From 2808fc615efe3ee0a0867457a085a763e487ed56 Mon Sep 17 00:00:00 2001
From: chrchr-github <78114321+chrchr-github@users.noreply.github.com>
Date: Sat, 24 Sep 2022 12:49:37 +0200
Subject: [PATCH] Fix  #10057 "statement without effect" / #4779 FN
 unusedScopedObject does not work for classes in different namespace (#4500)

* Partial fix for #10057 unused variable without assignment not detected

* Add test for #9672

* Fix #4779 FN unusedScopedObject does not work for classes in different namespace

* Merge

* Fix #10057 "statement without effect" (unused variable without assignment) not detected

* Format
---
 lib/checkother.cpp | 47 +++++++++++++++++++++++++++++++++++-----------
 test/testother.cpp | 25 ++++++++++++++++++++++++
 2 files changed, 61 insertions(+), 11 deletions(-)

diff --git a/lib/checkother.cpp b/lib/checkother.cpp
index cc51b00f3..43cc9a06e 100644
--- a/lib/checkother.cpp
+++ b/lib/checkother.cpp
@@ -2063,20 +2063,45 @@ void CheckOther::checkMisusedScopedObject()
     if (!mSettings->severity.isEnabled(Severity::style))
         return;
 
-    const SymbolDatabase * const symbolDatabase = mTokenizer->getSymbolDatabase();
+    auto getConstructorTok = [](const Token* tok, std::string& typeStr) -> const Token* {
+        if (!Token::Match(tok, "[;{}] %name%"))
+            return nullptr;
+        tok = tok->next();
+        typeStr.clear();
+        while (Token::Match(tok, "%name% ::")) {
+            typeStr += tok->str();
+            typeStr += "::";
+            tok = tok->tokAt(2);
+        }
+        typeStr += tok->str();
+        const Token* endTok = tok;
+        if (Token::Match(endTok, "%name% <"))
+            endTok = endTok->linkAt(1);
+        if (Token::Match(endTok, "%name%|> (|{") && Token::Match(endTok->linkAt(1), ")|} ; !!}") &&
+            !Token::simpleMatch(endTok->next()->astParent(), ";")) { // for loop condition
+            return tok;
+        }
+        return nullptr;
+    };
+
+    auto isLibraryConstructor = [&](const Token* tok, const std::string& typeStr) -> bool {
+        if (mSettings->library.getTypeCheck("unusedvar", typeStr) == Library::TypeCheck::check)
+            return true;
+        return mSettings->library.detectContainerOrIterator(tok);
+    };
+
+    const SymbolDatabase* const symbolDatabase = mTokenizer->getSymbolDatabase();
+    std::string typeStr;
     for (const Scope * scope : symbolDatabase->functionScopes) {
         for (const Token *tok = scope->bodyStart; tok && tok != scope->bodyEnd; tok = tok->next()) {
-            if ((tok->next()->type() || tok->next()->isStandardType() || (tok->next()->function() && tok->next()->function()->isConstructor())) // TODO: The rhs of || should be removed; It is a workaround for a symboldatabase bug
-                && Token::Match(tok, "[;{}] %name% (|{")
-                && Token::Match(tok->linkAt(2), ")|} ; !!}")
-                && (!tok->next()->function() || // is not a function on this scope
-                    tok->next()->function()->isConstructor()) // or is function in this scope and it's a ctor
-                && !Token::simpleMatch(tok->tokAt(2)->astParent(), ";") // for loop condition
-                && tok->next()->str() != "void") {
-                if (const Token* arg = tok->tokAt(2)->astOperand2()) {
+            const Token* ctorTok = getConstructorTok(tok, typeStr);
+            if (ctorTok && (((ctorTok->type() || ctorTok->isStandardType() || (ctorTok->function() && ctorTok->function()->isConstructor())) // TODO: The rhs of || should be removed; It is a workaround for a symboldatabase bug
+                             && (!ctorTok->function() || ctorTok->function()->isConstructor()) // // is not a function on this scope or is function in this scope and it's a ctor
+                             && ctorTok->str() != "void") || isLibraryConstructor(tok->next(), typeStr))) {
+                if (const Token* arg = ctorTok->next()->astOperand2()) {
                     if (!isConstStatement(arg, mTokenizer->isCPP()))
                         continue;
-                    if (tok->strAt(2) == "(") {
+                    if (ctorTok->strAt(1) == "(") {
                         if (arg->varId()) // TODO: check if this is a declaration
                             continue;
                         const Token* rml = nextAfterAstRightmostLeaf(arg);
@@ -2085,7 +2110,7 @@ void CheckOther::checkMisusedScopedObject()
                     }
                 }
                 tok = tok->next();
-                misusedScopeObjectError(tok, tok->str());
+                misusedScopeObjectError(ctorTok, typeStr);
                 tok = tok->next();
             }
         }
diff --git a/test/testother.cpp b/test/testother.cpp
index c63866036..38503f6c6 100644
--- a/test/testother.cpp
+++ b/test/testother.cpp
@@ -140,6 +140,7 @@ private:
         TEST_CASE(testMisusedScopeObjectInConstructor);
         TEST_CASE(testMisusedScopeObjectNoCodeAfter);
         TEST_CASE(testMisusedScopeObjectStandardType);
+        TEST_CASE(testMisusedScopeObjectNamespace);
         TEST_CASE(trac2071);
         TEST_CASE(trac2084);
         TEST_CASE(trac3693);
@@ -5088,6 +5089,30 @@ private:
         ASSERT_EQUALS("", errout.str());
     }
 
+    void testMisusedScopeObjectNamespace() {
+        check("namespace M {\n" // #4479
+              "    namespace N {\n"
+              "        struct S {};\n"
+              "    }\n"
+              "}\n"
+              "int f() {\n"
+              "    M::N::S();\n"
+              "    return 0;\n"
+              "}\n", "test.cpp");
+        ASSERT_EQUALS("[test.cpp:7]: (style) Instance of 'M::N::S' object is destroyed immediately.\n", errout.str());
+
+        check("void f() {\n" // #10057
+              "    std::string(\"abc\");\n"
+              "    std::string{ \"abc\" };\n"
+              "    std::pair<int, int>(1, 2);\n"
+              "    (void)0;\n"
+              "}\n", "test.cpp");
+        ASSERT_EQUALS("[test.cpp:2]: (style) Instance of 'std::string' object is destroyed immediately.\n"
+                      "[test.cpp:3]: (style) Instance of 'std::string' object is destroyed immediately.\n"
+                      "[test.cpp:4]: (style) Instance of 'std::pair' object is destroyed immediately.\n",
+                      errout.str());
+    }
+
     void trac2084() {
         check("void f()\n"
               "{\n"