[Bug c++/88115] Incorrect result from alignof in templates, if also using __alignof__.

[cvs-commit at gcc dot gnu.org]

https://gcc.gnu.org/bugzilla/show_bug.cgi?id=88115

--- Comment #13 from CVS Commits <cvs-commit at gcc dot gnu.org> ---
The releases/gcc-8 branch has been updated by Patrick Palka
<ppalka@gcc.gnu.org>:

https://gcc.gnu.org/g:a34c19926b87f9cadd5ea84f5c5b93ae76b14558

commit r8-10855-ga34c19926b87f9cadd5ea84f5c5b93ae76b14558
Author: Patrick Palka <ppalka@redhat.com>
Date:   Wed Oct 7 10:49:00 2020 -0400

    c++: Distinguish alignof and __alignof__ in cp_tree_equal [PR97273]

    cp_tree_equal currently considers alignof the same as __alignof__, but
    these operators are semantically different ever since r8-7957.  In the
    testcase below, this causes the second static_assert to fail on targets
    where alignof(double) != __alignof__(double) because the specialization
    table (which uses cp_tree_equal as its equality predicate) conflates the
    two dependent specializations integral_constant<__alignof__(T)> and
    integral_constant<alignof(T)>.

    This patch makes cp_tree_equal distinguish between these two operators
    by inspecting the ALIGNOF_EXPR_STD_P flag.

    gcc/cp/ChangeLog:

            PR c++/88115
            PR libstdc++/97273
            * tree.c (cp_tree_equal) <case ALIGNOF_EXPR>: Return false if
            ALIGNOF_EXPR_STD_P differ.

    gcc/testsuite/ChangeLog:

            PR c++/88115
            PR libstdc++/97273
            * g++.dg/template/alignof3.C: New test.

    (cherry picked from commit 592fe221735bdaa375b1834dd49ce125d0b600d8)