<article>
<title>cc65 Users Guide
<author>Ullrich von Bassewitz, <htmlurl url="mailto:uz@cc65.org" name="uz@cc65.org">
-<date>03.09.2000, 02.10.2001, 2005-8-1
+<date>2000-09-03, 2001-10-02, 2005-08-01
<abstract>
cc65 is a C compiler for 6502 targets. It supports several 6502 based home
up the changes made by me. I have made many more changes in the meantime
(and rewritten major parts of the compiler), so I will no longer do that,
since the list would be too large and of no use to anyone. Instead I will
-describe the compiler in respect to the ANSI/ISO C standard. In fact, I'm
-planning a complete rewrite (that is, a complete new compiler) for the
-next release, since there are too many limitations in the current code,
-and removing these limitations would mean a rewrite of many more parts of
-the compiler.
+describe the compiler in respect to the ANSI/ISO C standard.
There are separate documents named <url url="library.html"> and <url
url="funcref.html"> that cover the library that is available for the compiler.
-Os Inline some known functions
-T Include source as comment
-V Print the compiler version number
- -W Suppress warnings
+ -W name[,name] Enable or disable warnings
-d Debug mode
-g Add debug info to object file
-h Help (this text)
<descrip>
+ <label id="option-bss-name">
<tag><tt>--bss-name seg</tt></tag>
- Set the name of the bss segment.
+ Set the name of the bss segment. See also <tt/<ref id="pragma-bss-name"
+ name="#pragma bss-name">/.
+ <label id="option-check-stack">
<tag><tt>--check-stack</tt></tag>
Tells the compiler to generate code that checks for stack overflows. See
- <tt><ref id="pragma-checkstack" name="#pragma checkstack"></tt> for an
+ <tt/<ref id="pragma-check-stack" name="#pragma check-stack">/ for an
explanation of this feature.
+ <label id="option-code-name">
<tag><tt>--code-name seg</tt></tag>
- Set the name of the code segment.
+ Set the name of the code segment. See also <tt/<ref id="pragma-code-name"
+ name="#pragma code-name">/
<label id="option-codesize">
This options allows finer control about speed vs. size decisions in the code
generation and optimization phases. It gives the allowed size increase
factor (in percent). The default is 100 when not using <tt/-Oi/ and 200 when
- using <tt/-Oi/ (<tt/-Oi/ is the same as <tt/--codesize 200/).
+ using <tt/-Oi/ (<tt/-Oi/ is the same as <tt/-O --codesize 200/).
+ <label id="option-cpu">
<tag><tt>--cpu CPU</tt></tag>
A new, still experimental option. You may specify "6502" or "65C02" as
overwhelming.
+ <label id="option-create-dep">
<tag><tt>--create-dep</tt></tag>
Tells the compiler to generate a file containing the dependency list for
file with the extension replaced by <tt/.u/.
+ <label id="option-data-name">
+ <tag><tt>--data-name seg</tt></tag>
+
+ Set the name of the data segment. See also <tt/<ref id="pragma-data-name"
+ name="#pragma data-name">/
+
+
<tag><tt>-d, --debug</tt></tag>
Enables debug mode, something that should not be needed for mere
name of the C input file is used, with the extension replaced by ".s".
+ <label id="option-register-vars">
<tag><tt>-r, --register-vars</tt></tag>
<tt/-r/ will make the compiler honor the <tt/register/ keyword. Local
variables are of limited use without the optimizer, there is also a combined
switch: <tt/-Or/ will enable both, the optimizer and register variables.
- For more information about register variables see <ref id="regvars"
+ For more information about register variables see <ref id="register-vars"
name="register variables">.
The compiler setting can also be changed within the source file by using
- <tt><ref id="pragma-regvars" name="#pragma regvars"></tt>.
+ <tt/<ref id="pragma-register-vars" name="#pragma register-vars">/.
+ <label id="option-register-space">
<tag><tt>--register-space</tt></tag>
This option takes a numeric parameter and is used to specify, how much
If you don't know what all this means, please don't use this option.
+ <label id="option-rodata-name">
<tag><tt>--rodata-name seg</tt></tag>
Set the name of the rodata segment (the segment used for readonly data).
