[Bug tree-optimization/83671] Fix for false positive reported by -Wstringop-overflow does not work at -O1

[msebor at gcc dot gnu.org]

https://gcc.gnu.org/bugzilla/show_bug.cgi?id=83671

--- Comment #3 from Martin Sebor <msebor at gcc dot gnu.org> ---
Author: msebor
Date: Wed Jan 10 21:40:14 2018
New Revision: 256457

URL: https://gcc.gnu.org/viewcvs?rev=256457&root=gcc&view=rev
Log:
PR tree-optimization/83671 - Fix for false positive reported by
-Wstringop-overflow does not work with inlining

gcc/testsuite/ChangeLog:

        PR tree-optimization/83671
        * gcc.dg/strlenopt-40.c: New test.
        * gcc.dg/strlenopt-41.c: New test.

gcc/ChangeLog:

        PR tree-optimization/83671
        * builtins.c (c_strlen): Unconditionally return zero for the empty
        string.
        Use -Warray-bounds for warnings.
        * gimple-fold.c (get_range_strlen): Handle non-constant lengths
        for non-constant array indices with COMPONENT_REF, arrays of
        arrays, and pointers to arrays.
        (gimple_fold_builtin_strlen): Determine and set length range for
        non-constant character arrays.


Added:
    trunk/gcc/testsuite/gcc.dg/strlenopt-40.c
    trunk/gcc/testsuite/gcc.dg/strlenopt-41.c
Modified:
    trunk/gcc/ChangeLog
    trunk/gcc/builtins.c
    trunk/gcc/gimple-fold.c
    trunk/gcc/testsuite/ChangeLog
    trunk/gcc/testsuite/g++.dg/warn/string1.C