Path: utzoo!attcan!uunet!mcvax!ukc!stl!stc!idec!alice!fox
From: fox@alice.marlow.reuters.co.uk (Paul Fox)
Newsgroups: comp.unix.wizards
Subject: Re: signal 10 in malloc call???
Keywords: sys V rel 3.1, died in malloc?
Message-ID: <350@alice.marlow.reuters.co.uk>
Date: 16 May 88 10:42:08 GMT
References: <3989@killer.UUCP> <640@vsi.UUCP> <4016@killer.UUCP> <2149@quacky.mips.COM> <1620@rpp386.UUCP>
Reply-To: fox@alice.UUCP (Paul Fox)
Organization: Reuters Ltd PLC, Marlow, Bucks, England
Lines: 79

In article <1620@rpp386.UUCP> jfh@rpp386.UUCP (The Beach Bum) writes:
>In article <2149@quacky.mips.COM> dce@mips.COM (David Elliott) writes:
>
>below is some code i use to check the consistency of mallocs in a large
>database i am working on.  

Oh well, I may as well post some code ... the following is my front
end to malloc/free/realloc. I use this to ensure that I do not corrupt
my memory areas, or try to free something thats never been allocated.
This code is portable - but requires you to call chk_alloc/chk_free and 
chk_realloc although #defines could be used avoid changing existing code.

If this code is used, then any memory freed by a normal free() must have
been allocated by a malloc() (not chk_alloc()). Its usually best to
recompile everything and link in the library. 

If a section 3 function calls malloc() it will bypass chk_alloc, and so
the freeing of this memory must be done by free() (not chk_free()). 
-----cut here------

# include	<stdio.h>
extern char	*malloc();

# define	MAGIC	0x464f5859L	/* FOXY */
# define	FREED	0x46524545L	/* FREE */

int	cnt_alloc = 0;

char	*
chk_alloc(n)
{	register char	*cp = malloc(n + 4);
	register long	*lp = (long *) cp;

	if (lp) {
		*lp++ = MAGIC;
		cnt_alloc++;
		}

	return (char *) lp;
}
char	*
chk_realloc(ptr, n)
char	*ptr;
{	char	*realloc();
	long	*lp = (long *) ptr;

	if (*--lp != MAGIC)
		chk_failed("Realloc non-alloced memory.");
	lp = (long *) realloc((char *) lp, n+4);
	return (char *) (lp + 1);
}
chk_free(ptr)
char	*ptr;
{	long	*lp = (long *) ptr;

	if (*--lp == FREED)
		chk_failed("Trying to free already freed memory.");
	if (*lp != MAGIC)
		chk_failed("Freeing non-alloced memory.");
	cnt_alloc--;
	*lp = FREED;
	free((char *) lp);
}
chk_failed(str)
char	*str;
{
	fprintf(stderr, "CHK_ALLOC: %s\r\n", str);
	abort();
}

---- cut here ------

=====================
     //        o      All opinions are my own.
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  _/_/   _/_/         UUCP:     fox@alice.marlow.reuters.co.uk