+ See also <tt/<ref id="pragma-rodata-name" name="#pragma rodata-name">/
-
+ <label id="option-signed-chars">
<tag><tt>-j, --signed-chars</tt></tag>
Using this option, you can make the default characters signed. Since the
6502 has no provisions for sign extending characters (which is needed on
almost any load operation), this will make the code larger and slower. A
better way is to declare characters explicitly as "signed" if needed. You
- can also use <tt><ref id="pragma-signedchars"
- name="#pragma signedchars"></tt> for better control of this option.
-
+ can also use <tt><ref id="pragma-signed-chars"
+ name="#pragma signed-chars"></tt> for better control of this option.
+
<label id="option--standard">
<tag><tt>--standard std</tt></tag>
<item>cc65
</itemize>
+ Please note that the compiler does not support the c99 standard and never
+ will. c99 mode is actually c89 mode with a few selected c99 extensions
+ (// comments for example).
+
+ <label id="option-standard">
<tag><tt>-t target, --target target</tt></tag>
This option is used to set the target system. The target system
or warnings are encountered.
+ <label id="option-writable-strings">
<tag><tt>--writable-strings</tt></tag>
Make string literals writable by placing them into the data segment instead
- of the rodata segment.
+ of the rodata segment. You can also use <tt><ref id="pragma-writable-strings"
+ name="#pragma writable-strings"></tt> to control this option on a
+ per function basis.
+ <label id="option-static-locals">
<tag><tt>-Cl, --static-locals</tt></tag>
Use static storage for local variables instead of storage on the stack.
function is entered, and will keep the old value from one call of the
function to the next.
- You may also use <tt><ref id="pragma-staticlocals"
- name="#pragma staticlocals"></tt> to change this setting in your
+ You may also use <tt><ref id="pragma-static-locals"
+ name="#pragma static-locals"></tt> to change this setting in your
sources.
+ <label id="option-include-dir">
<tag><tt>-I dir, --include-dir dir</tt></tag>
Set a directory where the compiler searches for include files. You may
runtime functions would have been called, even if the generated code is
larger. This will not only remove the overhead for a function call, but will
make the code visible for the optimizer. <tt/-Oi/ is an alias for
- <tt/--codesize 200/.
+ <tt/-O --codesize 200/.
<tt/-Or/ will make the compiler honor the <tt/register/ keyword. Local
variables may be placed in registers (which are actually zero page
- locations). There is some overhead involved with register variables, since
- the old contents of the registers must be saved and restored. In addition,
- the current implementation does not make good use of register variables, so
- using <tt/-Or/ may make your program even slower and larger. Use with care!
+ locations). See also the <tt/<ref id="option-register-vars"
+ name="--register-vars">/ command line option, and the <ref
+ id="register-vars" name="discussion of register variables"> below.
Using <tt/-Os/ will force the compiler to inline some known functions from
the C library like strlen. Note: This has two consequences:
<label id="option-W">
- <tag><tt>-W</tt></tag>
-
- This option will suppress any warnings generated by the compiler. Since
- any source file may be written in a manner that it will not produce
- compiler warnings, using this option is usually not a good idea.
+ <tag><tt>-W name[,name]</tt></tag>
+
+ This option allows to control warnings generated by the compiler. It is
+ followed by a comma separated list of warnings that should be enabled or
+ disabled. To disable a warning, its name is prefixed by a minus sign. If
+ no such prefix exists, or the name is prefixed by a plus sign, the warning
+ is enabled.
+
+ The following warning names are currently recognized:
+ <descrip>
+ <tag><tt/error/</tag>
+ Treat all warnings as errors.
+ <tag><tt/unknown-pragma/</tag>
+ Warn about known #pragmas.
+ <tag><tt/unused-label/</tag>
+ Warn about unused labels.
+ <tag><tt/unused-param/</tag>
+ Warn about unused function parameters.
+ <tag><tt/unused-var/</tag>
+ Warn about unused variables.
+ </descrip>
+
+ You may also use <tt><ref id="pragma-warn" name="#pragma warn"></tt> to
+ control this setting for smaller pieces of code from within your code.
