Fix 10537: FN: knownConditionTrueFalse (std::string::c_str() never returns nullptr) (#3498)

Author: pfultz2

lib/valueflow.cpp

@@ -1560,6 +1560,25 @@ static void valueFlowImpossibleValues(TokenList* tokenList, const Settings* sett
             value.bound = ValueFlow::Value::Bound::Upper;
             value.setImpossible();
             setTokenValue(tok->next(), value, settings);
+        } else if (Token::Match(tok, ". data|c_str (") && astIsContainerOwned(tok->astOperand1())) {
+            const Library::Container* container = tok->astOperand1()->valueType()->container;
+            if (!container)
+                continue;
+            if (!container->stdStringLike)
+                continue;
+            if (container->view)
+                continue;
+            ValueFlow::Value value{0};
+            value.setImpossible();
+            setTokenValue(tok->tokAt(2), value, settings);
+        } else if (Token::Match(tok, "make_shared|make_unique <") && Token::simpleMatch(tok->linkAt(1), "> (")) {
+            ValueFlow::Value value{0};
+            value.setImpossible();
+            setTokenValue(tok->linkAt(1)->next(), value, settings);
+        } else if (tokenList->isCPP() && Token::simpleMatch(tok, "this")) {
+            ValueFlow::Value value{0};
+            value.setImpossible();
+            setTokenValue(tok, value, settings);
         }
     }
 }

test/testvalueflow.cpp

@@ -142,6 +142,7 @@ class TestValueFlow : public TestFixture {
         TEST_CASE(valueFlowIdempotent);
         TEST_CASE(valueFlowUnsigned);
         TEST_CASE(valueFlowMod);
+        TEST_CASE(valueFlowNotNull);
         TEST_CASE(valueFlowSymbolic);
         TEST_CASE(valueFlowSmartPointer);
     }
@@ -6197,6 +6198,43 @@ class TestValueFlow : public TestFixture {
         ASSERT_EQUALS(false, testValueOfXImpossible(code, 3U, 1));
     }
 
+    void valueFlowNotNull()
+    {
+        const char* code;
+
+        code = "int f(const std::string &str) {\n"
+               "    int x = str.c_str();\n"
+               "    return x;\n"
+               "}\n";
+        ASSERT_EQUALS(true, testValueOfXImpossible(code, 3U, 0));
+
+        code = "int f(const std::string_view &str) {\n"
+               "    int x = str.c_str();\n"
+               "    return x;\n"
+               "}\n";
+        ASSERT_EQUALS(false, testValueOfXImpossible(code, 3U, 0));
+
+        code = "auto f() {\n"
+               "    std::shared_ptr<int> x = std::make_shared<int>(1);\n"
+               "    return x;\n"
+               "}\n";
+        ASSERT_EQUALS(true, testValueOfXImpossible(code, 3U, 0));
+
+        code = "auto f() {\n"
+               "    std::unique_ptr<int> x = std::make_unique<int>(1);\n"
+               "    return x;\n"
+               "}\n";
+        ASSERT_EQUALS(true, testValueOfXImpossible(code, 3U, 0));
+
+        code = "struct A {\n"
+               "    A* f() {\n"
+               "        A* x = this;\n"
+               "        return x;\n"
+               "    }\n"
+               "};\n";
+        ASSERT_EQUALS(true, testValueOfXImpossible(code, 4U, 0));
+    }
+
     void valueFlowSymbolic() {
         const char* code;