c-ares' -no-undefined and --enable-curldebug adjustments

m4/cares-compilers.m4

@@ -16,7 +16,7 @@
 #***************************************************************************
 
 # File version for 'aclocal' use. Keep it a single number.
-# serial 54
+# serial 55
 
 
 dnl CARES_CHECK_COMPILER
@@ -1077,8 +1077,10 @@ dnl Settings which depend on configure's curldebug given
 dnl option, and other additional configure pre-requisites.
 dnl Using the curl debug memory tracking feature in c-ares
 dnl is a hack that actually can only be used/enabled when
-dnl c-ares is built as a static library directly in curl's
-dnl CVS tree along with an equally configured libcurl.
+dnl c-ares is built directly in curl's CVS tree, as a static
+dnl library or as a shared one on those systems on which
+dnl shared libraries support undefined symbols, along with
+dnl an equally configured libcurl.
 
 AC_DEFUN([CARES_CHECK_CURLDEBUG], [
   AC_REQUIRE([CARES_SHFUNC_SQUEEZE])dnl
@@ -1146,6 +1148,7 @@ AC_DEFUN([CARES_CHECK_CURLDEBUG], [
   fi
   #
   if test "$want_curldebug" = "yes"; then
+    dnl TODO: Verify if the BUILDING_LIBCURL definition is still required.
     AC_DEFINE(BUILDING_LIBCURL, 1, [when building as static part of libcurl])
     CPPFLAGS="$CPPFLAGS -DCURLDEBUG"
     squeeze CPPFLAGS
@@ -1155,13 +1158,18 @@ AC_DEFUN([CARES_CHECK_CURLDEBUG], [
 
 dnl CARES_CHECK_NO_UNDEFINED
 dnl -------------------------------------------------
+dnl Checks if the -no-undefined flag must be used when
+dnl building shared libraries. This is required on all
+dnl systems on which shared libraries should not have
+dnl references to undefined symbols. This check should
+dnl not be done before AC-PROG-LIBTOOL.
 
 AC_DEFUN([CARES_CHECK_NO_UNDEFINED], [
   AC_BEFORE([$0],[CARES_CHECK_CURLDEBUG])dnl
-  AC_MSG_CHECKING([if we need -no-undefined])
+  AC_MSG_CHECKING([if shared libraries need -no-undefined])
   need_no_undefined="no"
   case $host in
-    *-*-cygwin* | *-*-mingw* | *-*-pw32* | *-*-cegcc*)
+    *-*-cygwin* | *-*-mingw* | *-*-pw32* | *-*-cegcc* | *-*-aix*)
       need_no_undefined="yes"
       ;;
   esac
@@ -1170,11 +1178,6 @@ AC_DEFUN([CARES_CHECK_NO_UNDEFINED], [
   elif test "x$allow_undefined_flag" = "xunsupported"; then
     need_no_undefined="yes"
   fi
-  case $compiler_id in
-    IBM_C | INTEL_UNIX_C | INTEL_WINDOWS_C | SUNPRO_C)
-      need_no_undefined="yes"
-      ;;
-  esac
   AC_MSG_RESULT($need_no_undefined)
 ])