Date: Sat, 23 Jun 2001 16:17:36 -0400 (EDT) From: Zhihui Zhang <zzhang@cs.binghamton.edu> To: freebsd-questions@freebsd.org Subject: sbrk() and segment fault Message-ID: <Pine.SOL.4.21.0106231610180.23292-100000@opal>
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Out of curiosity, I tried the following program on FreeBSD 4.3-Release:
#include <stdio.h>
#include <unistd.h>
main()
{
char * ret, * endpt;
endpt = sbrk(0);
printf("endpt = %x after sbrk\n", (int)endpt);
#if 1
ret = brk(endpt);
if (ret == (char *) -1) {
printf("brk of %x failed\n", endpt);
exit(0);
}
#endif
printf("brk of %x succeed\n", (int)endpt);
}
dell# cc sbrk2.c; a.out
endpt = 8049708 after sbrk
Segmentation fault (core dumped)
If I change #if 1 to #if 0, then it runs OK. So why brk() to the SAME
address can cause problem? Is it some roundup done in obreak() in
vm_unix.c? Or maybe my understanding of break is not complete. Thanks for
any help.
-Zhihui
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