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 standard 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 --eagerly-inline-funcs Eagerly inline some known functions
92 --enable-opt name Enable an optimization step
93 --help Help (this text)
94 --include-dir dir Set an include directory search path
95 --inline-stdfuncs Inline some standard functions
96 --list-opt-steps List all optimizer steps and exit
97 --list-warnings List available warning types for -W
98 --local-strings Emit string literals immediately
99 --memory-model model Set the memory model
100 --register-space b Set space available for register variables
101 --register-vars Enable register variables
102 --rodata-name seg Set the name of the RODATA segment
103 --signed-chars Default characters are signed
104 --standard std Language standard (c89, c99, cc65)
105 --static-locals Make local variables static
106 --target sys Set the target system
107 --verbose Increase verbosity
108 --version Print the compiler version number
109 --writable-strings Make string literals writable
110 ---------------------------------------------------------------------------
114 <sect1>Command line options in detail<p>
116 Here is a description of all the command line options:
120 <tag><tt>--all-cdecl</tt></tag>
122 Tells the compiler that functions which aren't declared explicitly with
123 either the <tt/__cdecl__/ or <tt/__fastcall__/ calling conventions should
124 have the cdecl convention. (Normally, functions that aren't variadic are
128 <label id="option-bss-name">
129 <tag><tt>--bss-name seg</tt></tag>
131 Set the name of the bss segment. See also <tt/<ref id="pragma-bss-name"
132 name="#pragma bss-name">/.
135 <label id="option-check-stack">
136 <tag><tt>--check-stack</tt></tag>
138 Tells the compiler to generate code that checks for stack overflows. See
139 <tt/<ref id="pragma-check-stack" name="#pragma check-stack">/ for an
140 explanation of this feature.
143 <label id="option-code-name">
144 <tag><tt>--code-name seg</tt></tag>
146 Set the name of the code segment. See also <tt/<ref id="pragma-code-name"
147 name="#pragma code-name">/
150 <label id="option-codesize">
151 <tag><tt>--codesize x</tt></tag>
153 This options allows finer control about speed vs. size decisions in the code
154 generation and optimization phases. It gives the allowed size increase
155 factor (in percent). The default is 100 when not using <tt/-Oi/ and 200 when
156 using <tt/-Oi/ (<tt/-Oi/ is the same as <tt/-O --codesize 200/).
159 <label id="option--cpu">
160 <tag><tt>--cpu CPU</tt></tag>
162 Set the CPU, the compiler generates code for. You may specify "6502" or
163 "65C02" as the CPU. The default depends on the selected target (see option
164 <tt/<ref id="option-t" name="-t">/). It is the 6502 CPU for most targets or
165 if no target has been set. Specifying 65C02 will use a few 65C02
166 instructions when generating code. Don't expect too much from this option:
167 In most cases the difference in size and speed is just 1-2%.
170 <label id="option-create-dep">
171 <tag><tt>--create-dep name</tt></tag>
173 Tells the compiler to generate a file containing the dependency list for the
174 compiled module in makefile syntax. The output is written to a file with the
175 given name. The output does not include system include files (in angle
179 <label id="option-create-full-dep">
180 <tag><tt>--create-full-dep name</tt></tag>
182 Tells the compiler to generate a file containing the dependency list for the
183 compiled module in makefile syntax. The output is written to a file with the
184 given name. The output does include system include files (in angle
188 <label id="option-data-name">
189 <tag><tt>--data-name seg</tt></tag>
191 Set the name of the data segment. See also <tt/<ref id="pragma-data-name"
192 name="#pragma data-name">/
195 <tag><tt>-d, --debug</tt></tag>
197 Enables debug mode, something that should not be needed for mere
201 <label id="option-dep-target">
202 <tag><tt>--dep-target target</tt></tag>
204 When generating a dependency file, don't use the actual output file as the
205 target of the dependency, but the file specified with this option. The
206 option has no effect if neither <tt/<ref id="option-create-dep"
207 name="--create-dep">/ nor <tt/<ref id="option-create-full-dep"
208 name="--create-full-dep">/ is specified.
211 <tag><tt>-D sym[=definition]</tt></tag>
213 Define a macro on the command line. If no definition is given, the macro
214 is defined to the value "1".
217 <tag><tt>-g, --debug-info</tt></tag>
219 This will cause the compiler to insert a <tt/.DEBUGINFO/ command into the
220 generated assembler code. This will cause the assembler to include all
221 symbols in a special section in the object file.
224 <label id="option-eagerly-inline-funcs">
225 <tag><tt>--eagerly-inline-funcs</tt></tag>
227 Have the compiler eagerly inline these functions from the C library:
234 <item>most of the functions declared in <tt/<ctype.h>/
237 Note: This has two consequences:
239 <item>You may not use names of standard C functions for your own functions.
240 If you do that, your program is not standard-compliant anyway; but,
241 using <tt/--eagerly-inline-funcs/ actually will break things.
243 <item>The inlined string and memory functions will not handle strings or
244 memory areas larger than 255 bytes. Similarly, the inlined <tt/is..()/
245 functions will not work with values outside the char. range (such as
250 <tt/--eagerly-inline-funcs/ implies the <tt><ref id="option-inline-stdfuncs"
251 name="--inline-stdfuncs"></tt> command line option.
253 See also <tt><ref id="pragma-allow-eager-inline" name="#pragma allow-eager-inline"></tt>.
256 <tag><tt>-h, --help</tt></tag>
258 Print the short option summary shown above.
261 <label id="option-inline-stdfuncs">
262 <tag><tt>--inline-stdfuncs</tt></tag>
264 Allow the compiler to inline some standard functions from the C library like
265 strlen. This will not only remove the overhead for a function call, but will
266 make the code visible for the optimizer. See also the <tt><ref id="option-O"
267 name="-Os"></tt> command line option and <tt><ref id="pragma-inline-stdfuncs"
268 name="#pragma inline-stdfuncs"></tt>.
271 <label id="option-list-warnings">
272 <tag><tt>--list-warnings</tt></tag>
274 List the names of warning types available for use with <tt><ref
275 id="option-W" name="-W"></tt>.
