https://gcc.gnu.org/bugzilla/show_bug.cgi?id=109926
--- Comment #6 from Jonathan Wakely <redi at gcc dot gnu.org> ---
Please provide the i586-msdosdjgpp/libstdc++-v3/config.log file, not the
top-level one from configuring gcc.
The libstdc++ fenv.h has:
#include <bits/c++config.h>
#if _GLIBCXX_HAVE_FENV_H
# include_next <fenv.h>
#endif
And that check comes from:
AC_CHECK_HEADERS(fenv.h, ac_has_fenv_h=yes, ac_has_fenv_h=no)
So something is wrong with your config.
