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">
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 -->
20 cc65 was originally a C compiler for the Atari 8-bit machines written by
21 John R. Dunning. In prior releases I've described the compiler by listing
22 up the changes made by me. I have made many more changes in the meantime
23 (and rewritten major parts of the compiler), so I will no longer do that,
24 since the list would be too large and of no use to anyone. Instead I will
25 describe the compiler in respect to the ANSI/ISO C standard.
27 There are separate documents named <url url="library.html"> and <url
28 url="funcref.html"> that cover the library that is available for the compiler.
29 If you know C, and are interested in doing actual programming, the library
30 documentation is probably of much more use than this document.
32 If you need some hints for getting the best code out of the compiler, you
33 may have a look at <url url="coding.html"> which covers some code generation
40 The compiler translates C files into files containing assembly code that
41 may be translated by the ca65 macroassembler (for more information about
42 the assembler, have a look at <url url="ca65.html">).
45 <sect1>Command line option overview<p>
47 The compiler may be called as follows:
50 ---------------------------------------------------------------------------
51 Usage: cc65 [options] file
53 -Cl Make local variables static
54 -Dsym[=defn] Define a symbol
55 -E Stop after the preprocessing stage
56 -I dir Set an include directory search path
58 -Oi Optimize code, inline more code
59 -Or Enable register variables
60 -Os Inline some standard functions
61 -T Include source as comment
62 -V Print the compiler version number
63 -W warning[,...] Suppress warnings
65 -g Add debug info to object file
67 -j Default characters are signed
68 -mm model Set the memory model
69 -o name Name the output file
70 -r Enable register variables
71 -t sys Set the target system
75 --add-source Include source as comment
76 --all-cdecl Make functions default to __cdecl__
77 --bss-name seg Set the name of the BSS segment
78 --check-stack Generate stack overflow checks
79 --code-name seg Set the name of the CODE segment
80 --codesize x Accept larger code by factor x
81 --cpu type Set cpu type (6502, 65c02)
82 --create-dep name Create a make dependency file
83 --create-full-dep name Create a full make dependency file
84 --data-name seg Set the name of the DATA segment
86 --debug-info Add debug info to object file
87 --debug-opt name Debug optimization steps
88 --dep-target target Use this dependency target
89 --disable-opt name Disable an optimization step
90 --eagerly-inline-funcs Eagerly inline some known functions
91 --enable-opt name Enable an optimization step
92 --help Help (this text)
93 --include-dir dir Set an include directory search path
94 --inline-stdfuncs Inline some standard functions
95 --list-opt-steps List all optimizer steps and exit
96 --list-warnings List available warning types for -W
97 --local-strings Emit string literals immediately
98 --memory-model model Set the memory model
99 --register-space b Set space available for register variables
100 --register-vars Enable register variables
101 --rodata-name seg Set the name of the RODATA segment
102 --signed-chars Default characters are signed
103 --standard std Language standard (c89, c99, cc65)
104 --static-locals Make local variables static
105 --target sys Set the target system
106 --verbose Increase verbosity
107 --version Print the compiler version number
108 --writable-strings Make string literals writable
109 ---------------------------------------------------------------------------
113 <sect1>Command line options in detail<p>
115 Here is a description of all the command line options:
119 <tag><tt>--all-cdecl</tt></tag>
121 Tells the compiler that functions which aren't declared explicitly with
122 either the <tt/__cdecl__/ or <tt/__fastcall__/ calling conventions should
123 have the cdecl convention. (Normally, functions that aren't variadic are
127 <label id="option-bss-name">
128 <tag><tt>--bss-name seg</tt></tag>
130 Set the name of the bss segment. See also <tt/<ref id="pragma-bss-name"
131 name="#pragma bss-name">/.
134 <label id="option-check-stack">
135 <tag><tt>--check-stack</tt></tag>
137 Tells the compiler to generate code that checks for stack overflows. See
138 <tt/<ref id="pragma-check-stack" name="#pragma check-stack">/ for an
139 explanation of this feature.
142 <label id="option-code-name">
143 <tag><tt>--code-name seg</tt></tag>
145 Set the name of the code segment. See also <tt/<ref id="pragma-code-name"
146 name="#pragma code-name">/
149 <label id="option-codesize">
150 <tag><tt>--codesize x</tt></tag>
152 This options allows finer control about speed vs. size decisions in the code
153 generation and optimization phases. It gives the allowed size increase
154 factor (in percent). The default is 100 when not using <tt/-Oi/ and 200 when
155 using <tt/-Oi/ (<tt/-Oi/ is the same as <tt/-O --codesize 200/).
158 <label id="option--cpu">
159 <tag><tt>--cpu CPU</tt></tag>
161 Set the CPU, the compiler generates code for. You may specify "6502" or
162 "65C02" as the CPU. The default depends on the selected target (see option
163 <tt/<ref id="option-t" name="-t">/). It is the 6502 CPU for most targets or
164 if no target has been set. Specifying 65C02 will use a few 65C02
165 instructions when generating code. Don't expect too much from this option:
166 In most cases the difference in size and speed is just 1-2%.
169 <label id="option-create-dep">
170 <tag><tt>--create-dep name</tt></tag>
172 Tells the compiler to generate a file containing the dependency list for the
173 compiled module in makefile syntax. The output is written to a file with the
174 given name. The output does not include system include files (in angle
178 <label id="option-create-full-dep">
179 <tag><tt>--create-full-dep name</tt></tag>
181 Tells the compiler to generate a file containing the dependency list for the
182 compiled module in makefile syntax. The output is written to a file with the
183 given name. The output does include system include files (in angle
187 <label id="option-data-name">
188 <tag><tt>--data-name seg</tt></tag>
190 Set the name of the data segment. See also <tt/<ref id="pragma-data-name"
191 name="#pragma data-name">/
194 <tag><tt>-d, --debug</tt></tag>
196 Enables debug mode, something that should not be needed for mere
200 <label id="option-dep-target">
201 <tag><tt>--dep-target target</tt></tag>
203 When generating a dependency file, don't use the actual output file as the
204 target of the dependency, but the file specified with this option. The
205 option has no effect if neither <tt/<ref id="option-create-dep"
206 name="--create-dep">/ nor <tt/<ref id="option-create-full-dep"
207 name="--create-full-dep">/ is specified.
210 <tag><tt>-D sym[=definition]</tt></tag>
212 Define a macro on the command line. If no definition is given, the macro
213 is defined to the value "1".
