[Bug c++/98469] ICE in cxx_eval_constant_expression, at cp/constexpr.c:6350

[cvs-commit at gcc dot gnu.org]

https://gcc.gnu.org/bugzilla/show_bug.cgi?id=98469

--- Comment #2 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:606f2af1973d5c83877d327cb5adef97c4243a73

commit r11-6477-g606f2af1973d5c83877d327cb5adef97c4243a73
Author: Jakub Jelinek <jakub@redhat.com>
Date:   Tue Jan 5 17:17:57 2021 +0100

    c++: Fix ICE with __builtin_bit_cast [PR98469]

    On the following testcase we ICE during constexpr evaluation (for
warnings),
    because the IL has ADDR_EXPR of BIT_CAST_EXPR and ADDR_EXPR case asserts
    the result is not a CONSTRUCTOR.
    The patch punts on lval BIT_CAST_EXPR folding.

    > This change is OK, but part of the problem is that we're trying to do
    > overload resolution for an S copy/move constructor, which we shouldn't be
    > because bit_cast is a prvalue, so in C++17 and up we should use it to
    > directly initialize the target without any implied constructor call.

    This version therefore wraps it into a TARGET_EXPR then, it alone fixes
    the bug, but I've kept the constexpr.c change too.

    2021-01-05  Jakub Jelinek  <jakub@redhat.com>

            PR c++/98469
            * constexpr.c (cxx_eval_constant_expression) <case BIT_CAST_EXPR>:
            Punt if lval is true.
            * semantics.c (cp_build_bit_cast): Call get_target_expr_sfinae on
            the result if it has a class type.

            * g++.dg/cpp2a/bit-cast8.C: New test.
            * g++.dg/cpp2a/bit-cast9.C: New test.