[Bug c++/28480] Incorrect field ambiguity detection due to [[no_unique_address]]

["cvs-commit at gcc dot gnu.org" <sourceware-bugzilla@sourceware.org>]

https://sourceware.org/bugzilla/show_bug.cgi?id=28480

--- Comment #20 from cvs-commit at gcc dot gnu.org <cvs-commit at gcc dot gnu.org> ---
The master branch has been updated by Bruno Larsen <blarsen@sourceware.org>:

https://sourceware.org/git/gitweb.cgi?p=binutils-gdb.git;h=a41ad3474ceacba39e11c7478154c0e553784a01

commit a41ad3474ceacba39e11c7478154c0e553784a01
Author: Bruno Larsen <blarsen@redhat.com>
Date:   Fri Oct 29 17:56:28 2021 -0300

    PR gdb/28480: Improve ambiguous member detection

    Basic ambiguity detection assumes that when 2 fields with the same name
    have the same byte offset, it must be an unambiguous request. This is not
    always correct. Consider the following code:

    class empty { };

    class A {
    public:
      [[no_unique_address]] empty e;
    };

    class B {
    public:
      int e;
    };

    class C: public A, public B { };

    if we tried to use c.e in code, the compiler would warn of an ambiguity,
    however, since A::e does not demand an unique address, it gets the same
    address (and thus byte offset) of the members, making A::e and B::e have
the
    same address. however, "print c.e" would fail to report the ambiguity,
    and would instead print it as an empty class (first path found).

    The new code solves this by checking for other found_fields that have
    different m_struct_path.back() (final class that the member was found
    in), despite having the same byte offset.

    The testcase gdb.cp/ambiguous.exp was also changed to test for this
    behavior.

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