216 <tag><tt>-g, --debug-info</tt></tag>
218 This will cause the compiler to insert a <tt/.DEBUGINFO/ command into the
219 generated assembler code. This will cause the assembler to include all
220 symbols in a special section in the object file.
223 <label id="option-eagerly-inline-funcs">
224 <tag><tt>--eagerly-inline-funcs</tt></tag>
226 Have the compiler eagerly inline these functions from the C library:
233 <item>most of the functions declared in <tt/<ctype.h>/
236 Note: This has two consequences:
238 <item>You may not use names of standard C functions for your own functions.
239 If you do that, your program is not standard-compliant anyway; but,
240 using <tt/--eagerly-inline-funcs/ actually will break things.
242 <item>The inlined string and memory functions will not handle strings or
243 memory areas larger than 255 bytes. Similarly, the inlined <tt/is..()/
244 functions will not work with values outside the char. range (such as
249 <tt/--eagerly-inline-funcs/ implies the <tt><ref id="option-inline-stdfuncs"
250 name="--inline-stdfuncs"></tt> command line option.
252 See also <tt><ref id="pragma-allow-eager-inline" name="#pragma allow-eager-inline"></tt>.
255 <tag><tt>-h, --help</tt></tag>
257 Print the short option summary shown above.
260 <label id="option-inline-stdfuncs">
261 <tag><tt>--inline-stdfuncs</tt></tag>
263 Allow the compiler to inline some standard functions from the C library like
264 strlen. This will not only remove the overhead for a function call, but will
265 make the code visible for the optimizer. See also the <tt><ref id="option-O"
266 name="-Os"></tt> command line option and <tt><ref id="pragma-inline-stdfuncs"
267 name="#pragma inline-stdfuncs"></tt>.
270 <label id="option-list-warnings">
271 <tag><tt>--list-warnings</tt></tag>
273 List the names of warning types available for use with <tt><ref
274 id="option-W" name="-W"></tt>.
277 <label id="option-local-strings">
278 <tag><tt>--local-strings</tt></tag>
280 Emit string literals into the rodata segment as soon as they're encountered
281 in the source (even if you do nothing but get the sizeof those strings). The
282 default is to keep string literals until end of assembly, merge read only
283 literals if possible, and then output the literals into the data or rodata
284 segment that is active at that point. Use of this option prevents merging of
285 duplicate strings, but the options that change the name of one of the data
288 You can also use <tt><ref id="pragma-local-strings"
289 name="#pragma local-strings"></tt> for fine grained control.
292 <tag><tt>-o name</tt></tag>
294 Specify the name of the output file. If you don't specify a name, the
295 name of the C input file is used, with the extension replaced by ".s".
298 <label id="option-register-vars">
299 <tag><tt>-r, --register-vars</tt></tag>
301 <tt/-r/ will make the compiler honor the <tt/register/ keyword. Local
302 variables may be placed in registers (which are actually zero page
303 locations). There is some overhead involved with register variables, since
304 the old contents of the registers must be saved and restored. Since register
305 variables are of limited use without the optimizer, there is also a combined
306 switch: <tt/-Or/ will enable both, the optimizer and register variables.
308 For more information about register variables see <ref id="register-vars"
309 name="register variables">.
311 The compiler setting can also be changed within the source file by using
312 <tt/<ref id="pragma-register-vars" name="#pragma register-vars">/.
315 <label id="option-register-space">
316 <tag><tt>--register-space</tt></tag>
318 This option takes a numeric parameter and is used to specify, how much
319 zero page register space is available. Please note that just giving this
320 option will not increase or decrease by itself, it will just tell the
321 compiler about the available space. You will have to allocate that space
322 yourself using an assembler module with the necessary allocations, and a
323 linker configuration that matches the assembler module. The default value
324 for this option is 6 (bytes).
326 If you don't know what all this means, please don't use this option.
329 <label id="option-rodata-name">
330 <tag><tt>--rodata-name seg</tt></tag>
332 Set the name of the rodata segment (the segment used for readonly data).
333 See also <tt/<ref id="pragma-rodata-name" name="#pragma rodata-name">/
335 <label id="option-signed-chars">
336 <tag><tt>-j, --signed-chars</tt></tag>
338 Using this option, you can make the default characters signed. Since the
339 6502 has no provisions for sign extending characters (which is needed on
340 almost any load operation), this will make the code larger and slower. A
341 better way is to declare characters explicitly as "signed" if needed. You
342 can also use <tt><ref id="pragma-signed-chars"
343 name="#pragma signed-chars"></tt> for better control of this option.
346 <label id="option--standard">
347 <tag><tt>--standard std</tt></tag>
349 This option allows to set the language standard supported. The argument is
353 This disables anything that is illegal in C89/C90. Among those things
354 are <tt>//</tt> comments and the non-standard keywords without
355 underscores. Please note that cc65 is not a fully C89 compliant compiler
356 despite this option. A few more things (like floats) are missing.
359 This enables a few features from the C99 standard. With this option,
360 <tt>//</tt> comments are allowed. It will also cause warnings and even
361 errors in a few situations that are allowed with <tt/--standard c89/.
362 For example, a call to a function without a prototype is an error in
366 This is the default mode. It is like c99 mode, but additional features
367 are enabled. Among these are "void data", non-standard keywords without
368 the underlines, unnamed function parameters and the requirement for
369 main() to return an int.
372 Please note that the compiler does not support the C99 standard and never
373 will. c99 mode is actually c89 mode with a few selected C99 extensions.
376 <label id="option-t">
377 <tag><tt>-t target, --target target</tt></tag>
379 This option is used to set the target system. The target system determines
380 the character set that is used for strings and character constants and the
381 default CPU. The CPU setting can be overriden by use of the <tt/<ref
382 id="option--cpu" name="--cpu">/ option.
384 The following target systems are supported:
393 <item>c16 (works also for the c116 with memory up to 32K)
396 <item>cbm510 (CBM-II series with 40 column video)
397 <item>cbm610 (all CBM-II II computers with 80 column video)
404 <item>pet (all CBM PET systems except the 2001)
413 <tag><tt>-v, --verbose</tt></tag>
415 Using this option, the compiler will be somewhat more verbose if errors
416 or warnings are encountered.
