c/4607: Optimization bug, (miscompilation of boehm-gc)

[Martin Kahlert <martin dot kahlert at infineon dot com>]

>Number:         4607
>Category:       c
>Synopsis:       Optimization bug, (miscompilation of boehm-gc)
>Confidential:   no
>Severity:       serious
>Priority:       medium
>Responsible:    unassigned
>State:          open
>Class:          wrong-code
>Submitter-Id:   net
>Arrival-Date:   Thu Oct 18 02:06:01 PDT 2001
>Closed-Date:
>Last-Modified:
>Originator:     Martin Kahlert
>Release:        3.1 20011017 (experimental)
>Organization:
Infineon AG
>Environment:
System: Linux keksy 2.4.12 #1 SMP Thu Oct 11 16:34:10 MEST 2001 i686 unknown
Architecture: i686

	
host: i686-pc-linux-gnu
build: i686-pc-linux-gnu
target: i686-pc-linux-gnu
configured with: ../gcc-3.1/configure --prefix=/sw/gcc-3.1 --enable-languages=c++,f77,java --enable-threads=posix
>Description:
gcc miscompiles its sources (boehm-gc/mark_rts.c)
see http://gcc.gnu.org/ml/gcc/2001-10/msg01009.html for the original posting.
>How-To-Repeat:
$ cat t.c
#include <stdio.h>

struct exclusion
{
 int a1;
 int array[5];
} Table;

int *f(int start)
{
 return Table.array + start;
}

int main(int argc, char *argv[])
{
 int *next;

 if ( argc == 2 )
     next = f(atoi(argv[1]));
 else
     next = f(0);

 printf("next = %p, Table.array = %p, diff = %d\n",
         next, Table.array, next-Table.array);

 return 0;
}

$ gcc -O -o t t.c
$ t
next = 0x8049710, Table.array = 0x8049710, diff = 2

>Fix:
	do not use -O (but libjava is built using -O -g)
>Release-Note:
>Audit-Trail:
>Unformatted: