[forwarded from http://bugs.debian.org/386174]
bug submitter writes (4.1 and trunk):
In the following program, gcc fails to recognize that "n" is
uninitialized, unless the "sscanf" line is commented out. I expected
no change at all, since sscanf() is called after foo(). Since the
compiler is responsible for guaranteeing that the program runs as if
this order is true (even if it is not), I expect it to be aware of the
initialized state of the variables.
gcc-4.1 -std=gnu99 -W -Wall -O3 -g ss.c -o ss
ss.c: In function 'main':
ss.c:6: warning: 'n' is used uninitialized in this function
gcc-4.1 -DSS -std=gnu99 -W -Wall -O3 -g ss.c -o ss
[no warning]
#define _GNU_SOURCE
#include <stdio.h>
static void foo(size_t *n)
{
printf("%d\n", *n);
}
int main()
{
size_t n;
foo(&n);
#ifdef SS
sscanf("1234", "%zd", &n);
#endif
return 0;
}
--
Summary: gcc sometimes doesn't recognize uninitialized variables
Product: gcc
Version: 4.2.0
Status: UNCONFIRMED
Severity: normal
Priority: P3
Component: c
AssignedTo: unassigned at gcc dot gnu dot org
ReportedBy: debian-gcc at lists dot debian dot org
http://gcc.gnu.org/bugzilla/show_bug.cgi?id=29227
