buildsys: add cppcheck wrapper script (correct one)

Also incooperate vapier's suggestion on how to set REAL_CC once

Signed-off-by: Bernhard Reutner-Fischer <rep.dot.nop@gmail.com>

extra/scripts/cppcheck.sh

@@ -1,23 +1,56 @@
 #! /bin/sh
 
-${REAL_CC-gcc} $*
+# usage:
+#
+# make \
+#	REAL_CC=gcc-mine \
+#	CC=extra/scripts/cppcheck.sh \
+#	CPPCHECK_FLAGS="--enable=style,performance,portability,information,missingInclude --max-configs=256 -j $(($(getconf _NPROCESSORS_ONLN)-1))" \
+#	CPPCHECK_LIMIT="yes"
 
+# CPPCHECK_FLAGS are optional and are not set per default.
+# CPPCHECK_LIMIT limits cppcheck to the -D and -U that would be passed to CC.
+# Setting CPPCHECK_LIMIT greatly improves the check-time but obviously
+# just checks a small subset of the defines found in a file.
+
+: ${REAL_CC:=gcc}
+${REAL_CC} $@
 args=""
-add_next=0
+limits=""
+next_arg=0
+next_limit=0
 
-for i in $*
+for i in $@
 do
-  if [ $add_next -eq 1 ] ; then
+  if [ $next_arg -eq 1 ] ; then
+	next_arg=0
+	case "/$i" in
+	/-*) exit 0 ;;
+	esac
     [ "x$args" = "x" ] && args="$i" || args="$args $i"
-	add_next=0
+	continue
+  fi
+  if [ $next_limit -eq 1 ] ; then
+	next_limit=0
+    [ "x$limits" = "x" ] && limits="$i" || limits="$limits $i"
 	continue
   fi
   case "/$i" in
-  /-c) add_next=1 ;;
-  /-D*|/-I*|/-inc) [ "x$args" = "x" ] && args="$i" || args="$args $i" ;;
-  /-dumpversion|/--print*) ${CC-gcc} $i ; exit 0 ;;
+  /-c) next_arg=1 ;;
+  /-isystem)
+		next_arg=1;
+		[ "x$args" = "x" ] && args="-I" || args="$args -I" ;;
+  /-I)
+		next_arg=1;
+		[ "x$args" = "x" ] && args="$i" || args="$args $i" ;;
+  /-I*) [ "x$args" = "x" ] && args="$i" || args="$args $i" ;;
+  /-D|/-U)
+		next_limit=1;
+		[ "x$limit" = "x" ] && limit="$i" || limit="$limit $i" ;;
+  /-D*) [ "x$limits" = "x" ] && limits="$i" || limits="$limits $i" ;;
+  /-s|/-S|/-dump*|/--print*|/-print*) exit 0 ;;
   *) ;;
   esac
 done
-
-cppcheck $args
+[ -z "${CPPCHECK_LIMIT}" ] && limits=""
+[ -z "${args}" ] || exec cppcheck ${CPPCHECK_FLAGS} ${args} ${limits}