which restores the last pushed state, or by "on" or
1133 "off", optionally preceeded by "push" to push the current state before
1138 /* Don't warn about the unused parameter in function func */
1139 #pragma warn (unused-param, push, off)
1140 static int func (int unused)
1144 #pragma warn (unused-param, pop)
1147 <sect1><tt>#pragma writable-strings ([push,] on|off)</tt><label id="pragma-writable-strings"><p>
1149 Changes the storage location of string literals. For historical reasons,
1150 the C standard defines that string literals are of type "char[]", but
1151 writing to such a literal causes undefined behaviour. Most compilers
1152 (including cc65) place string literals in the read-only data segment, which
1153 may cause problems with old C code that writes to string literals.
1155 Using this pragma (or the corresponding command line option <tt/<ref
1156 name="--writable-strings" id="option-writable-strings">/) causes the
1157 literals to be placed in the data segment so they can be written to without
1160 The <tt/#pragma/ understands the push and pop parameters as explained above.
1163 <sect1><tt>#pragma zpsym (<name>)</tt><p>
1165 Tell the compiler that the -- previously as external declared -- symbol with
1166 the given name is a zero page symbol (usually from an assembler file).
1167 The compiler will create a matching import declaration for the assembler.
1172 #pragma zpsym ("foo"); /* foo is in the zeropage */
1178 <sect>Register variables<label id="register-vars"><p>
1180 The runtime for all supported platforms has 6 bytes of zero page space
1181 available for register variables (this could be increased, but I think it's a
1182 good value). So you can declare register variables up to a total size of 6 per
1183 function. The compiler will allocate register space on a "first come, first
1184 served" base and convert any <tt/register/ declarations that exceed the
1185 available register space silently to <tt/auto/. Parameters can also be
1186 declared as <tt/register/, this will in fact give slightly shorter code than
1187 using a register variable.
1189 Since a function must save the current values of the registers on entry and
1190 restore them on exit, there is an overhead associated with register variables,
1191 and this overhead is quite high (about 20 bytes per variable). This means that
1192 just declaring anything as <tt/register/ is not a good idea.
1194 The best use for register variables are pointers, especially those that point
1195 to structures. The magic number here is about 3 uses of a struct field: If the
1196 function contains this number or even more, the generated code will be usually
1197 shorter and faster when using a register variable for the struct pointer. The
1198 reason for this is that the register variable can in many cases be used as a
1199 pointer directly. Having a pointer in an auto variable means that this pointer
1200 must first be copied into a zero page location, before it can be dereferenced.
1202 Second best use for register variables are counters. However, there is not
1203 much difference in the code generated for counters, so you will need at least
1204 100 operations on this variable (for example in a loop) to make it worth the
1205 trouble. The only savings you get here are by the use of a zero page variable
1206 instead of one on the stack or in the data segment.
1208 Register variables must be explicitly enabled, either by using <tt/<ref
1209 name="-Or" id="option-O">/ or <tt/<ref name="--register-vars"
1210 id="option-register-vars">/ on the command line or by use of <tt/<ref
1211 name="#pragma register-vars" id="pragma-register-vars">/. Register variables
1212 are only accepted on function top level, register variables declared in
1213 interior blocks are silently converted to <tt/auto/. With register variables
1214 disabled, all variables declared as <tt/register/ are actually auto variables.
1216 Please take care when using register variables: While they are helpful and can
1217 lead to a tremendous speedup when used correctly, improper usage will cause
1218 bloated code and a slowdown.
1222 <sect>Inline assembler<label id="inline-asm"><p>
1224 The compiler allows to insert assembler statements into the output file. The
1228 asm [optional volatile] (<string literal>[, optional parameters]) ;
1232 __asm__ [optional volatile] (<string literal>[, optional parameters]) ;
1236 The first form is in the user namespace; and, is disabled by <tt><ref
1237 id="option--standard" name="--standard"></tt> if the argument is not <tt/cc65/.
1239 The <tt/asm/ statement can be used only inside a function. Please note that
1240 the result of an inline assembler expression is always of type <tt/void/.
1242 The contents of the string literal are preparsed by the compiler; and, inserted
1243 into the generated assembly output, so that it can be processed further by
1244 the backend -- and, especially the optimizer. For that reason, the compiler does
1245 allow only regular 6502 opcodes to be used with the inline assembler. Pseudo
1246 instructions (like <tt/.import/, <tt/.byte/, and so on) are <em/not/ allowed,
1247 even if the ca65 assembler (which is used to translate the generated assembler
1248 code) would accept them. The built-in inline assembler is not a replacement for
1249 the full-blown macro assembler which comes with the compiler.
1251 Note: Inline assembler statements are subject to all optimizations done by the
1252 compiler. There currently is no way to protect an inline assembler statement
1253 -- alone -- from being moved or removed completely by the optimizer. If in
1254 doubt, check the generated assembler output; or, disable optimizations (for
1257 As a shortcut, you can put the <tt/volatile/ qualifier in your <tt/asm/
1258 statements. It will disable optimization for the functions in which those
1259 <tt/asm volatile/ statements sit. The effect is the same as though you put
1260 </#pragma optimize(push, off)/ above those functions, and </#pragma
1261 optimize(pop)/ below those functions.
