223cc6685e
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285 lines
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<TITLE>cc65 Users Guide: #pragmas</TITLE>
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<H2><A NAME="pragmas"></A> <A NAME="s7">7.</A> <A HREF="cc65.html#toc7">#pragmas</A></H2>
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<P>The compiler understands some pragmas that may be used to change code
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generation and other stuff. Some of these pragmas understand a special form:
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If the first parameter is <CODE>push</CODE>, the old value is saved onto a stack
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before changing it. The value may later be restored by using the <CODE>pop</CODE>
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parameter with the <CODE>#pragma</CODE>.</P>
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<H2><A NAME="ss7.1">7.1</A> <A HREF="cc65.html#toc7.1"><CODE>#pragma bssseg ([push,]<name>)</CODE></A>
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</H2>
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<P>This pragma changes the name used for the BSS segment (the BSS segment
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is used to store uninitialized data). The argument is a string enclosed
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in double quotes.</P>
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<P>Note: The default linker configuration file does only map the standard
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segments. If you use other segments, you have to create a new linker
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configuration file.</P>
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<P>Beware: The startup code will zero only the default BSS segment. If you
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use another BSS segment, you have to do that yourself, otherwise
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uninitialized variables do not have the value zero.</P>
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<P>The <CODE>#pragma</CODE> understands the push and pop parameters as explained above.</P>
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<P>Example:
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<BLOCKQUOTE><CODE>
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<PRE>
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#pragma bssseg ("MyBSS")
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</PRE>
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</CODE></BLOCKQUOTE>
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</P>
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<H2><A NAME="ss7.2">7.2</A> <A HREF="cc65.html#toc7.2"><CODE>#pragma charmap (<index>, <code>)</CODE></A>
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</H2>
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<P>Each literal string and each literal character in the source is translated
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by use of a translation table. This translation table is preset when the
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compiler is started depending on the target system, for example to map
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ISO-8859-1 characters into PETSCII if the target is a commodore machine.</P>
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<P>This pragma allows to change entries in the translation table, so the
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translation for individual characters, or even the complete table may be
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adjusted.</P>
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<P>Both arguments are assumed to be unsigned characters with a valid range of
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1-255.</P>
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<P>Beware of two pitfalls:</P>
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<P>
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<UL>
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<LI>The character index is actually the code of the character in the
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C source, so character mappings do always depend on the source
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character set. This means that <CODE>#pragma charmap</CODE> is not
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portable -- it depends on the build environment.</LI>
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<LI>While it is possible to use character literals as indices, the
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result may be somewhat unexpected, since character literals are
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itself translated. For this reason I would suggest to avoid
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character literals and use numeric character codes instead.</LI>
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</UL>
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</P>
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<P>Example:
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<BLOCKQUOTE><CODE>
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<PRE>
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/* Use a space wherever an 'a' occurs in ISO-8859-1 source */
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#pragma charmap (0x61, 0x20);
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</PRE>
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</CODE></BLOCKQUOTE>
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</P>
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<H2><A NAME="pragma-checkstack"></A> <A NAME="ss7.3">7.3</A> <A HREF="cc65.html#toc7.3"><CODE>#pragma checkstack ([push,]on|off)</CODE></A>
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</H2>
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<P>Tells the compiler to insert calls to a stack checking subroutine to detect
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stack overflows. The stack checking code will lead to somewhat larger and
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slower programs, so you may want to use this pragma when debugging your
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program and switch it off for the release version. If a stack overflow is
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detected, the program is aborted.</P>
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<P>If the argument is "off", stack checks are disabled (the default), otherwise
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they're enabled.</P>
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<P>The <CODE>#pragma</CODE> understands the push and pop parameters as explained above.</P>
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<H2><A NAME="ss7.4">7.4</A> <A HREF="cc65.html#toc7.4"><CODE>#pragma codeseg ([push,]<name>)</CODE></A>
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</H2>
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<P>This pragma changes the name used for the CODE segment (the CODE segment
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is used to store executable code). The argument is a string enclosed in
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double quotes.</P>
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<P>Note: The default linker configuration file does only map the standard
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segments. If you use other segments, you have to create a new linker
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configuration file.</P>
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<P>The <CODE>#pragma</CODE> understands the push and pop parameters as explained above.</P>
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<P>Example:
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<BLOCKQUOTE><CODE>
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<PRE>
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#pragma codeseg ("MyCODE")
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</PRE>
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</CODE></BLOCKQUOTE>
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</P>
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<H2><A NAME="pragma-codesize"></A> <A NAME="ss7.5">7.5</A> <A HREF="cc65.html#toc7.5"><CODE>#pragma codesize ([push,]<int>)</CODE></A>
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</H2>
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<P>This pragma allows finer control about speed vs. size decisions in the code
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generation and optimization phase. It gives the allowed size increase factor
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(in percent). The default is can be changed by use of the <CODE>
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<A HREF="cc65-2.html#option-codesize">--codesize</A></CODE> compiler option.</P>
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<P>The <CODE>#pragma</CODE> understands the push and pop parameters as explained above.</P>
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<H2><A NAME="ss7.6">7.6</A> <A HREF="cc65.html#toc7.6"><CODE>#pragma dataseg ([push,]<name>)</CODE></A>
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</H2>
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<P>This pragma changes the name used for the DATA segment (the DATA segment
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is used to store initialized data). The argument is a string enclosed in
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double quotes.</P>
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<P>Note: The default linker configuration file does only map the standard
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segments. If you use other segments, you have to create a new linker
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configuration file.</P>
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<P>The <CODE>#pragma</CODE> understands the push and pop parameters as explained above.</P>
