[Bug c/20708] New: strict aliasing warning

[Bug c/20708] New: strict aliasing warning

[varun0005 at gmail dot com]

since in case where you are doing "float **q=(void *)&i" then
according to strict-aliasing rules we get " warning: dereferencing type-punned
pointer will break strict-aliasing rules" , but same thing if done using a
temporary variable then why strict-aliasing warning doesn't appear.. According
to my understanding of strict aliasing if some unqualified version of pointer is
pointing to the address space then it is violating  strict aliasing rule. So in
second case also float ** pointer is pointing to the int address space then why
strict aliasing rules are not violated. If ther is some error in my
understanding of strict aliasing then please inform .

 .the exact programs are following and command line was gcc -Wall -O2
test1.c test2.c....In this why test1.c not giving warning but test2.c giving
violation of strict-aliasing warning.
//test1.c
#include <stdio.h>
#include <stdlib.h>
int main()
{ int *i;
float **q;
int **r;
i =(int *)malloc(sizeof(int));
r=&i;
q=(float **)r;
return 0;
}
//test2.c
int main(){
int *i;
float **q; 
i =(int *)malloc(sizeof(int));
q= (float **) &i;
return 0;
}

-- 
           Summary: strict aliasing warning
           Product: gcc
           Version: 3.3.4
            Status: UNCONFIRMED
          Severity: critical
          Priority: P2
         Component: c
        AssignedTo: unassigned at gcc dot gnu dot org
        ReportedBy: varun0005 at gmail dot com
                CC: gcc-bugs at gcc dot gnu dot org


http://gcc.gnu.org/bugzilla/show_bug.cgi?id=20708

[Bug c/20708] strict aliasing warning

[pinskia at gcc dot gnu dot org]

------- Additional Comments From pinskia at gcc dot gnu dot org  2005-04-01 05:37 -------
Casting to void* first, makes the aliasing warning go way.  This is expected behavior.

Realy the only undefinedness is when you access via two different types.

-- 
           What    |Removed                     |Added
----------------------------------------------------------------------------
             Status|UNCONFIRMED                 |RESOLVED
         Resolution|                            |INVALID


http://gcc.gnu.org/bugzilla/show_bug.cgi?id=20708