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git-svn-id: svn://svn.compuextreme.de/Viitor/V963/Viitor_cc65@5933 504e572c-2e33-0410-9681-be2bf7408885
62 lines
2.4 KiB
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62 lines
2.4 KiB
HTML
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<TITLE>cc65 function reference: Alphabetical function reference: set_brk</TITLE>
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<H2><A NAME="set_brk"></A> 3.129 <A HREF="funcref.html#toc3.129">set_brk</A></H2>
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<P>
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<BLOCKQUOTE>
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<DL>
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<DT><B>Function</B><DD><P>Set the break vector to a user function.</P>
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<DT><B>Header</B><DD><P><CODE>
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<A HREF="funcref-3.html#6502.h">6502.h</A></CODE></P>
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<DT><B>Declaration</B><DD><P><CODE>void __fastcall__ set_brk (brk_handler func);</CODE></P>
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<DT><B>Description</B><DD><P><CODE>set_brk</CODE> allows a user program to handle breaks within the
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program code by letting the vector point to a user written C function. The
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runtime library installs a small stub that saves the registers into global
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variables that may be accessed (and changed) by the break handler.</P>
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<DT><B>Limits</B><DD><P>
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<UL>
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<LI>The function is only available as fastcall function, so it may only
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be used in presence of a prototype.</LI>
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<LI>The stub saves the zero page registers used by the C runtime and switches
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to a small break handler stack. This means that it is safe to execute C code,
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even if C code was interrupted. Be careful however not to use too many local
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variables, and do not enable stack checks for the handler function or any other
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function called from it.</LI>
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<LI>The <CODE>brk_pc</CODE> variable points to the <CODE>BRK</CODE> instruction. If you want
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the continue with the interrupted code, you have to adjust <CODE>brk_pc</CODE>,
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otherwise the <CODE>BRK</CODE> instruction will get executed over and over again.</LI>
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<LI>Since <CODE>set_brk</CODE> installs an exit handler, it is not strictly necessary
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to call <CODE>
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<A HREF="funcref-171.html#reset_brk">reset_brk</A></CODE> as part of the cleanup when
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the program terminates.</LI>
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</UL>
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</P>
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<DT><B>Availability</B><DD><P>cc65</P>
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<DT><B>See also</B><DD><P>
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<A HREF="funcref-171.html#reset_brk">reset_brk</A></P>
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<DT><B>Example</B><DD><P>None.</P>
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</DL>
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