+ AC_CACHE_CHECK([whether dup works], [gl_cv_func_dup_works],
+ [AC_RUN_IFELSE(
+ [AC_LANG_PROGRAM([[#include <unistd.h>
+ #include <fcntl.h>
+ #include <errno.h>]],
+ [[/* On OS/2 kLIBC, dup does not work on a directory fd. */
+ int fd = open (".", O_RDONLY);
+ return fd < 0 ? 1 : dup (fd) < 0 ? 2 : 0;
+ ]])
+ ],
+ [gl_cv_func_dup_works=yes],
+ [gl_cv_func_dup_works=no],
+ [case "$host_os" in
+ # Guess no on native Windows.
+ mingw*) gl_cv_func_dup_works="guessing no" ;;
+ *) gl_cv_func_dup_works="guessing yes" ;;
+ esac
+ ])
+ ])
+ case "$gl_cv_func_dup_works" in
+ *yes) ;;
+ *)
+ REPLACE_DUP=1
+ ;;
+ esac