[Bug c++/94041] [10 Regression] temporary object destructor called before the end of the full-expression since r10-5577

[Bug c++/94041] [10 Regression] temporary object destructor called before the end of the full-expression since r10-5577

[jason at gcc dot gnu.org]

https://gcc.gnu.org/bugzilla/show_bug.cgi?id=94041

--- Comment #4 from Jason Merrill <jason at gcc dot gnu.org> ---
This turned out to be a long-standing bug with split_nonconstant_init (since
4.7, apparently): initializion of individual elements of an aggregate are not a
full-expressions, but split_nonconstant_init was making full-expressions out of
them.  My fix for PR66139 extended the use of split_nonconstant_init, and thus
the bug, to aggregate initialization of temporaries within an expression, in
which context the bug is more noticeable.

This is a tricky one, getting back into the issues with cleanups not nesting
properly that wrap_temporary_cleanups handles some of, but not this example.

[Bug c++/94041] [10 Regression] temporary object destructor called before the end of the full-expression since r10-5577

[jason at gcc dot gnu.org]

https://gcc.gnu.org/bugzilla/show_bug.cgi?id=94041

Jason Merrill <jason at gcc dot gnu.org> changed:

           What    |Removed                     |Added
----------------------------------------------------------------------------
         Resolution|---                         |FIXED
             Status|ASSIGNED                    |RESOLVED

--- Comment #5 from Jason Merrill <jason at gcc dot gnu.org> ---
Fixed by reverting the fix for PR66139.

[Bug c++/94041] [10 Regression] temporary object destructor called before the end of the full-expression since r10-5577

[jakub at gcc dot gnu.org]

https://gcc.gnu.org/bugzilla/show_bug.cgi?id=94041

--- Comment #6 from Jakub Jelinek <jakub at gcc dot gnu.org> ---
commit r10-7110-g14af5d9b19b0f4ee1d929e505e245ae5c2f6bdc6
Author: Jason Merrill <jason@redhat.com>
Date:   Tue Mar 10 16:05:18 2020 -0400

    c++: Partially revert patch for PR66139.

    The patch for 66139 exposed a long-standing bug with
    split_nonconstant_init (since 4.7, apparently): initializion of individual
    elements of an aggregate are not a full-expressions, but
    split_nonconstant_init was making full-expressions out of them.  My fix for
    66139 extended the use of split_nonconstant_init, and thus the bug, to
    aggregate initialization of temporaries within an expression, in which
    context (PR94041) the bug is more noticeable.  PR93922 is a problem with my
    implementation strategy of splitting out at gimplification time,
introducing
    function calls that weren't in the GENERIC.  So I'm going to revert the
    patch now and try again for GCC 11.

    gcc/cp/ChangeLog
    2020-03-10  Jason Merrill  <jason@redhat.com>

            PR c++/93922
            PR c++/94041
            PR c++/52320
            PR c++/66139
            * cp-gimplify.c (cp_gimplify_init_expr): Partially revert patch for
            66139: Don't split_nonconstant_init.  Remove pre_p parameter.

[Bug c++/94041] [10 Regression] temporary object destructor called before the end of the full-expression since r10-5577

[cvs-commit at gcc dot gnu.org]

https://gcc.gnu.org/bugzilla/show_bug.cgi?id=94041

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

https://gcc.gnu.org/g:ce0ab8fb46f07b0bde56aa31e46d57b81379fde3

commit r12-6327-gce0ab8fb46f07b0bde56aa31e46d57b81379fde3
Author: Jason Merrill <jason@redhat.com>
Date:   Thu Mar 5 15:50:45 2020 -0500

    c++: temporary lifetime with aggregate init [PR94041]

    In C++98 the lifetime of temporaries in aggregate initialization was
    unclear, but C++11 DR201 clarified that only temporaries created for
    default-initialization of an array element with no corresponding
    initializer-clause are destroyed immediately; all others persist until the
    end of the full-expression.

    But we never implemented that, and continued treating individual element
    initializations as full-expressions, such as in my patch for PR50866 in
    r180442.  This blocked my attempted fix for PR66139, which extended the use
    of split_nonconstant_init, and thus the bug, to aggregate initialization of
    temporaries within an expression.

