configure: Allow valgrind support to be manually enabled

Irrespective of the DDX debug settings, some people wish to run Xorg
under valgrind and so prefer to have the cleaner output by making the
DDX valgrind aware.

(Actually Maarten wants valgrind support enabled by default...)

Suggested-by: Maarten Lankhorst <maarten.lankhorst@canonical.com>
Signed-off-by: Chris Wilson <chris@chris-wilson.co.uk>

configure.ac

@@ -353,6 +353,12 @@ AC_ARG_ENABLE(debug,
 			     [Enables internal debugging [default=no]]),
               [DEBUG="$enableval"],
               [DEBUG=no])
+AC_ARG_ENABLE(valgrind,
+	      AS_HELP_STRING([--enable-valgrind],
+			     [Enables valgrindified ioctls for debugging [default=no]]),
+              [VG="$enableval"],
+              [VG=no])
+
 # Store the list of server defined optional extensions in REQUIRED_MODULES
 XORG_DRIVER_CHECK_EXT(RANDR, randrproto)
 XORG_DRIVER_CHECK_EXT(RENDER, renderproto)
@@ -439,12 +445,22 @@ AM_CONDITIONAL(DEBUG, test x$DEBUG != xno)
 AM_CONDITIONAL(FULL_DEBUG, test x$DEBUG = xfull)
 if test "x$DEBUG" = xno; then
 	AC_DEFINE(NDEBUG,1,[Disable internal debugging])
+else
+	if test "x$VG" != xyes; then
+		VG=auto
+	fi
 fi
-if test "x$DEBUG" != xno; then
+if test "x$VG" != xno; then
 	PKG_CHECK_MODULES(VALGRIND, [valgrind], have_valgrind=yes, have_valgrind=no)
+	AC_MSG_CHECKING([whether to include valgrind support])
 	if test x$have_valgrind = xyes; then
 		AC_DEFINE([HAVE_VALGRIND], 1, [Use valgrind intrinsics to suppress false warnings])
+	else
+		if test "x$VG" = xyes; then
+			AC_MSG_ERROR([valgrind support requested, but valgrind-dev headers not found])
+		fi
 	fi
+	AC_MSG_RESULT([$have_valgrind ($VG)])
 fi
 if test "x$DEBUG" = xsync; then
 	AC_DEFINE(DEBUG_SYNC,1,[Enable synchronous rendering for debugging])