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<P>Example:
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<BLOCKQUOTE><CODE>
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<PRE>
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#pragma dataseg ("MyDATA")
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</PRE>
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</CODE></BLOCKQUOTE>
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</P>
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<H2><A NAME="pragma-optimize"></A> <A NAME="ss7.7">7.7</A> <A HREF="cc65.html#toc7.7"><CODE>#pragma optimize ([push,]on|off)</CODE></A>
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</H2>
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<P>Switch optimization on or off. If the argument is "off", optimization is
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disabled, otherwise it is enabled. Please note that this pragma only effects
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whole functions. The setting in effect when the function is encountered will
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determine if the generated code is optimized or not.</P>
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<P>Optimization and code generation is also controlled by the
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<A HREF="#pragma-codesize">codesize pragma</A>.</P>
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<P>The default is "off", but may be changed with the <CODE>
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<A HREF="cc65-2.html#option-O">-O</A></CODE> compiler option.</P>
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<P>The <CODE>#pragma</CODE> understands the push and pop parameters as explained above.</P>
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<H2><A NAME="ss7.8">7.8</A> <A HREF="cc65.html#toc7.8"><CODE>#pragma rodataseg ([push,]<name>)</CODE></A>
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</H2>
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<P>This pragma changes the name used for the RODATA segment (the RODATA
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segment is used to store readonly data). The argument is a string
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enclosed in double quotes.</P>
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<P>Note: The default linker configuration file does only map the standard
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segments. If you use other segments, you have to create a new linker
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configuration file.</P>
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<P>The <CODE>#pragma</CODE> understands the push and pop parameters as explained above.</P>
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<P>Example:
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<BLOCKQUOTE><CODE>
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<PRE>
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#pragma rodataseg ("MyRODATA")
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</PRE>
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</CODE></BLOCKQUOTE>
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</P>
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<H2><A NAME="ss7.9">7.9</A> <A HREF="cc65.html#toc7.9"><CODE>#pragma regvaraddr ([push,]on|off)</CODE></A>
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</H2>
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<P>The compiler does not allow to take the address of register variables.
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The regvaraddr pragma changes this. Taking the address of a register
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variable is allowed after using this pragma with "on" as argument.
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Using "off" as an argument switches back to the default behaviour.</P>
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<P>Beware: The C standard does not allow taking the address of a variable
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declared as register. So your programs become non-portable if you use
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this pragma. In addition, your program may not work. This is usually the
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case if a subroutine is called with the address of a register variable,
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and this subroutine (or a subroutine called from there) uses
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register variables. So be careful with this #pragma.</P>
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<P>The <CODE>#pragma</CODE> understands the push and pop parameters as explained above.</P>
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<P>Example:
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<BLOCKQUOTE><CODE>
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<PRE>
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#pragma regvaraddr(on) /* Allow taking the address
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* of register variables
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*/
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</PRE>
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</CODE></BLOCKQUOTE>
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</P>
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<H2><A NAME="pragma-regvars"></A> <A NAME="ss7.10">7.10</A> <A HREF="cc65.html#toc7.10"><CODE>#pragma regvars ([push,]on|off)</CODE></A>
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</H2>
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<P>Enables or disables use of register variables. If register variables are
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disabled (the default), the <CODE>register</CODE> keyword is ignored. Register
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variables are explained in more detail in
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<A HREF="cc65-8.html#regvars">a separate chapter</A>.</P>
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<P>The <CODE>#pragma</CODE> understands the push and pop parameters as explained above.</P>
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<H2><A NAME="pragma-signedchars"></A> <A NAME="ss7.11">7.11</A> <A HREF="cc65.html#toc7.11"><CODE>#pragma signedchars ([push,]on|off)</CODE></A>
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</H2>
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<P>Changes the signedness of the default character type. If the argument is
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"on", default characters are signed, otherwise characters are unsigned.
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The compiler default is to make characters unsigned since this creates a
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lot better code. This default may be overridden by the <CODE>--signed-chars</CODE>
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command line option.</P>
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<P>The <CODE>#pragma</CODE> understands the push and pop parameters as explained above.</P>
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<H2><A NAME="pragma-staticlocals"></A> <A NAME="ss7.12">7.12</A> <A HREF="cc65.html#toc7.12"><CODE>#pragma staticlocals ([push,]on|off)</CODE></A>
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</H2>
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<P>Use variables in the bss segment instead of variables on the stack. This
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pragma changes the default set by the compiler option <CODE>-Cl</CODE>. If the
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argument is "on", local variables are allocated in the BSS segment,
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leading to shorter and in most cases faster, but non-reentrant code.</P>
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<P>The <CODE>#pragma</CODE> understands the push and pop parameters as explained above.</P>
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<H2><A NAME="pragma-warn"></A> <A NAME="ss7.13">7.13</A> <A HREF="cc65.html#toc7.13"><CODE>#pragma warn ([push,]on|off)</CODE></A>
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</H2>
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<P>Switch compiler warnings on or off. If the argument is "off", warnings are
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disabled, otherwise they're enabled. The default is "on", but may be changed
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with the <CODE>
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<A HREF="cc65-2.html#option-W">-W</A></CODE> compiler option.</P>
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<P>The <CODE>#pragma</CODE> understands the push and pop parameters as explained above.</P>
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<H2><A NAME="ss7.14">7.14</A> <A HREF="cc65.html#toc7.14"><CODE>#pragma zpsym (<name>)</CODE></A>
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</H2>
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<P>Tell the compiler that the -- previously as external declared -- symbol with
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the given name is a zero page symbol (usually from an assembler file).
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The compiler will create a matching import declaration for the assembler.</P>
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<P>Example:
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<BLOCKQUOTE><CODE>
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<PRE>
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extern int foo;
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#pragma zpsym ("foo"); /* foo is in the zeropage */
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</PRE>
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</CODE></BLOCKQUOTE>
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</P>
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<HR>
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