278 <label id="option-local-strings">
279 <tag><tt>--local-strings</tt></tag>
281 Emit string literals into the rodata segment as soon as they're encountered
282 in the source (even if you do nothing but get the sizeof those strings). The
283 default is to keep string literals until end of assembly, merge read only
284 literals if possible, and then output the literals into the data or rodata
285 segment that is active at that point. Use of this option prevents merging of
286 duplicate strings, but the options that change the name of one of the data
289 You can also use <tt><ref id="pragma-local-strings"
290 name="#pragma local-strings"></tt> for fine grained control.
293 <tag><tt>-o name</tt></tag>
295 Specify the name of the output file. If you don't specify a name, the
296 name of the C input file is used, with the extension replaced by ".s".
299 <label id="option-register-vars">
300 <tag><tt>-r, --register-vars</tt></tag>
302 <tt/-r/ will make the compiler honor the <tt/register/ keyword. Local
303 variables may be placed in registers (which are actually zero page
304 locations). There is some overhead involved with register variables, since
305 the old contents of the registers must be saved and restored. Since register
306 variables are of limited use without the optimizer, there is also a combined
307 switch: <tt/-Or/ will enable both, the optimizer and register variables.
309 For more information about register variables see <ref id="register-vars"
310 name="register variables">.
312 The compiler setting can also be changed within the source file by using
313 <tt/<ref id="pragma-register-vars" name="#pragma register-vars">/.
316 <label id="option-register-space">
317 <tag><tt>--register-space</tt></tag>
319 This option takes a numeric parameter and is used to specify, how much
320 zero page register space is available. Please note that just giving this
321 option will not increase or decrease by itself, it will just tell the
322 compiler about the available space. You will have to allocate that space
323 yourself using an assembler module with the necessary allocations, and a
324 linker configuration that matches the assembler module. The default value
325 for this option is 6 (bytes).
327 If you don't know what all this means, please don't use this option.
330 <label id="option-rodata-name">
331 <tag><tt>--rodata-name seg</tt></tag>
333 Set the name of the rodata segment (the segment used for readonly data).
334 See also <tt/<ref id="pragma-rodata-name" name="#pragma rodata-name">/
336 <label id="option-signed-chars">
337 <tag><tt>-j, --signed-chars</tt></tag>
339 Using this option, you can make the default characters signed. Since the
340 6502 has no provisions for sign extending characters (which is needed on
341 almost any load operation), this will make the code larger and slower. A
342 better way is to declare characters explicitly as "signed" if needed. You
343 can also use <tt><ref id="pragma-signed-chars"
344 name="#pragma signed-chars"></tt> for better control of this option.
347 <label id="option--standard">
348 <tag><tt>--standard std</tt></tag>
350 This option allows to set the language standard supported. The argument is
354 This disables anything that is illegal in C89/C90. Among those things
355 are <tt>//</tt> comments and the non-standard keywords without
356 underscores. Please note that cc65 is not a fully C89 compliant compiler
357 despite this option. A few more things (like floats) are missing.
360 This enables a few features from the C99 standard. With this option,
361 <tt>//</tt> comments are allowed. It will also cause warnings and even
362 errors in a few situations that are allowed with <tt/--standard c89/.
363 For example, a call to a function without a prototype is an error in
367 This is the default mode. It is like c99 mode, but additional features
368 are enabled. Among these are "void data", non-standard keywords without
369 the underlines, unnamed function parameters and the requirement for
370 main() to return an int.
373 Please note that the compiler does not support the C99 standard and never
374 will. c99 mode is actually c89 mode with a few selected C99 extensions.
377 <label id="option-t">
378 <tag><tt>-t target, --target target</tt></tag>
380 This option is used to set the target system. The target system determines
381 the character set that is used for strings and character constants and the
382 default CPU. The CPU setting can be overriden by use of the <tt/<ref
383 id="option--cpu" name="--cpu">/ option.
385 The following target systems are supported:
394 <item>c16 (works also for the c116 with memory up to 32K)
397 <item>cbm510 (CBM-II series with 40 column video)
398 <item>cbm610 (all CBM-II II computers with 80 column video)
405 <item>pet (all CBM PET systems except the 2001)
414 <tag><tt>-v, --verbose</tt></tag>
416 Using this option, the compiler will be somewhat more verbose if errors
417 or warnings are encountered.
420 <label id="option-writable-strings">
421 <tag><tt>--writable-strings</tt></tag>
423 Make string literals writable by placing them into the data segment instead
424 of the rodata segment. You can also use <tt><ref id="pragma-writable-strings"
425 name="#pragma writable-strings"></tt> to control this option from within
429 <label id="option-static-locals">
430 <tag><tt>-Cl, --static-locals</tt></tag>
432 Use static storage for local variables instead of storage on the stack.
433 Since the stack is emulated in software, this gives shorter and usually
434 faster code, but the code is no longer reentrant. The difference between
435 <tt/-Cl/ and declaring local variables as static yourself is, that
436 initializer code is executed each time, the function is entered. So when
447 the variable <tt/a/ will always have the value <tt/1/ when entering the
448 function and using <tt/-Cl/, while in
453 static unsigned a = 1;
458 the variable <tt/a/ will have the value <tt/1/ only the first time that the
459 function is entered, and will keep the old value from one call of the
460 function to the next.
462 You may also use <tt><ref id="pragma-static-locals"
463 name="#pragma static-locals"></tt> to change this setting in your
467 <label id="option-include-dir">
468 <tag><tt>-I dir, --include-dir dir</tt></tag>
470 Set a directory where the compiler searches for include files. You may
471 use this option multiple times to add more than one directory to the
475 <label id="option-O">
476 <tag><tt>-O, -Oi, -Or, -Os</tt></tag>
478 Enable an optimizer run over the produced code.
480 Using <tt/-Oi/, the code generator will inline some code where otherwise a
481 runtime functions would have been called, even if the generated code is
482 larger. This will not only remove the overhead for a function call, but will
483 make the code visible for the optimizer. <tt/-Oi/ is an alias for
484 <tt/-O --codesize 200/.
