Due to a bug, GCC warns about forward declarations like: class JS_PUBLIC_API(Foo); If the definition of Foo has already been seen. Bug 1346389 added JS_BROKEN_GCC_ATTRIBUTE_WARNING, which is conditionally defined for GCC versions <= 6.4 and can be used to ignore these warnings. However this bug is still not fixed in latest GCC versions and building with GCC version > 6.4 will generate these warnings. The GCC bug is here: https://gcc.gnu.org/bugzilla/show_bug.cgi?id=50044

GCC 8 feature development has finished and there's no indication the bug will be fixed, so here's a patch to extend this macro to cover GCC up to 8.0.

Comment on attachment 8930086 [details] [diff] [review] bug1419002-gcc-forward-decls Review of attachment 8930086 [details] [diff] [review]: ----------------------------------------------------------------- ::: js/src/jstypes.h @@ +96,5 @@ > // gcc is buggy and warns on our attempts to JS_PUBLIC_API our > // forward-declarations or explicit template instantiations. See > // <https://gcc.gnu.org/bugzilla/show_bug.cgi?id=50044>. Add a way to detect > // that so we can locally disable that warning. > +#if !defined(__clang__) && defined(__GNUC__) && (__GNUC__ < 8 || (__GNUC__ == 8 && __GNUC_MINOR__ == 0)) Mind splitting this into #if MOZ_IS_GCC # if !MOZ_GCC_VERSION_AT_LEAST(8, 0, 0) # define JS_BROKEN_GCC_ATTRIBUTE_WARNING # endif #endif so we don't have to touch the entirety of the condition, just the parts of it that are actually busted?

Pushed by jcoppeard@mozilla.com: https://hg.mozilla.org/integration/mozilla-inbound/rev/0b6b9f1e29a9 Extend JS_BROKEN_GCC_ATTRIBUTE_WARNING up to GCC 8.0 r=Waldo