1263 The string literal may contain format specifiers from the following list. For
1264 each format specifier, an argument is expected which is inserted instead of
1265 the format specifier, before passing the assembly code line to the backend.
1268 <item><tt/%b/ - Numerical 8-bit value
1269 <item><tt/%w/ - Numerical 16-bit value
1270 <item><tt/%l/ - Numerical 32-bit value
1271 <item><tt/%v/ - Assembler name of a global variable or function
1272 <item><tt/%o/ - Stack offset of a local variable
1273 <item><tt/%g/ - Assembler name of a C label
1274 <item><tt/%s/ - The argument is converted to a string
1275 <item><tt/%%/ - The % sign itself
1278 Using those format specifiers, you can access C <tt/#defines/, variables, or
1279 similar stuff from the inline assembler. For example, to load the value of
1280 a C <tt/#define/ into the Y index register, one would use
1284 __asm__ ("ldy #%b", OFFS);
1287 Or, to access a struct member of a static variable:
1293 unsigned char color;
1295 static pixel_t pixel;
1296 __asm__ ("ldy #%b", offsetof(pixel_t, color));
1297 __asm__ ("lda %v,y", pixel);
1300 The next example shows how to use global variables to exchange data between C
1301 and assembler; and, how to handle assembler jumps:
1304 static unsigned char globalSubA, globalSubB, globalSubResult;
1306 /* return a-b, return 255 if b>a */
1307 unsigned char sub (unsigned char a, unsigned char b)
1312 __asm__ ("lda %v", globalSubA);
1313 __asm__ ("sbc %v", globalSubB);
1314 __asm__ ("bcs %g", jumpSubNoError);
1315 __asm__ ("lda #$FF");
1317 __asm__ ("sta %v", globalSubResult);
1318 return globalSubResult;
1323 Arrays also can be accessed:
1326 static const unsigned char globalSquareTable[] = {
1327 0, 1, 4, 9, 16, 25, 36, 49, 64, 81,
1328 100, 121, 144, 169, 196, 225
1330 static unsigned char globalSquareA, globalSquareResult;
1332 /* return a*a for a<16, else 255 */
1333 unsigned char square (unsigned char a)
1339 __asm__ ("ldx %v", globalSquareA);
1340 __asm__ ("lda %v,x", globalSquareTable);
1341 __asm__ ("sta %v", globalSquareResult);
1342 return globalSquareResult;
1347 Note: Do not embed the assembler labels that are used as names of global
1348 variables or functions into your <tt/asm/ statements. Code such as this:
1352 int bar (void) { return 1; }
1354 __asm__ ("lda _foo"); /* DON'T DO THAT! */
1356 __asm__ ("jsr _bar"); /* DON'T DO THAT EITHER! */
1360 might stop working if the way that the compiler generates those names is changed in
1361 a future version. Instead, use the format specifiers from the table above:
1364 __asm__ ("lda %v", foo); /* OK */
1366 __asm__ ("jsr %v", bar); /* OK */
1372 <sect>Implementation-defined behavior<p>
1374 This section describes the behavior of cc65 when the standard describes the
1375 behavior as implementation-defined.
1381 This is the original compiler copyright:
1384 --------------------------------------------------------------------------
1387 This is the copyright notice for RA65, LINK65, LIBR65, and other
1388 Atari 8-bit programs. Said programs are Copyright 1989, by John R.
1389 Dunning. All rights reserved, with the following exceptions:
1391 Anyone may copy or redistribute these programs, provided that:
1393 1: You don't charge anything for the copy. It is permissable to
1394 charge a nominal fee for media, etc.
1396 2: All source code and documentation for the programs is made
1397 available as part of the distribution.
1399 3: This copyright notice is preserved verbatim, and included in
1402 You are allowed to modify these programs, and redistribute the
1403 modified versions, provided that the modifications are clearly noted.
1405 There is NO WARRANTY with this software, it comes as is, and is
1406 distributed in the hope that it may be useful.
1408 This copyright notice applies to any program which contains
1409 this text, or the refers to this file.
1411 This copyright notice is based on the one published by the Free
1412 Software Foundation, sometimes known as the GNU project. The idea
1413 is the same as theirs, ie the software is free, and is intended to
1414 stay that way. Everybody has the right to copy, modify, and re-
1415 distribute this software. Nobody has the right to prevent anyone
1416 else from copying, modifying or redistributing it.
1418 --------------------------------------------------------------------------
1421 Small parts of the compiler (parts of the preprocessor and main parser) are
1422 still covered by this copyright. The main portion is covered by the usual
1423 cc65 license, which reads:
1425 This software is provided 'as-is', without any expressed or implied
1426 warranty. In no event will the authors be held liable for any damages
1427 arising from the use of this software.
1429 Permission is granted to anyone to use this software for any purpose,
1430 including commercial applications, and to alter it and redistribute it
1431 freely, subject to the following restrictions:
1434 <item> The origin of this software must not be misrepresented; you must not
1435 claim that you wrote the original software. If you use this software
1436 in a product, an acknowledgment in the product documentation would be
1437 appreciated but is not required.
1438 <item> Altered source versions must be plainly marked as such, and must not
1439 be misrepresented as being the original software.
1440 <item> This notice may not be removed or altered from any source