419 <label id="option-writable-strings">
420 <tag><tt>--writable-strings</tt></tag>
422 Make string literals writable by placing them into the data segment instead
423 of the rodata segment. You can also use <tt><ref id="pragma-writable-strings"
424 name="#pragma writable-strings"></tt> to control this option from within
428 <label id="option-static-locals">
429 <tag><tt>-Cl, --static-locals</tt></tag>
431 Use static storage for local variables instead of storage on the stack.
432 Since the stack is emulated in software, this gives shorter and usually
433 faster code, but the code is no longer reentrant. The difference between
434 <tt/-Cl/ and declaring local variables as static yourself is, that
435 initializer code is executed each time, the function is entered. So when
446 the variable <tt/a/ will always have the value <tt/1/ when entering the
447 function and using <tt/-Cl/, while in
452 static unsigned a = 1;
457 the variable <tt/a/ will have the value <tt/1/ only the first time that the
458 function is entered, and will keep the old value from one call of the
459 function to the next.
461 You may also use <tt><ref id="pragma-static-locals"
462 name="#pragma static-locals"></tt> to change this setting in your
466 <label id="option-include-dir">
467 <tag><tt>-I dir, --include-dir dir</tt></tag>
469 Set a directory where the compiler searches for include files. You may
470 use this option multiple times to add more than one directory to the
474 <label id="option-O">
475 <tag><tt>-O, -Oi, -Or, -Os</tt></tag>
477 Enable an optimizer run over the produced code.
479 Using <tt/-Oi/, the code generator will inline some code where otherwise a
480 runtime functions would have been called, even if the generated code is
481 larger. This will not only remove the overhead for a function call, but will
482 make the code visible for the optimizer. <tt/-Oi/ is an alias for
483 <tt/-O --codesize 200/.
485 <tt/-Or/ will make the compiler honor the <tt/register/ keyword. Local
486 variables may be placed in registers (which are actually zero page
487 locations). See also the <tt/<ref id="option-register-vars"
488 name="--register-vars">/ command line option, and the <ref
489 id="register-vars" name="discussion of register variables"> below.
491 Using <tt/-Os/ will allow the compiler to inline some standard functions
492 from the C library like strlen. This will not only remove the overhead
493 for a function call, but will make the code visible for the optimizer.
494 See also the <tt/<ref id="option-inline-stdfuncs" name="--inline-stdfuncs">/
497 It is possible to concatenate the modifiers for <tt/-O/. For example, to
498 enable register variables and inlining of standard functions, you may use
502 <tag><tt>-T, --add-source</tt></tag>
504 This include the source code as comments in the generated code. This is
508 <tag><tt>-V, --version</tt></tag>
510 Print the version number of the compiler. When submitting a bug report,
511 please include the operating system you're using, and the compiler
515 <label id="option-W">
516 <tag><tt>-W name[,name,...]</tt></tag>
518 This option allows to control warnings generated by the compiler. It is
519 followed by a comma-separated list of warnings that should be enabled or
520 disabled. To disable a warning, its name is prefixed by a minus sign. If
521 no such prefix exists, or the name is prefixed by a plus sign, the warning
524 The following warning names currently are recognized:
526 <tag><tt/const-comparison/</tag>
527 Warn if the result of a comparison is constant.
528 <tag><tt/error/</tag>
529 Treat all warnings as errors.
530 <tag><tt/no-effect/</tag>
531 Warn about statements that don't have an effect.
532 <tag><tt/remap-zero/</tag>
533 Warn about a <tt/<ref id="pragma-charmap" name="#pragma charmap()">/
534 that changes a character's code number from/to 0x00.
535 <tag><tt/struct-param/</tag>
536 Warn when passing structs by value.
537 <tag><tt/unknown-pragma/</tag>
538 Warn about #pragmas that aren't recognized by cc65.
539 <tag><tt/unused-label/</tag>
540 Warn about unused labels.
541 <tag><tt/unused-param/</tag>
542 Warn about unused function parameters.
543 <tag><tt/unused-var/</tag>
544 Warn about unused variables.
547 The full list of available warning names can be retrieved by using the
548 option <tt><ref id="option-list-warnings" name="--list-warnings"></tt>.
550 You may use also <tt><ref id="pragma-warn" name="#pragma warn"></tt> to
551 control this setting, for smaller pieces of code, from within your sources.
557 <sect>Input and output<p>
559 The compiler will accept one C file per invocation and create a file with
560 the same base name, but with the extension replaced by ".s". The output
561 file contains assembler code suitable for use with the ca65 macro
564 Include files in quotes are searched in the following places:
566 <item>The current file's directory.
567 <item>Any directory added with the <tt/-I/ option on the command line.
568 <item>The value of the environment variable <tt/CC65_INC/ if it is defined.
571 Include files in angle brackets are searched in the following places:
573 <item>Any directory added with the <tt/-I/ option on the command line.
574 <item>The value of the environment variable <tt/CC65_INC/ if it is defined.
575 <item>A subdirectory named <tt/include/ of the directory defined in the
576 environment variable <tt/CC65_HOME/, if it is defined.
577 <item>An optionally compiled-in directory.
582 <sect>Differences to the ISO standard<p>
584 Apart from the things listed below, the compiler does support additional
585 keywords, has several functions in the standard headers with names outside the
586 reserved namespace and a few syntax extensions. All these can be disabled with
587 the <tt><ref id="option--standard" name="--standard"></tt> command line
588 option. Its use for maximum standards compatibility is advised.
590 Here is a list of differences between the language, the compiler accepts,
591 and the one defined by the ISO standard:
595 <item> The datatypes "float" and "double" are not available.
597 <item> C Functions may not return structs (or unions), and structs may not
598 be passed as parameters by value. However, struct assignment *is*
601 <item> Most of the C library is available with only the fastcall calling
602 convention (<ref id="extension-fastcall" name="see below">). It means
603 that you must not mix pointers to those functions with pointers to
604 user-written, cdecl functions (the calling conventions are incompatible).
606 <item> The <tt/volatile/ keyword has almost no effect. That is not as bad
607 as it sounds, since the 6502 has so few registers that it isn't
608 possible to keep values in registers anyway.
612 There may be some more minor differences I'm currently not aware of. The
613 biggest problem is the missing float data type. With this limitation in
614 mind, you should be able to write fairly portable code.
