https://gcc.gnu.org/bugzilla/show_bug.cgi?id=68176
--- Comment #6 from joseph at codesourcery dot com <joseph at codesourcery dot com> --- The original concept for stdc-predef.h includes that it might include other headers - in particular, that it might #include_next <stdc-predef.h>, so that e.g. libdfp could provide its own stdc-predef.h that defines relevant __STDC_* macros to say that DFP library functionality is available before including the glibc version, when you use -isystem /usr/include/dfp. Now, libdfp currently doesn't do that, and such use of libdfp might not be expected to work with PCH, so fixincluding may well be sufficient for this bug at present.
