Fix #11881 FP returnStdMoveLocal / Fix FP incorrectStringBooleanError / Support std::string::starts/ends_with() (#5347)

cfg/std.cfg

@@ -6884,6 +6884,18 @@ The obsolete function 'gets' is called. With 'gets' you'll get a buffer overrun
       <not-uninit/>
     </arg>
   </function>
+  <!-- constexpr bool std::string::starts_with( std::basic_string_view<CharT,Traits> sv ) const noexcept; // since C++20 -->
+  <!-- constexpr bool starts_with( CharT ch ) const noexcept; // since C++20 -->
+  <!-- constexpr bool starts_with( const CharT* s ) const; // since C++20 -->
+  <function name="std::string::starts_with,std::wstring::starts_with,std::string::ends_with,std::wstring::ends_with">
+    <noreturn>false</noreturn>
+    <use-retval/>
+    <returnValue type="bool"/>
+    <const/>
+    <arg nr="1" direction="in">
+      <not-uninit/>
+    </arg>
+  </function>
   <!-- size_type std::string::copy( CharT* dest, size_type count, size_type pos = 0) const; -->
   <!-- size_type std::wstring::copy( CharT* dest, size_type count, size_type pos = 0) const; -->
   <function name="std::string::copy,std::wstring::copy">

lib/astutils.cpp

@@ -1477,19 +1477,6 @@ static bool astIsBoolLike(const Token* tok)
     return astIsBool(tok) || isUsedAsBool(tok);
 }
 
-bool isBooleanFuncArg(const Token* tok) {
-    if (tok->variable() && tok->variable()->valueType() && tok->variable()->valueType()->type == ValueType::BOOL) // skip trivial case: bool passed as bool
-        return false;
-    int argn{};
-    const Token* ftok = getTokenArgumentFunction(tok, argn);
-    if (!ftok)
-        return false;
-    std::vector<const Variable*> argvars = getArgumentVars(ftok, argn);
-    if (argvars.size() != 1)
-        return false;
-    return !argvars[0]->isReference() && argvars[0]->valueType() && argvars[0]->valueType()->type == ValueType::BOOL;
-}
-
 bool isSameExpression(bool cpp, bool macro, const Token *tok1, const Token *tok2, const Library& library, bool pure, bool followVar, ErrorPath* errors)
 {
     if (tok1 == nullptr && tok2 == nullptr)

lib/astutils.h

@@ -256,11 +256,6 @@ const Token* isInLoopCondition(const Token* tok);
  */
 CPPCHECKLIB bool isUsedAsBool(const Token* const tok, const Settings* settings = nullptr);
 
-/**
- * Is token passed to a function taking a bool argument
- */
-CPPCHECKLIB bool isBooleanFuncArg(const Token* tok);
-
 /**
  * Are two conditions opposite
  * @param isNot  do you want to know if cond1 is !cond2 or if cond1 and cond2 are non-overlapping. true: cond1==!cond2  false: cond1==true => cond2==false

lib/checkfunctions.cpp

@@ -673,7 +673,7 @@ void CheckFunctions::returnLocalStdMove()
     const SymbolDatabase *symbolDatabase = mTokenizer->getSymbolDatabase();
     for (const Scope *scope : symbolDatabase->functionScopes) {
         // Expect return by-value
-        if (Function::returnsReference(scope->function, true))
+        if (Function::returnsReference(scope->function, /*unknown*/ true, /*includeRValueRef*/ true))
             continue;
         const auto rets = Function::findReturns(scope->function);
         for (const Token* ret : rets) {

lib/checkstring.cpp

@@ -288,13 +288,7 @@ void CheckString::checkIncorrectStringCompare()
                         incorrectStringCompareError(tok->next(), "substr", end->strAt(1));
                     }
                 }
-            } else if (Token::Match(tok, "&&|%oror%|( %str%|%char% &&|%oror%|)") && !Token::Match(tok, "( %str%|%char% )")) {
+            } else if (Token::Match(tok, "%str%|%char%") && isUsedAsBool(tok))
-                incorrectStringBooleanError(tok->next(), tok->strAt(1));
-            } else if (Token::Match(tok, "if|while ( %str%|%char% )") && !tok->tokAt(2)->getValue(0)) {
-                incorrectStringBooleanError(tok->tokAt(2), tok->strAt(2));
-            } else if (tok->str() == "?" && Token::Match(tok->astOperand1(), "%str%|%char%")) {
-                incorrectStringBooleanError(tok->astOperand1(), tok->astOperand1()->str());
-            } else if (Token::Match(tok, "%str%") && isBooleanFuncArg(tok))
                 incorrectStringBooleanError(tok, tok->str());
         }
     }

test/cfg/std.cpp

@@ -4503,6 +4503,11 @@ void stdstring()
 
     // valid
     s.assign("a");
+
+#ifdef __cpp_lib_starts_ends_with
+    // cppcheck-suppress ignoredReturnValue
+    s.starts_with("abc");
+#endif
 }
 
 void stdvector()

test/testfunctions.cpp

@@ -1808,6 +1808,12 @@ private:
               "    std::cout << p->msg;\n"
               "}\n");
         ASSERT_EQUALS("", errout.str());
+
+        check("std::string&& f() {\n" // #11881
+              "    std::string s;\n"
+              "    return std::move(s);\n"
+              "}\n");
+        ASSERT_EQUALS("", errout.str());
     }
 
     void negativeMemoryAllocationSizeError() { // #389

test/teststring.cpp

@@ -735,7 +735,9 @@ private:
               "  if('\\0'){}\n"
               "  if(L'\\0'){}\n"
               "}");
-        ASSERT_EQUALS("", errout.str());
+        ASSERT_EQUALS("[test.cpp:2]: (warning) Conversion of char literal '\\0' to bool always evaluates to false.\n"
+                      "[test.cpp:3]: (warning) Conversion of char literal L'\\0' to bool always evaluates to false.\n",
+                      errout.str());
 
         check("void f() {\n"
               "  if('\\0' || cond){}\n"
@@ -750,6 +752,22 @@ private:
               "    f(\"abc\");\n"
               "}\n");
         ASSERT_EQUALS("[test.cpp:4]: (warning) Conversion of string literal \"abc\" to bool always evaluates to true.\n", errout.str());
+
+        check("void g(bool);\n"
+              "    void f(std::map<std::string, std::vector<int>>&m) {\n"
+              "    if (m.count(\"abc\"))\n"
+              "        g(m[\"abc\"][0] ? true : false);\n"
+              "}\n");
+        ASSERT_EQUALS("", errout.str());
+
+        check("void g(bool b);\n"
+              "void f() {\n"
+              "    g('\\0');\n"
+              "    g('a');\n"
+              "}\n");
+        ASSERT_EQUALS("[test.cpp:3]: (warning) Conversion of char literal '\\0' to bool always evaluates to false.\n"
+                      "[test.cpp:4]: (warning) Conversion of char literal 'a' to bool always evaluates to true.\n",
+                      errout.str());
     }
 
     void deadStrcmp() {