Fix 10290: false negative: container out of bounds (cppcheck-opensource#3269)

pfultz2 · web-flow · commit 8541e0503e34 · 2021-05-22T23:33:13.000+02:00
diff --git a/lib/forwardanalyzer.cpp b/lib/forwardanalyzer.cpp
@@ -111,8 +111,10 @@ struct ForwardTraversal {
             return Progress::Skip;
         T* firstOp = tok->astOperand1();
         T* secondOp = tok->astOperand2();
-        // Evaluate RHS of assignment before LHS
-        if (tok->isAssignmentOp())
+        // Evaluate: 
+        //     1. RHS of assignment before LHS
+        //     2. Unary op before operand
+        if (tok->isAssignmentOp() || !secondOp)
             std::swap(firstOp, secondOp);
         if (firstOp && traverseRecursive(firstOp, f, traverseUnknown, recursion+1) == Progress::Break)
             return Break();
diff --git a/lib/valueflow.cpp b/lib/valueflow.cpp
@@ -1244,7 +1244,7 @@ static void valueFlowPointerAlias(TokenList *tokenlist)
     }
 }
 
-static void valueFlowPointerAliasDeref(TokenList *tokenlist)
+static void valueFlowUninitPointerAliasDeref(TokenList *tokenlist)
 {
     for (Token *tok = tokenlist->front(); tok; tok = tok->next()) {
         if (!tok->isUnaryOp("*"))
@@ -6869,7 +6869,6 @@ void ValueFlow::setValues(TokenList *tokenlist, SymbolDatabase* symboldatabase,
     while (n > 0 && values < getTotalValues(tokenlist)) {
         values = getTotalValues(tokenlist);
         valueFlowImpossibleValues(tokenlist, settings);
-        valueFlowPointerAliasDeref(tokenlist);
         valueFlowArrayBool(tokenlist);
         valueFlowRightShift(tokenlist, settings);
         valueFlowAfterMove(tokenlist, symboldatabase, errorLogger, settings);
@@ -6883,6 +6882,7 @@ void ValueFlow::setValues(TokenList *tokenlist, SymbolDatabase* symboldatabase,
         valueFlowLifetime(tokenlist, symboldatabase, errorLogger, settings);
         valueFlowFunctionDefaultParameter(tokenlist, symboldatabase, errorLogger, settings);
         valueFlowUninit(tokenlist, symboldatabase, errorLogger, settings);
+        valueFlowUninitPointerAliasDeref(tokenlist);
         if (tokenlist->isCPP()) {
             valueFlowSmartPointer(tokenlist, errorLogger, settings);
             valueFlowIterators(tokenlist, settings);
diff --git a/test/teststl.cpp b/test/teststl.cpp
@@ -440,6 +440,13 @@ class TestStl : public TestFixture {
                     "   (*PArr)[i] = 1;\n"
                     "}\n");
         ASSERT_EQUALS("", errout.str());
+
+        checkNormal("int f() {\n"
+                    "    std::vector<int> v;\n"
+                    "    std::vector<int> * pv = &v;\n"
+                    "    return (*pv).at(42);\n"
+                    "}\n");
+        ASSERT_EQUALS("test.cpp:4:error:Out of bounds access in expression '(*pv).at(42)' because '*pv' is empty and 'at' may be non-zero.\n", errout.str());
     }
 
     void outOfBoundsIndexExpression() {
