[Bug c++/117114] [15 Regression] -Woverloaded-virtual false positives on multiple inheritance since r15-4282-g60163c85730e6b

[cvs-commit at gcc dot gnu.org]

https://gcc.gnu.org/bugzilla/show_bug.cgi?id=117114

--- Comment #8 from GCC Commits <cvs-commit at gcc dot gnu.org> ---
The master branch has been updated by Simon Martin <simartin@gcc.gnu.org>:

https://gcc.gnu.org/g:d346af2af88caf1e21a5cc1f0afa33596198fb60

commit r15-7350-gd346af2af88caf1e21a5cc1f0afa33596198fb60
Author: Simon Martin <simon@nasilyan.com>
Date:   Tue Feb 4 10:58:17 2025 +0100

    c++: Fix overeager Woverloaded-virtual with conversion operators [PR109918]

    We currently emit an incorrect -Woverloaded-virtual warning upon the
    following test case

    === cut here ===
    struct A {
      virtual operator int() { return 42; }
      virtual operator char() = 0;
    };
    struct B : public A {
      operator char() { return 'A'; }
    };
    === cut here ===

    The problem is that when iterating over ovl_range (fns), warn_hidden
    gets confused by the conversion operator marker, concludes that
    seen_non_override is true and therefore emits a warning for all
    conversion operators in A that do not convert to char, even if
    -Woverloaded-virtual is 1 (e.g. with -Wall, the case reported).

    A second set of problems is highlighted when -Woverloaded-virtual is 2.

    First, with the same test case, since base_fndecls contains all
    conversion operators in A (except the one to char, that's been removed
    when iterating over ovl_range (fns)), we emit a spurious warning for
    the conversion operator to int, even though it's unrelated.

    Second, in case there are several conversion operators with different
    cv-qualifiers to the same type in A, we rightfully emit a warning,
    however the note uses the location of the conversion operator marker
    instead of the right one; location_of should go over conv_op_marker.

    This patch fixes all these by explicitly keeping track of (1) base
    methods that are overriden, as well as (2) base methods that are hidden
    but not overriden (and by what), and warning about methods that are in
    (2) but not (1). It also ignores non virtual base methods, per
    "definition" of -Woverloaded-virtual.

    Co-authored-by: Jason Merrill <jason@redhat.com>

            PR c++/117114
            PR c++/109918

    gcc/cp/ChangeLog:

            * class.cc (warn_hidden): Keep track of overloaded and of hidden
            base methods.
            * error.cc (location_of): Skip over conv_op_marker.

    gcc/testsuite/ChangeLog:

            * g++.dg/warn/Woverloaded-virt1.C: Check that no warning is
            emitted for non virtual base methods.
            * g++.dg/warn/Woverloaded-virt10.C: New test.
            * g++.dg/warn/Woverloaded-virt11.C: New test.
            * g++.dg/warn/Woverloaded-virt12.C: New test.
            * g++.dg/warn/Woverloaded-virt13.C: New test.
            * g++.dg/warn/Woverloaded-virt5.C: New test.
            * g++.dg/warn/Woverloaded-virt6.C: New test.
            * g++.dg/warn/Woverloaded-virt7.C: New test.
            * g++.dg/warn/Woverloaded-virt8.C: New test.
            * g++.dg/warn/Woverloaded-virt9.C: New test.