[Bug c/28073] Type-punned pointer passed as function parameter generates bad assembly sequence

[sorenj at us dot ibm dot com]

------- Comment #2 from sorenj at us dot ibm dot com  2006-06-19 16:44 -------
Changing just one line of the test program to the (AFAIK) legal C code.  By
casting through void *, we are addressing Andrew's concerns about violating the
C rules. 

  Foo *pFoo = *(Foo **) ((void *)&longPtr); /* // BAD! */

eliminates the type-punned warning, even at the highest possible warning level,
and continues to generate code the results in a bad return value.  This test
case illustrates that this problem is actually worse than we originally
thought, as now incorrect code is generated without any warning.

$ gcc -Wstrict-aliasing=2 -Wall -O2 badcase.c
$ ./a.out ; echo $?
76
$ gcc -Wstrict-aliasing=2 -Wall -O2 -fno-strict-aliasing badcase.c
$ ./a.out ; echo $?
1


-- 

sorenj at us dot ibm dot com changed:

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


http://gcc.gnu.org/bugzilla/show_bug.cgi?id=28073