cares-functions.m4: update thread-safeness detection of getaddrinfo()

Take in account that POSIX standard Issue 7 drops h_errno support. Now, we also
consider getaddrinfo() to be thread-safe when (_POSIX_C_SOURCE >= 200809L) or
(_XOPEN_SOURCE >= 700) independently of whether h_errno exists or not.

Take in account that h_errno might be a modifiable lvalue not defined as
a C preprocessor macro.

diff --git a/m4/cares-functions.m4 b/m4/cares-functions.m4
index 68d2ba9..0deb6de 100644 (file)
--- a/m4/cares-functions.m4
+++ b/m4/cares-functions.m4
@@ -1,6 +1,6 @@
 #***************************************************************************
 #
-# Copyright (C) 2008 - 2011 by Daniel Stenberg et al
+# Copyright (C) 2008 - 2012 by Daniel Stenberg et al
 #
 # Permission to use, copy, modify, and distribute this software and its
 # documentation for any purpose and without fee is hereby granted, provided
@@ -15,7 +15,7 @@
 #***************************************************************************
 
 # File version for 'aclocal' use. Keep it a single number.
-# serial 43
+# serial 44
 
 
 dnl CARES_INCLUDES_ARPA_INET
@@ -883,6 +883,7 @@ AC_DEFUN([CARES_CHECK_FUNC_GETADDRINFO], [
   AC_REQUIRE([CARES_INCLUDES_STRING])dnl
   AC_REQUIRE([CARES_INCLUDES_SYS_SOCKET])dnl
   AC_REQUIRE([CARES_INCLUDES_NETDB])dnl
+  AC_REQUIRE([CURL_CHECK_NATIVE_WINDOWS])dnl
   #
   tst_links_getaddrinfo="unknown"
   tst_proto_getaddrinfo="unknown"
@@ -1059,19 +1060,58 @@ AC_DEFUN([CARES_CHECK_FUNC_GETADDRINFO], [
         tst_tsafe_getaddrinfo="yes"
         ;;
     esac
+    if test "$tst_tsafe_getaddrinfo" = "unknown" &&
+       test "$ac_cv_native_windows" = "yes"; then
+      tst_tsafe_getaddrinfo="yes"
+    fi
     if test "$tst_tsafe_getaddrinfo" = "unknown"; then
       CURL_CHECK_DEF_CC([h_errno], [
-        $cares_includes_ws2tcpip
         $cares_includes_sys_socket
         $cares_includes_netdb
         ], [silent])
-      if test "$curl_cv_have_def_h_errno" = "no"; then
+      if test "$curl_cv_have_def_h_errno" = "yes"; then
+        tst_h_errno_macro="yes"
+      else
+        tst_h_errno_macro="no"
+      fi
+      AC_COMPILE_IFELSE([
+        AC_LANG_PROGRAM([[
+          $cares_includes_sys_socket
+          $cares_includes_netdb
+        ]],[[
+          h_errno = 2;
+          if(0 != h_errno)
+            return 1;
+        ]])
+      ],[
+        tst_h_errno_modifiable_lvalue="yes"
+      ],[
+        tst_h_errno_modifiable_lvalue="no"
+      ])
+      AC_COMPILE_IFELSE([
+        AC_LANG_PROGRAM([[
+        ]],[[
+#if defined(_POSIX_C_SOURCE) && (_POSIX_C_SOURCE >= 200809L)
+          return 0;
+#elif defined(_XOPEN_SOURCE) && (_XOPEN_SOURCE >= 700)
+          return 0;
+#else
+          force compilation error
+#endif
+        ]])
+      ],[
+        tst_h_errno_sbs_issue_7="yes"
+      ],[
+        tst_h_errno_sbs_issue_7="no"
+      ])
+      if test "$tst_h_errno_macro" = "no" &&
+         test "$tst_h_errno_modifiable_lvalue" = "no" &&
+         test "$tst_h_errno_sbs_issue_7" = "no"; then
         tst_tsafe_getaddrinfo="no"
+      else
+        tst_tsafe_getaddrinfo="yes"
       fi
     fi
-    if test "$tst_tsafe_getaddrinfo" = "unknown"; then
-      tst_tsafe_getaddrinfo="yes"
-    fi
     AC_MSG_RESULT([$tst_tsafe_getaddrinfo])
     if test "$tst_tsafe_getaddrinfo" = "yes"; then
       AC_DEFINE_UNQUOTED(HAVE_GETADDRINFO_THREADSAFE, 1,