From:	"Greg Donnells" <gad AT donnesys DOT com>
Newsgroups:	comp.os.msdos.djgpp
References:	<3ac02f4b$0$14446$272ea4a1 AT news DOT execpc DOT com> <Um7w6.1128$eX4 DOT 241968 AT typhoon DOT tampabay DOT rr DOT com>
Subject:	Re: Hunting Sigsev Errors
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Date:	Tue, 27 Mar 2001 22:00:49 GMT
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Organization:	RoadRunner - TampaBay
To:	djgpp AT delorie DOT com
DJ-Gateway:	from newsgroup comp.os.msdos.djgpp
Reply-To:	djgpp AT delorie DOT com

Well, I've discovered something interesting regarding SIGSEV errors and gcc
(2.953). Consider the following code fragment:

-----------------------------------------------------
#include <stdio.h>
#include <string.h>

#define LOG(a,b) fprintf(stderr, a, b);
#define ARRAYMAX 1024
#define NUL (char)0

main (int argc, char *argv[])
{
     FILE *ifp, *ofp;
     int  i, p;
     char *pos, *j;

     struct hdr {
          char cbs[4];
          long start;
          long last;
     } cbs_hdr;

     struct rec {
          long index;
          char fname[512];
     } allrecs[ARRAYMAX];

    LOG("Starting with argc = %d\n", argc);
-----------------------------------------------------

This code fragment will ALWAYS generate a SIGSEV before the LOG call. If it
doesn't - I get real strange behavior out of the fread() function call.
Changing the ARRAYSIZE to 512 fixes this - no more SIGSEV and no more wierd
behavior out of fread(). Looks like some sort of allocation bug or internal
limit is being reached (1024x516= ~.5M, but 512x516=~.25M).

NOTE: The rest of the above program is another 50 lines of C code - that's
all - no subroutines, etc. Just a main() module.

- Raw text -