[Bug c++/70275] -w disables all -Werror flags

[msebor at gcc dot gnu.org]

https://gcc.gnu.org/bugzilla/show_bug.cgi?id=70275

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

           What    |Removed                     |Added
----------------------------------------------------------------------------
             Status|UNCONFIRMED                 |NEW
   Last reconfirmed|                            |2020-07-06
           Keywords|                            |diagnostic
                 CC|                            |msebor at gcc dot gnu.org
     Ever confirmed|0                           |1

--- Comment #5 from Martin Sebor <msebor at gcc dot gnu.org> ---
Let me confirm this bug report, in part because -w is documented to "Inhibit
all warning messages" but it does more than that, and also behaves differently
than Clang, and in my view not intuitively.  For example, the following
produces no output with GCC 10:

$ cat q.c && gcc -S -w -Wall -Werror -Wimplicit-int q.c
#pragma GCC diagnostic error "-Wimplicit-int"
f () { }

but reports an error with Clang:

$ clang -S -w -Wall -Werror -Wimplicit-int q.c
q.c:2:1: error: type specifier missing, defaults to 'int'
      [-Werror,-Wimplicit-int]
f () { }
^
1 error generated.

The Clang behavior makes more sense to me (it suppresses warnings but not
errors) but if there's some deeper logic in what GCC does it would be helpful
to mention it in the manual.