620 This cc65 version has some extensions to the ISO C standard.
624 <item> The compiler allows to insert assembler statements into the output
628 asm [optional volatile] (<string literal>[, optional parameters]) ;
632 __asm__ [optional volatile] (<string literal>[, optional parameters]) ;
635 The first form is in the user namespace; and, is disabled if the <tt/-A/
638 There is a whole section covering inline assembler statements,
639 <ref id="inline-asm" name="see there">.
642 <label id="extension-fastcall">
643 <item> The normal calling convention -- for non-variadic functions -- is
644 named "fastcall". The syntax for a function declaration that
645 <em/explicitly/ uses fastcall is
648 <return type> fastcall <function name> (<parameter list>)
652 <return type> __fastcall__ <function name> (<parameter list>)
656 void __fastcall__ f (unsigned char c)
658 The first form of the fastcall keyword is in the user namespace and can
659 therefore be disabled with the <tt><ref id="option--standard"
660 name="--standard"></tt> command line option.
662 For functions that are <tt/fastcall/, the rightmost parameter is not
663 pushed on the stack but left in the primary register when the function
664 is called. That significantly reduces the cost of calling those functions.
667 <item> There is another calling convention named "cdecl". Variadic functions
668 (their prototypes have an ellipsis [<tt/.../]) always use that
669 convention. The syntax for a function declaration using cdecl is
672 <return type> cdecl <function name> (<parameter list>)
676 <return type> __cdecl__ <function name> (<parameter list>)
680 int* __cdecl__ f (unsigned char c)
683 The first form of the cdecl keyword is in the user namespace;
684 and therefore, can be disabled with the <tt/<ref id="option--standard"
685 name="--standard">/ command-line option.
687 For functions that are <tt/cdecl/, the rightmost parameter is pushed
688 onto the stack before the function is called. That increases the cost
689 of calling those functions, especially when they are called from many
693 <item> There are two pseudo variables named <tt/__AX__/ and <tt/__EAX__/.
694 Both refer to the primary register that is used by the compiler to
695 evaluate expressions or return function results. <tt/__AX__/ is of
696 type <tt/unsigned int/ and <tt/__EAX__/ of type <tt/long unsigned int/
697 respectively. The pseudo variables may be used as lvalue and rvalue as
698 every other variable. They are most useful together with short
699 sequences of assembler code. For example, the macro
709 will give the high byte of any unsigned value.
712 <item> Inside a function, the identifier <tt/__func__/ gives the name of the
713 current function as a string. Outside of functions, <tt/__func__/ is
718 #define PRINT_DEBUG(s) printf ("%s: %s\n", __func__, s);
721 The macro will print the name of the current function plus a given
725 <item> cc65 allows the initialization of <tt/void/ variables. This may be
726 used to create arbitrary structures that are more compatible with
727 interfaces written for assembler languages. Here is an example:
730 void GCmd = { (char)3, (unsigned)0x2000, (unsigned)0x3000 };
733 That will be translated as follows:
742 Since the variable is of type <tt/void/, you may not use it as-is.
743 However, taking the address of the variable results in a <tt/void*/
744 which may be passed to any function expecting a pointer. Also, the
745 <tt/sizeof/ operator will give the length of the initializer:
751 will assign the value 5 to <tt/GLen/.
753 See the <url url="geos.html" name="GEOS library document"> for examples
754 on how to use that feature.
757 <item> cc65 implements flexible array struct members as defined in the C99 ISO
758 standard. As an extension, these fields may be initialized. There are
759 several exceptions, however (which is probably the reason why the
760 standard does not define this feature, because it is highly
761 unorthogonal). Flexible array members cannot be initialized ...
764 <item>... when defining an array of structs with flexible
766 <item>... if such a struct is a member field of another struct
767 which is not the last field.
768 <item>... if the struct which contains a flexible array member is
769 declared as <tt/register/, and the size and compiler settings
770 do allow the compiler actually to place the struct into the
771 register bank in the zero page.
774 Please note that -- as defined in the ISO C standard -- the <tt/sizeof/
775 operator returns the struct size with the flexible array member having
776 size zero, even if it is initialized.
784 <sect>Predefined macros<p>
786 The compiler defines several macros at startup:
789 <tag><tt>__APPLE2__</tt></tag>
791 This macro is defined if the target is the Apple ][ (-t apple2) or the enhanced Apple //e (-t apple2enh).
793 <tag><tt>__APPLE2ENH__</tt></tag>
795 This macro is defined if the target is the enhanced Apple //e (-t apple2enh).
797 <tag><tt>__ATARI2600__</tt></tag>
799 This macro is defined if the target is the Atari 2600 game console.
801 <tag><tt>__ATARI5200__</tt></tag>
803 This macro is defined if the target is the Atari 5200 game console.
805 <tag><tt>__ATARI__</tt></tag>
807 This macro is defined if the target is the Atari 400/800 (-t atari) or the Atari 800XL/130XE (-t atarixl).
809 <tag><tt>__ATARIXL__</tt></tag>
811 This macro is defined if the target is the Atari 800XL/130XE (-t atarixl).
813 <tag><tt>__ATMOS__</tt></tag>
815 This macro is defined if the target is the Oric Atmos (-t atmos).
817 <tag><tt>__C128__</tt></tag>
819 This macro is defined if the target is the Commodore 128 (-t c128).
821 <tag><tt>__C16__</tt></tag>
823 This macro is defined if the target is the Commodore 16/116 (-t c16) or the Commodore Plus/4 (-t plus4).
825 <tag><tt>__C64__</tt></tag>
827 This macro is defined if the target is the Commodore 64 (-t c64).
829 <tag><tt>__CBM__</tt></tag>
831 This macro is defined if the target system is one of the CBM targets.
833 <tag><tt>__CBM510__</tt></tag>
835 This macro is defined if the target is the CBM 500 series of computers.
837 <tag><tt>__CBM610__</tt></tag>
839 This macro is defined if the target is one of the CBM 600/700 family of
840 computers (called B series in the US).
842 <tag><tt>__CC65__</tt></tag>
844 This macro is always defined. Its value is the version number of the
845 compiler in hex. For example, version 2.14 of the compiler has this macro
846 defined as <tt/0x02E0/.
848 <tag><tt>__CC65_STD__</tt></tag>
850 This macro is defined to one of the following depending on the <tt><ref
851 id="option--standard" name="--standard"></tt> command line option:
853 <item><tt/__CC65_STD_C89__/
854 <item><tt/__CC65_STD_C99__/
855 <item><tt/__CC65_STD_CC65__/
858 <tag><tt>__DATE__</tt></tag>
860 This macro expands to the date of translation of the preprocessing
861 translation unit in the form "Mmm dd yyyy".
