Le 09/10/2018 à 16:52, Peter Maydell a écrit : > On 9 October 2018 at 12:59, Peter Maydell <peter.mayd...@linaro.org> wrote: >> On 5 October 2018 at 17:09, Laurent Vivier <laur...@vivier.eu> wrote: >>> Could it be a bug in _Pragma()? >> >> I got an f28 VM and can repro this. It looks like the problem >> only happens when the get_user/put_user stuff is used via some >> other macro, for some reason -- so the GET_ARG and SET_ARG >> macros in arm-semi.c and the NEW_AUX_ENT macro in elfload.c >> cause problems, but less indirect use does not. I'll try to >> trim this down to a smaller test case somehow... > > I think it is a bug in _Pragma(). I boiled it down to a > small test case, and tested using the compilers on godbolt.org. > The test fails with gcc 5, 6, 7 and 8 but works on 4 and on > gcc trunk. > > Trying to use _Pragma() inside a macro to disable warnings > seems to be pretty broken. The GCC bugzilla has: > https://gcc.gnu.org/bugzilla/show_bug.cgi?id=85153 > https://gcc.gnu.org/bugzilla/show_bug.cgi?id=69558 > https://gcc.gnu.org/bugzilla/show_bug.cgi?id=82335 > https://gcc.gnu.org/bugzilla/show_bug.cgi?id=66099 > https://gcc.gnu.org/bugzilla/show_bug.cgi?id=55578 > https://gcc.gnu.org/bugzilla/show_bug.cgi?id=69543 > > which are various bug reports in this area, with test cases > which variously are fixed in gcc 8, or fixed not in 8 but > in trunk, or still broken in trunk. So there isn't a single > bug here but a cluster of similar ones. > > I think the underlying difficulty is that the compiler decides > whether to suppress the warning by looking at the source location > for the warning, and at the source locations of the various > pragmas, and especially when macro expansion is involved the > "source location" can be harder to correctly identify. > > I'm not sure if there is some "safe" subset of _Pragma()-in-macro > use here that will work regardless of compiler version, or if > we should just give up on it as non-feasible and try to silence > the warnings some other way.
To keep it simple, and as I have suggested before, perhaps you can use only the _Pragma() we need to workaround clang bug with clang (#ifde __clang__)? Thanks, Laurent