486 <tt/-Or/ will make the compiler honor the <tt/register/ keyword. Local
487 variables may be placed in registers (which are actually zero page
488 locations). See also the <tt/<ref id="option-register-vars"
489 name="--register-vars">/ command line option, and the <ref
490 id="register-vars" name="discussion of register variables"> below.
492 Using <tt/-Os/ will allow the compiler to inline some standard functions
493 from the C library like strlen. This will not only remove the overhead
494 for a function call, but will make the code visible for the optimizer.
495 See also the <tt/<ref id="option-inline-stdfuncs" name="--inline-stdfuncs">/
498 It is possible to concatenate the modifiers for <tt/-O/. For example, to
499 enable register variables and inlining of standard functions, you may use
503 <tag><tt>-T, --add-source</tt></tag>
505 This include the source code as comments in the generated code. This is
509 <tag><tt>-V, --version</tt></tag>
511 Print the version number of the compiler. When submitting a bug report,
512 please include the operating system you're using, and the compiler
516 <label id="option-W">
517 <tag><tt>-W name[,name,...]</tt></tag>
519 This option allows to control warnings generated by the compiler. It is
520 followed by a comma-separated list of warnings that should be enabled or
521 disabled. To disable a warning, its name is prefixed by a minus sign. If
522 no such prefix exists, or the name is prefixed by a plus sign, the warning
525 The following warning names currently are recognized:
527 <tag><tt/const-comparison/</tag>
528 Warn if the result of a comparison is constant.
529 <tag><tt/error/</tag>
530 Treat all warnings as errors.
531 <tag><tt/no-effect/</tag>
532 Warn about statements that don't have an effect.
533 <tag><tt/remap-zero/</tag>
534 Warn about a <tt/<ref id="pragma-charmap" name="#pragma charmap()">/
535 that changes a character's code number from/to 0x00.
536 <tag><tt/struct-param/</tag>
537 Warn when passing structs by value.
538 <tag><tt/unknown-pragma/</tag>
539 Warn about #pragmas that aren't recognized by cc65.
540 <tag><tt/unused-label/</tag>
541 Warn about unused labels.
542 <tag><tt/unused-param/</tag>
543 Warn about unused function parameters.
544 <tag><tt/unused-var/</tag>
545 Warn about unused variables.
548 The full list of available warning names can be retrieved by using the
549 option <tt><ref id="option-list-warnings" name="--list-warnings"></tt>.
551 You may use also <tt><ref id="pragma-warn" name="#pragma warn"></tt> to
552 control this setting, for smaller pieces of code, from within your sources.
558 <sect>Input and output<p>
560 The compiler will accept one C file per invocation and create a file with
561 the same base name, but with the extension replaced by ".s". The output
562 file contains assembler code suitable for use with the ca65 macro
565 Include files in quotes are searched in the following places:
567 <item>The current file's directory.
568 <item>Any directory added with the <tt/-I/ option on the command line.
569 <item>The value of the environment variable <tt/CC65_INC/ if it is defined.
572 Include files in angle brackets are searched in the following places:
574 <item>Any directory added with the <tt/-I/ option on the command line.
575 <item>The value of the environment variable <tt/CC65_INC/ if it is defined.
576 <item>A subdirectory named <tt/include/ of the directory defined in the
577 environment variable <tt/CC65_HOME/, if it is defined.
578 <item>An optionally compiled-in directory.
583 <sect>Differences to the ISO standard<p>
585 Apart from the things listed below, the compiler does support additional
586 keywords, has several functions in the standard headers with names outside the
587 reserved namespace and a few syntax extensions. All these can be disabled with
588 the <tt><ref id="option--standard" name="--standard"></tt> command line
589 option. Its use for maximum standards compatibility is advised.
591 Here is a list of differences between the language, the compiler accepts,
592 and the one defined by the ISO standard:
596 <item> The datatypes "float" and "double" are not available.
598 <item> C Functions may not return structs (or unions), and structs may not
599 be passed as parameters by value. However, struct assignment *is*
602 <item> Most of the C library is available with only the fastcall calling
603 convention (<ref id="extension-fastcall" name="see below">). It means
604 that you must not mix pointers to those functions with pointers to
605 user-written, cdecl functions (the calling conventions are incompatible).
607 <item> The <tt/volatile/ keyword has almost no effect. That is not as bad
608 as it sounds, since the 6502 has so few registers that it isn't
609 possible to keep values in registers anyway.
613 There may be some more minor differences I'm currently not aware of. The
614 biggest problem is the missing float data type. With this limitation in
615 mind, you should be able to write fairly portable code.
621 This cc65 version has some extensions to the ISO C standard.
625 <item> The compiler allows to insert assembler statements into the output
629 asm [optional volatile] (<string literal>[, optional parameters]) ;
633 __asm__ [optional volatile] (<string literal>[, optional parameters]) ;
636 The first form is in the user namespace; and, is disabled if the <tt/-A/
639 There is a whole section covering inline assembler statements,
640 <ref id="inline-asm" name="see there">.
643 <label id="extension-fastcall">
644 <item> The normal calling convention -- for non-variadic functions -- is
645 named "fastcall". The syntax for a function declaration that
646 <em/explicitly/ uses fastcall is
649 <return type> fastcall <function name> (<parameter list>)
653 <return type> __fastcall__ <function name> (<parameter list>)
657 void __fastcall__ f (unsigned char c)
659 The first form of the fastcall keyword is in the user namespace and can
660 therefore be disabled with the <tt><ref id="option--standard"
661 name="--standard"></tt> command line option.
663 For functions that are <tt/fastcall/, the rightmost parameter is not
664 pushed on the stack but left in the primary register when the function
665 is called. That significantly reduces the cost of calling those functions.
668 <item> There is another calling convention named "cdecl". Variadic functions
669 (their prototypes have an ellipsis [<tt/.../]) always use that
670 convention. The syntax for a function declaration using cdecl is
673 <return type> cdecl <function name> (<parameter list>)
677 <return type> __cdecl__ <function name> (<parameter list>)
681 int* __cdecl__ f (unsigned char c)
684 The first form of the cdecl keyword is in the user namespace;
685 and therefore, can be disabled with the <tt/<ref id="option--standard"
686 name="--standard">/ command-line option.