863 <tag><tt>__EAGERLY_INLINE_FUNCS__</tt></tag>
865 Is defined if the compiler was called with the <tt><ref id="option-eagerly-inline-funcs"
866 name="--eagerly-inline-funcs"></tt> command line option.
868 <tag><tt>__FILE__</tt></tag>
870 This macro expands to a string containing the name of the C source file.
872 <tag><tt>__GEOS__</tt></tag>
874 This macro is defined if you are compiling for one of the GEOS systems.
876 <tag><tt>__GEOS_APPLE__</tt></tag>
878 This macro is defined if you are compiling for the Apple GEOS system (-t geos-apple).
880 <tag><tt>__GEOS_CBM__</tt></tag>
882 This macro is defined if you are compiling for the GEOS 64/128 system (-t geos-cbm).
884 <tag><tt>__LINE__</tt></tag>
886 This macro expands to the current line number.
888 <tag><tt>__LUNIX__</tt></tag>
890 This macro is defined if you are compiling for the LUnix system (-t lunix).
892 <tag><tt>__LYNX__</tt></tag>
894 This macro is defined if the target is the Atari Lynx (-t lynx).
896 <tag><tt>__NES__</tt></tag>
898 This macro is defined if the target is the Nintendo Entertainment System (-t nes).
900 <tag><tt>__OPT__</tt></tag>
902 Is defined if the compiler was called with the <tt/-O/ command line option.
904 <tag><tt>__OPT_i__</tt></tag>
906 Is defined if the compiler was called with the <tt/-Oi/ command line option.
908 <tag><tt>__OPT_r__</tt></tag>
910 Is defined if the compiler was called with the <tt/-Or/ command line option.
912 <tag><tt>__OPT_s__</tt></tag>
914 Is defined if the compiler was called with the <tt/-Os/ command line option.
916 <tag><tt>__OSIC1P__</tt></tag>
918 This macro is defined if the target is the Ohio Scientific Challenger 1P
921 <tag><tt>__PET__</tt></tag>
923 This macro is defined if the target is the PET family of computers (-t pet).
925 <tag><tt>__PLUS4__</tt></tag>
927 This macro is defined if the target is the Commodore Plus/4 (-t plus4).
929 <tag><tt>__STDC_HOSTED__</tt></tag>
931 This macro is expands to the integer constant 1.
933 <tag><tt>__SIM6502__</tt></tag>
935 This macro is defined if the target is sim65 in 6502 mode (-t sim6502).
937 <tag><tt>__SIM65C02__</tt></tag>
938 This macro is defined if the target is sim65 in 65C02 mode (-t sim65c02).
940 <tag><tt>__SUPERVISION__</tt></tag>
942 This macro is defined if the target is the Supervision (-t supervision).
944 <tag><tt>__TELESTRAT__</tt></tag>
946 This macro is defined if the target is the Telestrat (-t telestrat).
948 <tag><tt>__TIME__</tt></tag>
950 This macro expands to the time of translation of the preprocessing
951 translation unit in the form "hh:mm:ss".
953 <tag><tt>__VIC20__</tt></tag>
955 This macro is defined if the target is the Commodore VIC20 (-t vic20).
960 <sect>#pragmas<label id="pragmas"><p>
962 The compiler understands some pragmas that may be used to change code
963 generation and other stuff. Some of these pragmas understand a special form:
964 If the first parameter is <tt/push/, the old value is saved onto a stack
965 before changing it. The value may later be restored by using the <tt/pop/
966 parameter with the <tt/#pragma/.
969 <sect1><tt>#pragma allow-eager-inline ([push,] on|off)</tt><label id="pragma-allow-eager-inline"><p>
971 Allow eager inlining of known functions. If the argument is "off", eager
972 inlining is disabled, otherwise it is enabled. Please note that (in contrast
973 to the <tt><ref id="option-eagerly-inline-funcs" name="--eagerly-inline-funcs"></tt>
974 command line option) this pragma does not imply the <tt><ref id="option-inline-stdfuncs"
975 name="--inline-stdfuncs"></tt> command line option. Rather it marks code to be safe for
976 eager inlining of known functions if inlining of standard functions is enabled.
978 The <tt/#pragma/ understands the push and pop parameters as explained above.
981 <sect1><tt>#pragma bss-name ([push,] <name>)</tt><label id="pragma-bss-name"><p>
983 This pragma changes the name used for the BSS segment (the BSS segment
984 is used to store uninitialized data). The argument is a string enclosed
987 Note: The default linker configuration file does only map the standard
988 segments. If you use other segments, you have to create a new linker
991 Beware: The startup code will zero only the default BSS segment. If you
992 use another BSS segment, you have to do that yourself, otherwise
993 uninitialized variables do not have the value zero.
995 The <tt/#pragma/ understands the push and pop parameters as explained above.
999 #pragma bss-name ("MyBSS")
1003 <sect1><tt>#pragma charmap (<index>, <code>)</tt><label id="pragma-charmap"><p>
1005 Each literal string and each literal character in the source is translated
1006 by use of a translation table. That translation table is preset when the
1007 compiler is started, depending on the target system; for example, to map
1008 ISO-8859-1 characters into PETSCII if the target is a Commodore machine.
1010 This pragma allows to change entries in the translation table, so the
1011 translation for individual characters, or even the complete table may be
1012 adjusted. Both arguments are assumed to be unsigned characters with a valid
1015 Beware of some pitfalls:
1017 <item>The character index is actually the code of the character in the
1018 C source; so, character mappings do always depend on the source
1019 character set. That means that <tt/#pragma charmap()/ is not
1020 portable -- it depends on the build environment.
1021 <item>While it is possible to use character literals as indices, the
1022 result may be somewhat unexpected, since character literals are
1023 themselves translated. For that reason, I would suggest to avoid
1024 character literals, and use numeric character codes instead.
1025 <item>It is risky to change index <tt/0x00/, because string functions depend
1026 on it. If it is changed, then the <tt/'\0'/ at the end of string
1027 literals will become non-zero. Functions that are used on those
1028 literals won't stop at the end of them. cc65 will warn you if you do
1029 change that code number. You can turn off that <tt/remap-zero/ warning
1030 if you are certain that you know what you are doing (see <tt/<ref
1031 id="pragma-warn" name="#pragma warn()">/).
