--- dante-1.4.2/acinclude.m4.orig	2017-01-23 20:28:08.000000000 +0100
+++ dante-1.4.2/acinclude.m4	2017-04-16 11:08:02.385924479 +0200
@@ -1106,6 +1106,8 @@
 dnl test function that tries to determine if a specified errno error exists
 m4_define([checkerrno],
  [AC_MSG_CHECKING(for errno symbol $3)
+  CPPFLAGS_save="$CPPFLAGS"
+  CPPFLAGS="$CPPFLAGS -P"
   AC_PREPROC_IFELSE(
        [AC_LANG_PROGRAM([[#include <errno.h>]],
                         [[
@@ -1117,7 +1119,9 @@
        [AC_MSG_RESULT([OK])
         $1="$$1 $3"
         cat conftest.i | grep errnoval: >>$2],
-       [AC_MSG_RESULT([no])])])
+       [AC_MSG_RESULT([no])])
+  CPPFLAGS="$CPPFLAGS_save"
+])
 AC_DEFUN([L_CHECKERRNO],
  [checkerrno($@)])
 
@@ -1127,8 +1131,11 @@
 dnl test function that tries to determine if a specified errno error exists
 m4_define([checkgaierror],
  [AC_MSG_CHECKING(for getaddrinfo() error $3)
+  CPPFLAGS_save="$CPPFLAGS"
+  CPPFLAGS="$CPPFLAGS -P"
   AC_PREPROC_IFELSE(
        [AC_LANG_PROGRAM([[
+//#define _GNU_SOURCE 1
 #include <sys/types.h>
 #include <sys/socket.h>
 #include <netdb.h>]],
@@ -1142,7 +1149,9 @@
         $1="$$1 $3"
         AC_DEFINE(HAVE_ERR_$3, 1, [$3 gai error found])
         cat conftest.i | grep gaierrval: >>$2],
-       [AC_MSG_RESULT([no])])])
+       [AC_MSG_RESULT([no])])
+  CPPFLAGS="$CPPFLAGS_save"
+])
 AC_DEFUN([L_CHECKGAIERROR],
  [checkgaierror($@)])