posix: Add test case for gai_strerror()

Signed-off-by: Dridi Boukelmoune <dridi.boukelmoune@gmail.com>
Reviewed-by: Arjun Shankar <arjun@redhat.com>

posix/Makefile

@@ -275,6 +275,7 @@ tests := \
   tst-fnmatch6 \
   tst-fnmatch7 \
   tst-fork \
+  tst-gai_strerror \
   tst-getaddrinfo \
   tst-getaddrinfo2 \
   tst-getaddrinfo3 \

posix/tst-gai_strerror.c

@@ -0,0 +1,43 @@
+/* Test for gai_strerror()
+   Copyright The GNU Toolchain Authors.
+   This file is part of the GNU C Library.
+
+   The GNU C Library is free software; you can redistribute it and/or
+   modify it under the terms of the GNU Lesser General Public
+   License as published by the Free Software Foundation; either
+   version 2.1 of the License, or (at your option) any later version.
+
+   The GNU C Library is distributed in the hope that it will be useful,
+   but WITHOUT ANY WARRANTY; without even the implied warranty of
+   MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the GNU
+   Lesser General Public License for more details.
+
+   You should have received a copy of the GNU Lesser General Public
+   License along with the GNU C Library; if not, see
+   <https://www.gnu.org/licenses/>.  */
+
+#include <sys/types.h>
+#include <sys/socket.h>
+#include <netdb.h>
+#include <stdlib.h>
+#include <locale.h>
+
+#include <support/support.h>
+#include <support/check.h>
+
+static int
+do_test (void)
+{
+  unsetenv ("LANGUAGE");
+
+  xsetlocale (LC_ALL, "C");
+
+  TEST_COMPARE_STRING (gai_strerror (1), "Unknown error");
+  TEST_COMPARE_STRING (gai_strerror (0), "Success");
+  TEST_COMPARE_STRING (gai_strerror (EAI_OVERFLOW),
+                       "Result too large for supplied buffer");
+
+  return 0;
+}
+
+#include <support/test-driver.c>