688 For functions that are <tt/cdecl/, the rightmost parameter is pushed
689 onto the stack before the function is called. That increases the cost
690 of calling those functions, especially when they are called from many
694 <item> There are two pseudo variables named <tt/__AX__/ and <tt/__EAX__/.
695 Both refer to the primary register that is used by the compiler to
696 evaluate expressions or return function results. <tt/__AX__/ is of
697 type <tt/unsigned int/ and <tt/__EAX__/ of type <tt/long unsigned int/
698 respectively. The pseudo variables may be used as lvalue and rvalue as
699 every other variable. They are most useful together with short
700 sequences of assembler code. For example, the macro
710 will give the high byte of any unsigned value.
713 <item> Inside a function, the identifier <tt/__func__/ gives the name of the
714 current function as a string. Outside of functions, <tt/__func__/ is
719 #define PRINT_DEBUG(s) printf ("%s: %s\n", __func__, s);
722 The macro will print the name of the current function plus a given
726 <item> cc65 allows the initialization of <tt/void/ variables. This may be
727 used to create arbitrary structures that are more compatible with
728 interfaces written for assembler languages. Here is an example:
731 void GCmd = { (char)3, (unsigned)0x2000, (unsigned)0x3000 };
734 That will be translated as follows:
743 Since the variable is of type <tt/void/, you may not use it as-is.
744 However, taking the address of the variable results in a <tt/void*/
745 which may be passed to any function expecting a pointer. Also, the
746 <tt/sizeof/ operator will give the length of the initializer:
752 will assign the value 5 to <tt/GLen/.
754 See the <url url="geos.html" name="GEOS library document"> for examples
755 on how to use that feature.
758 <item> cc65 implements flexible array struct members as defined in the C99 ISO
759 standard. As an extension, these fields may be initialized. There are
760 several exceptions, however (which is probably the reason why the
761 standard does not define this feature, because it is highly
762 unorthogonal). Flexible array members cannot be initialized ...
765 <item>... when defining an array of structs with flexible
767 <item>... if such a struct is a member field of another struct
768 which is not the last field.
769 <item>... if the struct which contains a flexible array member is
770 declared as <tt/register/, and the size and compiler settings
771 do allow the compiler actually to place the struct into the
772 register bank in the zero page.
775 Please note that -- as defined in the ISO C standard -- the <tt/sizeof/
776 operator returns the struct size with the flexible array member having
777 size zero, even if it is initialized.
785 <sect>Predefined macros<p>
787 The compiler defines several macros at startup:
790 <tag><tt>__APPLE2__</tt></tag>
792 This macro is defined if the target is the Apple ][ (-t apple2) or the enhanced Apple //e (-t apple2enh).
794 <tag><tt>__APPLE2ENH__</tt></tag>
796 This macro is defined if the target is the enhanced Apple //e (-t apple2enh).
798 <tag><tt>__ATARI2600__</tt></tag>
800 This macro is defined if the target is the Atari 2600 game console.
802 <tag><tt>__ATARI5200__</tt></tag>
804 This macro is defined if the target is the Atari 5200 game console.
806 <tag><tt>__ATARI__</tt></tag>
808 This macro is defined if the target is the Atari 400/800 (-t atari) or the Atari 800XL/130XE (-t atarixl).
810 <tag><tt>__ATARIXL__</tt></tag>
812 This macro is defined if the target is the Atari 800XL/130XE (-t atarixl).
814 <tag><tt>__ATMOS__</tt></tag>
816 This macro is defined if the target is the Oric Atmos (-t atmos).
818 <tag><tt>__C128__</tt></tag>
820 This macro is defined if the target is the Commodore 128 (-t c128).
822 <tag><tt>__C16__</tt></tag>
824 This macro is defined if the target is the Commodore 16/116 (-t c16) or the Commodore Plus/4 (-t plus4).
826 <tag><tt>__C64__</tt></tag>
828 This macro is defined if the target is the Commodore 64 (-t c64).
830 <tag><tt>__CBM__</tt></tag>
832 This macro is defined if the target system is one of the CBM targets.
834 <tag><tt>__CBM510__</tt></tag>
836 This macro is defined if the target is the CBM 500 series of computers.
838 <tag><tt>__CBM610__</tt></tag>
840 This macro is defined if the target is one of the CBM 600/700 family of
841 computers (called B series in the US).
843 <tag><tt>__CC65__</tt></tag>
845 This macro is always defined. Its value is the version number of the
846 compiler in hex. For example, version 2.14 of the compiler has this macro
847 defined as <tt/0x02E0/.
849 <tag><tt>__CC65_STD__</tt></tag>
851 This macro is defined to one of the following depending on the <tt><ref
852 id="option--standard" name="--standard"></tt> command line option:
854 <item><tt/__CC65_STD_C89__/
855 <item><tt/__CC65_STD_C99__/
856 <item><tt/__CC65_STD_CC65__/
859 <tag><tt>__DATE__</tt></tag>
861 This macro expands to the date of translation of the preprocessing
862 translation unit in the form "Mmm dd yyyy".
864 <tag><tt>__EAGERLY_INLINE_FUNCS__</tt></tag>
866 Is defined if the compiler was called with the <tt><ref id="option-eagerly-inline-funcs"
867 name="--eagerly-inline-funcs"></tt> command line option.
