1 files changed, 54 insertions, 0 deletions
diff --git a/m4/dup.m4 b/m4/dup.m4
new file mode 100644
index 0000000..892de99
--- /dev/null
+++ b/m4/dup.m4
@@ -0,0 +1,54 @@
+# dup.m4 serial 7
+dnl Copyright (C) 2011-2020 Free Software Foundation, Inc.
+dnl This file is free software; the Free Software Foundation
+dnl gives unlimited permission to copy and/or distribute it,
+dnl with or without modifications, as long as this notice is preserved.
+
+AC_DEFUN([gl_FUNC_DUP],
+[
+  AC_REQUIRE([gl_UNISTD_H_DEFAULTS])
+  AC_REQUIRE([AC_CANONICAL_HOST]) dnl for cross-compiles
+  m4_ifdef([gl_MSVC_INVAL], [
+    AC_REQUIRE([gl_MSVC_INVAL])
+    if test $HAVE_MSVC_INVALID_PARAMETER_HANDLER = 1; then
+      REPLACE_DUP=1
+    fi
+  ])
+  dnl Replace dup() for supporting the gnulib-defined fchdir() function,
+  dnl to keep fchdir's bookkeeping up-to-date.
+  m4_ifdef([gl_FUNC_FCHDIR], [
+    gl_TEST_FCHDIR
+    if test $HAVE_FCHDIR = 0; then
+      REPLACE_DUP=1
+    fi
+  ])
+  AC_CACHE_CHECK([whether dup works], [gl_cv_func_dup_works],
+    [AC_RUN_IFELSE(
+      [AC_LANG_PROGRAM([[#include <unistd.h>
+                         #include <fcntl.h>
+                         #include <errno.h>
+                       ]GL_MDA_DEFINES],
+         [[/* On OS/2 kLIBC, dup does not work on a directory fd.  */
+           int fd = open (".", O_RDONLY);
+           return fd < 0 ? 1 : dup (fd) < 0 ? 2 : 0;
+         ]])
+      ],
+      [gl_cv_func_dup_works=yes],
+      [gl_cv_func_dup_works=no],
+      [case "$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
+])
+
+# Prerequisites of lib/dup.c.
+AC_DEFUN([gl_PREREQ_DUP], [:])