diff --git a/m4/cares-compilers.m4 b/m4/cares-compilers.m4
index 2b98a68..a4e1636 100644
--- a/m4/cares-compilers.m4
+++ b/m4/cares-compilers.m4
@@ -142,19 +142,12 @@ AC_DEFUN([CARES_CHECK_COMPILER_GNU_C], [
     gccvhi=`echo $gccver | cut -d . -f1`
     gccvlo=`echo $gccver | cut -d . -f2`
     compiler_num=`(expr $gccvhi "*" 100 + $gccvlo) 2>/dev/null`
-    flags_dbg_all="-g -g0 -g1 -g2 -g3"
-    flags_dbg_all="$flags_dbg_all -ggdb"
-    flags_dbg_all="$flags_dbg_all -gstabs"
-    flags_dbg_all="$flags_dbg_all -gstabs+"
-    flags_dbg_all="$flags_dbg_all -gcoff"
-    flags_dbg_all="$flags_dbg_all -gxcoff"
-    flags_dbg_all="$flags_dbg_all -gdwarf-2"
-    flags_dbg_all="$flags_dbg_all -gvms"
-    flags_dbg_yes="-g"
-    flags_dbg_off="-g0"
-    flags_opt_all="-O -O0 -O1 -O2 -O3 -Os"
-    flags_opt_yes="-O2"
-    flags_opt_off="-O0"
+    flags_dbg_all=""
+    flags_dbg_yes=""
+    flags_dbg_off=""
+    flags_opt_all=""
+    flags_opt_yes=""
+    flags_opt_off=""
     CURL_CHECK_DEF([_WIN32], [], [silent])
   else
     AC_MSG_RESULT([no])
diff --git a/m4/cares-compilers.m4.optflags b/m4/cares-compilers.m4.optflags
new file mode 100644
index 0000000..2b98a68
--- /dev/null
+++ b/m4/cares-compilers.m4.optflags
@@ -0,0 +1,1587 @@
+#***************************************************************************
+#
+# Copyright (C) 2009-2013 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
+# that the above copyright notice appear in all copies and that both that
+# copyright notice and this permission notice appear in supporting
+# documentation, and that the name of M.I.T. not be used in advertising or
+# publicity pertaining to distribution of the software without specific,
+# written prior permission.  M.I.T. makes no representations about the
+# suitability of this software for any purpose.  It is provided "as is"
+# without express or implied warranty.
+#
+#***************************************************************************
+
+# File version for 'aclocal' use. Keep it a single number.
+# serial 75
+
+
+dnl CARES_CHECK_COMPILER
+dnl -------------------------------------------------
+dnl Verify if the C compiler being used is known.
+
+AC_DEFUN([CARES_CHECK_COMPILER], [
+  #
+  compiler_id="unknown"
+  compiler_num="0"
+  #
+  flags_dbg_all="unknown"
+  flags_dbg_yes="unknown"
+  flags_dbg_off="unknown"
+  flags_opt_all="unknown"
+  flags_opt_yes="unknown"
+  flags_opt_off="unknown"
+  #
+  flags_prefer_cppflags="no"
+  #
+  CARES_CHECK_COMPILER_DEC_C
+  CARES_CHECK_COMPILER_HPUX_C
+  CARES_CHECK_COMPILER_IBM_C
+  CARES_CHECK_COMPILER_INTEL_C
+  CARES_CHECK_COMPILER_CLANG
+  CARES_CHECK_COMPILER_GNU_C
+  CARES_CHECK_COMPILER_LCC
+  CARES_CHECK_COMPILER_SGI_MIPSPRO_C
+  CARES_CHECK_COMPILER_SGI_MIPS_C
+  CARES_CHECK_COMPILER_SUNPRO_C
+  CARES_CHECK_COMPILER_TINY_C
+  CARES_CHECK_COMPILER_WATCOM_C
+  #
+  if test "$compiler_id" = "unknown"; then
+  cat <<_EOF 1>&2
+***
+*** Warning: This configure script does not have information about the
+*** compiler you are using, relative to the flags required to enable or
+*** disable generation of debug info, optimization options or warnings.
+***
+*** Whatever settings are present in CFLAGS will be used for this run.
+***
+*** If you wish to help the c-ares project to better support your compiler
+*** you can report this and the required info on the c-ares development
+*** mailing list: http://cool.haxx.se/mailman/listinfo/c-ares/
+***
+_EOF
+  fi
+])
+
+
+dnl CARES_CHECK_COMPILER_CLANG
+dnl -------------------------------------------------
+dnl Verify if compiler being used is clang.
+
+AC_DEFUN([CARES_CHECK_COMPILER_CLANG], [
+  AC_BEFORE([$0],[CARES_CHECK_COMPILER_GNU_C])dnl
+  AC_MSG_CHECKING([if compiler is clang])
+  CURL_CHECK_DEF([__clang__], [], [silent])
+  if test "$curl_cv_have_def___clang__" = "yes"; then
+    AC_MSG_RESULT([yes])
+    compiler_id="CLANG"
+    clangver=`$CC -dumpversion`
+    clangvhi=`echo $clangver | cut -d . -f1`
+    clangvlo=`echo $clangver | cut -d . -f2`
+    compiler_num=`(expr $clangvhi "*" 100 + $clangvlo) 2>/dev/null`
+    flags_dbg_all="-g -g0 -g1 -g2 -g3"
+    flags_dbg_all="$flags_dbg_all -ggdb"
+    flags_dbg_all="$flags_dbg_all -gstabs"
+    flags_dbg_all="$flags_dbg_all -gstabs+"
+    flags_dbg_all="$flags_dbg_all -gcoff"
+    flags_dbg_all="$flags_dbg_all -gxcoff"
+    flags_dbg_all="$flags_dbg_all -gdwarf-2"
+    flags_dbg_all="$flags_dbg_all -gvms"
+    flags_dbg_yes="-g"
+    flags_dbg_off="-g0"
+    flags_opt_all="-O -O0 -O1 -O2 -Os -O3 -O4"
+    flags_opt_yes="-Os"
+    flags_opt_off="-O0"
+  else
+    AC_MSG_RESULT([no])
+  fi
+])
+
+
+dnl CARES_CHECK_COMPILER_DEC_C
+dnl -------------------------------------------------
+dnl Verify if compiler being used is DEC C.
+
+AC_DEFUN([CARES_CHECK_COMPILER_DEC_C], [
+  AC_MSG_CHECKING([if compiler is DEC/Compaq/HP C])
+  CURL_CHECK_DEF([__DECC], [], [silent])
+  CURL_CHECK_DEF([__DECC_VER], [], [silent])
+  if test "$curl_cv_have_def___DECC" = "yes" &&
+    test "$curl_cv_have_def___DECC_VER" = "yes"; then
+    AC_MSG_RESULT([yes])
+    compiler_id="DEC_C"
+    flags_dbg_all="-g -g0 -g1 -g2 -g3"
+    flags_dbg_yes="-g2"
+    flags_dbg_off="-g0"
+    flags_opt_all="-O -O0 -O1 -O2 -O3 -O4"
+    flags_opt_yes="-O1"
+    flags_opt_off="-O0"
+  else
+    AC_MSG_RESULT([no])
+  fi
+])
+
+
+dnl CARES_CHECK_COMPILER_GNU_C
+dnl -------------------------------------------------
+dnl Verify if compiler being used is GNU C.
+
+AC_DEFUN([CARES_CHECK_COMPILER_GNU_C], [
+  AC_REQUIRE([CARES_CHECK_COMPILER_INTEL_C])dnl
+  AC_REQUIRE([CARES_CHECK_COMPILER_CLANG])dnl
+  AC_MSG_CHECKING([if compiler is GNU C])
+  CURL_CHECK_DEF([__GNUC__], [], [silent])
+  if test "$curl_cv_have_def___GNUC__" = "yes" &&
+    test "$compiler_id" = "unknown"; then
+    AC_MSG_RESULT([yes])
+    compiler_id="GNU_C"
+    gccver=`$CC -dumpversion`
+    gccvhi=`echo $gccver | cut -d . -f1`
+    gccvlo=`echo $gccver | cut -d . -f2`
+    compiler_num=`(expr $gccvhi "*" 100 + $gccvlo) 2>/dev/null`
+    flags_dbg_all="-g -g0 -g1 -g2 -g3"
+    flags_dbg_all="$flags_dbg_all -ggdb"
+    flags_dbg_all="$flags_dbg_all -gstabs"
+    flags_dbg_all="$flags_dbg_all -gstabs+"
+    flags_dbg_all="$flags_dbg_all -gcoff"
+    flags_dbg_all="$flags_dbg_all -gxcoff"
+    flags_dbg_all="$flags_dbg_all -gdwarf-2"
+    flags_dbg_all="$flags_dbg_all -gvms"
+    flags_dbg_yes="-g"
+    flags_dbg_off="-g0"
+    flags_opt_all="-O -O0 -O1 -O2 -O3 -Os"
+    flags_opt_yes="-O2"
+    flags_opt_off="-O0"
+    CURL_CHECK_DEF([_WIN32], [], [silent])
+  else
+    AC_MSG_RESULT([no])
+  fi
+])
+
+
+dnl CARES_CHECK_COMPILER_HPUX_C
+dnl -------------------------------------------------
+dnl Verify if compiler being used is HP-UX C.
+
+AC_DEFUN([CARES_CHECK_COMPILER_HPUX_C], [
+  AC_MSG_CHECKING([if compiler is HP-UX C])
+  CURL_CHECK_DEF([__HP_cc], [], [silent])
+  if test "$curl_cv_have_def___HP_cc" = "yes"; then
+    AC_MSG_RESULT([yes])
+    compiler_id="HP_UX_C"
+    flags_dbg_all="-g -s"
+    flags_dbg_yes="-g"
+    flags_dbg_off="-s"
+    flags_opt_all="-O +O0 +O1 +O2 +O3 +O4"
+    flags_opt_yes="+O2"
+    flags_opt_off="+O0"
+  else
+    AC_MSG_RESULT([no])
+  fi
+])
+
+
+dnl CARES_CHECK_COMPILER_IBM_C
+dnl -------------------------------------------------
+dnl Verify if compiler being used is IBM C.
+
+AC_DEFUN([CARES_CHECK_COMPILER_IBM_C], [
+  AC_MSG_CHECKING([if compiler is IBM C])
+  CURL_CHECK_DEF([__IBMC__], [], [silent])
+  if test "$curl_cv_have_def___IBMC__" = "yes"; then
+    AC_MSG_RESULT([yes])
+    compiler_id="IBM_C"
+    flags_dbg_all="-g -g0 -g1 -g2 -g3"
+    flags_dbg_yes="-g"
+    flags_dbg_off=""
+    flags_opt_all="-O -O0 -O1 -O2 -O3 -O4 -O5"
+    flags_opt_all="$flags_opt_all -qnooptimize"
+    flags_opt_all="$flags_opt_all -qoptimize=0"
+    flags_opt_all="$flags_opt_all -qoptimize=1"
+    flags_opt_all="$flags_opt_all -qoptimize=2"
+    flags_opt_all="$flags_opt_all -qoptimize=3"
+    flags_opt_all="$flags_opt_all -qoptimize=4"
+    flags_opt_all="$flags_opt_all -qoptimize=5"
+    flags_opt_yes="-O2"
+    flags_opt_off="-qnooptimize"
+    flags_prefer_cppflags="yes"
+  else
+    AC_MSG_RESULT([no])
+  fi
+])
+
+
+dnl CARES_CHECK_COMPILER_INTEL_C
+dnl -------------------------------------------------
+dnl Verify if compiler being used is Intel C.
+
+AC_DEFUN([CARES_CHECK_COMPILER_INTEL_C], [
+  AC_BEFORE([$0],[CARES_CHECK_COMPILER_GNU_C])dnl
+  AC_MSG_CHECKING([if compiler is Intel C])
+  CURL_CHECK_DEF([__INTEL_COMPILER], [], [silent])
+  if test "$curl_cv_have_def___INTEL_COMPILER" = "yes"; then
+    AC_MSG_RESULT([yes])
+    compiler_num="$curl_cv_def___INTEL_COMPILER"
+    CURL_CHECK_DEF([__unix__], [], [silent])
+    if test "$curl_cv_have_def___unix__" = "yes"; then
+      compiler_id="INTEL_UNIX_C"
+      flags_dbg_all="-g -g0"
+      flags_dbg_yes="-g"
+      flags_dbg_off="-g0"
+      flags_opt_all="-O -O0 -O1 -O2 -O3 -Os"
+      flags_opt_yes="-O2"
+      flags_opt_off="-O0"
+    else
+      compiler_id="INTEL_WINDOWS_C"
+      flags_dbg_all="/ZI /Zi /zI /zi /ZD /Zd /zD /zd /Z7 /z7 /Oy /Oy-"
+      flags_dbg_all="$flags_dbg_all /debug"
+      flags_dbg_all="$flags_dbg_all /debug:none"
+      flags_dbg_all="$flags_dbg_all /debug:minimal"
+      flags_dbg_all="$flags_dbg_all /debug:partial"
+      flags_dbg_all="$flags_dbg_all /debug:full"
+      flags_dbg_all="$flags_dbg_all /debug:semantic_stepping"
+      flags_dbg_all="$flags_dbg_all /debug:extended"
+      flags_dbg_yes="/Zi /Oy-"
+      flags_dbg_off="/debug:none /Oy-"
+      flags_opt_all="/O /O0 /O1 /O2 /O3 /Od /Og /Og- /Oi /Oi-"
+      flags_opt_yes="/O2"
+      flags_opt_off="/Od"
+    fi
+  else
+    AC_MSG_RESULT([no])
+  fi
+])
+
+
+dnl CARES_CHECK_COMPILER_LCC
+dnl -------------------------------------------------
+dnl Verify if compiler being used is LCC.
+
+AC_DEFUN([CARES_CHECK_COMPILER_LCC], [
+  AC_MSG_CHECKING([if compiler is LCC])
+  CURL_CHECK_DEF([__LCC__], [], [silent])
+  if test "$curl_cv_have_def___LCC__" = "yes"; then
+    AC_MSG_RESULT([yes])
+    compiler_id="LCC"
+    flags_dbg_all="-g"
+    flags_dbg_yes="-g"
+    flags_dbg_off=""
+    flags_opt_all=""
+    flags_opt_yes=""
+    flags_opt_off=""
+  else
+    AC_MSG_RESULT([no])
+  fi
+])
+
+
+dnl CARES_CHECK_COMPILER_SGI_MIPS_C
+dnl -------------------------------------------------
+dnl Verify if compiler being used is SGI MIPS C.
+
+AC_DEFUN([CARES_CHECK_COMPILER_SGI_MIPS_C], [
+  AC_REQUIRE([CARES_CHECK_COMPILER_SGI_MIPSPRO_C])dnl
+  AC_MSG_CHECKING([if compiler is SGI MIPS C])
+  CURL_CHECK_DEF([__GNUC__], [], [silent])
+  CURL_CHECK_DEF([__sgi], [], [silent])
+  if test "$curl_cv_have_def___GNUC__" = "no" &&
+    test "$curl_cv_have_def___sgi" = "yes" &&
+    test "$compiler_id" = "unknown"; then
+    AC_MSG_RESULT([yes])
+    compiler_id="SGI_MIPS_C"
+    flags_dbg_all="-g -g0 -g1 -g2 -g3"
+    flags_dbg_yes="-g"
+    flags_dbg_off="-g0"
+    flags_opt_all="-O -O0 -O1 -O2 -O3 -Ofast"
+    flags_opt_yes="-O2"
+    flags_opt_off="-O0"
+  else
+    AC_MSG_RESULT([no])
+  fi
+])
+
+
+dnl CARES_CHECK_COMPILER_SGI_MIPSPRO_C
+dnl -------------------------------------------------
+dnl Verify if compiler being used is SGI MIPSpro C.
+
+AC_DEFUN([CARES_CHECK_COMPILER_SGI_MIPSPRO_C], [
+  AC_BEFORE([$0],[CARES_CHECK_COMPILER_SGI_MIPS_C])dnl
+  AC_MSG_CHECKING([if compiler is SGI MIPSpro C])
+  CURL_CHECK_DEF([__GNUC__], [], [silent])
+  CURL_CHECK_DEF([_COMPILER_VERSION], [], [silent])
+  CURL_CHECK_DEF([_SGI_COMPILER_VERSION], [], [silent])
+  if test "$curl_cv_have_def___GNUC__" = "no" &&
+    (test "$curl_cv_have_def__SGI_COMPILER_VERSION" = "yes" ||
+     test "$curl_cv_have_def__COMPILER_VERSION" = "yes"); then
+    AC_MSG_RESULT([yes])
+    compiler_id="SGI_MIPSPRO_C"
+    flags_dbg_all="-g -g0 -g1 -g2 -g3"
+    flags_dbg_yes="-g"
+    flags_dbg_off="-g0"
+    flags_opt_all="-O -O0 -O1 -O2 -O3 -Ofast"
+    flags_opt_yes="-O2"
+    flags_opt_off="-O0"
+  else
+    AC_MSG_RESULT([no])
+  fi
+])
+
+
+dnl CARES_CHECK_COMPILER_SUNPRO_C
+dnl -------------------------------------------------
+dnl Verify if compiler being used is SunPro C.
+
+AC_DEFUN([CARES_CHECK_COMPILER_SUNPRO_C], [
+  AC_MSG_CHECKING([if compiler is SunPro C])
+  CURL_CHECK_DEF([__SUNPRO_C], [], [silent])
+  if test "$curl_cv_have_def___SUNPRO_C" = "yes"; then
+    AC_MSG_RESULT([yes])
+    compiler_id="SUNPRO_C"
+    flags_dbg_all="-g -s"
+    flags_dbg_yes="-g"
+    flags_dbg_off="-s"
+    flags_opt_all="-O -xO -xO1 -xO2 -xO3 -xO4 -xO5"
+    flags_opt_yes="-xO2"
+    flags_opt_off=""
+  else
+    AC_MSG_RESULT([no])
+  fi
+])
+
+
+dnl CARES_CHECK_COMPILER_TINY_C
+dnl -------------------------------------------------
+dnl Verify if compiler being used is Tiny C.
+
+AC_DEFUN([CARES_CHECK_COMPILER_TINY_C], [
+  AC_MSG_CHECKING([if compiler is Tiny C])
+  CURL_CHECK_DEF([__TINYC__], [], [silent])
+  if test "$curl_cv_have_def___TINYC__" = "yes"; then
+    AC_MSG_RESULT([yes])
+    compiler_id="TINY_C"
+    flags_dbg_all="-g -b"
+    flags_dbg_yes="-g"
+    flags_dbg_off=""
+    flags_opt_all=""
+    flags_opt_yes=""
+    flags_opt_off=""
+  else
+    AC_MSG_RESULT([no])
+  fi
+])
+
+
+dnl CARES_CHECK_COMPILER_WATCOM_C
+dnl -------------------------------------------------
+dnl Verify if compiler being used is Watcom C.
+
+AC_DEFUN([CARES_CHECK_COMPILER_WATCOM_C], [
+  AC_MSG_CHECKING([if compiler is Watcom C])
+  CURL_CHECK_DEF([__WATCOMC__], [], [silent])
+  if test "$curl_cv_have_def___WATCOMC__" = "yes"; then
+    AC_MSG_RESULT([yes])
+    CURL_CHECK_DEF([__UNIX__], [], [silent])
+    if test "$curl_cv_have_def___UNIX__" = "yes"; then
+      compiler_id="WATCOM_UNIX_C"
+      flags_dbg_all="-g1 -g1+ -g2 -g3"
+      flags_dbg_yes="-g2"
+      flags_dbg_off=""
+      flags_opt_all="-O0 -O1 -O2 -O3"
+      flags_opt_yes="-O2"
+      flags_opt_off="-O0"
+    else
+      compiler_id="WATCOM_WINDOWS_C"
+      flags_dbg_all=""
+      flags_dbg_yes=""
+      flags_dbg_off=""
+      flags_opt_all=""
+      flags_opt_yes=""
+      flags_opt_off=""
+    fi
+  else
+    AC_MSG_RESULT([no])
+  fi
+])
+
+
+dnl CARES_CONVERT_INCLUDE_TO_ISYSTEM
+dnl -------------------------------------------------
+dnl Changes standard include paths present in CFLAGS
+dnl and CPPFLAGS into isystem include paths. This is
+dnl done to prevent GNUC from generating warnings on
+dnl headers from these locations, although on ancient
+dnl GNUC versions these warnings are not silenced.
+
+AC_DEFUN([CARES_CONVERT_INCLUDE_TO_ISYSTEM], [
+  AC_REQUIRE([CARES_SHFUNC_SQUEEZE])dnl
+  AC_REQUIRE([CARES_CHECK_COMPILER])dnl
+  if test "$compiler_id" = "GNU_C" ||
+    test "$compiler_id" = "CLANG"; then
+    tmp_has_include="no"
+    tmp_chg_FLAGS="$CFLAGS"
+    for word1 in $tmp_chg_FLAGS; do
+      case "$word1" in
+        -I*)
+          tmp_has_include="yes"
+          ;;
+      esac
+    done
+    if test "$tmp_has_include" = "yes"; then
+      tmp_chg_FLAGS=`echo "$tmp_chg_FLAGS" | "$SED" 's/^-I/ -isystem /g'`
+      tmp_chg_FLAGS=`echo "$tmp_chg_FLAGS" | "$SED" 's/ -I/ -isystem /g'`
+      CFLAGS="$tmp_chg_FLAGS"
+      squeeze CFLAGS
+    fi
+    tmp_has_include="no"
+    tmp_chg_FLAGS="$CPPFLAGS"
+    for word1 in $tmp_chg_FLAGS; do
+      case "$word1" in
+        -I*)
+          tmp_has_include="yes"
+          ;;
+      esac
+    done
+    if test "$tmp_has_include" = "yes"; then
+      tmp_chg_FLAGS=`echo "$tmp_chg_FLAGS" | "$SED" 's/^-I/ -isystem /g'`
+      tmp_chg_FLAGS=`echo "$tmp_chg_FLAGS" | "$SED" 's/ -I/ -isystem /g'`
+      CPPFLAGS="$tmp_chg_FLAGS"
+      squeeze CPPFLAGS
+    fi
+  fi
+])
+
+
+dnl CARES_COMPILER_WORKS_IFELSE ([ACTION-IF-WORKS], [ACTION-IF-NOT-WORKS])
+dnl -------------------------------------------------
+dnl Verify if the C compiler seems to work with the
+dnl settings that are 'active' at the time the test
+dnl is performed.
+
+AC_DEFUN([CARES_COMPILER_WORKS_IFELSE], [
+  dnl compilation capability verification
+  tmp_compiler_works="unknown"
+  AC_COMPILE_IFELSE([
+    AC_LANG_PROGRAM([[
+    ]],[[
+      int i = 1;
+      return i;
+    ]])
+  ],[
+    tmp_compiler_works="yes"
+  ],[
+    tmp_compiler_works="no"
+    echo " " >&6
+    sed 's/^/cc-fail: /' conftest.err >&6
+    echo " " >&6
+  ])
+  dnl linking capability verification
+  if test "$tmp_compiler_works" = "yes"; then
+    AC_LINK_IFELSE([
+      AC_LANG_PROGRAM([[
+      ]],[[
+        int i = 1;
+        return i;
+      ]])
+    ],[
+      tmp_compiler_works="yes"
+    ],[
+      tmp_compiler_works="no"
+      echo " " >&6
+      sed 's/^/link-fail: /' conftest.err >&6
+      echo " " >&6
+    ])
+  fi
+  dnl only do runtime verification when not cross-compiling
+  if test "x$cross_compiling" != "xyes" &&
+    test "$tmp_compiler_works" = "yes"; then
+    AC_RUN_IFELSE([
+      AC_LANG_PROGRAM([[
+#       ifdef __STDC__
+#         include <stdlib.h>
+#       endif
+      ]],[[
+        int i = 0;
+        exit(i);
+      ]])
+    ],[
+      tmp_compiler_works="yes"
+    ],[
+      tmp_compiler_works="no"
+      echo " " >&6
+      echo "run-fail: test program exited with status $ac_status" >&6
+      echo " " >&6
+    ])
+  fi
+  dnl branch upon test result
+  if test "$tmp_compiler_works" = "yes"; then
+  ifelse($1,,:,[$1])
+  ifelse($2,,,[else
+    $2])
+  fi
+])
+
+
+dnl CARES_SET_COMPILER_BASIC_OPTS
+dnl -------------------------------------------------
+dnl Sets compiler specific options/flags which do not
+dnl depend on configure's debug, optimize or warnings
+dnl options.
+
+AC_DEFUN([CARES_SET_COMPILER_BASIC_OPTS], [
+  AC_REQUIRE([CARES_CHECK_COMPILER])dnl
+  AC_REQUIRE([CARES_SHFUNC_SQUEEZE])dnl
+  #
+  if test "$compiler_id" != "unknown"; then
+    #
+    if test "$compiler_id" = "GNU_C" ||
+      test "$compiler_id" = "CLANG"; then
+      CARES_CONVERT_INCLUDE_TO_ISYSTEM
+    fi
+    #
+    tmp_save_CPPFLAGS="$CPPFLAGS"
+    tmp_save_CFLAGS="$CFLAGS"
+    tmp_CPPFLAGS=""
+    tmp_CFLAGS=""
+    #
+    case "$compiler_id" in
+        #
+      CLANG)
+        #
+        dnl Disable warnings for unused arguments, otherwise clang will
+        dnl warn about compile-time arguments used during link-time, like
+        dnl -O and -g and -pedantic.
