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optimization/7728: Invalid statement reordering gcc 3.2 -O2
- From: ghouston at arglist dot com
- To: gcc-gnats at gcc dot gnu dot org
- Date: 26 Aug 2002 18:20:28 -0000
- Subject: optimization/7728: Invalid statement reordering gcc 3.2 -O2
>Number: 7728
>Category: optimization
>Synopsis: Invalid statement reordering gcc 3.2 -O2
>Confidential: no
>Severity: critical
>Priority: medium
>Responsible: unassigned
>State: open
>Class: wrong-code
>Submitter-Id: net
>Arrival-Date: Mon Aug 26 11:26:00 PDT 2002
>Closed-Date:
>Last-Modified:
>Originator: Gary Houston
>Release: 3.2
>Organization:
>Environment:
System: Linux x.localnet 2.4.18 #1 Sat Apr 6 12:54:37 BST 2002 i686 unknown
Architecture: i686
host: i686-pc-linux-gnu
build: i686-pc-linux-gnu
target: i686-pc-linux-gnu
configured with: ../gcc-3.2/configure --prefix=/usr --enable-threads=posix --enable-shared
>Description:
Output of program below, compiled with gcc -O:
154
153
153
153
153
153
9
64
Output when compiled with gcc -O2:
0
0
0
0
153
153
9
64
>How-To-Repeat:
#include <stdlib.h>
#include <string.h>
typedef struct
{
unsigned long * type;
unsigned long * pad;
double real;
} x_double;
void * make_z (double x)
{
void *z = malloc (50);
memset (z, 0, 50);
((unsigned long *) z) [2] = 0;
((x_double *) z)->real = x;
return z;
}
main ()
{
void *z = make_z (3.2);
double d = ((x_double *) z)->real;
int i;
for (i = 0; i < sizeof (double); i++)
{
printf ("%d\n", ((unsigned char *) &d)[i]);
}
return 0;
}
>Fix:
reduce optimization
>Release-Note:
>Audit-Trail:
>Unformatted: