Initial attempt to support configure's --(dis|en)able-optimize

option to specify dis(activation) of compiler optimizations.

If option is specified, it will be honored independant of the
--(dis|en)able-debug option.

6 files changed, 704 insertions, 87 deletions

diff --git a/ares/configure.ac b/ares/configure.ac
index 39c249554..685caa131 100644
--- a/ares/configure.ac
+++ b/ares/configure.ac
@@ -9,6 +9,7 @@ AM_CONFIG_HEADER([config.h])
 AM_MAINTAINER_MODE
 
 CARES_CHECK_OPTION_DEBUG
+CARES_CHECK_OPTION_OPTIMIZE
 CARES_CHECK_OPTION_WARNINGS
 
 dnl SED is mandatory for configure process and libtool.
@@ -67,7 +68,7 @@ AC_CANONICAL_HOST
 dnl Get system canonical name
 AC_DEFINE_UNQUOTED(OS, "${host}", [cpu-machine-OS])
 
-AC_PROG_CC
+CARES_CHECK_PROG_CC
 AM_PROG_CC_C_O
 AC_PROG_INSTALL
 
@@ -142,9 +143,10 @@ dnl platform/compiler/architecture specific checks/flags
 dnl **********************************************************************
 
 CARES_CHECK_COMPILER
-CARES_PROCESS_CC_BASIC_OPTS
-CARES_PROCESS_CC_DEBUG_OPTS
-CARES_PROCESS_CC_WARNING_OPTS
+CARES_SET_COMPILER_BASIC_OPTS
+CARES_SET_COMPILER_DEBUG_OPTS
+CARES_SET_COMPILER_OPTIMIZE_OPTS
+CARES_SET_COMPILER_WARNING_OPTS
 
 case $host in
   #
@@ -882,5 +884,15 @@ fi
 CARES_PRIVATE_LIBS="$LIBS"
 AC_SUBST(CARES_PRIVATE_LIBS)
 
+dnl squeeze whitespace out of some variables
+
+CFLAGS=`eval echo $CFLAGS`
+CPPFLAGS=`eval echo $CPPFLAGS`
+DEFS=`eval echo $DEFS`
+LDFLAGS=`eval echo $LDFLAGS`
+LIBS=`eval echo $LIBS`
+
+CARES_PRIVATE_LIBS=`eval echo $CARES_PRIVATE_LIBS`
+
 AC_CONFIG_FILES([Makefile libcares.pc])
 AC_OUTPUT
diff --git a/ares/m4/cares-compilers.m4 b/ares/m4/cares-compilers.m4
index 5dcf03ee4..8af70637b 100644
--- a/ares/m4/cares-compilers.m4
+++ b/ares/m4/cares-compilers.m4
@@ -16,7 +16,7 @@
 #***************************************************************************
 
 # File version for 'aclocal' use. Keep it a single number.
-# serial 2
+# serial 3
 
 
 dnl CARES_CHECK_COMPILER
@@ -28,11 +28,33 @@ 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"
+  #
   CARES_CHECK_COMPILER_DEC
   CARES_CHECK_COMPILER_IBM
   CARES_CHECK_COMPILER_INTEL
   CARES_CHECK_COMPILER_GNU
   #
+  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
 ])
 
 
@@ -48,6 +70,12 @@ AC_DEFUN([CARES_CHECK_COMPILER_DEC], [
     test "$curl_cv_have_def___DECC_VER" = "yes"; then
     AC_MSG_RESULT([yes])
     compiler_id="DECC"
+    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
@@ -71,6 +99,19 @@ AC_DEFUN([CARES_CHECK_COMPILER_GNU], [
     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"
   else
     AC_MSG_RESULT([no])
   fi
@@ -87,6 +128,19 @@ AC_DEFUN([CARES_CHECK_COMPILER_IBM], [
   if test "$curl_cv_have_def___IBMC__" = "yes"; then
     AC_MSG_RESULT([yes])
     compiler_id="IBMC"
+    flags_dbg_all="-g -g0 -g1 -g2 -g3"
+    flags_dbg_yes="-g"
+    flags_dbg_off=""
+    flags_opt_all="-O -O0 -O1 -O2 -O3 -O4 -O5"
+    flags_opt_all="$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"
   else
     AC_MSG_RESULT([no])
   fi
@@ -106,8 +160,27 @@ AC_DEFUN([CARES_CHECK_COMPILER_INTEL], [
     CURL_CHECK_DEF([__unix__], [], [silent])
     if test "$curl_cv_have_def___unix__" = "yes"; then
       compiler_id="ICC_unix"
+      flags_dbg_all="-g -g0"
+      flags_dbg_yes="-g -fp"
+      flags_dbg_off="-g0"
+      flags_opt_all="-O -O0 -O1 -O2 -O3 -Os"
+      flags_opt_yes="-O2"
+      flags_opt_off="-O0"
     else
       compiler_id="ICC_windows"
+      flags_dbg_all="/ZI /Zi /zI /zi /ZD /Zd /zD /zd /Z7 /z7"
+      flags_dbg_all="$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=""
+      flags_opt_all="/O /O0 /O1 /O2 /O3 /Os"
+      flags_opt_yes="/O2"
+      flags_opt_off=""
     fi
     compiler_num="$curl_cv_def___INTEL_COMPILER"
   else
@@ -116,12 +189,13 @@ AC_DEFUN([CARES_CHECK_COMPILER_INTEL], [
 ])
 
 
-dnl CARES_PROCESS_CC_BASIC_OPTS
+dnl CARES_SET_COMPILER_BASIC_OPTS
 dnl -------------------------------------------------
-dnl Sets compiler options/flags which are independant
-dnl of configure's debug or warnings options.
+dnl Sets compiler specific options/flags which do not
+dnl depend on configure's debug, optimize or warnings
+dnl options.
 