869 <tag><tt>__FILE__</tt></tag>
871 This macro expands to a string containing the name of the C source file.
873 <tag><tt>__GEOS__</tt></tag>
875 This macro is defined if you are compiling for one of the GEOS systems.
877 <tag><tt>__GEOS_APPLE__</tt></tag>
879 This macro is defined if you are compiling for the Apple GEOS system (-t geos-apple).
881 <tag><tt>__GEOS_CBM__</tt></tag>
883 This macro is defined if you are compiling for the GEOS 64/128 system (-t geos-cbm).
885 <tag><tt>__LINE__</tt></tag>
887 This macro expands to the current line number.
889 <tag><tt>__LUNIX__</tt></tag>
891 This macro is defined if you are compiling for the LUnix system (-t lunix).
893 <tag><tt>__LYNX__</tt></tag>
895 This macro is defined if the target is the Atari Lynx (-t lynx).
897 <tag><tt>__NES__</tt></tag>
899 This macro is defined if the target is the Nintendo Entertainment System (-t nes).
901 <tag><tt>__OPT__</tt></tag>
903 Is defined if the compiler was called with the <tt/-O/ command line option.
905 <tag><tt>__OPT_i__</tt></tag>
907 Is defined if the compiler was called with the <tt/-Oi/ command line option.
909 <tag><tt>__OPT_r__</tt></tag>
911 Is defined if the compiler was called with the <tt/-Or/ command line option.
913 <tag><tt>__OPT_s__</tt></tag>
915 Is defined if the compiler was called with the <tt/-Os/ command line option.
917 <tag><tt>__OSIC1P__</tt></tag>
919 This macro is defined if the target is the Ohio Scientific Challenger 1P
922 <tag><tt>__PET__</tt></tag>
924 This macro is defined if the target is the PET family of computers (-t pet).
926 <tag><tt>__PLUS4__</tt></tag>
928 This macro is defined if the target is the Commodore Plus/4 (-t plus4).
930 <tag><tt>__STDC_HOSTED__</tt></tag>
932 This macro is expands to the integer constant 1.
934 <tag><tt>__SIM6502__</tt></tag>
936 This macro is defined if the target is sim65 in 6502 mode (-t sim6502).
938 <tag><tt>__SIM65C02__</tt></tag>
939 This macro is defined if the target is sim65 in 65C02 mode (-t sim65c02).
941 <tag><tt>__SUPERVISION__</tt></tag>
943 This macro is defined if the target is the Supervision (-t supervision).
945 <tag><tt>__TELESTRAT__</tt></tag>
947 This macro is defined if the target is the Telestrat (-t telestrat).
949 <tag><tt>__TIME__</tt></tag>
951 This macro expands to the time of translation of the preprocessing
952 translation unit in the form "hh:mm:ss".
954 <tag><tt>__VIC20__</tt></tag>
956 This macro is defined if the target is the Commodore VIC20 (-t vic20).
961 <sect>#pragmas<label id="pragmas"><p>
963 The compiler understands some pragmas that may be used to change code
964 generation and other stuff. Some of these pragmas understand a special form:
965 If the first parameter is <tt/push/, the old value is saved onto a stack
966 before changing it. The value may later be restored by using the <tt/pop/
967 parameter with the <tt/#pragma/.
970 <sect1><tt>#pragma allow-eager-inline ([push,] on|off)</tt><label id="pragma-allow-eager-inline"><p>
972 Allow eager inlining of known functions. If the argument is "off", eager
973 inlining is disabled, otherwise it is enabled. Please note that (in contrast
974 to the <tt><ref id="option-eagerly-inline-funcs" name="--eagerly-inline-funcs"></tt>
975 command line option) this pragma does not imply the <tt><ref id="option-inline-stdfuncs"
976 name="--inline-stdfuncs"></tt> command line option. Rather it marks code to be safe for
977 eager inlining of known functions if inlining of standard functions is enabled.
979 The <tt/#pragma/ understands the push and pop parameters as explained above.
982 <sect1><tt>#pragma bss-name ([push,] <name>)</tt><label id="pragma-bss-name"><p>
984 This pragma changes the name used for the BSS segment (the BSS segment
985 is used to store uninitialized data). The argument is a string enclosed
988 Note: The default linker configuration file does only map the standard
989 segments. If you use other segments, you have to create a new linker
992 Beware: The startup code will zero only the default BSS segment. If you
993 use another BSS segment, you have to do that yourself, otherwise
994 uninitialized variables do not have the value zero.
996 The <tt/#pragma/ understands the push and pop parameters as explained above.
1000 #pragma bss-name ("MyBSS")
1004 <sect1><tt>#pragma charmap (<index>, <code>)</tt><label id="pragma-charmap"><p>
1006 Each literal string and each literal character in the source is translated
1007 by use of a translation table. That translation table is preset when the
1008 compiler is started, depending on the target system; for example, to map
1009 ISO-8859-1 characters into PETSCII if the target is a Commodore machine.
1011 This pragma allows to change entries in the translation table, so the
1012 translation for individual characters, or even the complete table may be
1013 adjusted. Both arguments are assumed to be unsigned characters with a valid
1016 Beware of some pitfalls:
1018 <item>The character index is actually the code of the character in the
1019 C source; so, character mappings do always depend on the source
1020 character set. That means that <tt/#pragma charmap()/ is not
1021 portable -- it depends on the build environment.
1022 <item>While it is possible to use character literals as indices, the
1023 result may be somewhat unexpected, since character literals are
1024 themselves translated. For that reason, I would suggest to avoid
1025 character literals, and use numeric character codes instead.
1026 <item>It is risky to change index <tt/0x00/, because string functions depend
1027 on it. If it is changed, then the <tt/'\0'/ at the end of string
1028 literals will become non-zero. Functions that are used on those
1029 literals won't stop at the end of them. cc65 will warn you if you do
1030 change that code number. You can turn off that <tt/remap-zero/ warning
1031 if you are certain that you know what you are doing (see <tt/<ref
1032 id="pragma-warn" name="#pragma warn()">/).
1037 /* Use a space wherever an 'a' occurs in ISO-8859-1 source */
1038 #pragma charmap (0x61, 0x20);
1042 <sect1><tt>#pragma check-stack ([push,] on|off)</tt><label id="pragma-check-stack"><p>
1044 Tells the compiler to insert calls to a stack checking subroutine to detect
1045 stack overflows. The stack checking code will lead to somewhat larger and
1046 slower programs, so you may want to use this pragma when debugging your
1047 program and switch it off for the release version. If a stack overflow is
1048 detected, the program is aborted.
