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From: "cvs-commit at gcc dot gnu.org" <gcc-bugzilla@gcc.gnu.org>
To: gcc-bugs@gcc.gnu.org
Subject: [Bug analyzer/108475] -Wanalyzer-deref-before-check false positives
 seen in haproxy's tcpcheck.c
Date: Fri, 10 Mar 2023 13:22:42 +0000
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https://gcc.gnu.org/bugzilla/show_bug.cgi?id=3D108475

--- 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:c4fd232f9843bb800548a906653aeb0723cdb411

commit r13-6581-gc4fd232f9843bb800548a906653aeb0723cdb411
Author: David Malcolm <dmalcolm@redhat.com>
Date:   Fri Mar 10 08:20:10 2023 -0500

    analyzer: fix deref-before-check false +ves seen in haproxy
[PR108475,PR109060]

    Integration testing showed various false positives from
    -Wanalyzer-deref-before-check where the expression that's dereferenced
    is different from the one that's checked, but the diagnostic is emitted
    because they both evaluate to the same symbolic value.

    This patch rejects such warnings, unless we have tree expressions for
    both and that both tree expressions are "spelled the same way" i.e.
    would be printed to the same user-facing string.

    gcc/analyzer/ChangeLog:
            PR analyzer/108475
            PR analyzer/109060
            * sm-malloc.cc (deref_before_check::deref_before_check):
            Initialize new field m_deref_expr.  Assert that arg is non-NULL.
            (deref_before_check::emit): Reject cases where the spelling of =
the
            thing that was dereferenced differs from that of what is checke=
d,
            or if the dereference expression was not found.  Remove code to
            handle NULL m_arg.
            (deref_before_check::describe_state_change): Remove code to han=
dle
            NULL m_arg.
            (deref_before_check::describe_final_event): Likewise.
            (deref_before_check::sufficiently_similar_p): New.
            (deref_before_check::m_deref_expr): New field.
            (malloc_state_machine::maybe_complain_about_deref_before_check):
            Don't warn if the diag_ptr is NULL.

    gcc/testsuite/ChangeLog:
            PR analyzer/108475
            PR analyzer/109060
            * gcc.dg/analyzer/deref-before-check-pr108475-1.c: New test.
            * gcc.dg/analyzer/deref-before-check-pr108475-haproxy-tcpcheck.=
c:
            New test.
            * gcc.dg/analyzer/deref-before-check-pr109060-haproxy-cfgparse.=
c:
            New test.

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