new loplugin mergeclasses

Idea from Norbert (shm_get) - look for classes that are
(a) not instantiated
(b) have zero or one subclasses
and warn about them - would allow us to remove a bunch of abstract
classes that can be merged into one class and simplified

Change-Id: I4e43fdd2f549b5cbe25dcb7cee5e9dd3c1df8ba0

compilerplugins/clang/mergeclasses.py

@@ -0,0 +1,73 @@
+#!/usr/bin/python
+
+import sys
+
+instantiatedSet = set()
+definitionSet = set()
+parentChildDict = {}
+definitionToFileDict = {}
+
+with open("mergeclasses.log") as txt:
+    for line in txt:
+    
+        if line.startswith("instantiated:\t"):
+            idx1 = line.find("\t")
+            clazzName = line[idx1+1 : len(line)-1]
+            if (clazzName.startswith("const ")):
+                clazzName = clazzName[6:]
+            if (clazzName.startswith("class ")):
+                clazzName = clazzName[6:]
+            if (clazzName.endswith(" &")):
+                clazzName = clazzName[:len(clazzName)-3]
+            instantiatedSet.add(clazzName)
+            
+        elif line.startswith("definition:\t"):
+            idx1 = line.find("\t")
+            idx2 = line.find("\t", idx1+1)
+            clazzName = line[idx1+1 : idx2]
+            fileName  = line[idx2+1 : len(line)-1]
+            definitionSet.add(clazzName)
+            definitionToFileDict[clazzName] = fileName
+            
+        elif line.startswith("has-subclass:\t"):
+            idx1 = line.find("\t")
+            idx2 = line.find("\t", idx1+1)
+            child  = line[idx1+1 : idx2]
+            parent = line[idx2+1 : len(line)-1]
+            if (parent.startswith("class ")):
+                parent = parent[6:]
+            elif (parent.startswith("struct ")):
+                parent = parent[7:]
+            if (child.startswith("class ")):
+                child = child[6:]
+            elif (child.startswith("struct ")):
+                child = child[7:]
+            if (parent not in parentChildDict):
+                parentChildDict[parent] = set()
+            parentChildDict[parent].add(child)
+            
+def extractModuleName(clazz):
+    filename = definitionToFileDict[clazz]
+    if filename.startswith("include/"):
+        filename = filename[8:]
+    idx = filename.find("/")
+    return filename[:idx]
+
+for clazz in sorted(definitionSet - instantiatedSet):
+    # find uninstantiated classes without any subclasses
+    if (not(clazz in parentChildDict)) or (len(parentChildDict[clazz]) != 1):
+        continue
+    # exclude some common false positives
+    a = ['Dialog', 'Dlg', 'com::sun', 'Base']
+    if any(x in clazz for x in a):
+        continue
+    # ignore base class that contain the word "mutex", they are normally there to
+    # help with the WeakComponentImpl template magic
+    if clazz.find("mutex") != -1 or clazz.find("Mutex") != -1:
+        continue
+    otherclazz = next(iter(parentChildDict[clazz]))
+   # exclude combinations that span modules because we often use those to make cross-module dependencies more manageable.
+    if extractModuleName(clazz) != extractModuleName(otherclazz):
+        continue
+    print "merge", clazz, "with", otherclazz
+