+        tmp_CFLAGS="$tmp_CFLAGS -Qunused-arguments"
+        ;;
+        #
+      DEC_C)
+        #
+        dnl Select strict ANSI C compiler mode
+        tmp_CFLAGS="$tmp_CFLAGS -std1"
+        dnl Turn off optimizer ANSI C aliasing rules
+        tmp_CFLAGS="$tmp_CFLAGS -noansi_alias"
+        dnl Generate warnings for missing function prototypes
+        tmp_CFLAGS="$tmp_CFLAGS -warnprotos"
+        dnl Change some warnings into fatal errors
+        tmp_CFLAGS="$tmp_CFLAGS -msg_fatal toofewargs,toomanyargs"
+        ;;
+        #
+      GNU_C)
+        #
+        dnl Placeholder
+        tmp_CFLAGS="$tmp_CFLAGS"
+        ;;
+        #
+      HP_UX_C)
+        #
+        dnl Disallow run-time dereferencing of null pointers
+        tmp_CFLAGS="$tmp_CFLAGS -z"
+        dnl Disable some remarks
+        dnl #4227: padding struct with n bytes to align member
+        dnl #4255: padding size of struct with n bytes to alignment boundary
+        tmp_CFLAGS="$tmp_CFLAGS +W 4227,4255"
+        ;;
+        #
+      IBM_C)
+        #
+        dnl Ensure that compiler optimizations are always thread-safe.
+        tmp_CPPFLAGS="$tmp_CPPFLAGS -qthreaded"
+        dnl Disable type based strict aliasing optimizations, using worst
+        dnl case aliasing assumptions when compiling. Type based aliasing
+        dnl would restrict the lvalues that could be safely used to access
+        dnl a data object.
+        tmp_CPPFLAGS="$tmp_CPPFLAGS -qnoansialias"
+        dnl Force compiler to stop after the compilation phase, without
+        dnl generating an object code file when compilation has errors.
+        tmp_CPPFLAGS="$tmp_CPPFLAGS -qhalt=e"
+        ;;
+        #
+      INTEL_UNIX_C)
+        #
+        dnl On unix this compiler uses gcc's header files, so
+        dnl we select ANSI C89 dialect plus GNU extensions.
+        tmp_CFLAGS="$tmp_CFLAGS -std=gnu89"
+        dnl Change some warnings into errors
+        dnl #140: too many arguments in function call
+        dnl #147: declaration is incompatible with 'previous one'
+        dnl #165: too few arguments in function call
+        dnl #266: function declared implicitly
+        tmp_CPPFLAGS="$tmp_CPPFLAGS -we 140,147,165,266"
+        dnl Disable some remarks
+        dnl #279: controlling expression is constant
+        dnl #981: operands are evaluated in unspecified order
+        dnl #1469: "cc" clobber ignored
+        tmp_CPPFLAGS="$tmp_CPPFLAGS -wd 279,981,1469"
+        ;;
+        #
+      INTEL_WINDOWS_C)
+        #
+        dnl Placeholder
+        tmp_CFLAGS="$tmp_CFLAGS"
+        ;;
+        #
+      LCC)
+        #
+        dnl Disallow run-time dereferencing of null pointers
+        tmp_CFLAGS="$tmp_CFLAGS -n"
+        ;;
+        #
+      SGI_MIPS_C)
+        #
+        dnl Placeholder
+        tmp_CFLAGS="$tmp_CFLAGS"
+        ;;
+        #
+      SGI_MIPSPRO_C)
+        #
+        dnl Placeholder
+        tmp_CFLAGS="$tmp_CFLAGS"
+        ;;
+        #
+      SUNPRO_C)
+        #
+        dnl Placeholder
+        tmp_CFLAGS="$tmp_CFLAGS"
+        ;;
+        #
+      TINY_C)
+        #
+        dnl Placeholder
+        tmp_CFLAGS="$tmp_CFLAGS"
+        ;;
+        #
+      WATCOM_UNIX_C)
+        #
+        dnl Placeholder
+        tmp_CFLAGS="$tmp_CFLAGS"
+        ;;
+        #
+      WATCOM_WINDOWS_C)
+        #
+        dnl Placeholder
+        tmp_CFLAGS="$tmp_CFLAGS"
+        ;;
+        #
+    esac
+    #
+    squeeze tmp_CPPFLAGS
+    squeeze tmp_CFLAGS
+    #
+    if test ! -z "$tmp_CFLAGS" || test ! -z "$tmp_CPPFLAGS"; then
+      AC_MSG_CHECKING([if compiler accepts some basic options])
+      CPPFLAGS="$tmp_save_CPPFLAGS $tmp_CPPFLAGS"
+      CFLAGS="$tmp_save_CFLAGS $tmp_CFLAGS"
+      squeeze CPPFLAGS
+      squeeze CFLAGS
+      CARES_COMPILER_WORKS_IFELSE([
+        AC_MSG_RESULT([yes])
+        AC_MSG_NOTICE([compiler options added: $tmp_CFLAGS $tmp_CPPFLAGS])
+      ],[
+        AC_MSG_RESULT([no])
+        AC_MSG_WARN([compiler options rejected: $tmp_CFLAGS $tmp_CPPFLAGS])
+        dnl restore initial settings
+        CPPFLAGS="$tmp_save_CPPFLAGS"
+        CFLAGS="$tmp_save_CFLAGS"
+      ])
+    fi
+    #
+  fi
+])
+
+
+dnl CARES_SET_COMPILER_DEBUG_OPTS
+dnl -------------------------------------------------
+dnl Sets compiler specific options/flags which depend
+dnl on configure's debug option.
+
+AC_DEFUN([CARES_SET_COMPILER_DEBUG_OPTS], [
+  AC_REQUIRE([CARES_CHECK_OPTION_DEBUG])dnl
+  AC_REQUIRE([CARES_CHECK_COMPILER])dnl
+  AC_REQUIRE([CARES_SHFUNC_SQUEEZE])dnl
+  #
+  if test "$compiler_id" != "unknown"; then
+    #
+    tmp_save_CFLAGS="$CFLAGS"
+    tmp_save_CPPFLAGS="$CPPFLAGS"
+    #
+    tmp_options=""
+    tmp_CFLAGS="$CFLAGS"
+    tmp_CPPFLAGS="$CPPFLAGS"
+    CARES_VAR_STRIP([tmp_CFLAGS],[$flags_dbg_all])
+    CARES_VAR_STRIP([tmp_CPPFLAGS],[$flags_dbg_all])
+    #
+    if test "$want_debug" = "yes"; then
+      AC_MSG_CHECKING([if compiler accepts debug enabling options])
+      tmp_options="$flags_dbg_yes"
+    fi
+    if test "$want_debug" = "no"; then
+      AC_MSG_CHECKING([if compiler accepts debug disabling options])
+      tmp_options="$flags_dbg_off"
+    fi
+    #
+    if test "$flags_prefer_cppflags" = "yes"; then
+      CPPFLAGS="$tmp_CPPFLAGS $tmp_options"
+      CFLAGS="$tmp_CFLAGS"
+    else
+      CPPFLAGS="$tmp_CPPFLAGS"
+      CFLAGS="$tmp_CFLAGS $tmp_options"
+    fi
+    squeeze CPPFLAGS
+    squeeze CFLAGS
+    CARES_COMPILER_WORKS_IFELSE([
+      AC_MSG_RESULT([yes])
+      AC_MSG_NOTICE([compiler options added: $tmp_options])
+    ],[
+      AC_MSG_RESULT([no])
+      AC_MSG_WARN([compiler options rejected: $tmp_options])
+      dnl restore initial settings
+      CPPFLAGS="$tmp_save_CPPFLAGS"
+      CFLAGS="$tmp_save_CFLAGS"
+    ])
+    #
+  fi
+])
+
+
+dnl CARES_SET_COMPILER_OPTIMIZE_OPTS
+dnl -------------------------------------------------
+dnl Sets compiler specific options/flags which depend
+dnl on configure's optimize option.
+
+AC_DEFUN([CARES_SET_COMPILER_OPTIMIZE_OPTS], [
+  AC_REQUIRE([CARES_CHECK_OPTION_OPTIMIZE])dnl
+  AC_REQUIRE([CARES_CHECK_COMPILER])dnl
+  AC_REQUIRE([CARES_SHFUNC_SQUEEZE])dnl
+  #
+  if test "$compiler_id" != "unknown"; then
+    #
+    tmp_save_CFLAGS="$CFLAGS"
+    tmp_save_CPPFLAGS="$CPPFLAGS"
+    #
+    tmp_options=""
+    tmp_CFLAGS="$CFLAGS"
+    tmp_CPPFLAGS="$CPPFLAGS"
+    honor_optimize_option="yes"
+    #
+    dnl If optimization request setting has not been explicitly specified,
+    dnl it has been derived from the debug setting and initially assumed.
