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Merge pull request #435 from greg-king5/wrapped-call

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Add more info to the docs about "#pragma wrapped-call".
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Oliver Schmidt 2017-05-20 12:28:24 +02:00 committed by GitHub
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doc/cc65.sgml
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@ -4,7 +4,7 @@
<title>cc65 Users Guide <title>cc65 Users Guide
<author><url url="mailto:uz@cc65.org" name="Ullrich von Bassewitz">,<newline> <author><url url="mailto:uz@cc65.org" name="Ullrich von Bassewitz">,<newline>
<url url="mailto:gregdk@users.sf.net" name="Greg King"> <url url="mailto:gregdk@users.sf.net" name="Greg King">
<date>2017-03-21 <date>2017-05-20
<abstract> <abstract>
cc65 is a C compiler for 6502 targets. It supports several 6502 based home cc65 is a C compiler for 6502 targets. It supports several 6502 based home
@ -1229,27 +1229,36 @@ parameter with the <tt/#pragma/.
</verb></tscreen> </verb></tscreen>
<sect1><tt>#pragma wrapped-call (&lt;push&rt;, &lt;name&gt;, &lt;identifier&gt;)</tt><label id="pragma-wrapped-call"><p> <sect1><tt>#pragma wrapped-call (push, &lt;name&gt;, &lt;identifier&gt;)</tt><label id="pragma-wrapped-call"><p>
This pragma sets a wrapper for functions, often used for trampolines. This pragma sets a wrapper for functions, often used for trampolines.
The name is a function returning void and taking no parameters.
The identifier is an 8-bit number that's set to tmp4.
The address of the function is passed in ptr4. The name is a function returning <tt/void/, and taking no parameters.
It must preserve the CPU's <tt/A/ and <tt/X/ registers if it wraps any
<tt/__fastcall__/ functions that have parameters. It must preserve
the <tt/Y/ register if it wraps any variadic functions (they have "<tt/.../"
in their prototypes).
This is useful for example with banked memory, to automatically The identifier is an 8-bit number that's set into <tt/tmp4/.
switch banks to where this function resides, and then restore
the bank when it returns.
The <tt/#pragma/ requires the push and pop parameters as explained above. The address of a wrapped function is passed in <tt/ptr4/. The wrapper can
call that function by using "<tt/jsr callptr4/".
This feature is useful, for example, with banked memory, to switch banks
automatically to where a wrapped function resides, and then to restore the
previous bank when it returns.
The <tt/#pragma/ requires the push or pop argument as explained above.
Example: Example:
<tscreen><verb> <tscreen><verb>
void mytrampoline(void); /* Note that this code can be in a header. */
void mytrampoline(void); /* Doesn't corrupt __AX__ */
#pragma wrapped-call (push, mytrampoline, 0) #pragma wrapped-call (push, mytrampoline, 5)
void somefunc(void); void somefunc1(void);
#pragma wrapped-call (pop) void somefunc2(int, char *);
#pragma wrapped-call (pop)
</verb></tscreen> </verb></tscreen>