</descrip><p>
file contains assembler code suitable for the use with the ca65 macro
assembler.
-In addition to the paths named in the <tt/-I/ option on the command line, the
-directory named in the environment variable <tt/CC65_INC/ is added to the
-search path for include files on startup.
+Include files in single quotes are searched in the following places:
+<enum>
+<item>The current directory.
+<item>The value of the environment variable <tt/CC65_INC/ if it is defined.
+<item>Any directory added with the <tt/-I/ option on the command line.
+</enum>
+
+Include files in angle brackets are searched in the following places:
+<enum>
+<item>A compiled in directory which is often <tt>/usr/lib/cc65/include</tt> on
+ Linux systems.
+<item>The value of the environment variable <tt/CC65_INC/ if it is defined.
+<item>A subdirectory named <tt/include/ of the directory defined in the
+ environment variable <tt/CC65_HOME/, if it is defined.
+<item>Any directory added with the <tt/-I/ option on the command line.
+</enum>
<sect>Differences to the ISO standard<p>
+Apart from the things listed below, the compiler does support additional
+keywords, has several functions in the standard headers with names outside the
+reserved namespace and a few syntax extensions. All these can be disabled with
+the <tt><ref id="option--standard" name="--standard"></tt> command line
+option. Its use for maximum standards compatibility is advised.
+
Here is a list of differences between the language, the compiler accepts,
and the one defined by the ISO standard:
<itemize>
-<item> The compiler allows unnamed parameters in parameter lists. The
- compiler will not issue warnings about unused parameters that don't
- have a name. This feature can be disabled with the <tt><ref
- id="option--standard" name="--standard"></tt> command line option.
- <p>
-<item> The compiler has some additional keywords:
- <p>
- <itemize>
- <item><tt/asm/
- <item><tt/__asm__/
- <item><tt/fastcall/
- <item><tt/__fastcall__/
- <item><tt/__AX__/
- <item><tt/__EAX__/
- <item><tt/__func__/
- <item><tt/__attribute__/
- </itemize>
- <p>
- The keywords without the underlines can be disabled with the
- <tt><ref id="option--standard" name="--standard"></tt> command line
- option.
- <p>
<item> The datatypes "float" and "double" are not available.
<p>
-<item> The compiler does not support bit fields.
- <p>
<item> C Functions may not return structs (or unions), and structs may not
be passed as parameters by value. However, struct assignment *is*
possible.
conventions (see below). It means that you must not mix pointers to
those functions with pointers to user-written, not-fastcall functions.
<p>
+<item> The <tt/volatile/ keyword doesn't have an effect. This is not as bad
+ as it sounds, since the 6502 has so few registers that it isn't
+ possible to keep values in registers anyway.
+ <p>
</itemize>
There may be some more minor differences I'm currently not aware of. The
before changing it. The value may later be restored by using the <tt/pop/
parameter with the <tt/#pragma/.
-<sect1><tt>#pragma bss
seg ([push,]<name>)</tt><p>
+<sect1><tt>#pragma bss
-name ([push,] <name>)</tt><label id="pragma-bss-name"><p>
This pragma changes the name used for the BSS segment (the BSS segment
is used to store uninitialized data). The argument is a string enclosed
Example:
<tscreen><verb>
- #pragma bssseg ("MyBSS")
+ #pragma bss-name ("MyBSS")
</verb></tscreen>
-<sect1><tt>#pragma charmap (<index>, <code>)</tt><p>
+<sect1><tt>#pragma charmap (<index>, <code>)</tt><label id="pragma-charmap"><p>
Each literal string and each literal character in the source is translated
by use of a translation table. This translation table is preset when the
</verb></tscreen>
-<sect1><tt>#pragma check
stack ([push,]on|off)</tt><label id="pragma-checkstack"><p>
+<sect1><tt>#pragma check
-stack ([push,] on|off)</tt><label id="pragma-check-stack"><p>
Tells the compiler to insert calls to a stack checking subroutine to detect
stack overflows. The stack checking code will lead to somewhat larger and
The <tt/#pragma/ understands the push and pop parameters as explained above.