-AC_DEFUN([CARES_PROCESS_CC_BASIC_OPTS], [
+AC_DEFUN([CARES_SET_COMPILER_BASIC_OPTS], [
   AC_REQUIRE([CARES_CHECK_COMPILER])dnl
   #
   if test "$compiler_id" = "DECC"; then
@@ -174,44 +248,134 @@ AC_DEFUN([CARES_PROCESS_CC_BASIC_OPTS], [
 ])
 
 
-dnl CARES_PROCESS_CC_DEBUG_OPTS
+dnl CARES_SET_COMPILER_DEBUG_OPTS
 dnl -------------------------------------------------
-dnl Sets compiler options/flags which depend on
-dnl configure's debug given option.
+dnl Sets compiler specific options/flags which depend
+dnl on configure's debug option.
 
-AC_DEFUN([CARES_PROCESS_CC_DEBUG_OPTS], [
+AC_DEFUN([CARES_SET_COMPILER_DEBUG_OPTS], [
   AC_REQUIRE([CARES_CHECK_OPTION_DEBUG])dnl
   AC_REQUIRE([CARES_CHECK_COMPILER])dnl
   #
-  if test "$want_debug" = "yes"; then
-    CFLAGS="$CFLAGS -g"
+  if test "$compiler_id" != "unknown"; then
+    #
+    ac_save_CFLAGS="$CFLAGS"
+    ac_save_CPPFLAGS="$CPPFLAGS"
+    #
+    honor_debug_option="yes"
+    CARES_VAR_STRIP([CFLAGS],[${flags_dbg_all}])
+    CARES_VAR_STRIP([CPPFLAGS],[${flags_dbg_all}])
+    if test "$want_debug" = "yes"; then
+      CFLAGS="$CFLAGS $flags_dbg_yes"
+      AC_MSG_CHECKING([if compiler accepts debug enabling flags $flags_dbg_yes])
+    fi
+    if test "$want_debug" = "no"; then
+      CFLAGS="$CFLAGS $flags_dbg_off"
+      AC_MSG_CHECKING([if compiler accepts debug disabling flags $flags_dbg_off])
+    fi
+    AC_COMPILE_IFELSE([
+      AC_LANG_PROGRAM([[
+      ]],[[
+        int i = 1;
+        return i;
+      ]])
+    ],[
+      AC_MSG_RESULT([yes])
+    ],[
+      AC_MSG_RESULT([no])
+      honor_debug_option="no"
+    ])
+    #
+    if test "$honor_debug_option" = "no"; then
+      CFLAGS="$ac_save_CFLAGS"
+      CPPFLAGS="$ac_save_CPPFLAGS"
+    fi
+    #
   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
   #
-  if test "$want_debug" = "no"; then
-    dnl strip off optimizer flags
-    NEWFLAGS=""
-    for flag in $CFLAGS; do
-      case "$flag" in
-        -O*)
-          dnl echo "cut off $flag"
-          ;;
-        *)
-          NEWFLAGS="$NEWFLAGS $flag"
-          ;;
-      esac
-    done
-    CFLAGS=$NEWFLAGS
+  if test "$compiler_id" != "unknown"; then
+    #
+    ac_save_CFLAGS="$CFLAGS"
+    ac_save_CPPFLAGS="$CPPFLAGS"
+    #
+    dnl If optimization request setting has not been explicitly specified,
+    dnl it has been derived from the debug setting and initially assumed.
+    dnl This initially assumed optimizer setting will finally be ignored
+    dnl if CFLAGS or CPPFLAGS already hold optimizer flags. This implies
+    dnl that an initially assumed optimizer setting might not be honored.
+    #
+    honor_optimize_option="yes"
+    if test "$want_optimize" = "assume_no" ||
+       test "$want_optimize" = "assume_yes"; then
+      AC_MSG_CHECKING([if compiler optimizer assumed setting might be used])
+      CARES_VAR_MATCH_IFELSE([CFLAGS],[${flags_opt_all}],[
+        honor_optimize_option="no"
+      ])
+      CARES_VAR_MATCH_IFELSE([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([CFLAGS],[${flags_opt_all}])
+      CARES_VAR_STRIP([CPPFLAGS],[${flags_opt_all}])
+      if test "$want_optimize" = "yes"; then
+        CFLAGS="$CFLAGS $flags_opt_yes"
+        AC_MSG_CHECKING([if compiler accepts optimizer enabling flags $flags_opt_yes])
+      fi
+      if test "$want_optimize" = "no"; then
+        CFLAGS="$CFLAGS $flags_opt_off"
+        AC_MSG_CHECKING([if compiler accepts optimizer disabling flags $flags_opt_off])
+      fi
+      AC_COMPILE_IFELSE([
+        AC_LANG_PROGRAM([[
+        ]],[[
+          int i = 1;
+          return i;
+        ]])
+      ],[
+        AC_MSG_RESULT([yes])
+      ],[
+        AC_MSG_RESULT([no])
+        honor_optimize_option="no"
+      ])
+    fi
+    #
+    if test "$honor_optimize_option" = "no"; then
+      CFLAGS="$ac_save_CFLAGS"
+      CPPFLAGS="$ac_save_CPPFLAGS"
+    fi
+    #
   fi
-  #
 ])
 
