AC_CHECK_HEADERS is missing newlines in autoconf-git current. This is starting with:
commit 0e2eecedb12dd472c9a008748be6edd6ea68fa0e Author: Paolo Bonzini <bonz...@gnu.org> Date: Mon Oct 31 18:08:07 2016 +0100 autoconf: prefer an unrolled loop for trivial AC_CHECK_HEADERS Here is the issue: (The PA_ADD_HEADERS stuff is from nasm configury) $ cat aclocal.m4 dnl -------------------------------------------------------------------------- dnl PA_ADD_HEADERS(headers...) dnl dnl Call AC_CHECK_HEADERS(), and add to ac_includes_default if found dnl -------------------------------------------------------------------------- AC_DEFUN(_PA_ADD_HEADER, [AC_CHECK_HEADERS([$1],[ac_includes_default="$ac_includes_default #include <$1>" ])]) AC_DEFUN(PA_ADD_HEADERS, [m4_map_args_w([$1],[_PA_ADD_HEADER(],[)])]) $ cat configure.ac AC_INIT PA_ADD_HEADERS(endian.h sys/endian.h machine/endian.h) The relevart parts of the diff between the good and the bad configure generated is the following: -done -for ac_header in sys/endian.h +donefor ac_header in sys/endian.h [...] -done -for ac_header in machine/endian.h +donefor ac_header in machine/endian.h As a result the generated configure fails to run, of course. -- O.S.