value flow: starting to refactor CheckNullPointer::nullPointerDeRefThenCheck

lib/checknullpointer.cpp

@@ -753,6 +753,31 @@ void CheckNullPointer::nullPointerByDeRefAndChec()
 {
     const SymbolDatabase *symbolDatabase = _tokenizer->getSymbolDatabase();
 
+    if (_settings->valueFlow) {
+        for (const Token *tok = _tokenizer->tokens(); tok; tok = tok->next()) {
+            if (!tok->isName() || !tok->values.empty())
+                continue;
+
+            const Variable *var = tok->variable();
+            if (!var || !var->isPointer())
+                continue;
+
+            bool unknown = false;
+            if (!isPointerDeRef(tok,unknown))
+                continue;
+
+            for (std::list<ValueFlow::Value>::const_iterator it = tok->values.begin(); it != tok->values.end(); ++it) {
+                if (it->intvalue != 0)
+                    continue;
+                if (it->condition == NULL)
+                    nullPointerError(tok);
+                else if (_settings->isEnabled("warning"))
+                    nullPointerError(tok, tok->str(), it->condition, false);
+            }
+        }
+        return;
+    }
+
     // Dereferencing a pointer and then checking if it's NULL..
     // This check will first scan for the check. And then scan backwards
     // from the check, searching for dereferencing.

lib/valueflow.cpp

@@ -103,7 +103,7 @@ static void valueFlowBeforeCondition(TokenList *tokenlist, ErrorLogger *errorLog
 
             if (tok2->varId() == varid) {
                 // bailout: assignment
-                if (Token::Match(tok2, "%var% =")) {
+                if (Token::Match(tok2->previous(), "!!* %var% =")) {
                     if (settings->debugwarnings)
                         bailout(tokenlist, errorLogger, tok2, "assignment of " + tok2->str());
                     break;

test/testnullpointer.cpp

@@ -86,6 +86,7 @@ private:
         Settings settings;
         settings.addEnabled("warning");
         settings.inconclusive = inconclusive;
+        //settings.valueFlow = true;
 
         // Tokenize..
         Tokenizer tokenizer(&settings, this);

test/testvalueflow.cpp

@@ -91,6 +91,12 @@ private:
         ASSERT_EQUALS(true, testValueOfX(code, 2U, 1));
         ASSERT_EQUALS(true, testValueOfX(code, 2U, 0));
 
+        code = "void f(int *x) {\n"
+               "    *x = 100;\n"
+               "    if (x) {}\n"
+               "}";
+        ASSERT_EQUALS(true, testValueOfX(code, 2U, 0));
+
         // bailout: ?:
         bailout("void f(int x) {\n"
                 "    y = ((x<0) ? x : ((x==2)?3:4));\n"