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Subject: [Bug c++/97790] constexpr evaluation reports false positive memory
 leak
Date: Thu, 12 Nov 2020 09:48:39 +0000
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https://gcc.gnu.org/bugzilla/show_bug.cgi?id=3D97790

--- Comment #4 from CVS Commits <cvs-commit at gcc dot gnu.org> ---
The master branch has been updated by Jakub Jelinek <jakub@gcc.gnu.org>:

https://gcc.gnu.org/g:fc531c2ed3ce456efca946e995544b216b3c16df

commit r11-4936-gfc531c2ed3ce456efca946e995544b216b3c16df
Author: Jakub Jelinek <jakub@redhat.com>
Date:   Thu Nov 12 10:46:04 2020 +0100

    c++: Fix up constexpr CLEANUP_POINT_EXPR and TRY_FINALLY_EXPR handling
[PR97790]

    As the testcase shows, CLEANUP_POINT_EXPR (and I think TRY_FINALLY_EXPR
too)
    suffer from the same problem that I was trying to fix in
    r10-3597-g1006c9d4395a939820df76f37c7b085a4a1a003f
    for CLEANUP_STMT, namely that if in the middle of the body expression of
    those stmts is e.g. return stmt, goto, break or continue (something that
    changes *jump_target and makes it start skipping stmts), we then skip t=
he
    cleanups too, which is not appropriate - the cleanups were either queue=
d up
    during the non-skipping execution of the body (for CLEANUP_POINT_EXPR),=
 or
    for TRY_FINALLY_EXPR are relevant already after entering the body block.

    > Would it make sense to always use a NULL jump_target when evaluating
    > cleanups?

    I was afraid of that, especially for TRY_FINALLY_EXPR, but it seems that
    during constexpr evaluation the cleanups will most often be just very
simple
    destructor calls (or calls to cleanup attribute functions).
    Furthermore, for neither of these 3 tree codes we'll reach that code if
    jump_target && *jump_target initially (there is a return NULL_TREE much
    earlier for those except for trees that could embed labels etc. in it a=
nd
    clearly these 3 don't count in that).

    2020-11-12  Jakub Jelinek  <jakub@redhat.com>

            PR c++/97790
            * constexpr.c (cxx_eval_constant_expression) <case
CLEANUP_POINT_EXPR,
            case TRY_FINALLY_EXPR, case CLEANUP_STMT>: Don't pass jump_targ=
et
to
            cxx_eval_constant_expression when evaluating the cleanups.

            * g++.dg/cpp2a/constexpr-dtor9.C: New test.=