Re: [PATCH v2] cpp/c: Add -Wexpansion-to-defined

[Paolo Bonzini <bonzini@gnu.org>]

On 10/08/2016 13:31, Manuel López-Ibáñez wrote:
> My only fear is that people not using -Wpedantic nor -pedantic-errors
> expect that GNU extensions work. This is a GNU extension that defines
> something that is undefined according to ISO. Enabling the warning
> with -Wextra is just annoying those people who may not care about
> other compilers.

I think this warning falls in the same category as
-Wshift-negative-value.  (In fact I dislike -Wshift-negative-value a
lot, and would put that one under -Wpedantic only).

It is interesting that GCC has been relying for a long time on such
behavior in the HAVE_DESIGNATED_INITIALIZERS macro, despite GCC not
having any interest in compiling with -Wpedantic.  I think this
reinforces the choice of adding the warning to -Wextra.

People using -Wextra are used to having to remove some warnings
manually, and this one probably doesn't have many hits (1 in QEMU, which
is what motivated me to add it to GCC; and 2 in GCC not counting the
duplicate code between gcc/system.h and libcpp/system.h).

Paolo