1036 /* Use a space wherever an 'a' occurs in ISO-8859-1 source */
1037 #pragma charmap (0x61, 0x20);
1041 <sect1><tt>#pragma check-stack ([push,] on|off)</tt><label id="pragma-check-stack"><p>
1043 Tells the compiler to insert calls to a stack checking subroutine to detect
1044 stack overflows. The stack checking code will lead to somewhat larger and
1045 slower programs, so you may want to use this pragma when debugging your
1046 program and switch it off for the release version. If a stack overflow is
1047 detected, the program is aborted.
1049 If the argument is "off", stack checks are disabled (the default), otherwise
1052 The <tt/#pragma/ understands the push and pop parameters as explained above.
1055 <sect1><tt>#pragma code-name ([push,] <name>)</tt><label id="pragma-code-name"><p>
1057 This pragma changes the name used for the CODE segment (the CODE segment
1058 is used to store executable code). The argument is a string enclosed in
1061 Note: The default linker configuration file does only map the standard
1062 segments. If you use other segments, you have to create a new linker
1065 The <tt/#pragma/ understands the push and pop parameters as explained above.
1069 #pragma code-name ("MyCODE")
1073 <sect1><tt>#pragma codesize ([push,] <int>)</tt><label id="pragma-codesize"><p>
1075 This pragma allows finer control about speed vs. size decisions in the code
1076 generation and optimization phase. It gives the allowed size increase factor
1077 (in percent). The default is can be changed by use of the <tt/<ref
1078 id="option-codesize" name="--codesize">/ compiler option.
1080 The <tt/#pragma/ understands the push and pop parameters as explained above.
1083 <sect1><tt>#pragma data-name ([push,] <name>)</tt><label id="pragma-data-name"><p>
1085 This pragma changes the name used for the DATA segment (the DATA segment
1086 is used to store initialized data). The argument is a string enclosed in
1089 Note: The default linker configuration file does only map the standard
1090 segments. If you use other segments, you have to create a new linker
1093 The <tt/#pragma/ understands the push and pop parameters as explained above.
1097 #pragma data-name ("MyDATA")
1101 <sect1><tt>#pragma inline-stdfuncs ([push,] on|off)</tt><label id="pragma-inline-stdfuncs"><p>
1103 Allow the compiler to inline some standard functions from the C library like
1104 strlen. If the argument is "off", inlining is disabled, otherwise it is enabled.
1106 See also the <tt/<ref id="option-inline-stdfuncs" name="--inline-stdfuncs">/
1107 command line option.
1109 The <tt/#pragma/ understands the push and pop parameters as explained above.
1112 <sect1><tt>#pragma local-strings ([push,] on|off)</tt><label id="pragma-local-strings"><p>
1114 When "on", emit string literals to the data segment when they're encountered
1115 in the source. The default ("off") is to keep string literals until end of
1116 assembly, merge read only literals if possible, and then output the literals
1117 into the data or rodata segment that is active at that point.
1119 Using this <tt/#pragma/ it is possible to control the behaviour from within
1120 the source. When <tt/#pragma local-strings/ is active, string literals are
1121 output immediately, which means that they go into the currently active data
1122 or rodata segment, but cannot be merged. When inactive, string literals are
1123 remembered and output as a whole when translation is finished.
1126 <sect1><tt>#pragma message (<message>)</tt><label id="pragma-message"><p>
1128 This pragma is used to display informational messages at compile-time.
1130 The message intented to be displayed must be a string literal.
1134 #pragma message ("in a bottle")
1137 Results in the compiler outputting the following to stderr:
1139 example.c(42): Note: in a bottle
1143 <sect1><tt>#pragma optimize ([push,] on|off)</tt><label id="pragma-optimize"><p>
1145 Switch optimization on or off. If the argument is "off", optimization is
1146 disabled, otherwise it is enabled. Please note that this pragma only effects
1147 whole functions. The setting in effect when the function is encountered will
1148 determine if the generated code is optimized or not.
1150 Optimization and code generation is also controlled by the <ref
1151 id="pragma-codesize" name="codesize pragma">.
1153 The default is "off", but may be changed with the <tt/<ref name="-O"
1154 id="option-O">/ compiler option.
1156 The <tt/#pragma/ understands the push and pop parameters as explained above.
1159 <sect1><tt>#pragma rodata-name ([push,] <name>)</tt><label id="pragma-rodata-name"><p>
1161 This pragma changes the name used for the RODATA segment (the RODATA
1162 segment is used to store readonly data). The argument is a string
1163 enclosed in double quotes.
1165 Note: The default linker configuration file does only map the standard
1166 segments. If you use other segments, you have to create a new linker
1169 The <tt/#pragma/ understands the push and pop parameters as explained above.
1173 #pragma rodata-name ("MyRODATA")
1177 <sect1><tt>#pragma regvaraddr ([push,] on|off)</tt><label id="pragma-regvaraddr"><p>
1179 The compiler does not allow to take the address of register variables.
1180 The regvaraddr pragma changes this. Taking the address of a register
1181 variable is allowed after using this pragma with "on" as argument.
1182 Using "off" as an argument switches back to the default behaviour.
1184 Beware: The C standard does not allow taking the address of a variable
1185 declared as register. So your programs become non-portable if you use
1186 this pragma. In addition, your program may not work. This is usually the
1187 case if a subroutine is called with the address of a register variable,
1188 and this subroutine (or a subroutine called from there) uses
1189 register variables. So be careful with this #pragma.
1191 The <tt/#pragma/ understands the push and pop parameters as explained above.
1195 #pragma regvaraddr(on) /* Allow taking the address
1196 * of register variables
1201 <sect1><tt>#pragma register-vars ([push,] on|off)</tt><label id="pragma-register-vars"><p>
1203 Enables or disables use of register variables. If register variables are
1204 disabled (the default), the <tt/register/ keyword is ignored. Register
1205 variables are explained in more detail in <ref id="register-vars" name="a separate
1208 The <tt/#pragma/ understands the push and pop parameters as explained above.
1211 <sect1><tt>#pragma signed-chars ([push,] on|off)</tt><label id="pragma-signed-chars"><p>
1213 Changes the signedness of the default character type. If the argument is
1214 "on", default characters are signed, otherwise characters are unsigned. The
1215 compiler default is to make characters unsigned since this creates a lot
1216 better code. This default may be overridden by the <tt/<ref
1217 name="--signed-chars" id="option-signed-chars">/ command line option.
