Fix 10023: ValueFlow; Wrong result of post-increment in reverse analysis (#3289)

lib/reverseanalyzer.cpp

@@ -42,6 +42,11 @@ struct ReverseTraversal {
     bool updateRecursive(Token* start) {
         bool continueB = true;
         visitAstNodes(start, [&](Token* tok) {
+            const Token* parent = tok->astParent();
+            while (Token::simpleMatch(parent, ":"))
+                parent = parent->astParent();
+            if (isUnevaluated(tok) || isDeadCode(tok, parent))
+                return ChildrenToVisit::none;
             continueB &= update(tok);
             if (continueB)
                 return ChildrenToVisit::op1_and_op2;
@@ -73,9 +78,11 @@ struct ReverseTraversal {
         return result;
     }
 
-    Token* isDeadCode(Token* tok) {
+    Token* isDeadCode(Token* tok, const Token* end = nullptr) {
         int opSide = 0;
         for (; tok && tok->astParent(); tok = tok->astParent()) {
+            if (tok == end)
+                break;
             Token* parent = tok->astParent();
             if (Token::simpleMatch(parent, ":")) {
                 if (astIsLHS(tok))
@@ -178,8 +185,7 @@ struct ReverseTraversal {
                 }
                 if (!continueB)
                     break;
-                Analyzer::Action a = valueFlowGenericForward(assignTop->astOperand2(), analyzer, settings);
-                if (a.isModified())
+                if (!updateRecursive(assignTop->astOperand2()))
                     break;
                 tok = previousBeforeAstLeftmostLeaf(assignTop)->next();
                 continue;

test/testbufferoverrun.cpp

@@ -133,6 +133,7 @@ private:
         TEST_CASE(array_index_53); // #4750
         TEST_CASE(array_index_54); // #10268
         TEST_CASE(array_index_55); // #10254
+        TEST_CASE(array_index_57); // #10023
         TEST_CASE(array_index_multidim);
         TEST_CASE(array_index_switch_in_for);
         TEST_CASE(array_index_for_in_for);   // FP: #2634
@@ -1593,6 +1594,34 @@ private:
         ASSERT_EQUALS("", errout.str());
     }
 
+    void array_index_57() {
+        check("void f(std::vector<int>& v) {\n"
+              "    int a[3] = { 1, 2, 3 };\n"
+              "    int i = 0;\n"
+              "    for (auto& x : v) {\n"
+              "        int c = a[i++];\n"
+              "        if (i == 3)\n"
+              "            i = 0;\n"
+              "        x = c;\n"
+              "    }\n"
+              "}\n");
+        ASSERT_EQUALS("", errout.str());
+
+        check("void f(std::vector<int>& v) {\n"
+              "    int a[3] = { 1, 2, 3 };\n"
+              "    int i = 0;\n"
+              "    for (auto& x : v) {\n"
+              "        int c = a[i++];\n"
+              "        if (i == 4)\n"
+              "            i = 0;\n"
+              "        x = c;\n"
+              "    }\n"
+              "}\n");
+        ASSERT_EQUALS(
+            "[test.cpp:6] -> [test.cpp:5]: (warning) Either the condition 'i==4' is redundant or the array 'a[3]' is accessed at index 3, which is out of bounds.\n",
+            errout.str());
+    }
+
     void array_index_multidim() {
         check("void f()\n"
               "{\n"

test/testnullpointer.cpp

@@ -728,9 +728,8 @@ private:
               "    if (!p)\n"
               "        ;\n"
               "}");
-        TODO_ASSERT_EQUALS(
+        ASSERT_EQUALS(
             "[test.cpp:4] -> [test.cpp:3]: (warning) Either the condition '!p' is redundant or there is possible null pointer dereference: p.\n",
-            "",
             errout.str());
 
         // while