[Bug analyzer/104369] False positive from -Wanalyzer-use-of-uninitialized-value with realloc moving buffer

[cvs-commit at gcc dot gnu.org]

https://gcc.gnu.org/bugzilla/show_bug.cgi?id=104369

--- Comment #1 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:3ef328c293a336df0aead2d72c0c5ed9781a9861

commit r12-7040-g3ef328c293a336df0aead2d72c0c5ed9781a9861
Author: David Malcolm <dmalcolm@redhat.com>
Date:   Wed Feb 2 16:39:12 2022 -0500

    analyzer: fixes to realloc-handling [PR104369]

    This patch fixes various issues with how -fanalyzer handles "realloc"
    seen when debugging PR analyzer/104369.

    Previously it wasn't correctly copying over the contents of the old
    buffer for the success-with-move case, leading to false
    -Wanalyzer-use-of-uninitialized-value diagnostics.

    I also noticed that -fanalyzer failed to properly handle "realloc" for
    cases where the ptr's region had unknown dynamic extents, and an ICE
    for the case where a tainted value is used as a realloc size argument.

    This patch fixes these issues, including the false uninit diagnostics
    seen in PR analyzer/104369.

    gcc/analyzer/ChangeLog:
            PR analyzer/104369
            * engine.cc (exploded_graph::process_node): Use the node for any
            diagnostics, avoiding ICE if a bifurcation update adds a
            saved_diagnostic, such as for a tainted realloc size.
            * region-model-impl-calls.cc
            (region_model::impl_call_realloc::success_no_move::update_model):
            Require the old pointer to be non-NULL to be able successfully
            grow in place.  Use model->deref_rvalue rather than
maybe_get_region
            to support the old pointer being symbolic.
            (region_model::impl_call_realloc::success_with_move::update_model):
            Likewise.  Add a constraint that the new pointer != the old
pointer.
            Use a sized_region when setting the value of the new region.
            Handle the case where we don't know the dynamic size of the old
            region by marking the new region as unknown.
            * sm-taint.cc (tainted_allocation_size::tainted_allocation_size):
            Update assertion to also allow for MEMSPACE_UNKNOWN.
            (tainted_allocation_size::emit): Likewise.
            (region_model::check_dynamic_size_for_taint): Likewise.

    gcc/testsuite/ChangeLog:
            PR analyzer/104369
            * gcc.dg/analyzer/pr104369-1.c: New test.
            * gcc.dg/analyzer/pr104369-2.c: New test.
            * gcc.dg/analyzer/realloc-3.c: New test.
            * gcc.dg/analyzer/realloc-4.c: New test.
            * gcc.dg/analyzer/taint-realloc.c: New test.

    Signed-off-by: David Malcolm <dmalcolm@redhat.com>