1219 The <tt/#pragma/ understands the push and pop parameters as explained above.
1222 <sect1><tt>#pragma static-locals ([push,] on|off)</tt><label id="pragma-static-locals"<p>
1224 Use variables in the bss segment instead of variables on the stack. This
1225 pragma changes the default set by the compiler option <tt/<ref
1226 name="--static-locals" id="option-static-locals">/. If the argument is "on",
1227 local variables are allocated in the BSS segment, leading to shorter and in
1228 most cases faster, but non-reentrant code.
1230 The <tt/#pragma/ understands the push and pop parameters as explained above.
1233 <sect1><tt>#pragma warn (name, [push,] on|off)</tt><label id="pragma-warn"><p>
1235 Switch compiler warnings on or off. "name" is the name of a warning (see the
1236 <tt/<ref name="-W" id="option-W">/ compiler option for a list). The name is
1237 followed either by "pop", which restores the last pushed state, or by "on" or
1238 "off", optionally preceeded by "push" to push the current state before
1243 /* Don't warn about the unused parameter in function func */
1244 #pragma warn (unused-param, push, off)
1245 static int func (int unused)
1249 #pragma warn (unused-param, pop)
1253 <sect1><tt>#pragma wrapped-call (push, <name>, <identifier>)</tt><label id="pragma-wrapped-call"><p>
1255 This pragma sets a wrapper for functions, often used for trampolines.
1257 The name is a function returning <tt/void/, and taking no parameters.
1258 It must preserve the CPU's <tt/A/ and <tt/X/ registers if it wraps any
1259 <tt/__fastcall__/ functions that have parameters. It must preserve
1260 the <tt/Y/ register if it wraps any variadic functions (they have "<tt/.../"
1261 in their prototypes).
1263 The identifier is an 8-bit number that's set into <tt/tmp4/.
1265 The address of a wrapped function is passed in <tt/ptr4/. The wrapper can
1266 call that function by using "<tt/jsr callptr4/".
1268 This feature is useful, for example, with banked memory, to switch banks
1269 automatically to where a wrapped function resides, and then to restore the
1270 previous bank when it returns.
1272 The <tt/#pragma/ requires the push or pop argument as explained above.
1276 /* Note that this code can be in a header. */
1277 void mytrampoline(void); /* Doesn't corrupt __AX__ */
1279 #pragma wrapped-call (push, mytrampoline, 5)
1280 void somefunc1(void);
1281 void somefunc2(int, char *);
1282 #pragma wrapped-call (pop)
1286 <sect1><tt>#pragma writable-strings ([push,] on|off)</tt><label id="pragma-writable-strings"><p>
1288 Changes the storage location of string literals. For historical reasons,
1289 the C standard defines that string literals are of type "char[]", but
1290 writing to such a literal causes undefined behaviour. Most compilers
1291 (including cc65) place string literals in the read-only data segment, which
1292 may cause problems with old C code that writes to string literals.
1294 Using this pragma (or the corresponding command line option <tt/<ref
1295 name="--writable-strings" id="option-writable-strings">/) causes the
1296 literals to be placed in the data segment so they can be written to without
1299 The <tt/#pragma/ understands the push and pop parameters as explained above.
1302 <sect1><tt>#pragma zpsym (<name>)</tt><p>
1304 Tell the compiler that the -- previously as external declared -- symbol with
1305 the given name is a zero page symbol (usually from an assembler file).
1306 The compiler will create a matching import declaration for the assembler.
1311 #pragma zpsym ("foo"); /* foo is in the zeropage */
1316 <sect>Register variables<label id="register-vars"><p>
1318 The runtime for all supported platforms has 6 bytes of zero page space
1319 available for register variables (this could be increased, but I think it's a
1320 good value). So you can declare register variables up to a total size of 6 per
1321 function. The compiler will allocate register space on a "first come, first
1322 served" base and convert any <tt/register/ declarations that exceed the
1323 available register space silently to <tt/auto/. Parameters can also be
1324 declared as <tt/register/, this will in fact give slightly shorter code than
1325 using a register variable.
1327 Since a function must save the current values of the registers on entry and
1328 restore them on exit, there is an overhead associated with register variables,
1329 and this overhead is quite high (about 20 bytes per variable). This means that
1330 just declaring anything as <tt/register/ is not a good idea.
1332 The best use for register variables are pointers, especially those that point
1333 to structures. The magic number here is about 3 uses of a struct field: If the
1334 function contains this number or even more, the generated code will be usually
1335 shorter and faster when using a register variable for the struct pointer. The
1336 reason for this is that the register variable can in many cases be used as a
1337 pointer directly. Having a pointer in an auto variable means that this pointer
1338 must first be copied into a zero page location, before it can be dereferenced.
1340 Second best use for register variables are counters. However, there is not
1341 much difference in the code generated for counters, so you will need at least
1342 100 operations on this variable (for example in a loop) to make it worth the
1343 trouble. The only savings you get here are by the use of a zero page variable
1344 instead of one on the stack or in the data segment.
1346 Register variables must be explicitly enabled, either by using <tt/<ref
1347 name="-Or" id="option-O">/ or <tt/<ref name="--register-vars"
1348 id="option-register-vars">/ on the command line or by use of <tt/<ref
1349 name="#pragma register-vars" id="pragma-register-vars">/. Register variables
1350 are only accepted on function top level, register variables declared in
1351 interior blocks are silently converted to <tt/auto/. With register variables
1352 disabled, all variables declared as <tt/register/ are actually auto variables.
1354 Please take care when using register variables: While they are helpful and can
1355 lead to a tremendous speedup when used correctly, improper usage will cause
1356 bloated code and a slowdown.
1360 <sect>Inline assembler<label id="inline-asm"><p>
1362 The compiler allows to insert assembler statements into the output file. The
1366 asm [optional volatile] (<string literal>[, optional parameters]) ;
1370 __asm__ [optional volatile] (<string literal>[, optional parameters]) ;
1374 The first form is in the user namespace; and, is disabled by <tt><ref
1375 id="option--standard" name="--standard"></tt> if the argument is not <tt/cc65/.
1377 The <tt/asm/ statement can be used only inside a function. Please note that
1378 the result of an inline assembler expression is always of type <tt/void/.