+    dnl This initially assumed optimizer setting will finally be ignored
+    dnl if CFLAGS or CPPFLAGS already hold optimizer flags. This implies
+    dnl that an initially assumed optimizer setting might not be honored.
+    #
+    if test "$want_optimize" = "assume_no" ||
+       test "$want_optimize" = "assume_yes"; then
+      AC_MSG_CHECKING([if compiler optimizer assumed setting might be used])
+      CARES_VAR_MATCH_IFELSE([tmp_CFLAGS],[$flags_opt_all],[
+        honor_optimize_option="no"
+      ])
+      CARES_VAR_MATCH_IFELSE([tmp_CPPFLAGS],[$flags_opt_all],[
+        honor_optimize_option="no"
+      ])
+      AC_MSG_RESULT([$honor_optimize_option])
+      if test "$honor_optimize_option" = "yes"; then
+        if test "$want_optimize" = "assume_yes"; then
+          want_optimize="yes"
+        fi
+        if test "$want_optimize" = "assume_no"; then
+          want_optimize="no"
+        fi
+      fi
+    fi
+    #
+    if test "$honor_optimize_option" = "yes"; then
+      CARES_VAR_STRIP([tmp_CFLAGS],[$flags_opt_all])
+      CARES_VAR_STRIP([tmp_CPPFLAGS],[$flags_opt_all])
+      if test "$want_optimize" = "yes"; then
+        AC_MSG_CHECKING([if compiler accepts optimizer enabling options])
+        tmp_options="$flags_opt_yes"
+      fi
+      if test "$want_optimize" = "no"; then
+        AC_MSG_CHECKING([if compiler accepts optimizer disabling options])
+        tmp_options="$flags_opt_off"
+      fi
+      if test "$flags_prefer_cppflags" = "yes"; then
+        CPPFLAGS="$tmp_CPPFLAGS $tmp_options"
+        CFLAGS="$tmp_CFLAGS"
+      else
+        CPPFLAGS="$tmp_CPPFLAGS"
+        CFLAGS="$tmp_CFLAGS $tmp_options"
+      fi
+      squeeze CPPFLAGS
+      squeeze CFLAGS
+      CARES_COMPILER_WORKS_IFELSE([
+        AC_MSG_RESULT([yes])
+        AC_MSG_NOTICE([compiler options added: $tmp_options])
+      ],[
+        AC_MSG_RESULT([no])
+        AC_MSG_WARN([compiler options rejected: $tmp_options])
+        dnl restore initial settings
+        CPPFLAGS="$tmp_save_CPPFLAGS"
+        CFLAGS="$tmp_save_CFLAGS"
+      ])
+    fi
+    #
+  fi
+])
+
+
+dnl CARES_SET_COMPILER_WARNING_OPTS
+dnl -------------------------------------------------
+dnl Sets compiler options/flags which depend on
+dnl configure's warnings given option.
+
+AC_DEFUN([CARES_SET_COMPILER_WARNING_OPTS], [
+  AC_REQUIRE([CARES_CHECK_OPTION_WARNINGS])dnl
+  AC_REQUIRE([CARES_CHECK_COMPILER])dnl
+  AC_REQUIRE([CARES_SHFUNC_SQUEEZE])dnl
+  #
+  if test "$compiler_id" != "unknown"; then
+    #
+    tmp_save_CPPFLAGS="$CPPFLAGS"
+    tmp_save_CFLAGS="$CFLAGS"
+    tmp_CPPFLAGS=""
+    tmp_CFLAGS=""
+    #
+    case "$compiler_id" in
+        #
+      CLANG)
+        #
+        if test "$want_warnings" = "yes"; then
+          tmp_CFLAGS="$tmp_CFLAGS -pedantic"
+          tmp_CFLAGS="$tmp_CFLAGS -Wall -Wextra"
+          tmp_CFLAGS="$tmp_CFLAGS -Wpointer-arith -Wwrite-strings"
+          tmp_CFLAGS="$tmp_CFLAGS -Wshadow"
+          tmp_CFLAGS="$tmp_CFLAGS -Winline -Wnested-externs"
+          tmp_CFLAGS="$tmp_CFLAGS -Wmissing-declarations"
+          tmp_CFLAGS="$tmp_CFLAGS -Wmissing-prototypes"
+          tmp_CFLAGS="$tmp_CFLAGS -Wno-long-long"
+          tmp_CFLAGS="$tmp_CFLAGS -Wfloat-equal"
+          tmp_CFLAGS="$tmp_CFLAGS -Wno-multichar -Wsign-compare"
+          tmp_CFLAGS="$tmp_CFLAGS -Wundef"
+          tmp_CFLAGS="$tmp_CFLAGS -Wno-format-nonliteral"
+          tmp_CFLAGS="$tmp_CFLAGS -Wendif-labels -Wstrict-prototypes"
+          tmp_CFLAGS="$tmp_CFLAGS -Wdeclaration-after-statement"
+          tmp_CFLAGS="$tmp_CFLAGS -Wcast-align"
+          tmp_CFLAGS="$tmp_CFLAGS -Wno-system-headers"
+          tmp_CFLAGS="$tmp_CFLAGS -Wshorten-64-to-32"
+          #
+          dnl Only clang 1.1 or later
+          if test "$compiler_num" -ge "101"; then
+            tmp_CFLAGS="$tmp_CFLAGS -Wunused"
+          fi
+        fi
+        ;;
+        #
+      DEC_C)
+        #
+        if test "$want_warnings" = "yes"; then
+          dnl Select a higher warning level than default level2
+          tmp_CFLAGS="$tmp_CFLAGS -msg_enable level3"
+        fi
+        ;;
+        #
+      GNU_C)
+        #
+        if test "$want_warnings" = "yes"; then
+          #
+          dnl Do not enable -pedantic when cross-compiling with a gcc older
+          dnl than 3.0, to avoid warnings from third party system headers.
+          if test "x$cross_compiling" != "xyes" ||
+            test "$compiler_num" -ge "300"; then
+            tmp_CFLAGS="$tmp_CFLAGS -pedantic"
+          fi
+          #
+          dnl Set of options we believe *ALL* gcc versions support:
+          tmp_CFLAGS="$tmp_CFLAGS -Wall -W"
+          #
+          dnl Only gcc 1.4 or later
+          if test "$compiler_num" -ge "104"; then
+            tmp_CFLAGS="$tmp_CFLAGS -Wpointer-arith -Wwrite-strings"
+            dnl If not cross-compiling with a gcc older than 3.0
+            if test "x$cross_compiling" != "xyes" ||
+              test "$compiler_num" -ge "300"; then
+              tmp_CFLAGS="$tmp_CFLAGS -Wunused -Wshadow"
+            fi
+          fi
+          #
+          dnl Only gcc 2.7 or later
+          if test "$compiler_num" -ge "207"; then
+            tmp_CFLAGS="$tmp_CFLAGS -Winline -Wnested-externs"
+            dnl If not cross-compiling with a gcc older than 3.0
+            if test "x$cross_compiling" != "xyes" ||
+              test "$compiler_num" -ge "300"; then
+              tmp_CFLAGS="$tmp_CFLAGS -Wmissing-declarations"
+              tmp_CFLAGS="$tmp_CFLAGS -Wmissing-prototypes"
+            fi
+          fi
+          #
+          dnl Only gcc 2.95 or later
+          if test "$compiler_num" -ge "295"; then
+            tmp_CFLAGS="$tmp_CFLAGS -Wno-long-long"
+          fi
+          #
+          dnl Only gcc 2.96 or later
+          if test "$compiler_num" -ge "296"; then
+            tmp_CFLAGS="$tmp_CFLAGS -Wfloat-equal"
+            tmp_CFLAGS="$tmp_CFLAGS -Wno-multichar -Wsign-compare"
+            dnl -Wundef used only if gcc is 2.96 or later since we get
+            dnl lots of "`_POSIX_C_SOURCE' is not defined" in system
+            dnl headers with gcc 2.95.4 on FreeBSD 4.9
+            tmp_CFLAGS="$tmp_CFLAGS -Wundef"
+          fi
+          #
+          dnl Only gcc 2.97 or later
+          if test "$compiler_num" -ge "297"; then
+            tmp_CFLAGS="$tmp_CFLAGS -Wno-format-nonliteral"
+          fi
+          #
+          dnl Only gcc 3.0 or later
+          if test "$compiler_num" -ge "300"; then
+            dnl -Wunreachable-code seems totally unreliable on my gcc 3.3.2 on
+            dnl on i686-Linux as it gives us heaps with false positives.