1050 If the argument is "off", stack checks are disabled (the default), otherwise
1053 The <tt/#pragma/ understands the push and pop parameters as explained above.
1056 <sect1><tt>#pragma code-name ([push,] <name>)</tt><label id="pragma-code-name"><p>
1058 This pragma changes the name used for the CODE segment (the CODE segment
1059 is used to store executable code). The argument is a string enclosed in
1062 Note: The default linker configuration file does only map the standard
1063 segments. If you use other segments, you have to create a new linker
1066 The <tt/#pragma/ understands the push and pop parameters as explained above.
1070 #pragma code-name ("MyCODE")
1074 <sect1><tt>#pragma codesize ([push,] <int>)</tt><label id="pragma-codesize"><p>
1076 This pragma allows finer control about speed vs. size decisions in the code
1077 generation and optimization phase. It gives the allowed size increase factor
1078 (in percent). The default is can be changed by use of the <tt/<ref
1079 id="option-codesize" name="--codesize">/ compiler option.
1081 The <tt/#pragma/ understands the push and pop parameters as explained above.
1084 <sect1><tt>#pragma data-name ([push,] <name>)</tt><label id="pragma-data-name"><p>
1086 This pragma changes the name used for the DATA segment (the DATA segment
1087 is used to store initialized data). The argument is a string enclosed in
1090 Note: The default linker configuration file does only map the standard
1091 segments. If you use other segments, you have to create a new linker
1094 The <tt/#pragma/ understands the push and pop parameters as explained above.
1098 #pragma data-name ("MyDATA")
1102 <sect1><tt>#pragma inline-stdfuncs ([push,] on|off)</tt><label id="pragma-inline-stdfuncs"><p>
1104 Allow the compiler to inline some standard functions from the C library like
1105 strlen. If the argument is "off", inlining is disabled, otherwise it is enabled.
1107 See also the <tt/<ref id="option-inline-stdfuncs" name="--inline-stdfuncs">/
1108 command line option.
1110 The <tt/#pragma/ understands the push and pop parameters as explained above.
1113 <sect1><tt>#pragma local-strings ([push,] on|off)</tt><label id="pragma-local-strings"><p>
1115 When "on", emit string literals to the data segment when they're encountered
1116 in the source. The default ("off") is to keep string literals until end of
1117 assembly, merge read only literals if possible, and then output the literals
1118 into the data or rodata segment that is active at that point.
1120 Using this <tt/#pragma/ it is possible to control the behaviour from within
1121 the source. When <tt/#pragma local-strings/ is active, string literals are
1122 output immediately, which means that they go into the currently active data
1123 or rodata segment, but cannot be merged. When inactive, string literals are
1124 remembered and output as a whole when translation is finished.
1127 <sect1><tt>#pragma message (<message>)</tt><label id="pragma-message"><p>
1129 This pragma is used to display informational messages at compile-time.
1131 The message intented to be displayed must be a string literal.
1135 #pragma message ("in a bottle")
1138 Results in the compiler outputting the following to stderr:
1140 example.c(42): Note: in a bottle
1144 <sect1><tt>#pragma optimize ([push,] on|off)</tt><label id="pragma-optimize"><p>
1146 Switch optimization on or off. If the argument is "off", optimization is
1147 disabled, otherwise it is enabled. Please note that this pragma only effects
1148 whole functions. The setting in effect when the function is encountered will
1149 determine if the generated code is optimized or not.
1151 Optimization and code generation is also controlled by the <ref
1152 id="pragma-codesize" name="codesize pragma">.
1154 The default is "off", but may be changed with the <tt/<ref name="-O"
1155 id="option-O">/ compiler option.
1157 The <tt/#pragma/ understands the push and pop parameters as explained above.
1160 <sect1><tt>#pragma rodata-name ([push,] <name>)</tt><label id="pragma-rodata-name"><p>
1162 This pragma changes the name used for the RODATA segment (the RODATA
1163 segment is used to store readonly data). The argument is a string
1164 enclosed in double quotes.
1166 Note: The default linker configuration file does only map the standard
1167 segments. If you use other segments, you have to create a new linker
1170 The <tt/#pragma/ understands the push and pop parameters as explained above.
1174 #pragma rodata-name ("MyRODATA")
1178 <sect1><tt>#pragma regvaraddr ([push,] on|off)</tt><label id="pragma-regvaraddr"><p>
1180 The compiler does not allow to take the address of register variables.
1181 The regvaraddr pragma changes this. Taking the address of a register
1182 variable is allowed after using this pragma with "on" as argument.
1183 Using "off" as an argument switches back to the default behaviour.
1185 Beware: The C standard does not allow taking the address of a variable
1186 declared as register. So your programs become non-portable if you use
1187 this pragma. In addition, your program may not work. This is usually the
1188 case if a subroutine is called with the address of a register variable,
1189 and this subroutine (or a subroutine called from there) uses
1190 register variables. So be careful with this #pragma.
1192 The <tt/#pragma/ understands the push and pop parameters as explained above.
1196 #pragma regvaraddr(on) /* Allow taking the address
1197 * of register variables
1202 <sect1><tt>#pragma register-vars ([push,] on|off)</tt><label id="pragma-register-vars"><p>
1204 Enables or disables use of register variables. If register variables are
1205 disabled (the default), the <tt/register/ keyword is ignored. Register
1206 variables are explained in more detail in <ref id="register-vars" name="a separate
1209 The <tt/#pragma/ understands the push and pop parameters as explained above.
1212 <sect1><tt>#pragma signed-chars ([push,] on|off)</tt><label id="pragma-signed-chars"><p>
1214 Changes the signedness of the default character type. If the argument is
1215 "on", default characters are signed, otherwise characters are unsigned. The
1216 compiler default is to make characters unsigned since this creates a lot
1217 better code. This default may be overridden by the <tt/<ref
1218 name="--signed-chars" id="option-signed-chars">/ command line option.
1220 The <tt/#pragma/ understands the push and pop parameters as explained above.
1223 <sect1><tt>#pragma static-locals ([push,] on|off)</tt><label id="pragma-static-locals"<p>
1225 Use variables in the bss segment instead of variables on the stack. This
1226 pragma changes the default set by the compiler option <tt/<ref
1227 name="--static-locals" id="option-static-locals">/. If the argument is "on",
1228 local variables are allocated in the BSS segment, leading to shorter and in
1229 most cases faster, but non-reentrant code.