1380 The contents of the string literal are preparsed by the compiler; and, inserted
1381 into the generated assembly output, so that it can be processed further by
1382 the backend -- and, especially the optimizer. For that reason, the compiler does
1383 allow only regular 6502 opcodes to be used with the inline assembler. Pseudo
1384 instructions (like <tt/.import/, <tt/.byte/, and so on) are <em/not/ allowed,
1385 even if the ca65 assembler (which is used to translate the generated assembler
1386 code) would accept them. The built-in inline assembler is not a replacement for
1387 the full-blown macro assembler which comes with the compiler.
1389 Note: Inline assembler statements are subject to all optimizations done by the
1390 compiler. There currently is no way to protect an inline assembler statement
1391 -- alone -- from being moved or removed completely by the optimizer. If in
1392 doubt, check the generated assembler output; or, disable optimizations (for
1395 As a shortcut, you can put the <tt/volatile/ qualifier in your <tt/asm/
1396 statements. It will disable optimization for the functions in which those
1397 <tt/asm volatile/ statements sit. The effect is the same as though you put
1398 <tt/#pragma optimize(push, off)/ above those functions, and <tt/#pragma
1399 optimize(pop)/ below those functions.
1401 The string literal may contain format specifiers from the following list. For
1402 each format specifier, an argument is expected which is inserted instead of
1403 the format specifier, before passing the assembly code line to the backend.
1406 <item><tt/%b/ - Numerical 8-bit value
1407 <item><tt/%w/ - Numerical 16-bit value
1408 <item><tt/%l/ - Numerical 32-bit value
1409 <item><tt/%v/ - Assembler name of a global variable or function
1410 <item><tt/%o/ - Stack offset of a local variable
1411 <item><tt/%g/ - Assembler name of a C label
1412 <item><tt/%s/ - The argument is converted to a string
1413 <item><tt/%%/ - The % sign itself
1416 Using those format specifiers, you can access C <tt/#defines/, variables, or
1417 similar stuff from the inline assembler. For example, to load the value of
1418 a C <tt/#define/ into the Y index register, one would use
1422 __asm__ ("ldy #%b", OFFS);
1425 Or, to access a struct member of a static variable:
1431 unsigned char color;
1433 static pixel_t pixel;
1434 __asm__ ("ldy #%b", offsetof(pixel_t, color));
1435 __asm__ ("lda %v,y", pixel);
1438 The next example shows how to use global variables to exchange data between C
1439 and assembler; and, how to handle assembler jumps:
1442 static unsigned char globalSubA, globalSubB, globalSubResult;
1444 /* return a-b, return 255 if b>a */
1445 unsigned char sub (unsigned char a, unsigned char b)
1450 __asm__ ("lda %v", globalSubA);
1451 __asm__ ("sbc %v", globalSubB);
1452 __asm__ ("bcs %g", jumpSubNoError);
1453 __asm__ ("lda #$FF");
1455 __asm__ ("sta %v", globalSubResult);
1456 return globalSubResult;
1461 Arrays also can be accessed:
1464 static const unsigned char globalSquareTable[] = {
1465 0, 1, 4, 9, 16, 25, 36, 49, 64, 81,
1466 100, 121, 144, 169, 196, 225
1468 static unsigned char globalSquareA, globalSquareResult;
1470 /* return a*a for a<16, else 255 */
1471 unsigned char square (unsigned char a)
1477 __asm__ ("ldx %v", globalSquareA);
1478 __asm__ ("lda %v,x", globalSquareTable);
1479 __asm__ ("sta %v", globalSquareResult);
1480 return globalSquareResult;
1485 Note: Do not embed the assembler labels that are used as names of global
1486 variables or functions into your <tt/asm/ statements. Code such as this:
1490 int bar (void) { return 1; }
1492 __asm__ ("lda _foo"); /* DON'T DO THAT! */
1494 __asm__ ("jsr _bar"); /* DON'T DO THAT EITHER! */
1498 might stop working if the way that the compiler generates those names is changed in
1499 a future version. Instead, use the format specifiers from the table above:
1502 __asm__ ("lda %v", foo); /* OK */
1504 __asm__ ("jsr %v", bar); /* OK */
1510 <sect>Implementation-defined behavior<p>
1512 This section describes the behavior of cc65 when the standard describes the
1513 behavior as implementation-defined.
1519 This is the original compiler copyright:
1522 --------------------------------------------------------------------------
1525 This is the copyright notice for RA65, LINK65, LIBR65, and other
1526 Atari 8-bit programs. Said programs are Copyright 1989, by John R.
1527 Dunning. All rights reserved, with the following exceptions:
1529 Anyone may copy or redistribute these programs, provided that:
1531 1: You don't charge anything for the copy. It is permissable to
1532 charge a nominal fee for media, etc.
1534 2: All source code and documentation for the programs is made
1535 available as part of the distribution.
1537 3: This copyright notice is preserved verbatim, and included in
1540 You are allowed to modify these programs, and redistribute the
1541 modified versions, provided that the modifications are clearly noted.
1543 There is NO WARRANTY with this software, it comes as is, and is
1544 distributed in the hope that it may be useful.
1546 This copyright notice applies to any program which contains
1547 this text, or the refers to this file.
1549 This copyright notice is based on the one published by the Free
1550 Software Foundation, sometimes known as the GNU project. The idea
1551 is the same as theirs, ie the software is free, and is intended to
1552 stay that way. Everybody has the right to copy, modify, and re-
1553 distribute this software. Nobody has the right to prevent anyone
1554 else from copying, modifying or redistributing it.
1556 --------------------------------------------------------------------------
1559 Small parts of the compiler (parts of the preprocessor and main parser) are
1560 still covered by this copyright. The main portion is covered by the usual
1561 cc65 license, which reads:
1563 This software is provided 'as-is', without any expressed or implied
1564 warranty. In no event will the authors be held liable for any damages
1565 arising from the use of this software.
1567 Permission is granted to anyone to use this software for any purpose,
1568 including commercial applications, and to alter it and redistribute it
1569 freely, subject to the following restrictions:
1572 <item> The origin of this software must not be misrepresented; you must not
1573 claim that you wrote the original software. If you use this software
1574 in a product, an acknowledgment in the product documentation would be
1575 appreciated but is not required.
1576 <item> Altered source versions must be plainly marked as such, and must not
1577 be misrepresented as being the original software.
1578 <item> This notice may not be removed or altered from any source