+            dnl Also, on gcc 4.0.X it is totally unbearable and complains all
+            dnl over making it unusable for generic purposes. Let's not use it.
+            tmp_CFLAGS="$tmp_CFLAGS"
+          fi
+          #
+          dnl Only gcc 3.3 or later
+          if test "$compiler_num" -ge "303"; then
+            tmp_CFLAGS="$tmp_CFLAGS -Wendif-labels -Wstrict-prototypes"
+          fi
+          #
+          dnl Only gcc 3.4 or later
+          if test "$compiler_num" -ge "304"; then
+            tmp_CFLAGS="$tmp_CFLAGS -Wdeclaration-after-statement"
+          fi
+          #
+          dnl Only gcc 4.0 or later
+          if test "$compiler_num" -ge "400"; then
+            tmp_CFLAGS="$tmp_CFLAGS -Wstrict-aliasing=3"
+          fi
+          #
+          dnl Only gcc 4.2 or later
+          if test "$compiler_num" -ge "402"; then
+            tmp_CFLAGS="$tmp_CFLAGS -Wcast-align"
+          fi
+          #
+          dnl Only gcc 4.3 or later
+          if test "$compiler_num" -ge "403"; then
+            tmp_CFLAGS="$tmp_CFLAGS -Wtype-limits -Wold-style-declaration"
+            tmp_CFLAGS="$tmp_CFLAGS -Wmissing-parameter-type -Wempty-body"
+            tmp_CFLAGS="$tmp_CFLAGS -Wclobbered -Wignored-qualifiers"
+            tmp_CFLAGS="$tmp_CFLAGS -Wconversion -Wno-sign-conversion -Wvla"
+          fi
+          #
+          dnl Only gcc 4.5 or later
+          if test "$compiler_num" -ge "405"; then
+            dnl Only windows targets
+            if test "$curl_cv_have_def__WIN32" = "yes"; then
+              tmp_CFLAGS="$tmp_CFLAGS -Wno-pedantic-ms-format"
+            fi
+          fi
+          #
+        fi
+        #
+        dnl Do not issue warnings for code in system include paths.
+        if test "$compiler_num" -ge "300"; then
+          tmp_CFLAGS="$tmp_CFLAGS -Wno-system-headers"
+        else
+          dnl When cross-compiling with a gcc older than 3.0, disable
+          dnl some warnings triggered on third party system headers.
+          if test "x$cross_compiling" = "xyes"; then
+            if test "$compiler_num" -ge "104"; then
+              dnl gcc 1.4 or later
+              tmp_CFLAGS="$tmp_CFLAGS -Wno-unused -Wno-shadow"
+            fi
+            if test "$compiler_num" -ge "207"; then
+              dnl gcc 2.7 or later
+              tmp_CFLAGS="$tmp_CFLAGS -Wno-missing-declarations"
+              tmp_CFLAGS="$tmp_CFLAGS -Wno-missing-prototypes"
+            fi
+          fi
+        fi
+        ;;
+        #
+      HP_UX_C)
+        #
+        if test "$want_warnings" = "yes"; then
+          dnl Issue all warnings
+          tmp_CFLAGS="$tmp_CFLAGS +w1"
+        fi
+        ;;
+        #
+      IBM_C)
+        #
+        dnl Placeholder
+        tmp_CFLAGS="$tmp_CFLAGS"
+        ;;
+        #
+      INTEL_UNIX_C)
+        #
+        if test "$want_warnings" = "yes"; then
+          if test "$compiler_num" -gt "600"; then
+            dnl Show errors, warnings, and remarks
+            tmp_CPPFLAGS="$tmp_CPPFLAGS -Wall -w2"
+            dnl Perform extra compile-time code checking
+            tmp_CPPFLAGS="$tmp_CPPFLAGS -Wcheck"
+            dnl Warn on nested comments
+            tmp_CPPFLAGS="$tmp_CPPFLAGS -Wcomment"
+            dnl Show warnings relative to deprecated features
+            tmp_CPPFLAGS="$tmp_CPPFLAGS -Wdeprecated"
+            dnl Enable warnings for missing prototypes
+            tmp_CPPFLAGS="$tmp_CPPFLAGS -Wmissing-prototypes"
+            dnl Enable warnings for 64-bit portability issues
+            tmp_CPPFLAGS="$tmp_CPPFLAGS -Wp64"
+            dnl Enable warnings for questionable pointer arithmetic
+            tmp_CPPFLAGS="$tmp_CPPFLAGS -Wpointer-arith"
+            dnl Check for function return typw issues
+            tmp_CPPFLAGS="$tmp_CPPFLAGS -Wreturn-type"
+            dnl Warn on variable declarations hiding a previous one
+            tmp_CPPFLAGS="$tmp_CPPFLAGS -Wshadow"
+            dnl Warn when a variable is used before initialized
+            tmp_CPPFLAGS="$tmp_CPPFLAGS -Wuninitialized"
+            dnl Warn if a declared function is not used
+            tmp_CPPFLAGS="$tmp_CPPFLAGS -Wunused-function"
+          fi
+        fi
+        dnl Disable using EBP register in optimizations
+        tmp_CFLAGS="$tmp_CFLAGS -fno-omit-frame-pointer"
+        dnl Disable use of ANSI C aliasing rules in optimizations
+        tmp_CFLAGS="$tmp_CFLAGS -fno-strict-aliasing"
+        dnl Value-safe optimizations on floating-point data
+        tmp_CFLAGS="$tmp_CFLAGS -fp-model precise"
+        dnl Only icc 10.0 or later
+        if test "$compiler_num" -ge "1000"; then
+          dnl Disable vectorizer diagnostic information
+          tmp_CFLAGS="$tmp_CFLAGS -vec-report0"
+        fi
+        ;;
+        #
+      INTEL_WINDOWS_C)
+        #
+        dnl Placeholder
+        tmp_CFLAGS="$tmp_CFLAGS"
+        ;;
+        #
+      LCC)
+        #
+        if test "$want_warnings" = "yes"; then
+          dnl Highest warning level is double -A, next is single -A.
+          dnl Due to the big number of warnings these trigger on third
+          dnl party header files it is impractical for us to use any of
+          dnl them here. If you want them simply define it in CPPFLAGS.
+          tmp_CFLAGS="$tmp_CFLAGS"
+        fi
+        ;;
+        #
+      SGI_MIPS_C)
+        #
+        if test "$want_warnings" = "yes"; then
+          dnl Perform stricter semantic and lint-like checks
+          tmp_CFLAGS="$tmp_CFLAGS -fullwarn"
+        fi
+        ;;
+        #
+      SGI_MIPSPRO_C)
+        #
+        if test "$want_warnings" = "yes"; then
+          dnl Perform stricter semantic and lint-like checks
+          tmp_CFLAGS="$tmp_CFLAGS -fullwarn"
+          dnl Disable some remarks
+          dnl #1209: controlling expression is constant
+          tmp_CFLAGS="$tmp_CFLAGS -woff 1209"
+        fi
+        ;;
+        #
+      SUNPRO_C)
+        #
+        if test "$want_warnings" = "yes"; then
+          dnl Perform stricter semantic and lint-like checks
+          tmp_CFLAGS="$tmp_CFLAGS -v"
+        fi
+        ;;
+        #
+      TINY_C)
+        #
+        if test "$want_warnings" = "yes"; then
+          dnl Activate all warnings
+          tmp_CFLAGS="$tmp_CFLAGS -Wall"
+          dnl Make string constants be of type const char *
+          tmp_CFLAGS="$tmp_CFLAGS -Wwrite-strings"
+          dnl Warn use of unsupported GCC features ignored by TCC
+          tmp_CFLAGS="$tmp_CFLAGS -Wunsupported"
+        fi
+        ;;
+        #
+      WATCOM_UNIX_C)
+        #
+        if test "$want_warnings" = "yes"; then
+          dnl Issue all warnings
+          tmp_CFLAGS="$tmp_CFLAGS -Wall -Wextra"
+        fi
+        ;;
+        #
+      WATCOM_WINDOWS_C)
+        #
+        dnl Placeholder
+        tmp_CFLAGS="$tmp_CFLAGS"
+        ;;
+        #
+    esac
+    #
+    squeeze tmp_CPPFLAGS
+    squeeze tmp_CFLAGS
+    #
+    if test ! -z "$tmp_CFLAGS" || test ! -z "$tmp_CPPFLAGS"; then
+      AC_MSG_CHECKING([if compiler accepts strict warning options])
+      CPPFLAGS="$tmp_save_CPPFLAGS $tmp_CPPFLAGS"
+      CFLAGS="$tmp_save_CFLAGS $tmp_CFLAGS"
+      squeeze CPPFLAGS
+      squeeze CFLAGS
+      CARES_COMPILER_WORKS_IFELSE([
+        AC_MSG_RESULT([yes])
+        AC_MSG_NOTICE([compiler options added: $tmp_CFLAGS $tmp_CPPFLAGS])
+      ],[
+        AC_MSG_RESULT([no])
+        AC_MSG_WARN([compiler options rejected: $tmp_CFLAGS $tmp_CPPFLAGS])
+        dnl restore initial settings
+        CPPFLAGS="$tmp_save_CPPFLAGS"
+        CFLAGS="$tmp_save_CFLAGS"
+      ])
+    fi
+    #
+  fi
+])
+
+
+dnl CARES_SHFUNC_SQUEEZE
+dnl -------------------------------------------------
+dnl Declares a shell function squeeze() which removes
+dnl redundant whitespace out of a shell variable.
