Fixed #9420 (False positive - redundantInitialization)

Author: danmar

lib/astutils.cpp

@@ -1681,6 +1681,15 @@ struct FwdAnalysis::Result FwdAnalysis::checkRecursive(const Token *expr, const
             return Result(Result::Type::BAILOUT);
         }
 
+        if (mWhat == What::Reassign &&
+            Token::simpleMatch(tok, ";") &&
+            Token::simpleMatch(tok->astParent(), ";") &&
+            Token::simpleMatch(tok->astParent()->astParent(), "(") &&
+            Token::simpleMatch(tok->astParent()->astParent()->previous(), "for (") &&
+            !isUnchanged(tok, tok->astParent()->astParent()->link(), exprVarIds, local))
+            // TODO: This is a quick bailout to avoid FP #9420, there are false negatives (TODO_ASSERT_EQUALS)
+            return Result(Result::Type::BAILOUT);
+
         if (expr->isName() && Token::Match(tok, "%name% (") && tok->str().find("<") != std::string::npos && tok->str().find(expr->str()) != std::string::npos)
             return Result(Result::Type::BAILOUT);
 

test/testother.cpp

@@ -6629,6 +6629,19 @@ class TestOther : public TestFixture {
               "     } while (false);\n"
               "}");
         ASSERT_EQUALS("", errout.str());
+
+        check("void foo(int num) {\n" // #9420 FP
+              "  int a = num;\n"
+              "  for (int b = 0; b < num; a = b++)\n"
+              "    dostuff(a);\n"
+              "}");
+        ASSERT_EQUALS("", errout.str());
+
+        check("void foo(int num) {\n" // #9420 FN
+              "  int a = num;\n"
+              "  for (int b = 0; b < num; a = b++);\n"
+              "}");
+        TODO_ASSERT_EQUALS("error", "", errout.str());
     }
 
     void redundantVarAssignment_after_switch() {