[Bug tree-optimization/92157] [10 Regression] incorrect strcmp() == 0 result for unknown strings

[msebor at gcc dot gnu.org]

https://gcc.gnu.org/bugzilla/show_bug.cgi?id=92157

Martin Sebor <msebor at gcc dot gnu.org> changed:

           What    |Removed                     |Added
----------------------------------------------------------------------------
             Status|UNCONFIRMED                 |ASSIGNED
           Keywords|                            |wrong-code
   Last reconfirmed|                            |2019-10-18
           Assignee|unassigned at gcc dot gnu.org      |msebor at gcc dot gnu.org
             Blocks|                            |83819
           See Also|                            |https://gcc.gnu.org/bugzill
                   |                            |a/show_bug.cgi?id=92155
     Ever confirmed|0                           |1
            Summary|incorrect strcmp() == 0     |[10 Regression] incorrect
                   |result for unknown strings  |strcmp() == 0 result for
                   |                            |unknown strings

--- Comment #1 from Martin Sebor <msebor at gcc dot gnu.org> ---
The test for the optimization, strlenopt-69.c, actually passes because of the
bug, and also because of the missing memset optimization reported in pr92155. 
The test_empty_string() function calls memset to zero out two arrays, a and b,
and expects strcmp(a, b) == 0 to be folded to true.  It is folded, but not
because the strlen pass knows the strings are the same (the missing
optimization), but because of this bug.


Referenced Bugs:

https://gcc.gnu.org/bugzilla/show_bug.cgi?id=83819
[Bug 83819] [meta-bug] missing strlen optimizations