Fix #12365 checkLibraryFunction for std::string constructor (#5893)

I wonder why both `%name%` and `%type%` match `return`.

Author: chrchr-github

lib/checkfunctions.cpp

@@ -662,7 +662,7 @@ void CheckFunctions::checkLibraryMatchFunctions()
             continue;
 
         const Token* start = tok;
-        while (Token::Match(start->tokAt(-2), "%name% ::"))
+        while (Token::Match(start->tokAt(-2), "%name% ::") && !start->tokAt(-2)->isKeyword())
             start = start->tokAt(-2);
         if (mSettings->library.detectContainerOrIterator(start))
             continue;

lib/checkleakautovar.cpp

@@ -939,6 +939,8 @@ void CheckLeakAutoVar::functionCall(const Token *tokName, const Token *tokOpenin
     const bool isLeakIgnore = mSettings->library.isLeakIgnore(mSettings->library.getFunctionName(tokName));
     if (mSettings->library.getReallocFuncInfo(tokName))
         return;
+    if (tokName->next()->valueType() && tokName->next()->valueType()->container && tokName->next()->valueType()->container->stdStringLike)
+        return;
 
     const Token * const tokFirstArg = tokOpeningPar->next();
     if (!tokFirstArg || tokFirstArg->str() == ")") {

test/testfunctions.cpp

@@ -2041,6 +2041,11 @@ class TestFunctions : public TestFixture {
               "    if (t.at(0)) {}\n"
               "};\n", "test.cpp", &s);
         ASSERT_EQUALS("", errout.str());
+
+        check("::std::string f(const char* c) {\n" // #12365
+              "    return ::std::string(c);\n"
+              "}\n", "test.cpp", &s);
+        ASSERT_EQUALS("", errout.str());
     }
 
     void checkUseStandardLibrary1() {

test/testleakautovar.cpp

@@ -1757,8 +1757,14 @@ class TestLeakAutoVar : public TestFixture {
               "        auto s = new S;\n"
               "        v.push_back(std::unique_ptr<S>(s));\n"
               "    }\n"
-              "}\n", &s);
+              "}\n", /*cpp*/ true, &s);
         ASSERT_EQUALS("", errout.str()); // don't crash
+
+        check("void g(size_t len) {\n" // #12365
+              "    char* b = new char[len + 1]{};\n"
+              "    std::string str = std::string(b);\n"
+              "}", /*cpp*/ true, &s);
+        ASSERT_EQUALS("[test.cpp:4]: (error) Memory leak: b\n", errout.str());
     }
 
     void goto1() {