+
+AC_DEFUN([CARES_SHFUNC_SQUEEZE], [
+squeeze() {
+  _sqz_result=""
+  eval _sqz_input=\[$][$]1
+  for _sqz_token in $_sqz_input; do
+    if test -z "$_sqz_result"; then
+      _sqz_result="$_sqz_token"
+    else
+      _sqz_result="$_sqz_result $_sqz_token"
+    fi
+  done
+  eval [$]1=\$_sqz_result
+  return 0
+}
+])
+
+
+dnl CARES_CHECK_CURLDEBUG
+dnl -------------------------------------------------
+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 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([XC_LIBTOOL])dnl
+  AC_REQUIRE([CARES_SHFUNC_SQUEEZE])dnl
+  cares_builddir=`pwd`
+  supports_curldebug="unknown"
+  if test "$want_curldebug" = "yes"; then
+    if test "x$enable_shared" != "xno" &&
+      test "x$enable_shared" != "xyes"; then
+      AC_MSG_WARN([unknown enable_shared setting.])
+      supports_curldebug="no"
+    fi
+    if test "x$enable_static" != "xno" &&
+      test "x$enable_static" != "xyes"; then
+      AC_MSG_WARN([unknown enable_static setting.])
+      supports_curldebug="no"
+    fi
+    if test "$supports_curldebug" != "no"; then
+      if test "$enable_shared" = "yes" &&
+        test "x$xc_lt_shlib_use_no_undefined" = 'xyes'; then
+        supports_curldebug="no"
+        AC_MSG_WARN([shared library does not support undefined symbols.])
+      fi
+      if test ! -f "$srcdir/../include/curl/curlbuild.h.dist"; then
+        AC_MSG_WARN([c-ares source not embedded in curl's CVS tree.])
+        supports_curldebug="no"
+      elif test ! -f "$srcdir/../include/curl/Makefile.in"; then
+        AC_MSG_WARN([curl's buildconf has not been run.])
+        supports_curldebug="no"
+      elif test ! -f "$cares_builddir/../libcurl.pc" ||
+        test ! -f "$cares_builddir/../include/curl/curlbuild.h"; then
+        AC_MSG_WARN([curl's configure has not been run.])
+        supports_curldebug="no"
+      elif test ! -f "$cares_builddir/../lib/curl_config.h"; then
+        AC_MSG_WARN([libcurl's curl_config.h is missing.])
+        supports_curldebug="no"
+      elif test ! -f "$cares_builddir/../config.status"; then
+        AC_MSG_WARN([curl's config.status is missing.])
+        supports_curldebug="no"
+      fi
+      if test "$supports_curldebug" != "no"; then
+        grep '^#define USE_ARES' "$cares_builddir/../lib/curl_config.h" >/dev/null
+        if test "$?" -ne "0"; then
+          AC_MSG_WARN([libcurl configured without c-ares support.])
+          supports_curldebug="no"
+        fi
+      fi
+      if test "$supports_curldebug" != "no"; then
+        grep 'CPPFLAGS.*CURLDEBUG' "$cares_builddir/../config.status" >/dev/null
+        if test "$?" -ne "0"; then
+          AC_MSG_WARN([libcurl configured without curldebug support.])
+          supports_curldebug="no"
+        fi
+      fi
+    fi
+  fi
+  #
+  if test "$want_curldebug" = "yes"; then
+    AC_MSG_CHECKING([if curl debug memory tracking can be enabled])
+    test "$supports_curldebug" = "no" || supports_curldebug="yes"
+    AC_MSG_RESULT([$supports_curldebug])
+    if test "$supports_curldebug" = "no"; then
+      AC_MSG_WARN([cannot enable curl debug memory tracking.])
+      want_curldebug="no"
+    fi
+  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="-DCURLDEBUG $CPPFLAGS"
+    squeeze CPPFLAGS
+  fi
+  #
+  if test "$want_debug" = "yes"; then
+    CPPFLAGS="-DDEBUGBUILD $CPPFLAGS"
+    squeeze CPPFLAGS
+  fi
+])
+
+
+dnl CARES_CHECK_COMPILER_HALT_ON_ERROR
+dnl -------------------------------------------------
+dnl Verifies if the compiler actually halts after the
+dnl compilation phase without generating any object
+dnl code file, when the source compiles with errors.
+
+AC_DEFUN([CARES_CHECK_COMPILER_HALT_ON_ERROR], [
+  AC_MSG_CHECKING([if compiler halts on compilation errors])
+  AC_COMPILE_IFELSE([
+    AC_LANG_PROGRAM([[
+    ]],[[
+      force compilation error
+    ]])
+  ],[
+    AC_MSG_RESULT([no])
+    AC_MSG_ERROR([compiler does not halt on compilation errors.])
+  ],[
+    AC_MSG_RESULT([yes])
+  ])
+])
+
+
+dnl CARES_CHECK_COMPILER_ARRAY_SIZE_NEGATIVE
+dnl -------------------------------------------------
+dnl Verifies if the compiler actually halts after the
+dnl compilation phase without generating any object
+dnl code file, when the source code tries to define a
+dnl type for a constant array with negative dimension.
+
+AC_DEFUN([CARES_CHECK_COMPILER_ARRAY_SIZE_NEGATIVE], [
+  AC_REQUIRE([CARES_CHECK_COMPILER_HALT_ON_ERROR])dnl
+  AC_MSG_CHECKING([if compiler halts on negative sized arrays])
+  AC_COMPILE_IFELSE([
+    AC_LANG_PROGRAM([[
+      typedef char bad_t[sizeof(char) == sizeof(int) ? -1 : -1 ];
+    ]],[[
+      bad_t dummy;
+    ]])
+  ],[
+    AC_MSG_RESULT([no])
+    AC_MSG_ERROR([compiler does not halt on negative sized arrays.])
+  ],[
+    AC_MSG_RESULT([yes])
+  ])
+])
+
+
+dnl CARES_CHECK_COMPILER_STRUCT_MEMBER_SIZE
+dnl -------------------------------------------------
+dnl Verifies if the compiler is capable of handling the
+dnl size of a struct member, struct which is a function
+dnl result, as a compilation-time condition inside the
+dnl type definition of a constant array.
+
+AC_DEFUN([CARES_CHECK_COMPILER_STRUCT_MEMBER_SIZE], [
+  AC_REQUIRE([CARES_CHECK_COMPILER_ARRAY_SIZE_NEGATIVE])dnl
+  AC_MSG_CHECKING([if compiler struct member size checking works])
+  tst_compiler_check_one_works="unknown"
+  AC_COMPILE_IFELSE([
+    AC_LANG_PROGRAM([[
+      struct mystruct {
+        int  mi;
+        char mc;
+        struct mystruct *next;
+      };
+      struct mystruct myfunc();
+      typedef char good_t1[sizeof(myfunc().mi) == sizeof(int)  ? 1 : -1 ];
+      typedef char good_t2[sizeof(myfunc().mc) == sizeof(char) ? 1 : -1 ];
+    ]],[[
+      good_t1 dummy1;
+      good_t2 dummy2;
+    ]])
+  ],[
+    tst_compiler_check_one_works="yes"
+  ],[
+    tst_compiler_check_one_works="no"
+    sed 's/^/cc-src: /' conftest.$ac_ext >&6
+    sed 's/^/cc-err: /' conftest.err >&6
+  ])
+  tst_compiler_check_two_works="unknown"
+  AC_COMPILE_IFELSE([
+    AC_LANG_PROGRAM([[
+      struct mystruct {
+        int  mi;
+        char mc;
+        struct mystruct *next;
+      };
+      struct mystruct myfunc();
+      typedef char bad_t1[sizeof(myfunc().mi) != sizeof(int)  ? 1 : -1 ];
+      typedef char bad_t2[sizeof(myfunc().mc) != sizeof(char) ? 1 : -1 ];
+    ]],[[
+      bad_t1 dummy1;
+      bad_t2 dummy2;
+    ]])
+  ],[
+    tst_compiler_check_two_works="no"
+  ],[
+    tst_compiler_check_two_works="yes"
+  ])
+  if test "$tst_compiler_check_one_works" = "yes" &&
+    test "$tst_compiler_check_two_works" = "yes"; then
+    AC_MSG_RESULT([yes])
+  else
+    AC_MSG_RESULT([no])
+    AC_MSG_ERROR([compiler fails struct member size checking.])