 
-dnl CARES_PROCESS_CC_WARNING_OPTS
+dnl CARES_SET_COMPILER_WARNING_OPTS
 dnl -------------------------------------------------
 dnl Sets compiler options/flags which depend on
 dnl configure's warnings given option.
 
-AC_DEFUN([CARES_PROCESS_CC_WARNING_OPTS], [
+AC_DEFUN([CARES_SET_COMPILER_WARNING_OPTS], [
   AC_REQUIRE([CARES_CHECK_OPTION_WARNINGS])dnl
   AC_REQUIRE([CARES_CHECK_COMPILER])dnl
   #
@@ -236,7 +400,7 @@ AC_DEFUN([CARES_PROCESS_CC_WARNING_OPTS], [
   if test "$compiler_id" = "GNUC"; then
     #
     # FIXME: Some of these warnings should be changed into errors
-    #        and moved to CARES-PROCESS-CC-BASIC-OPTS
+    #        and moved to CARES-SET-COMPILER-BASIC-OPTS
     #
     if test "$want_warnings" = "yes"; then
       dnl this is a set of options we believe *ALL* gcc versions support:
@@ -295,6 +459,7 @@ dnl CARES_PROCESS_DEBUG_BUILD_OPTS
 dnl -------------------------------------------------
 dnl Settings which depend on configure's debug given
 dnl option, and further configure the build process.
+dnl Don't use this macro for compiler dependant stuff.
 
 AC_DEFUN([CARES_PROCESS_DEBUG_BUILD_OPTS], [
   AC_REQUIRE([CARES_CHECK_OPTION_DEBUG])dnl
@@ -311,9 +476,86 @@ AC_DEFUN([CARES_PROCESS_DEBUG_BUILD_OPTS], [
     dnl libcurl stuff so this BUILDING_LIBCURL is not THAT much uglier
     AC_DEFINE(BUILDING_LIBCURL, 1, [when building as static part of libcurl])
 
-    CPPFLAGS="$CPPFLAGS -DCURLDEBUG -I$srcdir/../include"
+    CPPFLAGS="$CPPFLAGS -DCURLDEBUG"
+
+    dnl CHECKME: Do we still need so specify this include path here?
+    CPPFLAGS="$CPPFLAGS -I$srcdir/../include"
+
   fi
   #
 ])
 
 
+dnl CARES_CHECK_PROG_CC
+dnl -------------------------------------------------
+dnl Check for compiler program, preventing CFLAGS and
+dnl CPPFLAGS from being unexpectedly changed.
+
+AC_DEFUN([CARES_CHECK_PROG_CC], [
+  ac_save_CFLAGS="$CFLAGS"
+  ac_save_CPPFLAGS="$CPPFLAGS"
+  AC_PROG_CC
+  CFLAGS="$ac_save_CFLAGS"
+  CPPFLAGS="$ac_save_CPPFLAGS"
+])
+
+
+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
+    [$4]])
+  fi
+])
+
+
+dnl CARES_VAR_STRIP (VARNAME, VALUE)
+dnl -------------------------------------------------
+dnl Contents of variable VARNAME and VALUE are handled
+dnl as whitespace separated lists of words. Each word
+dnl from VALUE is removed from VARNAME when present.
+
+AC_DEFUN([CARES_VAR_STRIP], [
+  ac_var_stripped=""
+  for word1 in "${[$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]=`eval echo $[$1]`
+])
diff --git a/ares/m4/cares-confopts.m4 b/ares/m4/cares-confopts.m4
index 2299b6074..17a6875f3 100644
--- a/ares/m4/cares-confopts.m4
+++ b/ares/m4/cares-confopts.m4
@@ -16,7 +16,7 @@
 #***************************************************************************
 
 # File version for 'aclocal' use. Keep it a single number.
-# serial 1
+# serial 2
 
 
 dnl CARES_CHECK_OPTION_DEBUG
@@ -27,13 +27,13 @@ dnl variable want_debug value as appropriate.
 
