Super unnecessary snarkiness. On Fri, Apr 16, 2021, 8:00 PM Rich Felker wrote: > On Fri, Apr 16, 2021 at 06:12:52PM -0400, James Y Knight wrote: > > Ugh, I thought Clang had added support for this years ago. But it looks > > like the change (https://reviews.llvm.org/D34158) never actually made it > > in; it ran into some test failures after being committed and was > > reverted, and then never reapplied. :( > > The story of LLVM.. Random junk getting committed and kept, actually > important and correct changes getting reverted because of bogus tests. > > Rich > > > On Fri, Apr 16, 2021 at 2:51 PM Rich Felker wrote: > > > > > On Fri, Apr 16, 2021 at 02:57:21PM -0300, Érico Nogueira wrote: > > > > Em 16/04/2021 11:26, Rich Felker escreveu: > > > > >On Thu, Apr 15, 2021 at 09:35:21PM -0300, Érico Nogueira wrote: > > > > >>GCC source code does contain a function to pre-include the > > > > >> header for glibc targets, but even so glibc still > > > > > > > > I seem to have been mistaken about the feature being glibc specific; > > > using > > > > > > > > echo "" | cc -xc - -E > > > > > > > > it seems the file does end up being included automatically. > > > > > > > > However, when using clang instead of gcc, it isn't included > > > > automatically. I don't know if this is something that clang ought to > > > > fix, is there some sort of standard about ? Michael > > > > Forney's cproc compiler doesn't seem to touch it either. > > > > > > It's not a standard, but given that it's established I don't see any > > > reasonable argument for other compilers not to just do the same. You > > > can always fix them manually with CC="clang -include stdc-predef.h" or > > > similar though. > > > > > > > >>includes it in their own header. furthermore, even if > GCC > > > > >>implemented this for musl targets, it is still necessary for other > > > > >>compilers or previous versions of GCC. > > > > >>--- > > > > >> include/features.h | 2 ++ > > > > >> 1 file changed, 2 insertions(+) > > > > >> > > > > >>diff --git a/include/features.h b/include/features.h > > > > >>index 85cfb72a..f3d53cbe 100644 > > > > >>--- a/include/features.h > > > > >>+++ b/include/features.h > > > > >>@@ -1,6 +1,8 @@ > > > > >> #ifndef _FEATURES_H > > > > >> #define _FEATURES_H > > > > >>+#include > > > > >>+ > > > > >> #if defined(_ALL_SOURCE) && !defined(_GNU_SOURCE) > > > > >> #define _GNU_SOURCE 1 > > > > >> #endif > > > > >>-- > > > > >>2.31.1 > > > > > > > > > >I've hesitated to do this because features.h is not consistently > > > > >included from all standard headers (only if it's needed), and the > > > > >result would be inconsistent exposure of these macros. (Also > > > > >inconsistent if they're checked before any standard headers are > > > > >included, which is unfixable.) I think it makes more sense to just > add > > > > >"-include stdc-predef.h" to the compiler specfile or equivalent if > it > > > > >doesn't auto-include it, so that you get behavior that actually > > > > >matches the spec. > > > > > > > > Do you know if clang can use the specfile? That would make it worth > > > > it adding the entry, since GCC has the expected behavior already. > > > > > > No; specfiles are highly tied to GCC's compiler driver architecture. > > > clang might have some other equivalent mechanism though. > > > > > > Rich > > > >