[Bug c/43651] add warning for duplicate qualifier

[manu at gcc dot gnu.org]

https://gcc.gnu.org/bugzilla/show_bug.cgi?id=43651

--- Comment #7 from Manuel López-Ibáñez <manu at gcc dot gnu.org> ---
> Recently I came across such problem in the code base, which I work with. In
> that case it was clearly a mistake, because the author meant 'const char
> *const data', so it would be nice if GCC could warn about this.

I think that a patch that warns for 

const Type const x;

but not for:

typedef Type const X;
const X x;

and neither for

#define TYPE Type const
const TYPE;

would be accepted. But someone has to write it.