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Added more info to the documentation of "#pragma wrapped-call".

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Greg King 2017-05-20 01:41:49 -04:00
parent 938fd5e655
commit 39e55bdb77
1 changed files with 22 additions and 13 deletions
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doc/cc65.sgml
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@ -4,7 +4,7 @@
<title>cc65 Users Guide
<author><url url="mailto:uz@cc65.org" name="Ullrich von Bassewitz">,<newline>
<url url="mailto:gregdk@users.sf.net" name="Greg King">
<date>2017-03-21
<date>2017-05-20
<abstract>
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>
<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.
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
switch banks to where this function resides, and then restore
the bank when it returns.
The identifier is an 8-bit number that's set into <tt/tmp4/.
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:
<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)
void somefunc(void);
#pragma wrapped-call (pop)
#pragma wrapped-call (push, mytrampoline, 5)
void somefunc1(void);
void somefunc2(int, char *);
#pragma wrapped-call (pop)
</verb></tscreen>