    The longer temporary lifetime creates further EH region overlap problems
    like the ones that wrap_temporary_cleanups addresses: in aggr7.C, we start
    out with a normal nesting of

    A1
     c.b1
       A2
        c.b2
         ...
       ~A2
    ~A1

    where on the way in, throwing from one of the inits will clean up from the
    previous inits.  But once c.b2 is initialized, throwing from ~A2 must not
    clean up c.b1; instead it needs to clean up c.  So as in build_new_1, we
    deal with this by guarding the B cleanups with flags that are cleared once
c
    is fully constructed; throwing from one of the ~A still hits that region,
    but does not call ~B.  And then wrap_temporary_cleanups deals with calling
    ~C, but we need to tell it not to wrap the subobject cleanups.

    The change from expressing the subobject cleanups with CLEANUP_STMT to
    TARGET_EXPR was also necessary because we need them to collate with the ~A
    in gimplify_cleanup_point_expr; the CLEANUP_STMT representation only worked
    with treating subobject initializations as full-expressions.

            PR c++/94041

    gcc/cp/ChangeLog:

            * decl.c (check_initializer): Remove obsolete comment.
            (wrap_cleanups_r): Don't wrap CLEANUP_EH_ONLY.
            (initialize_local_var): Change assert to test.
            * typeck2.c (maybe_push_temp_cleanup): New.
            (split_nonconstant_init_1): Use it.
            (split_nonconstant_init): Clear cleanup flags.

    gcc/testsuite/ChangeLog:

            * g++.dg/init/aggr7-eh.C: New test.
            * g++.dg/cpp0x/initlist122.C: Also test aggregate variable.

[Bug c++/94041] [10 Regression] temporary object destructor called before the end of the full-expression since r10-5577

[cvs-commit at gcc dot gnu.org]

https://gcc.gnu.org/bugzilla/show_bug.cgi?id=94041

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

https://gcc.gnu.org/g:beaee0a871b6485d20573fe050b1fd425581e56a

commit r12-6328-gbeaee0a871b6485d20573fe050b1fd425581e56a
Author: Jason Merrill <jason@redhat.com>
Date:   Sat Jan 1 16:00:22 2022 -0500

    c++: temporary lifetime with array aggr init [PR94041]

    The previous patch fixed temporary lifetime for aggregate initialization of
    classes; this one extends that fix to arrays.  This specifically reverses
my
    r74790, the patch for PR12253, which was made wrong when these semantics
    were specified in DR201.

    Since the array cleanup region encloses the regions for any temporaries, we
    don't need to add an additional region for the array object itself in
either
    initialize_local_var or split_nonconstant_init; we do, however, need to
tell
    split_nonconstant_init how to disable the cleanup once an enclosing object
    is fully constructed, at which point we want to run that destructor
instead.

            PR c++/94041

    gcc/cp/ChangeLog:

            * decl.c (initialize_local_var): Fix comment.
            * init.c (build_new_1): Do stabilize array init.
            (build_vec_init): Use TARGET_EXPR for cleanup.  Initialization
            of an element from an explicit initializer is not a
            full-expression.
            * tree.c (expand_vec_init_expr): Pass flags through.
            * typeck2.c (split_nonconstant_init_1): Handle VEC_INIT_EXPR.
            (split_nonconstant_init): Handle array cleanups.
            * cp-tree.h: Adjust.

    gcc/testsuite/ChangeLog:

            * g++.dg/init/array12.C:
            * g++.dg/init/aggr7-eh2.C: New test.
            * g++.dg/init/aggr7-eh3.C: New test.

[Bug c++/94041] [10 Regression] temporary object destructor called before the end of the full-expression since r10-5577

[jason at gcc dot gnu.org]

https://gcc.gnu.org/bugzilla/show_bug.cgi?id=94041
Bug 94041 depends on bug 66139, which changed state.

Bug 66139 Summary: destructor not called for members of partially constructed anonymous struct/array
https://gcc.gnu.org/bugzilla/show_bug.cgi?id=66139

           What    |Removed                     |Added
----------------------------------------------------------------------------
             Status|ASSIGNED                    |RESOLVED
         Resolution|---                         |FIXED