 AC_DEFUN([CARES_CHECK_OPTION_DEBUG], [
   AC_BEFORE([$0],[CARES_CHECK_OPTION_WARNINGS])dnl
-  AC_BEFORE([$0],[AC_PROG_CC])dnl
+  AC_BEFORE([$0],[CARES_CHECK_PROG_CC])dnl
   AC_MSG_CHECKING([whether to enable debug build options])
   OPT_DEBUG_BUILD="default"
   AC_ARG_ENABLE(debug,
-    AC_HELP_STRING([--enable-debug],[Enable debug build options])
-    AC_HELP_STRING([--disable-debug],[Disable debug build options]),
-    OPT_DEBUG_BUILD=$enableval)
+AC_HELP_STRING([--enable-debug],[Enable debug build options])
+AC_HELP_STRING([--disable-debug],[Disable debug build options]),
+  OPT_DEBUG_BUILD=$enableval)
   case "$OPT_DEBUG_BUILD" in
     no)
       dnl --disable-debug option used
@@ -52,21 +52,77 @@ AC_DEFUN([CARES_CHECK_OPTION_DEBUG], [
 ])
 
 
+dnl CARES_CHECK_OPTION_OPTIMIZE
+dnl -------------------------------------------------
+dnl Verify if configure has been invoked with option
+dnl --enable-optimize or --disable-optimize, and set
+dnl shell variable want_optimize value as appropriate.
+
+AC_DEFUN([CARES_CHECK_OPTION_OPTIMIZE], [
+  AC_REQUIRE([CARES_CHECK_OPTION_DEBUG])dnl
+  AC_BEFORE([$0],[CARES_CHECK_PROG_CC])dnl
+  AC_MSG_CHECKING([whether to enable compiler optimizer])
+  OPT_COMPILER_OPTIMIZE="default"
+  AC_ARG_ENABLE(optimize,
+AC_HELP_STRING([--enable-optimize(=OPT)],[Enable compiler optimizations (default=-O2)])
+AC_HELP_STRING([--disable-optimize],[Disable compiler optimizations]),
+  OPT_COMPILER_OPTIMIZE=$enableval)
+  case "$OPT_COMPILER_OPTIMIZE" in
+    no)
+      dnl --disable-optimize option used. We will handle this as
+      dnl a request to disable compiler optimizations if possible.
+      dnl If the compiler is known CFLAGS and CPPFLAGS will be
+      dnl overridden, otherwise this can not be honored.
+      want_optimize="no"
+      AC_MSG_RESULT([no])
+      ;;
+    default)
+      dnl configure's optimize option not specified. Initially we will
+      dnl handle this as a a request contrary to configure's setting
+      dnl for --enable-debug. IOW, initially, for debug-enabled builds
+      dnl this will be handled as a request to disable optimizations if
+      dnl possible, and for debug-disabled builds this will be handled
+      dnl initially as a request to enable optimizations if possible.
+      dnl Finally, if the compiler is known and CFLAGS and CPPFLAGS do
+      dnl not have any optimizer flag the request will be honored, in
+      dnl any other case the request can not be honored.
+      dnl IOW, existing optimizer flags defined in CFLAGS or CPPFLAGS
+      dnl will always take precedence over any initial assumption.
+      if test "$want_debug" = "yes"; then
+        want_optimize="assume_no"
+        AC_MSG_RESULT([not specified (assuming no)])
+      else
+        want_optimize="assume_yes"
+        AC_MSG_RESULT([not specified (assuming yes)])
+      fi
+      ;;
+    *)
+      dnl --enable-optimize option used. We will handle this as
+      dnl a request to enable compiler optimizations if possible.
+      dnl If the compiler is known CFLAGS and CPPFLAGS will be
+      dnl overridden, otherwise this can not be honored.
+      want_optimize="yes"
+      AC_MSG_RESULT([yes])
+      ;;
+  esac
+])
+
+
 dnl CARES_CHECK_OPTION_WARNINGS
 dnl -------------------------------------------------
 dnl Verify if configure has been invoked with option
 dnl --enable-warnings or --disable-warnings, and set
-DNL shell variable want_warnings as appropriate.
+dnl shell variable want_warnings as appropriate.
 
 AC_DEFUN([CARES_CHECK_OPTION_WARNINGS], [
   AC_REQUIRE([CARES_CHECK_OPTION_DEBUG])dnl
-  AC_BEFORE([$0],[AC_PROG_CC])dnl
+  AC_BEFORE([$0],[CARES_CHECK_PROG_CC])dnl
   AC_MSG_CHECKING([whether to enable strict compiler warnings])
   OPT_COMPILER_WARNINGS="default"
   AC_ARG_ENABLE(warnings,
-    AC_HELP_STRING([--enable-warnings],[Enable strict compiler warnings])
-    AC_HELP_STRING([--disable-warnings],[Disable strict compiler warnings]),
-    OPT_COMPILER_WARNINGS=$enableval)
+AC_HELP_STRING([--enable-warnings],[Enable strict compiler warnings])
+AC_HELP_STRING([--disable-warnings],[Disable strict compiler warnings]),
+  OPT_COMPILER_WARNINGS=$enableval)
   case "$OPT_COMPILER_WARNINGS" in
     no)
       dnl --disable-warnings option used
diff --git a/configure.ac b/configure.ac
index 935ee46cb..bf86bf038 100644
--- a/configure.ac
+++ b/configure.ac
@@ -37,6 +37,7 @@ AM_CONFIG_HEADER(lib/config.h src/config.h include/curl/curlbuild.h)
 AM_MAINTAINER_MODE
 