-<sect1><tt>#pragma code
seg ([push,]<name>)</tt><p>
+<sect1><tt>#pragma code
-name ([push,] <name>)</tt><label id="pragma-code-name"><p>
This pragma changes the name used for the CODE segment (the CODE segment
is used to store executable code). The argument is a string enclosed in
Example:
<tscreen><verb>
- #pragma codeseg ("MyCODE")
+ #pragma code-name ("MyCODE")
</verb></tscreen>
-<sect1><tt>#pragma codesize ([push,]<int>)</tt><label id="pragma-codesize"><p>
+<sect1><tt>#pragma codesize ([push,]
<int>)</tt><label id="pragma-codesize"><p>
This pragma allows finer control about speed vs. size decisions in the code
generation and optimization phase. It gives the allowed size increase factor
The <tt/#pragma/ understands the push and pop parameters as explained above.
-<sect1><tt>#pragma data
seg ([push,]<name>)</tt><p>
+<sect1><tt>#pragma data
-name ([push,] <name>)</tt><label id="pragma-data-name"><p>
This pragma changes the name used for the DATA segment (the DATA segment
is used to store initialized data). The argument is a string enclosed in
Example:
<tscreen><verb>
- #pragma dataseg ("MyDATA")
+ #pragma data-name ("MyDATA")
</verb></tscreen>
-<sect1><tt>#pragma optimize ([push,]on|off)</tt><label id="pragma-optimize"><p>
+<sect1><tt>#pragma optimize ([push,]
on|off)</tt><label id="pragma-optimize"><p>
Switch optimization on or off. If the argument is "off", optimization is
disabled, otherwise it is enabled. Please note that this pragma only effects
The <tt/#pragma/ understands the push and pop parameters as explained above.
-<sect1><tt>#pragma rodata
seg ([push,]<name>)</tt><p>
+<sect1><tt>#pragma rodata
-name ([push,] <name>)</tt><label id="pragma-rodata-name"><p>
This pragma changes the name used for the RODATA segment (the RODATA
segment is used to store readonly data). The argument is a string
Example:
<tscreen><verb>
- #pragma rodataseg ("MyRODATA")
+ #pragma rodata-name ("MyRODATA")
</verb></tscreen>
-<sect1><tt>#pragma regvaraddr ([push,]
on|off)</tt><p>
+<sect1><tt>#pragma regvaraddr ([push,]
on|off)</tt><label id="pragma-regvaraddr"><p>
The compiler does not allow to take the address of register variables.
The regvaraddr pragma changes this. Taking the address of a register
</verb></tscreen>
-<sect1><tt>#pragma reg
vars ([push,]on|off)</tt><label id="pragma-regvars"><p>
+<sect1><tt>#pragma reg
ister-vars ([push,] on|off)</tt><label id="pragma-register-vars"><p>
Enables or disables use of register variables. If register variables are
disabled (the default), the <tt/register/ keyword is ignored. Register
- variables are explained in more detail in <ref id="regvars" name="a separate
+ variables are explained in more detail in <ref id="register-vars" name="a separate
chapter">.
The <tt/#pragma/ understands the push and pop parameters as explained above.
-<sect1><tt>#pragma signed
chars ([push,]on|off)</tt><label id="pragma-signedchars"><p>
+<sect1><tt>#pragma signed
-chars ([push,] on|off)</tt><label id="pragma-signed-chars"><p>
Changes the signedness of the default character type. If the argument is
- "on", default characters are signed, otherwise characters are unsigned.
- The compiler default is to make characters unsigned since this creates a
- lot better code. This default may be overridden by the <tt/--signed-chars/
- command line option.
+ "on", default characters are signed, otherwise characters are unsigned. The
+ compiler default is to make characters unsigned since this creates a lot
+ better code. This default may be overridden by the <tt/<ref
+ name="--signed-chars" id="option-signed-chars">/ command line option.
The <tt/#pragma/ understands the push and pop parameters as explained above.
