+ else
+ AC_CACHE_CHECK([whether dup2 works], [gl_cv_func_dup2_works],
+ [AC_RUN_IFELSE([
+ AC_LANG_PROGRAM([[#include <unistd.h>
+#include <errno.h>]],
+ [if (dup2 (1, 1) == 0)
+ return 1;
+ close (0);
+ if (dup2 (0, 0) != -1)
+ return 2;
+ /* Many gnulib modules require POSIX conformance of EBADF. */
+ if (dup2 (1, 1000000) == -1 && errno != EBADF)
+ return 3;
+ return 0;
+ ])
+ ],
+ [gl_cv_func_dup2_works=yes], [gl_cv_func_dup2_works=no],
+ [case "$host_os" in
+ mingw*) # on this platform, dup2 always returns 0 for success
+ gl_cv_func_dup2_works=no;;
+ cygwin*) # on cygwin 1.5.x, dup2(1,1) returns 0
+ gl_cv_func_dup2_works=no;;
+ linux*) # On linux between 2008-07-27 and 2009-05-11, dup2 of a
+ # closed fd may yield -EBADF instead of -1 / errno=EBADF.
+ gl_cv_func_dup2_works=no;;
+ freebsd*) # on FreeBSD 6.1, dup2(1,1000000) gives EMFILE, not EBADF.
+ gl_cv_func_dup2_works=no;;
+ *) gl_cv_func_dup2_works=yes;;
+ esac])
+ ])
+ if test "$gl_cv_func_dup2_works" = no; then
+ gl_REPLACE_DUP2
+ fi