--- a/sbsv2/raptor/RELEASE-NOTES.txt	Fri Jan 29 09:52:16 2010 +0000
+++ b/sbsv2/raptor/RELEASE-NOTES.txt	Fri Feb 05 20:24:19 2010 +0000
@@ -1,6 +1,10 @@
 
 Release Notes for Symbian Build System v2
 
+Next Version
+Defect Fixes:
+- Better error messages for make-engine selection.  e.g. "sbs -e arm" will now produce a useful error message rather than a traceback. "arm" is a real variant but it's not a make engine.  In the past sbs would have tried to use it and would have failed with a complicated traceback. Also doesn't traceback for non-existent make engines.
+
 version 2.12.1
 
 Defect Fixes:

--- a/sbsv2/raptor/python/raptor.py	Fri Jan 29 09:52:16 2010 +0000
+++ b/sbsv2/raptor/python/raptor.py	Fri Feb 05 20:24:19 2010 +0000
@@ -631,7 +631,7 @@
 		return True
 
 	def SetMakeEngine(self, makeEngine):
-		self.makeEngine = makeEngine
+		self.makeEngineName = makeEngine
 		return True
 
 	def AddMakeOption(self, makeOption):
@@ -1276,15 +1276,17 @@
 			if self.toolcheck != 'off':
 				self.CheckConfigs(buildUnitsToBuild)
 			else:
-				self.Info(" Not Checking Tool Versions")
+				self.Info("Not Checking Tool Versions")
 
 			self.AssertBuildOK()
 
 			# Setup a make engine.
 			if not self.maker:
-				self.maker = raptor_make.MakeEngine(self)
-				if self.maker == None:
-					self.Error("No make engine present")
+				try:
+					self.maker = raptor_make.MakeEngine(self, self.makeEngineName)
+				except raptor_make.BadMakeEngineException,e:
+					self.Error("Unable to use make engine: %s " % str(e))
+					
 
 			self.AssertBuildOK()
 

--- a/sbsv2/raptor/python/raptor_data.py	Fri Jan 29 09:52:16 2010 +0000
+++ b/sbsv2/raptor/python/raptor_data.py	Fri Feb 05 20:24:19 2010 +0000
@@ -884,6 +884,20 @@
 			vars.append(m)
 		return [ BuildUnit(name=name, variants=vars) ]
 
+	def isChildOf(self, progenitor, cache):
+		r = False
+		pname = self.extends
+		while pname is not None and pname is not '':
+			parent = cache.FindNamedVariant(pname)
+			if parent is None:
+				break
+			if parent.name == progenitor:
+				r = True
+				break
+			pname = parent.extends
+
+		return r
+
 	def __str__(self):
 		s = "<var name='%s' extends='%s'>\n" % (self.name, self.extends)
 		for op in self.ops:

--- a/sbsv2/raptor/python/raptor_make.py	Fri Jan 29 09:52:16 2010 +0000
+++ b/sbsv2/raptor/python/raptor_make.py	Fri Feb 05 20:24:19 2010 +0000
@@ -33,18 +33,19 @@
 from xml.sax.saxutils import escape
 
 
+class BadMakeEngineException(Exception):
+	pass
+
 # raptor_make module classes
 
 class MakeEngine(object):
 
-	def __init__(self, Raptor):
+	def __init__(self, Raptor, engine):
 		self.raptor = Raptor
 		self.valid = True
 		self.descrambler = None
 		self.descrambler_started = False
 
-		engine = Raptor.makeEngine
-		
 		# look for an alias first as this gives end-users a chance to modify
 		# the shipped variant rather than completely replacing it.
 		if engine in Raptor.cache.aliases:
@@ -52,8 +53,10 @@
 		elif engine in Raptor.cache.variants:
 			avar = Raptor.cache.FindNamedVariant(engine)
 		else:
-			Raptor.Error("No settings found for build engine '%s'", engine)
-			return
+			raise BadMakeEngineException("'%s' does not appear to be a make engine - no settings found for it" % engine)
+
+		if not avar.isChildOf("make_engine", Raptor.cache):
+			raise BadMakeEngineException("'%s' is not a build engine (it's a variant but it does not extend 'make_engine')" % engine)
 					
 		# find the variant and extract the values
 		try:
@@ -105,14 +108,13 @@
 				self.selectors = []
 
 		except KeyError:
-			Raptor.Error("Bad '%s' configuration found.", engine)
 			self.valid = False
-			return
+			raise BadMakeEngineException("Bad '%s' configuration found." % engine)
 
 		# there must at least be a build command...
 		if not self.buildCommand:
-				Raptor.Error("No build command for '%s'", engine)
-				self.valid = False
+			self.valid = False
+			raise BadMakeEngineException("No build command for '%s'"% engine)
 
 
 		if self.usetalon: