Fix 10238: FP knownConditionTrueFalse std::string from const char* assumed non-empty (#3288)

lib/valueflow.cpp

@@ -6307,25 +6307,60 @@ static void valueFlowIteratorInfer(TokenList *tokenlist, const Settings *setting
     }
 }
 
-static std::vector<ValueFlow::Value> getInitListSize(const Token* tok,
+static std::vector<ValueFlow::Value> getContainerValues(const Token* tok)
-        const Library::Container* container,
-        bool known = true)
 {
-    std::vector<const Token*> args = getArguments(tok);
+    std::vector<ValueFlow::Value> values;
-    if ((args.size() == 1 && astIsContainer(args[0]) && args[0]->valueType()->container == container) ||
+    if (tok) {
-        (args.size() == 2 && astIsIterator(args[0]) && astIsIterator(args[1]))) {
+        std::copy_if(tok->values().begin(),
-        std::vector<ValueFlow::Value> values;
+                     tok->values().end(),
-        std::copy_if(args[0]->values().begin(),
-                     args[0]->values().end(),
                      std::back_inserter(values),
                      std::mem_fn(&ValueFlow::Value::isContainerSizeValue));
-        return values;
     }
-    ValueFlow::Value value(args.size());
+    return values;
+}
+
+static ValueFlow::Value makeContainerSizeValue(std::size_t s, bool known = true)
+{
+    ValueFlow::Value value(s);
     value.valueType = ValueFlow::Value::ValueType::CONTAINER_SIZE;
     if (known)
         value.setKnown();
-    return {value};
+    return value;
+}
+
+static std::vector<ValueFlow::Value> makeContainerSizeValue(const Token* tok, bool known = true)
+{
+    if (tok->hasKnownIntValue())
+        return {makeContainerSizeValue(tok->values().front().intvalue, known)};
+    return {};
+}
+
+static std::vector<ValueFlow::Value> getInitListSize(const Token* tok,
+                                                     const Library::Container* container,
+                                                     bool known = true)
+{
+    std::vector<const Token*> args = getArguments(tok);
+    // Strings dont use an init list
+    if (!args.empty() && container->stdStringLike) {
+        if (astIsIntegral(args[0], false)) {
+            if (args.size() > 1)
+                return {makeContainerSizeValue(args[0], known)};
+        } else if (astIsPointer(args[0])) {
+            // TODO: Try to read size of string literal
+            if (args.size() == 2 && astIsIntegral(args[1], false))
+                return {makeContainerSizeValue(args[1], known)};
+        } else if (astIsContainer(args[0])) {
+            if (args.size() == 1)
+                return getContainerValues(args[0]);
+            if (args.size() == 3)
+                return {makeContainerSizeValue(args[2], known)};
+        }
+        return {};
+    } else if ((args.size() == 1 && astIsContainer(args[0]) && args[0]->valueType()->container == container) ||
+               (args.size() == 2 && astIsIterator(args[0]) && astIsIterator(args[1]))) {
+        return getContainerValues(args[0]);
+    }
+    return {makeContainerSizeValue(args.size(), known)};
 }
 
 static void valueFlowContainerSize(TokenList *tokenlist, SymbolDatabase* symboldatabase, ErrorLogger * /*errorLogger*/, const Settings *settings)

test/teststl.cpp

@@ -527,6 +527,16 @@ private:
                     "    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());
+
+        checkNormal("std::string f(const char* DirName) {\n"
+                    "  if (DirName == nullptr)\n"
+                    "      return {};\n"
+                    "  std::string Name{ DirName };\n"
+                    "  if (!Name.empty() && Name.back() != '\\')\n"
+                    "    Name += '\\';\n"
+                    "  return Name;\n"
+                    "}\n");
+        ASSERT_EQUALS("", errout.str());
     }
 
     void outOfBoundsIndexExpression() {