[Bug c++/103745] New: Warn on throwing an exception not derived from std::exception

[Bug c++/103745] New: Warn on throwing an exception not derived from std::exception

[antoshkka at gmail dot com]

https://gcc.gnu.org/bugzilla/show_bug.cgi?id=103745

            Bug ID: 103745
           Summary: Warn on throwing an exception not derived from
                    std::exception
           Product: gcc
           Version: 12.0
            Status: UNCONFIRMED
          Keywords: diagnostic
          Severity: normal
          Priority: P3
         Component: c++
          Assignee: unassigned at gcc dot gnu.org
          Reporter: antoshkka at gmail dot com
  Target Milestone: ---

Throwing an exception that is derived from std::exception is a common practice.
Cases when that practice should be skipped are very rare. However, many
beginners do not know about that and erroneously do not derive their exceptions
from std::exception. There are also cases when classes have close names and
users throw the wrong type by a typo.

Please add a warning about throwing an exception not derived from
std::exception.

Godbolt playground: https://godbolt.org/z/7Phf3nafW

[Bug c++/103745] Warn on throwing an exception not derived from std::exception

[pinskia at gcc dot gnu.org]

https://gcc.gnu.org/bugzilla/show_bug.cgi?id=103745

Andrew Pinski <pinskia at gcc dot gnu.org> changed:

           What    |Removed                     |Added
----------------------------------------------------------------------------
           Severity|normal                      |enhancement

--- Comment #1 from Andrew Pinski <pinskia at gcc dot gnu.org> ---
> Throwing an exception that is derived from std::exception is a common practice.

Common practice where? in the standard library yes, outside of the wild not so
much.
I think this should be an optional warning which a project can turn on if they
want to or not.

[Bug c++/103745] Warn on throwing an exception not derived from std::exception

[egallager at gcc dot gnu.org]

https://gcc.gnu.org/bugzilla/show_bug.cgi?id=103745

Eric Gallager <egallager at gcc dot gnu.org> changed:

           What    |Removed                     |Added
----------------------------------------------------------------------------
                 CC|                            |egallager at gcc dot gnu.org

--- Comment #2 from Eric Gallager <egallager at gcc dot gnu.org> ---
Could this go under the existing -Wexceptions flag?

[Bug c++/103745] Warn on throwing an exception not derived from std::exception

[redi at gcc dot gnu.org]

https://gcc.gnu.org/bugzilla/show_bug.cgi?id=103745

--- Comment #3 from Jonathan Wakely <redi at gcc dot gnu.org> ---
I don't think so. What -Wexceptions warns about is almost always a bug (why
would you write a shadowed catch handler that can never catch anything?).

But the choice of whether to only throw things derived from std::exception or
not is purely stylistic, it's not about correctness. Users who want to know
about buggy catch handlers might not want warnings about a style issue they
don't agree with.