+  fi
+])
+
+
+dnl CARES_CHECK_COMPILER_SYMBOL_HIDING
+dnl -------------------------------------------------
+dnl Verify if compiler supports hiding library internal symbols, setting
+dnl shell variable supports_symbol_hiding value as appropriate, as well as
+dnl variables symbol_hiding_CFLAGS and symbol_hiding_EXTERN when supported.
+
+AC_DEFUN([CARES_CHECK_COMPILER_SYMBOL_HIDING], [
+  AC_REQUIRE([CARES_CHECK_COMPILER])dnl
+  AC_BEFORE([$0],[CARES_CONFIGURE_SYMBOL_HIDING])dnl
+  AC_MSG_CHECKING([if compiler supports hiding library internal symbols])
+  supports_symbol_hiding="no"
+  symbol_hiding_CFLAGS=""
+  symbol_hiding_EXTERN=""
+  tmp_CFLAGS=""
+  tmp_EXTERN=""
+  case "$compiler_id" in
+    CLANG)
+      dnl All versions of clang support -fvisibility=
+      tmp_EXTERN="__attribute__ ((__visibility__ (\"default\")))"
+      tmp_CFLAGS="-fvisibility=hidden"
+      supports_symbol_hiding="yes"
+      ;;
+    GNU_C)
+      dnl Only gcc 3.4 or later
+      if test "$compiler_num" -ge "304"; then
+        if $CC --help --verbose 2>&1 | grep fvisibility= > /dev/null ; then
+          tmp_EXTERN="__attribute__ ((__visibility__ (\"default\")))"
+          tmp_CFLAGS="-fvisibility=hidden"
+          supports_symbol_hiding="yes"
+        fi
+      fi
+      ;;
+    INTEL_UNIX_C)
+      dnl Only icc 9.0 or later
+      if test "$compiler_num" -ge "900"; then
+        if $CC --help --verbose 2>&1 | grep fvisibility= > /dev/null ; then
+          tmp_save_CFLAGS="$CFLAGS"
+          CFLAGS="$CFLAGS -fvisibility=hidden"
+          AC_LINK_IFELSE([
+            AC_LANG_PROGRAM([[
+#             include <stdio.h>
+            ]],[[
+              printf("icc fvisibility bug test");
+            ]])
+          ],[
+            tmp_EXTERN="__attribute__ ((__visibility__ (\"default\")))"
+            tmp_CFLAGS="-fvisibility=hidden"
+            supports_symbol_hiding="yes"
+          ])
+          CFLAGS="$tmp_save_CFLAGS"
+        fi
+      fi
+      ;;
+    SUNPRO_C)
+      if $CC 2>&1 | grep flags >/dev/null && $CC -flags | grep xldscope= >/dev/null ; then
+        tmp_EXTERN="__global"
+        tmp_CFLAGS="-xldscope=hidden"
+        supports_symbol_hiding="yes"
+      fi
+      ;;
+  esac
+  if test "$supports_symbol_hiding" = "yes"; then
+    tmp_save_CFLAGS="$CFLAGS"
+    CFLAGS="$tmp_save_CFLAGS $tmp_CFLAGS"
+    squeeze CFLAGS
+    AC_COMPILE_IFELSE([
+      AC_LANG_PROGRAM([[
+        $tmp_EXTERN char *dummy(char *buff);
+        char *dummy(char *buff)
+        {
+         if(buff)
+           return ++buff;
+         else
+           return buff;
+        }
+      ]],[[
+        char b[16];
+        char *r = dummy(&b[0]);
+        if(r)
+          return (int)*r;
+      ]])
+    ],[
+      supports_symbol_hiding="yes"
+      if test -f conftest.err; then
+        grep 'visibility' conftest.err >/dev/null
+        if test "$?" -eq "0"; then
+          supports_symbol_hiding="no"
+        fi
+      fi
+    ],[
+      supports_symbol_hiding="no"
+      echo " " >&6
+      sed 's/^/cc-src: /' conftest.$ac_ext >&6
+      sed 's/^/cc-err: /' conftest.err >&6
+      echo " " >&6
+    ])
+    CFLAGS="$tmp_save_CFLAGS"
+  fi
+  if test "$supports_symbol_hiding" = "yes"; then
+    AC_MSG_RESULT([yes])
+    symbol_hiding_CFLAGS="$tmp_CFLAGS"
+    symbol_hiding_EXTERN="$tmp_EXTERN"
+  else
+    AC_MSG_RESULT([no])
+  fi
+])
+
+
+dnl CARES_CHECK_COMPILER_PROTOTYPE_MISMATCH
+dnl -------------------------------------------------
+dnl Verifies if the compiler actually halts after the
+dnl compilation phase without generating any object
+dnl code file, when the source code tries to redefine
+dnl a prototype which does not match previous one.
+
+AC_DEFUN([CARES_CHECK_COMPILER_PROTOTYPE_MISMATCH], [
+  AC_REQUIRE([CARES_CHECK_COMPILER_HALT_ON_ERROR])dnl
+  AC_MSG_CHECKING([if compiler halts on function prototype mismatch])
+  AC_COMPILE_IFELSE([
+    AC_LANG_PROGRAM([[
+#     include <stdlib.h>
+      int rand(int n);
+      int rand(int n)
+      {
+        if(n)
+          return ++n;
+        else
+          return n;
+      }
+    ]],[[
+      int i[2];
+      int j = rand(i[0]);
+      if(j)
+        return j;
+    ]])
+  ],[
+    AC_MSG_RESULT([no])
+    AC_MSG_ERROR([compiler does not halt on function prototype mismatch.])
+  ],[
+    AC_MSG_RESULT([yes])
+  ])
+])
+
+
+dnl CARES_VAR_MATCH (VARNAME, VALUE)
+dnl -------------------------------------------------
+dnl Verifies if shell variable VARNAME contains VALUE.
+dnl Contents of variable VARNAME and VALUE are handled
+dnl as whitespace separated lists of words. If at least
+dnl one word of VALUE is present in VARNAME the match
+dnl is considered positive, otherwise false.
+
+AC_DEFUN([CARES_VAR_MATCH], [
+  ac_var_match_word="no"
+  for word1 in $[$1]; do
+    for word2 in [$2]; do
+      if test "$word1" = "$word2"; then
+        ac_var_match_word="yes"
+      fi
+    done
+  done
+])
+
+
+dnl CARES_VAR_MATCH_IFELSE (VARNAME, VALUE,
+dnl                        [ACTION-IF-MATCH], [ACTION-IF-NOT-MATCH])
+dnl -------------------------------------------------
+dnl This performs a CURL_VAR_MATCH check and executes
+dnl first branch if the match is positive, otherwise
+dnl the second branch is executed.
+
+AC_DEFUN([CARES_VAR_MATCH_IFELSE], [
+  CARES_VAR_MATCH([$1],[$2])
+  if test "$ac_var_match_word" = "yes"; then
+  ifelse($3,,:,[$3])
+  ifelse($4,,,[else
+    $4])
+  fi
+])
+
+
+dnl CARES_VAR_STRIP (VARNAME, VALUE)
+dnl -------------------------------------------------
+dnl Contents of variable VARNAME and VALUE are handled
+dnl as whitespace separated lists of words. Each word
+dnl from VALUE is removed from VARNAME when present.
+
+AC_DEFUN([CARES_VAR_STRIP], [
+  AC_REQUIRE([CARES_SHFUNC_SQUEEZE])dnl
+  ac_var_stripped=""
+  for word1 in $[$1]; do
+    ac_var_strip_word="no"
+    for word2 in [$2]; do
+      if test "$word1" = "$word2"; then
+        ac_var_strip_word="yes"
+      fi
+    done
+    if test "$ac_var_strip_word" = "no"; then
+      ac_var_stripped="$ac_var_stripped $word1"
+    fi
+  done
+  dnl squeeze whitespace out of result
+  [$1]="$ac_var_stripped"
+  squeeze [$1]
+])
+