Newsgroups: comp.std.c
Path: utzoo!utgpu!cunews!dgbt!don
From: don@dgbt.doc.ca (Donald McLachlan)
Subject: pointers to functions, dereferencing, first byte of func
Message-ID: <1991Jan30.031315.9427@dgbt.doc.ca>
Sender: don@dgbt.doc.ca (Donald McLachlan)
Organization: The Communications Research Centre, Ottawa, Canada
Distribution: na
Date: Wed, 30 Jan 91 03:13:15 GMT


I recently wanted to write a nastly bit of code for a PC (self modifying)
so ...

char *c;
extern char func();

c = func;

some code putting new hex values into the address space of the function


now for the fun stuff. Under microsoft C, c[1] ... c[MAX_INT] worked,
but c[0] would sometimes bugger me up. *c had the exact same unreliable
results (as it should since *c is supposed to be identicle to c[0]).

what I had to do to get at the first byte of executable code was ...
char *c1;

c1 = &(c[1]);
--c1;		/* should equal c[0] */
*c1 = char constant.

hows that for bastardising code to fool a compiler!!!