1231 The <tt/#pragma/ understands the push and pop parameters as explained above.
1234 <sect1><tt>#pragma warn (name, [push,] on|off)</tt><label id="pragma-warn"><p>
1236 Switch compiler warnings on or off. "name" is the name of a warning (see the
1237 <tt/<ref name="-W" id="option-W">/ compiler option for a list). The name is
1238 followed either by "pop", which restores the last pushed state, or by "on" or
1239 "off", optionally preceeded by "push" to push the current state before
1244 /* Don't warn about the unused parameter in function func */
1245 #pragma warn (unused-param, push, off)
1246 static int func (int unused)
1250 #pragma warn (unused-param, pop)
1254 <sect1><tt>#pragma wrapped-call (push, <name>, <identifier>)</tt><label id="pragma-wrapped-call"><p>
1256 This pragma sets a wrapper for functions, often used for trampolines.
1258 The name is a function returning <tt/void/, and taking no parameters.
1259 It must preserve the CPU's <tt/A/ and <tt/X/ registers if it wraps any
1260 <tt/__fastcall__/ functions that have parameters. It must preserve
1261 the <tt/Y/ register if it wraps any variadic functions (they have "<tt/.../"
1262 in their prototypes).
1264 The identifier is an 8-bit number that's set into <tt/tmp4/.
1266 The address of a wrapped function is passed in <tt/ptr4/. The wrapper can
1267 call that function by using "<tt/jsr callptr4/".
1269 This feature is useful, for example, with banked memory, to switch banks
1270 automatically to where a wrapped function resides, and then to restore the
1271 previous bank when it returns.
1273 The <tt/#pragma/ requires the push or pop argument as explained above.
1277 /* Note that this code can be in a header. */
1278 void mytrampoline(void); /* Doesn't corrupt __AX__ */
1280 #pragma wrapped-call (push, mytrampoline, 5)
1281 void somefunc1(void);
1282 void somefunc2(int, char *);
1283 #pragma wrapped-call (pop)
1287 <sect1><tt>#pragma writable-strings ([push,] on|off)</tt><label id="pragma-writable-strings"><p>
1289 Changes the storage location of string literals. For historical reasons,
1290 the C standard defines that string literals are of type "char[]", but
1291 writing to such a literal causes undefined behaviour. Most compilers
1292 (including cc65) place string literals in the read-only data segment, which
1293 may cause problems with old C code that writes to string literals.
1295 Using this pragma (or the corresponding command line option <tt/<ref
1296 name="--writable-strings" id="option-writable-strings">/) causes the
1297 literals to be placed in the data segment so they can be written to without
1300 The <tt/#pragma/ understands the push and pop parameters as explained above.
1303 <sect1><tt>#pragma zpsym (<name>)</tt><p>
1305 Tell the compiler that the -- previously as external declared -- symbol with
1306 the given name is a zero page symbol (usually from an assembler file).
1307 The compiler will create a matching import declaration for the assembler.
1312 #pragma zpsym ("foo"); /* foo is in the zeropage */
1317 <sect>Register variables<label id="register-vars"><p>
1319 The runtime for all supported platforms has 6 bytes of zero page space
1320 available for register variables (this could be increased, but I think it's a
1321 good value). So you can declare register variables up to a total size of 6 per
1322 function. The compiler will allocate register space on a "first come, first
1323 served" base and convert any <tt/register/ declarations that exceed the
1324 available register space silently to <tt/auto/. Parameters can also be
1325 declared as <tt/register/, this will in fact give slightly shorter code than
1326 using a register variable.
1328 Since a function must save the current values of the registers on entry and
1329 restore them on exit, there is an overhead associated with register variables,
1330 and this overhead is quite high (about 20 bytes per variable). This means that
1331 just declaring anything as <tt/register/ is not a good idea.
1333 The best use for register variables are pointers, especially those that point
1334 to structures. The magic number here is about 3 uses of a struct field: If the
1335 function contains this number or even more, the generated code will be usually
1336 shorter and faster when using a register variable for the struct pointer. The
1337 reason for this is that the register variable can in many cases be used as a
1338 pointer directly. Having a pointer in an auto variable means that this pointer
1339 must first be copied into a zero page location, before it can be dereferenced.
1341 Second best use for register variables are counters. However, there is not
1342 much difference in the code generated for counters, so you will need at least
1343 100 operations on this variable (for example in a loop) to make it worth the
1344 trouble. The only savings you get here are by the use of a zero page variable
1345 instead of one on the stack or in the data segment.
1347 Register variables must be explicitly enabled, either by using <tt/<ref
1348 name="-Or" id="option-O">/ or <tt/<ref name="--register-vars"
1349 id="option-register-vars">/ on the command line or by use of <tt/<ref
1350 name="#pragma register-vars" id="pragma-register-vars">/. Register variables
1351 are only accepted on function top level, register variables declared in
1352 interior blocks are silently converted to <tt/auto/. With register variables
1353 disabled, all variables declared as <tt/register/ are actually auto variables.
1355 Please take care when using register variables: While they are helpful and can
1356 lead to a tremendous speedup when used correctly, improper usage will cause
1357 bloated code and a slowdown.
1361 <sect>Inline assembler<label id="inline-asm"><p>
1363 The compiler allows to insert assembler statements into the output file. The
1367 asm [optional volatile] (<string literal>[, optional parameters]) ;
1371 __asm__ [optional volatile] (<string literal>[, optional parameters]) ;
1375 The first form is in the user namespace; and, is disabled by <tt><ref
1376 id="option--standard" name="--standard"></tt> if the argument is not <tt/cc65/.
1378 The <tt/asm/ statement can be used only inside a function. Please note that
1379 the result of an inline assembler expression is always of type <tt/void/.
1381 The contents of the string literal are preparsed by the compiler; and, inserted
1382 into the generated assembly output, so that it can be processed further by
1383 the backend -- and, especially the optimizer. For that reason, the compiler does
1384 allow only regular 6502 opcodes to be used with the inline assembler. Pseudo
1385 instructions (like <tt/.import/, <tt/.byte/, and so on) are <em/not/ allowed,
1386 even if the ca65 assembler (which is used to translate the generated assembler
1387 code) would accept them. The built-in inline assembler is not a replacement for
1388 the full-blown macro assembler which comes with the compiler.
1390 Note: Inline assembler statements are subject to all optimizations done by the
1391 compiler. There currently is no way to protect an inline assembler statement
1392 -- alone -- from being moved or removed completely by the optimizer. If in
1393 doubt, check the generated assembler output; or, disable optimizations (for
1396 As a shortcut, you can put the <tt/volatile/ qualifier in your <tt/asm/
1397 statements. It will disable optimization for the functions in which those
1398 <tt/asm volatile/ statements sit. The effect is the same as though you put
1399 <tt/#pragma optimize(push, off)/ above those functions, and <tt/#pragma
1400 optimize(pop)/ below those functions.
1402 The string literal may contain format specifiers from the following list. For
1403 each format specifier, an argument is expected which is inserted instead of
1404 the format specifier, before passing the assembly code line to the backend.
1407 <item><tt/%b/ - Numerical 8-bit value
1408 <item><tt/%w/ - Numerical 16-bit value
1409 <item><tt/%l/ - Numerical 32-bit value
1410 <item><tt/%v/ - Assembler name of a global variable or function
1411 <item><tt/%o/ - Stack offset of a local variable
1412 <item><tt/%g/ - Assembler name of a C label
1413 <item><tt/%s/ - The argument is converted to a string
1414 <item><tt/%%/ - The % sign itself
1417 Using those format specifiers, you can access C <tt/#defines/, variables, or
1418 similar stuff from the inline assembler. For example, to load the value of
1419 a C <tt/#define/ into the Y index register, one would use
1423 __asm__ ("ldy #%b", OFFS);
1426 Or, to access a struct member of a static variable:
1432 unsigned char color;
1434 static pixel_t pixel;
1435 __asm__ ("ldy #%b", offsetof(pixel_t, color));
1436 __asm__ ("lda %v,y", pixel);
1439 The next example shows how to use global variables to exchange data between C
1440 and assembler; and, how to handle assembler jumps:
1443 static unsigned char globalSubA, globalSubB, globalSubResult;
1445 /* return a-b, return 255 if b>a */
1446 unsigned char sub (unsigned char a, unsigned char b)
1451 __asm__ ("lda %v", globalSubA);
1452 __asm__ ("sbc %v", globalSubB);
1453 __asm__ ("bcs %g", jumpSubNoError);
1454 __asm__ ("lda #$FF");
1456 __asm__ ("sta %v", globalSubResult);
1457 return globalSubResult;
1462 Arrays also can be accessed:
1465 static const unsigned char globalSquareTable[] = {
1466 0, 1, 4, 9, 16, 25, 36, 49, 64, 81,
1467 100, 121, 144, 169, 196, 225
1469 static unsigned char globalSquareA, globalSquareResult;
1471 /* return a*a for a<16, else 255 */
1472 unsigned char square (unsigned char a)
1478 __asm__ ("ldx %v", globalSquareA);
1479 __asm__ ("lda %v,x", globalSquareTable);
1480 __asm__ ("sta %v", globalSquareResult);
1481 return globalSquareResult;
1486 Note: Do not embed the assembler labels that are used as names of global
1487 variables or functions into your <tt/asm/ statements. Code such as this:
1491 int bar (void) { return 1; }
1493 __asm__ ("lda _foo"); /* DON'T DO THAT! */
1495 __asm__ ("jsr _bar"); /* DON'T DO THAT EITHER! */
1499 might stop working if the way that the compiler generates those names is changed in
1500 a future version. Instead, use the format specifiers from the table above:
1503 __asm__ ("lda %v", foo); /* OK */
1505 __asm__ ("jsr %v", bar); /* OK */
1511 <sect>Implementation-defined behavior<p>
1513 This section describes the behavior of cc65 when the standard describes the
1514 behavior as implementation-defined.
1520 This is the original compiler copyright:
1523 --------------------------------------------------------------------------
1526 This is the copyright notice for RA65, LINK65, LIBR65, and other
1527 Atari 8-bit programs. Said programs are Copyright 1989, by John R.
1528 Dunning. All rights reserved, with the following exceptions:
1530 Anyone may copy or redistribute these programs, provided that:
1532 1: You don't charge anything for the copy. It is permissable to
1533 charge a nominal fee for media, etc.
1535 2: All source code and documentation for the programs is made
1536 available as part of the distribution.
1538 3: This copyright notice is preserved verbatim, and included in
1541 You are allowed to modify these programs, and redistribute the
1542 modified versions, provided that the modifications are clearly noted.
1544 There is NO WARRANTY with this software, it comes as is, and is
1545 distributed in the hope that it may be useful.
1547 This copyright notice applies to any program which contains
1548 this text, or the refers to this file.
1550 This copyright notice is based on the one published by the Free
1551 Software Foundation, sometimes known as the GNU project. The idea
1552 is the same as theirs, ie the software is free, and is intended to
1553 stay that way. Everybody has the right to copy, modify, and re-
1554 distribute this software. Nobody has the right to prevent anyone
1555 else from copying, modifying or redistributing it.
1557 --------------------------------------------------------------------------
1560 Small parts of the compiler (parts of the preprocessor and main parser) are
1561 still covered by this copyright. The main portion is covered by the usual
1562 cc65 license, which reads:
1564 This software is provided 'as-is', without any expressed or implied
1565 warranty. In no event will the authors be held liable for any damages
1566 arising from the use of this software.
1568 Permission is granted to anyone to use this software for any purpose,
1569 including commercial applications, and to alter it and redistribute it
1570 freely, subject to the following restrictions:
1573 <item> The origin of this software must not be misrepresented; you must not
1574 claim that you wrote the original software. If you use this software
1575 in a product, an acknowledgment in the product documentation would be
1576 appreciated but is not required.
1577 <item> Altered source versions must be plainly marked as such, and must not
1578 be misrepresented as being the original software.
1579 <item> This notice may not be removed or altered from any source