[Bug driver/66293] Support -Weverything to enable all warnings

["msebor at gcc dot gnu.org" <gcc-bugzilla at gcc dot gnu dot org>]

https://gcc.gnu.org/bugzilla/show_bug.cgi?id=66293

Martin Sebor <msebor at gcc dot gnu.org> changed:

           What    |Removed                     |Added
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                 CC|                            |msebor at gcc dot gnu.org

--- Comment #4 from Martin Sebor <msebor at gcc dot gnu.org> ---
In my experience, options like -Weverything tend to be too noisy to be
generally useful for projects of non-trivial size.

At the same time, I would find an option like -Weverything quite useful when
debugging GCC's support for diagnostics.  I use -Wall -Wextra -Wpedantic but
there are some warnings that aren't enabled even with these three.  That said,
if -Weverything were to be provided, it wouldn't be able to enable every single
diagnostic because some are mutually exclusive (for example, the -Wabi=version
warnings for distinct ABI versions).  It also wouldn't be guaranteed to enable
diagnostics controlled by non-warning options.  But I wouldn't view these
limitations as reasons not to provide such a feature.  Many other popular
compilers  besides Clang provide it.  Below are examples of a few other
implementations that do:

EDG eccp has --remarks to enable informational diagnostics that are normally
disabled.
HP aCC has +w that if memory serves enables all warnings (including EDG
remarks, since aCC uses the EDG front end).
IBM XLC/C++ has -qinfo=all.
Intel ICC has a -diag-enable= option similar to XLC/C++ -qinfo= (ICC also uses
the EDG front end but has many more diagnostics).
Oracle CC has the -erroff=%none option that (IIRC) enables all warnings.
Microsoft Visual C++ has /Wall that's documented to enable all diagnostic.