 CURL_CHECK_OPTION_DEBUG
+CURL_CHECK_OPTION_OPTIMIZE
 CURL_CHECK_OPTION_WARNINGS
 
 dnl SED is mandatory for configure process and libtool.
@@ -133,7 +134,7 @@ dnl Get system canonical name
 AC_DEFINE_UNQUOTED(OS, "${host}", [cpu-machine-OS])
 
 dnl Checks for programs.
-AC_PROG_CC
+CURL_CHECK_PROG_CC
 
 dnl Our curl_off_t internal and external configure settings
 CURL_CONFIGURE_CURL_OFF_T
@@ -251,9 +252,10 @@ dnl platform/compiler/architecture specific checks/flags
 dnl **********************************************************************
 
 CURL_CHECK_COMPILER
-CURL_PROCESS_CC_BASIC_OPTS
-CURL_PROCESS_CC_DEBUG_OPTS
-CURL_PROCESS_CC_WARNING_OPTS
+CURL_SET_COMPILER_BASIC_OPTS
+CURL_SET_COMPILER_DEBUG_OPTS
+CURL_SET_COMPILER_OPTIMIZE_OPTS
+CURL_SET_COMPILER_WARNING_OPTS
 
 case $host in
   #
@@ -2529,6 +2531,18 @@ fi
 
 AC_SUBST(SUPPORT_PROTOCOLS)
 
+dnl squeeze whitespace out of some variables
+
+CFLAGS=`eval echo $CFLAGS`
+CPPFLAGS=`eval echo $CPPFLAGS`
+DEFS=`eval echo $DEFS`
+LDFLAGS=`eval echo $LDFLAGS`
+LIBS=`eval echo $LIBS`
+
+CURL_LIBS=`eval echo $CURL_LIBS`
+LIBCURL_LIBS=`eval echo $LIBCURL_LIBS`
+TEST_SERVER_LIBS=`eval echo $TEST_SERVER_LIBS`
+
 AC_CONFIG_FILES([Makefile \
            docs/Makefile \
            docs/examples/Makefile \
diff --git a/m4/curl-compilers.m4 b/m4/curl-compilers.m4
index a132ec28b..1cff5be01 100644
--- a/m4/curl-compilers.m4
+++ b/m4/curl-compilers.m4
@@ -22,7 +22,7 @@
 #***************************************************************************
 
 # File version for 'aclocal' use. Keep it a single number.
-# serial 1
+# serial 2
 
 
 dnl CURL_CHECK_COMPILER
@@ -34,11 +34,33 @@ AC_DEFUN([CURL_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"
+  #
   CURL_CHECK_COMPILER_DEC
   CURL_CHECK_COMPILER_IBM
   CURL_CHECK_COMPILER_INTEL
   CURL_CHECK_COMPILER_GNU
   #
+  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 cURL project to better support your compiler
+*** you can report this and the required info on the libcurl development
+*** mailing list: http://cool.haxx.se/mailman/listinfo/curl-library/
+***
+_EOF
+  fi
 ])
 
 
@@ -54,6 +76,12 @@ AC_DEFUN([CURL_CHECK_COMPILER_DEC], [
     test "$curl_cv_have_def___DECC_VER" = "yes"; then
     AC_MSG_RESULT([yes])
     compiler_id="DECC"
+    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
@@ -77,6 +105,19 @@ AC_DEFUN([CURL_CHECK_COMPILER_GNU], [
     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"
   else
     AC_MSG_RESULT([no])
   fi
@@ -93,6 +134,19 @@ AC_DEFUN([CURL_CHECK_COMPILER_IBM], [
   if test "$curl_cv_have_def___IBMC__" = "yes"; then
     AC_MSG_RESULT([yes])
     compiler_id="IBMC"
+    flags_dbg_all="-g -g0 -g1 -g2 -g3"
+    flags_dbg_yes="-g"
+    flags_dbg_off=""
+    flags_opt_all="-O -O0 -O1 -O2 -O3 -O4 -O5"
+    flags_opt_all="$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"
   else
     AC_MSG_RESULT([no])
   fi
@@ -112,8 +166,27 @@ AC_DEFUN([CURL_CHECK_COMPILER_INTEL], [
     CURL_CHECK_DEF([__unix__], [], [silent])
     if test "$curl_cv_have_def___unix__" = "yes"; then
       compiler_id="ICC_unix"
+      flags_dbg_all="-g -g0"
+      flags_dbg_yes="-g -fp"
+      flags_dbg_off="-g0"
+      flags_opt_all="-O -O0 -O1 -O2 -O3 -Os"
+      flags_opt_yes="-O2"
+      flags_opt_off="-O0"
     else
       compiler_id="ICC_windows"
+      flags_dbg_all="/ZI /Zi /zI /zi /ZD /Zd /zD /zd /Z7 /z7"
+      flags_dbg_all="$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=""
+      flags_opt_all="/O /O0 /O1 /O2 /O3 /Os"
+      flags_opt_yes="/O2"
+      flags_opt_off=""
     fi
     compiler_num="$curl_cv_def___INTEL_COMPILER"
   else
@@ -122,12 +195,13 @@ AC_DEFUN([CURL_CHECK_COMPILER_INTEL], [
 ])
 
 
-dnl CURL_PROCESS_CC_BASIC_OPTS
+dnl CURL_SET_COMPILER_BASIC_OPTS
 dnl -------------------------------------------------
-dnl Sets compiler options/flags which are independant
-dnl of configure's debug or warnings options.
+dnl Sets compiler specific options/flags which do not
+dnl depend on configure's debug, optimize or warnings
+dnl options.
 
-AC_DEFUN([CURL_PROCESS_CC_BASIC_OPTS], [
+AC_DEFUN([CURL_SET_COMPILER_BASIC_OPTS], [
   AC_REQUIRE([CURL_CHECK_COMPILER])dnl
   #
   if test "$compiler_id" = "DECC"; then
@@ -180,44 +254,134 @@ AC_DEFUN([CURL_PROCESS_CC_BASIC_OPTS], [
 ])
 
 
-dnl CURL_PROCESS_CC_DEBUG_OPTS
+dnl CURL_SET_COMPILER_DEBUG_OPTS
 dnl -------------------------------------------------
-dnl Sets compiler options/flags which depend on
-dnl configure's debug given option.
+dnl Sets compiler specific options/flags which depend
+dnl on configure's debug option.
 
-AC_DEFUN([CURL_PROCESS_CC_DEBUG_OPTS], [
+AC_DEFUN([CURL_SET_COMPILER_DEBUG_OPTS], [
   AC_REQUIRE([CURL_CHECK_OPTION_DEBUG])dnl
   AC_REQUIRE([CURL_CHECK_COMPILER])dnl
   #
-  if test "$want_debug" = "yes"; then
-    CFLAGS="$CFLAGS -g"
+  if test "$compiler_id" != "unknown"; then
+    #
+    ac_save_CFLAGS="$CFLAGS"
+    ac_save_CPPFLAGS="$CPPFLAGS"
+    #
+    honor_debug_option="yes"
+    CURL_VAR_STRIP([CFLAGS],[${flags_dbg_all}])
+    CURL_VAR_STRIP([CPPFLAGS],[${flags_dbg_all}])
+    if test "$want_debug" = "yes"; then
+      CFLAGS="$CFLAGS $flags_dbg_yes"
+      AC_MSG_CHECKING([if compiler accepts debug enabling flags $flags_dbg_yes])
+    fi
+    if test "$want_debug" = "no"; then
+      CFLAGS="$CFLAGS $flags_dbg_off"
+      AC_MSG_CHECKING([if compiler accepts debug disabling flags $flags_dbg_off])
+    fi
+    AC_COMPILE_IFELSE([
+      AC_LANG_PROGRAM([[
+      ]],[[
+        int i = 1;
+        return i;
+      ]])
+    ],[
+      AC_MSG_RESULT([yes])
+    ],[
+      AC_MSG_RESULT([no])
+      honor_debug_option="no"
+    ])
+    #
+    if test "$honor_debug_option" = "no"; then
+      CFLAGS="$ac_save_CFLAGS"
+      CPPFLAGS="$ac_save_CPPFLAGS"
+    fi
+    #
   fi
+])
+
+
+dnl CURL_SET_COMPILER_OPTIMIZE_OPTS
+dnl -------------------------------------------------
+dnl Sets compiler specific options/flags which depend
+dnl on configure's optimize option.
+
+AC_DEFUN([CURL_SET_COMPILER_OPTIMIZE_OPTS], [
+  AC_REQUIRE([CURL_CHECK_OPTION_OPTIMIZE])dnl
+  AC_REQUIRE([CURL_CHECK_COMPILER])dnl
   #
-  if test "$want_debug" = "no"; then
-    dnl strip off optimizer flags
-    NEWFLAGS=""
-    for flag in $CFLAGS; do
-      case "$flag" in
-        -O*)
-          dnl echo "cut off $flag"
-          ;;
-        *)
-          NEWFLAGS="$NEWFLAGS $flag"
-          ;;
-      esac
-    done
-    CFLAGS=$NEWFLAGS
+  if test "$compiler_id" != "unknown"; then
+    #
+    ac_save_CFLAGS="$CFLAGS"
+    ac_save_CPPFLAGS="$CPPFLAGS"
+    #
+    dnl If optimization request setting has not been explicitly specified,
+    dnl it has been derived from the debug setting and initially assumed.
+    dnl This initially assumed optimizer setting will finally be ignored
+    dnl if CFLAGS or CPPFLAGS already hold optimizer flags. This implies
+    dnl that an initially assumed optimizer setting might not be honored.
+    #
+    honor_optimize_option="yes"
+    if test "$want_optimize" = "assume_no" ||
+       test "$want_optimize" = "assume_yes"; then
+      AC_MSG_CHECKING([if compiler optimizer assumed setting might be used])
+      CURL_VAR_MATCH_IFELSE([CFLAGS],[${flags_opt_all}],[
+        honor_optimize_option="no"
+      ])
+      CURL_VAR_MATCH_IFELSE([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
+      CURL_VAR_STRIP([CFLAGS],[${flags_opt_all}])
+      CURL_VAR_STRIP([CPPFLAGS],[${flags_opt_all}])
+      if test "$want_optimize" = "yes"; then
+        CFLAGS="$CFLAGS $flags_opt_yes"
+        AC_MSG_CHECKING([if compiler accepts optimizer enabling flags $flags_opt_yes])
+      fi
+      if test "$want_optimize" = "no"; then
+        CFLAGS="$CFLAGS $flags_opt_off"
+        AC_MSG_CHECKING([if compiler accepts optimizer disabling flags $flags_opt_off])
+      fi
+      AC_COMPILE_IFELSE([
+        AC_LANG_PROGRAM([[
+        ]],[[
+          int i = 1;
+          return i;
+        ]])
+      ],[
+        AC_MSG_RESULT([yes])
+      ],[
+        AC_MSG_RESULT([no])
+        honor_optimize_option="no"
+      ])
+    fi
+    #
+    if test "$honor_optimize_option" = "no"; then
+      CFLAGS="$ac_save_CFLAGS"
+      CPPFLAGS="$ac_save_CPPFLAGS"
+    fi
+    #
   fi
-  #
 ])
 
