[Bug middle-end/90404] No warning on attempts to modify a const object

["cvs-commit at gcc dot gnu.org" <gcc-bugzilla@gcc.gnu.org>]

https://gcc.gnu.org/bugzilla/show_bug.cgi?id=90404

--- Comment #7 from CVS Commits <cvs-commit at gcc dot gnu.org> ---
The master branch has been updated by David Malcolm <dmalcolm@gcc.gnu.org>:

https://gcc.gnu.org/g:3175d40fc52fb8eb3c3b18cc343d773da24434fb

commit r11-3829-g3175d40fc52fb8eb3c3b18cc343d773da24434fb
Author: David Malcolm <dmalcolm@redhat.com>
Date:   Wed Oct 7 18:34:09 2020 -0400

    analyzer: add warnings about writes to constant regions [PR95007]

    This patch adds two new warnings:
      -Wanalyzer-write-to-const
      -Wanalyzer-write-to-string-literal
    for code paths where the analyzer detects a write to a constant region.

    As noted in the documentation part of the patch, the analyzer doesn't
    prioritize detection of such writes, in that the state-merging logic
    will blithely lose the distinction between const and non-const regions.
    Hence false negatives are likely to arise due to state-merging.

    However, if the analyzer does happen to spot such a write, it seems worth
    reporting, hence this patch.

    gcc/analyzer/ChangeLog:
            * analyzer.opt (Wanalyzer-write-to-const): New.
            (Wanalyzer-write-to-string-literal): New.
            * region-model-impl-calls.cc (region_model::impl_call_memcpy):
            Call check_for_writable_region.
            (region_model::impl_call_memset): Likewise.
            (region_model::impl_call_strcpy): Likewise.
            * region-model.cc (class write_to_const_diagnostic): New.
            (class write_to_string_literal_diagnostic): New.
            (region_model::check_for_writable_region): New.
            (region_model::set_value): Call check_for_writable_region.
            * region-model.h (region_model::check_for_writable_region): New
            decl.

    gcc/ChangeLog:
            * doc/invoke.texi: Document -Wanalyzer-write-to-const and
            -Wanalyzer-write-to-string-literal.

    gcc/testsuite/ChangeLog:
            PR c/83347
            PR middle-end/90404
            PR analyzer/95007
            * gcc.dg/analyzer/write-to-const-1.c: New test.
            * gcc.dg/analyzer/write-to-string-literal-1.c: New test.