+ dnl cygwin 1.5.x F_DUPFD has wrong errno, and allows negative target
+ dnl haiku alpha 2 F_DUPFD has wrong errno
+ AC_CACHE_CHECK([whether fcntl handles F_DUPFD correctly],
+ [gl_cv_func_fcntl_f_dupfd_works],
+ [AC_RUN_IFELSE([AC_LANG_PROGRAM([[
+#include <fcntl.h>
+#include <errno.h>
+]], [[int result = 0;
+ if (fcntl (0, F_DUPFD, -1) != -1) result |= 1;
+ if (errno != EINVAL) result |= 2;
+ return result;
+ ]])],
+ [gl_cv_func_fcntl_f_dupfd_works=yes],
+ [gl_cv_func_fcntl_f_dupfd_works=no],
+ [# Guess that it works on glibc systems
+ case $host_os in #((
+ *-gnu*) gl_cv_func_fcntl_f_dupfd_works="guessing yes";;
+ *) gl_cv_func_fcntl_f_dupfd_works="guessing no";;
+ esac])])
+ case $gl_cv_func_fcntl_f_dupfd_works in
+ *yes) ;;
+ *) gl_REPLACE_FCNTL
+ AC_DEFINE([FCNTL_DUPFD_BUGGY], [1], [Define this to 1 if F_DUPFD
+ behavior does not match POSIX]) ;;
+ esac
+
+ dnl Many systems lack F_DUPFD_CLOEXEC