[Bug c/17665] New:

["gcc-bugzilla at gcc dot gnu dot org" <gcc-bugzilla at gcc dot gnu dot org>]

The wrong code is generated for -O2 on a dereference of a pointer to a 'void
*'.

Environment:
System: Linux youknow.youwant.to 2.4.20-28.7smp #1 SMP Thu Dec 18 11:18:31 EST 2003 i686 unknown
Architecture: i686

	
host: i686-pc-linux-gnu
build: i686-pc-linux-gnu
target: i686-pc-linux-gnu
configured with: ../configure --enable-languages=c++,java --enable-shared --enable-threads=posix --disable-checking --with-system-zlib --program-suffix=342

How-To-Repeat:

#include <stdio.h>
#include <stdlib.h>

// Optimization issue with g++ 2.96 and 3.4.2 and probably others.
// With -O2, I get "3 1 0" and "3 1 2"
// With -O1, I get "3 1 2" and "3 1 2"

void *GetBlocks(void)
{
 void *block1=malloc(64);
 void *block2=malloc(64);
 void *block3=malloc(64);
 *(void **) block1=block2;
 *(void **) block2=block3;
 *(void **) block3=NULL;
 return block1;
}

int CountList(void *a)
{
 int ret=0;
 while(a!=NULL)
 {
  ret++;
  a=*(void **) a;
 }
 return ret;
}


void RemoveOneA(void *head)
{
 int l1, l2, l3;
 void *newhead;
 l1=CountList(head);
 newhead=*(void **) head;
 *(char **) head=NULL;
 l2=CountList(head);
 l3=CountList(newhead);
 printf("%d %d %d\n", l1, l2, l3);
}

void RemoveOneB(void *head)
{
 int l1, l2, l3;
 void *newhead;
 l1=CountList(head);
 newhead=*(char **) head;
 *(char **) head=0;
 l2=CountList(head);
 l3=CountList(newhead);
 printf("%d %d %d\n", l1, l2, l3);
}

int main(void)
{
 RemoveOneA(GetBlocks());
 RemoveOneB(GetBlocks());
}
------- Additional Comments From davids at webmaster dot com  2004-09-24 23:13 -------
Fix:

The same code should be generated. Or see the other 'RemoveOne'
implementation.

David Schwartz
<davids@webmaster.com>

-- 
           Product: gcc
           Version: 3.4.2
            Status: UNCONFIRMED
          Severity: normal
          Priority: P1
         Component: c
        AssignedTo: unassigned at gcc dot gnu dot org
        ReportedBy: davids at webmaster dot com
                CC: gcc-bugs at gcc dot gnu dot org
 GCC build triplet: i686-pc-linux-gnu
  GCC host triplet: i686-pc-linux-gnu
GCC target triplet: i686-pc-linux-gnu


http://gcc.gnu.org/bugzilla/show_bug.cgi?id=17665