-<sect1><tt>#pragma static
locals ([push,]on|off)</tt><label id="pragma-staticlocals"<p>
+<sect1><tt>#pragma static
-locals ([push,] on|off)</tt><label id="pragma-static-locals"<p>
Use variables in the bss segment instead of variables on the stack. This
- pragma changes the default set by the compiler option <tt/-Cl/. If the
- argument is "on", local variables are allocated in the BSS segment,
- leading to shorter and in most cases faster, but non-reentrant code.
+ pragma changes the default set by the compiler option <tt/<ref
+ name="--static-locals" id="option-static-locals">/. If the argument is "on",
+ local variables are allocated in the BSS segment, leading to shorter and in
+ most cases faster, but non-reentrant code.
The <tt/#pragma/ understands the push and pop parameters as explained above.
-<sect1><tt>#pragma warn (
[push,]on|off)</tt><label id="pragma-warn"><p>
+<sect1><tt>#pragma warn (
name, [push,] on|off)</tt><label id="pragma-warn"><p>
- Switch compiler warnings on or off. If the argument is "off", warnings are
- disabled, otherwise they're enabled. The default is "on", but may be changed
- with the <tt/<ref name="-W" id="option-W">/ compiler option.
+ Switch compiler warnings on or off. "name" is the name of a warning (see the
+ <tt/<ref name="-W" id="option-W">/ compiler option for a list). The name is
+ either followed by "pop", which restores the last pushed state, or by "on" or
+ "off", optionally preceeded by "push" to push the current state before
+ changing it.
+
+ Example:
+ <tscreen><verb>
+ /* Don't warn about the unused parameter in function func */
+ #pragma warn (unused-param, push, off)
+ static int func (int unused)
+ {
+ return 0;
+ }
+ #pragma warn (unused-param, pop)
+ </verb></tscreen>
+
+<sect1><tt>#pragma writable-strings ([push,] on|off)</tt><label id="pragma-writable-strings"><p>
+
+ Changes the storage location of string literals. For historical reasons,
+ the C standard defines that string literals are of type "char[]", but
+ writing to such a literal causes undefined behaviour. Most compilers
+ (including cc65) place string literals in the read-only data segment, which
+ may cause problems with old C code that writes to string literals.
+
+ Using this pragma (or the corresponding command line option <tt/<ref
+ name="--writable-strings" id="option-writable-strings">/) causes the
+ literals to be placed in the data segment so they can be written to without
+ worry.
+
+ Please note that the value of this flag that is in effect when a function
+ is encountered, determines where the literals are stored. Changing the
+ <tt/#pragma/ within a function doesn't have an effect for this function.
The <tt/#pragma/ understands the push and pop parameters as explained above.
-<sect>Register variables<label id="regvars"><p>
+<sect>Register variables<label id="reg
ister-vars"><p>
The runtime for all supported platforms has 6 bytes of zero page space
available for register variables (this could be increased, but I think it's a
trouble. The only savings you get here are by the use of a zero page variable
instead of one on the stack or in the data segment.
-Register variables must be explicitly enabled by using <tt/-Or/ or <tt/-r/ on
-the command line. Register variables are only accepted on function top level,
-register variables declared in interior blocks are silently converted to
-<tt/auto/. With register variables disabled, all variables declared as
-<tt/register/ are actually auto variables.
+Register variables must be explicitly enabled, either by using <tt/<ref
+name="-Or" id="option-O">/ or <tt/<ref name="--register-vars"
+id="option-register-vars">/ on the command line or by use of <tt/<ref
+name="#pragma register-vars" id="pragma-register-vars">/. Register variables
+are only accepted on function top level, register variables declared in
+interior blocks are silently converted to <tt/auto/. With register variables
+disabled, all variables declared as <tt/register/ are actually auto variables.
Please take care when using register variables: While they are helpful and can
lead to a tremendous speedup when used correctly, improper usage will cause
<p>
+<sect>Implementation-defined behavior<p>
+
+This section describes the behavior of cc65 when the standard describes the
+behavior as implementation-defined.
+
+(to be done)
+
<sect>Bugs/Feedback<p>
If you have problems using the compiler, if you find any bugs, or if you're
projects / cc65 / blobdiff