[Bug c++/93728] New: First half of warning message suppressed because code pointed to is in system header

[loximann at gmail dot com]

https://gcc.gnu.org/bugzilla/show_bug.cgi?id=93728

            Bug ID: 93728
           Summary: First half of warning message suppressed because code
                    pointed to is in system header
           Product: gcc
           Version: 9.2.1
            Status: UNCONFIRMED
          Severity: normal
          Priority: P3
         Component: c++
          Assignee: unassigned at gcc dot gnu.org
          Reporter: loximann at gmail dot com
  Target Milestone: ---

Created attachment 47833
  --> https://gcc.gnu.org/bugzilla/attachment.cgi?id=47833&action=edit
Minimal reproducible example

-Woverloaded-virtual shows only the second half of a warning, making it
confusing, when several circumstances happen:
- A class with two virtual methods with the same name and different signature
exists in a system header.
- Another class inheriting from the previous class does not override any
methods.
- Another class inheriting from the previous class overrides only one method.

The output is this:

    $ make
    g++ -isystem include -Woverloaded-virtual Woverloaded-virtual.cpp -c
    Woverloaded-virtual.cpp:8:9: warning:   by ‘virtual void Bar::f(int)’
[-Woverloaded-virtual]
        8 |    void f(int) final {};
          |         ^

Including the header as a regular header shows also the first half.

    sergio@bnct1:~/src/playground/Woverloaded-virtual$ make        
    g++ -Iinclude -Woverloaded-virtual Woverloaded-virtual.cpp -c
    In file included from Woverloaded-virtual.cpp:1:
    include/Woverloaded-virtual.h:4:16: warning: ‘virtual void Foo::f(int,
int)’ was hidden [-Woverloaded-virtual]
        4 |   virtual void f(int, int){};
          |                ^
    Woverloaded-virtual.cpp:8:9: warning:   by ‘virtual void Bar::f(int)’
[-Woverloaded-virtual]
        8 |    void f(int) final {};
          |         ^


Minimal reproducible example also available here:

https://gitlab.com/loximann/woverloaded-virtual