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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 c++/92407] Destruction of objects returned from functions
 skipped by goto
Date: Wed, 07 Jun 2023 01:33:41 +0000
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https://gcc.gnu.org/bugzilla/show_bug.cgi?id=3D92407

--- Comment #8 from CVS Commits <cvs-commit at gcc dot gnu.org> ---
The trunk branch has been updated by Jason Merrill <jason@gcc.gnu.org>:

https://gcc.gnu.org/g:7e0b65b239c3a0d68ce94896b236b03de666ffd6

commit r14-1593-g7e0b65b239c3a0d68ce94896b236b03de666ffd6
Author: Jason Merrill <jason@redhat.com>
Date:   Sun Jun 4 12:09:11 2023 -0400

    c++: enable NRVO from inner block [PR51571]

    Our implementation of the named return value optimization has been limi=
ted
    to variables declared in the outermost block of the function, to avoid
    needing to handle the case where the variable needs to be destroyed due=
 to
    going out of scope.  PR92407 pointed out a case we were missing, where =
the
    variable goes out of scope due to a goto and we were failing to destroy=
 it.

    It occurred to me that this problem is the flip side of PR33799, where =
we
    need to be sure to destroy the return value if a cleanup throws on retu=
rn;
    here we want to avoid destroying the return value when exiting the
    variable's scope on return.  We can use the same flag to indicate to bo=
th
    cleanups that we're returning.

    This implements the guaranteed copy elision specified by P2025 (which is
not
    yet part of the draft standard).

            PR c++/51571
            PR c++/92407

    gcc/cp/ChangeLog:

            * decl.cc (finish_function): Simplify NRV handling.
            * except.cc (maybe_set_retval_sentinel): Also set if NRV.
            (maybe_splice_retval_cleanup): Don't add the cleanup region
            if we don't need it.
            * semantics.cc (nrv_data): Add simple field.
            (finalize_nrv): Set it.
            (finalize_nrv_r): Check it and retval sentinel.
            * cp-tree.h (finalize_nrv): Adjust declaration.
            * typeck.cc (check_return_expr): Remove named_labels check.

    gcc/testsuite/ChangeLog:

            * g++.dg/opt/nrv23.C: New test.=