[Bug optimization/9196] [3.4 regression] pointer arithmetic is misoptimized

[zack at gcc dot gnu dot org]

PLEASE REPLY TO gcc-bugzilla@gcc.gnu.org ONLY, *NOT* gcc-bugs@gcc.gnu.org.

http://gcc.gnu.org/bugzilla/show_bug.cgi?id=9196


zack at gcc dot gnu dot org changed:

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


------- Additional Comments From zack at gcc dot gnu dot org  2003-08-25 20:10 -------
The C semantics for pointer arithmetic mean that GCC is allowed to assume that
this line

  return __res + 1;

never causes a null pointer to be returned.  The "mis-optimized" code has been
optimized based on that assumption.  In short, the bug is in glibc.

The simplest fix is to write "incl %0" as the last instruction of the assembly
block rather than trying to do this calculation in C.