 
-dnl CURL_PROCESS_CC_WARNING_OPTS
+dnl CURL_SET_COMPILER_WARNING_OPTS
 dnl -------------------------------------------------
 dnl Sets compiler options/flags which depend on
 dnl configure's warnings given option.
 
-AC_DEFUN([CURL_PROCESS_CC_WARNING_OPTS], [
+AC_DEFUN([CURL_SET_COMPILER_WARNING_OPTS], [
   AC_REQUIRE([CURL_CHECK_OPTION_WARNINGS])dnl
   AC_REQUIRE([CURL_CHECK_COMPILER])dnl
   #
@@ -242,7 +406,7 @@ AC_DEFUN([CURL_PROCESS_CC_WARNING_OPTS], [
   if test "$compiler_id" = "GNUC"; then
     #
     # FIXME: Some of these warnings should be changed into errors
-    #        and moved to CURL-PROCESS-CC-BASIC-OPTS
+    #        and moved to CURL-SET-COMPILER-BASIC-OPTS
     #
     if test "$want_warnings" = "yes"; then
       dnl this is a set of options we believe *ALL* gcc versions support:
@@ -301,6 +465,7 @@ dnl CURL_PROCESS_DEBUG_BUILD_OPTS
 dnl -------------------------------------------------
 dnl Settings which depend on configure's debug given
 dnl option, and further configure the build process.
+dnl Don't use this macro for compiler dependant stuff.
 
 AC_DEFUN([CURL_PROCESS_DEBUG_BUILD_OPTS], [
   AC_REQUIRE([CURL_CHECK_OPTION_DEBUG])dnl
@@ -313,4 +478,76 @@ AC_DEFUN([CURL_PROCESS_DEBUG_BUILD_OPTS], [
 ])
 
 
+dnl CURL_CHECK_PROG_CC
+dnl -------------------------------------------------
+dnl Check for compiler program, preventing CFLAGS and
+dnl CPPFLAGS from being unexpectedly changed.
+
+AC_DEFUN([CURL_CHECK_PROG_CC], [
+  ac_save_CFLAGS="$CFLAGS"
+  ac_save_CPPFLAGS="$CPPFLAGS"
+  AC_PROG_CC
+  CFLAGS="$ac_save_CFLAGS"
+  CPPFLAGS="$ac_save_CPPFLAGS"
+])
+
+
+dnl CURL_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([CURL_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 CURL_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([CURL_VAR_MATCH_IFELSE], [
+  CURL_VAR_MATCH([$1],[$2])
+  if test "$ac_var_match_word" = "yes"; then
+  ifelse($3,,:,[$3])
+  ifelse($4,,,[else
+    [$4]])
+  fi
+])
+
+
+dnl CURL_VAR_STRIP (VARNAME, VALUE)
+dnl -------------------------------------------------
+dnl Contents of variable VARNAME and VALUE are handled
+dnl as whitespace separated lists of words. Each word
+dnl from VALUE is removed from VARNAME when present.
+
+AC_DEFUN([CURL_VAR_STRIP], [
+  ac_var_stripped=""
+  for word1 in "${[$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]=`eval echo $[$1]`
+])
diff --git a/m4/curl-confopts.m4 b/m4/curl-confopts.m4
index 0c125d9c3..b0c1f3cd4 100644
--- a/m4/curl-confopts.m4
+++ b/m4/curl-confopts.m4
@@ -22,7 +22,7 @@
 #***************************************************************************
 
 # File version for 'aclocal' use. Keep it a single number.
-# serial 2
+# serial 3
 
 
 dnl CURL_CHECK_OPTION_DEBUG
@@ -33,13 +33,13 @@ dnl variable want_debug value as appropriate.
 
