Index: compile_rules_graph.py
==================================================================
--- compile_rules_graph.py
+++ compile_rules_graph.py
@@ -261,10 +261,46 @@
         return [sOption, sCondition, cAction, sAction]
     else:
         print("# Unknown action at line " + sActionId)
         return None
 
+
+def checkRegexes (dAllGraph):
+    "check validity of regexes"
+    print("  checking regexes...")
+    for sGraphName, dGraph in dAllGraph.items():
+        for nKey, dVal in dGraph.items():
+            if "<re_value>" in dVal:
+                for sRegex in dVal["<re_value>"]:
+                    _checkRegex(sRegex)
+            if "<re_morph>" in dVal:
+                for sRegex in dVal["<re_morph>"]:
+                    _checkRegex(sRegex)
+
+def _checkRegex (sRegex):
+    #print(sRegex)
+    if "¬" in sRegex:
+        sPattern, sNegPattern = sRegex.split("¬")
+        try:
+            if not sNegPattern:
+                print("# Warning! Empty negpattern:", sRegex)
+            re.compile(sPattern)
+            re.compile(sNegPattern)
+        except:
+            print("# Error. Wrong regex:", sRegex)
+            traceback.print_exc()
+            exit()
+    else:
+        try:
+            if not sRegex:
+                print("# Warning! Empty pattern:", sRegex)
+            re.compile(sRegex)
+        except:
+            print("# Error. Wrong regex:", sRegex)
+            traceback.print_exc()
+            exit()
+
 
 def make (lRule, dDef, sLang, bJavaScript):
     "compile rules, returns a dictionary of values"
     # for clarity purpose, don’t create any file here
 
@@ -378,12 +414,14 @@
         print("\nActions:")
         for sActionName, aAction in dACTIONS.items():
             print(sActionName, aAction)
         print("\nFunctions:")
         print(sPyCallables)
+
+    checkRegexes(dAllGraph)
 
     # Result
     return {
         "graph_callables": sPyCallables,
         "rules_graphs": dAllGraph,
         "rules_actions": dACTIONS
     }