Autoconf 2.62 has changed the behaviour of the AC_AIX macro which we use.

Prior versions of autoconf defined _ALL_SOURCE if _AIX was defined. But,
autoconf 2.62 version of AC_AIX defines _ALL_SOURCE along with other four
preprocessor symbols no matter if the system is AIX or not. To keep the
traditional behaviour, as well as an uniform one, across autoconf versions
AC_AIX is replaced with our own internal macro.

CHANGES

@@ -1,6 +1,14 @@
   Changelog for the c-ares project
 
-* Aug 01 2008 (Yang Tse)
+* Aug 4 2008 (Yang Tse)
+- Autoconf 2.62 has changed the behaviour of the AC_AIX macro which we use.
+  Prior versions of autoconf defined _ALL_SOURCE if _AIX was defined. 2.62
+  version of AC_AIX defines _ALL_SOURCE and other four preprocessor symbols
+  no matter if the system is AIX or not. To keep the traditional behaviour,
+  and an uniform one across autoconf versions AC_AIX is replaced with our
+  own internal macro CARES_CHECK_AIX_ALL_SOURCE.
+
+* Aug 1 2008 (Yang Tse)
 - Configure process now checks if the preprocessor _REENTRANT symbol is already
   defined. If it isn't currently defined a set of checks are performed to test
   if its definition is required to make visible to the compiler a set of *_r

acinclude.m4

@@ -47,7 +47,7 @@ AC_DEFUN([CURL_CHECK_COMPILER_ARRAY_SIZE_NEGATIVE], [
 ])
 
 
-dnl CURL_CHECK_DEF(SYMBOL, [INCLUDES], [SILENT])
+dnl CURL_CHECK_DEF (SYMBOL, [INCLUDES], [SILENT])
 dnl -------------------------------------------------
 dnl Use the C preprocessor to find out if the given object-style symbol
 dnl is defined and get its expansion. This macro will not use default
@@ -94,6 +94,34 @@ CURL_DEF_TOKEN $1
 ])
 
 
+dnl CARES_CHECK_AIX_ALL_SOURCE
+dnl -------------------------------------------------
+dnl Provides a replacement of traditional AC_AIX with
+dnl an uniform behaviour across all autoconf versions,
+dnl and with our own placement rules.
+
+AC_DEFUN([CARES_CHECK_AIX_ALL_SOURCE], [
+  AH_VERBATIM([_ALL_SOURCE],
+    [/* Define to 1 if OS is AIX. */
+#ifndef _ALL_SOURCE
+#  undef _ALL_SOURCE
+#endif])
+  AC_BEFORE([$0], [AC_SYS_LARGEFILE])dnl
+  AC_BEFORE([$0], [CARES_CONFIGURE_REENTRANT])dnl
+  AC_MSG_CHECKING([if OS is AIX (to define _ALL_SOURCE)])
+  AC_EGREP_CPP([yes_this_is_aix],[
+#ifdef _AIX
+   yes_this_is_aix
+#endif
+  ],[
+    AC_MSG_RESULT([yes])
+    AC_DEFINE(_ALL_SOURCE)
+  ],[
+    AC_MSG_RESULT([no])
+  ])
+])
+
+
 dnl CURL_CHECK_HEADER_WINDOWS
 dnl -------------------------------------------------
 dnl Check for compilable and valid windows.h header 

configure.ac

@@ -64,11 +64,13 @@ AC_CANONICAL_HOST
 dnl Get system canonical name
 AC_DEFINE_UNQUOTED(OS, "${host}", [cpu-machine-OS])
 
-AC_AIX
 AC_PROG_CC
 AM_PROG_CC_C_O
 AC_PROG_INSTALL
 
+dnl This defines _ALL_SOURCE for AIX
+CARES_CHECK_AIX_ALL_SOURCE
+
 dnl Our configure and build reentrant settings
 CARES_CONFIGURE_REENTRANT