 AC_DEFUN([CURL_CHECK_OPTION_DEBUG], [
   AC_BEFORE([$0],[CURL_CHECK_OPTION_WARNINGS])dnl
-  AC_BEFORE([$0],[AC_PROG_CC])dnl
+  AC_BEFORE([$0],[CURL_CHECK_PROG_CC])dnl
   AC_MSG_CHECKING([whether to enable debug build options])
   OPT_DEBUG_BUILD="default"
   AC_ARG_ENABLE(debug,
-    AC_HELP_STRING([--enable-debug],[Enable debug build options])
-    AC_HELP_STRING([--disable-debug],[Disable debug build options]),
-    OPT_DEBUG_BUILD=$enableval)
+AC_HELP_STRING([--enable-debug],[Enable debug build options])
+AC_HELP_STRING([--disable-debug],[Disable debug build options]),
+  OPT_DEBUG_BUILD=$enableval)
   case "$OPT_DEBUG_BUILD" in
     no)
       dnl --disable-debug option used
@@ -58,21 +58,77 @@ AC_DEFUN([CURL_CHECK_OPTION_DEBUG], [
 ])
 
 
+dnl CURL_CHECK_OPTION_OPTIMIZE
+dnl -------------------------------------------------
+dnl Verify if configure has been invoked with option
+dnl --enable-optimize or --disable-optimize, and set
+dnl shell variable want_optimize value as appropriate.
+
+AC_DEFUN([CURL_CHECK_OPTION_OPTIMIZE], [
+  AC_REQUIRE([CURL_CHECK_OPTION_DEBUG])dnl
+  AC_BEFORE([$0],[CURL_CHECK_PROG_CC])dnl
+  AC_MSG_CHECKING([whether to enable compiler optimizer])
+  OPT_COMPILER_OPTIMIZE="default"
+  AC_ARG_ENABLE(optimize,
+AC_HELP_STRING([--enable-optimize],[Enable compiler optimizations])
+AC_HELP_STRING([--disable-optimize],[Disable compiler optimizations]),
+  OPT_COMPILER_OPTIMIZE=$enableval)
+  case "$OPT_COMPILER_OPTIMIZE" in
+    no)
+      dnl --disable-optimize option used. We will handle this as
+      dnl a request to disable compiler optimizations if possible.
+      dnl If the compiler is known CFLAGS and CPPFLAGS will be
+      dnl overridden, otherwise this can not be honored.
+      want_optimize="no"
+      AC_MSG_RESULT([no])
+      ;;
+    default)
+      dnl configure's optimize option not specified. Initially we will
+      dnl handle this as a a request contrary to configure's setting
+      dnl for --enable-debug. IOW, initially, for debug-enabled builds
+      dnl this will be handled as a request to disable optimizations if
+      dnl possible, and for debug-disabled builds this will be handled
+      dnl initially as a request to enable optimizations if possible.
+      dnl Finally, if the compiler is known and CFLAGS and CPPFLAGS do
+      dnl not have any optimizer flag the request will be honored, in
+      dnl any other case the request can not be honored.
+      dnl IOW, existing optimizer flags defined in CFLAGS or CPPFLAGS
+      dnl will always take precedence over any initial assumption.
+      if test "$want_debug" = "yes"; then
+        want_optimize="assume_no"
+        AC_MSG_RESULT([not specified (assuming no)])
+      else
+        want_optimize="assume_yes"
+        AC_MSG_RESULT([not specified (assuming yes)])
+      fi
+      ;;
+    *)
+      dnl --enable-optimize option used. We will handle this as
+      dnl a request to enable compiler optimizations if possible.
+      dnl If the compiler is known CFLAGS and CPPFLAGS will be
+      dnl overridden, otherwise this can not be honored.
+      want_optimize="yes"
+      AC_MSG_RESULT([yes])
+      ;;
+  esac
+])
+
+
 dnl CURL_CHECK_OPTION_WARNINGS
 dnl -------------------------------------------------
 dnl Verify if configure has been invoked with option
 dnl --enable-warnings or --disable-warnings, and set
-DNL shell variable want_warnings as appropriate.
+dnl shell variable want_warnings as appropriate.
 
 AC_DEFUN([CURL_CHECK_OPTION_WARNINGS], [
   AC_REQUIRE([CURL_CHECK_OPTION_DEBUG])dnl
-  AC_BEFORE([$0],[AC_PROG_CC])dnl
+  AC_BEFORE([$0],[CURL_CHECK_PROG_CC])dnl
   AC_MSG_CHECKING([whether to enable strict compiler warnings])
   OPT_COMPILER_WARNINGS="default"
   AC_ARG_ENABLE(warnings,
-    AC_HELP_STRING([--enable-warnings],[Enable strict compiler warnings])
-    AC_HELP_STRING([--disable-warnings],[Disable strict compiler warnings]),
-    OPT_COMPILER_WARNINGS=$enableval)
+AC_HELP_STRING([--enable-warnings],[Enable strict compiler warnings])
+AC_HELP_STRING([--disable-warnings],[Disable strict compiler warnings]),
+  OPT_COMPILER_WARNINGS=$enableval)
   case "$OPT_COMPILER_WARNINGS" in
     no)
       dnl --disable-warnings option used