Fix 10592: False positive: returnDanglingLifetime (#3557)

Author: pfultz2

lib/astutils.cpp

@@ -259,6 +259,15 @@ bool astIsSmartPointer(const Token* tok)
     return tok && tok->valueType() && tok->valueType()->smartPointerTypeToken;
 }
 
+bool astIsUniqueSmartPointer(const Token* tok)
+{
+    if (!astIsSmartPointer(tok))
+        return false;
+    if (!tok->valueType()->smartPointer)
+        return false;
+    return tok->valueType()->smartPointer->unique;
+}
+
 bool astIsIterator(const Token *tok)
 {
     return tok && tok->valueType() && tok->valueType()->type == ValueType::Type::ITERATOR;

lib/astutils.h

@@ -82,6 +82,7 @@ bool astIsBool(const Token *tok);
 bool astIsPointer(const Token *tok);
 
 bool astIsSmartPointer(const Token* tok);
+bool astIsUniqueSmartPointer(const Token* tok);
 
 bool astIsIterator(const Token *tok);
 

lib/checkautovariables.cpp

@@ -557,6 +557,21 @@ static const Token* getParentLifetime(bool cpp, const Token* tok, const Library*
     if (std::any_of(it.base() - 1, members.end() - 1, [&](const Token* tok2) {
         if (astIsPointer(tok2) || astIsContainerView(tok2) || astIsIterator(tok2))
             return true;
+        if (!astIsUniqueSmartPointer(tok2)) {
+            if (astIsSmartPointer(tok2))
+                return true;
+            const Token* dotTok = tok2->next();
+            if (!Token::simpleMatch(dotTok, ".")) {
+                const Token* endTok = nextAfterAstRightmostLeaf(tok2);
+                if (Token::simpleMatch(endTok, "."))
+                    dotTok = endTok;
+                else if (Token::simpleMatch(endTok->next(), "."))
+                    dotTok = endTok->next();
+            }
+            // If we are dereferencing the member variable then treat it as borrowed
+            if (Token::simpleMatch(dotTok, ".") && dotTok->originalName() == "->")
+                return true;
+        }
         const Variable* var = tok2->variable();
         return var && var->isReference();
     }))

lib/valueflow.cpp

@@ -2885,15 +2885,6 @@ static void valueFlowReverse(TokenList* tokenlist,
     valueFlowReverse(tok, nullptr, varToken, values, tokenlist, settings);
 }
 
-static bool isUniqueSmartPointer(const Token* tok)
-{
-    if (!astIsSmartPointer(tok))
-        return false;
-    if (!tok->valueType()->smartPointer)
-        return false;
-    return tok->valueType()->smartPointer->unique;
-}
-
 std::string lifetimeType(const Token *tok, const ValueFlow::Value *val)
 {
     std::string result;
@@ -3090,8 +3081,7 @@ static std::vector<LifetimeToken> getLifetimeTokens(const Token* tok,
             return {{tok, std::move(errorPath)}};
         const Variable *tokvar = vartok->variable();
         const bool isContainer = astIsContainer(vartok) && !astIsPointer(vartok);
-        if (!isUniqueSmartPointer(vartok) && !isContainer &&
-            !(tokvar && tokvar->isArray() && !tokvar->isArgument()) &&
+        if (!astIsUniqueSmartPointer(vartok) && !isContainer && !(tokvar && tokvar->isArray() && !tokvar->isArgument()) &&
             (Token::Match(vartok->astParent(), "[|*") || vartok->astParent()->originalName() == "->")) {
             for (const ValueFlow::Value &v : vartok->values()) {
                 if (!v.isLocalLifetimeValue())
@@ -4158,7 +4148,7 @@ static void valueFlowLifetime(TokenList *tokenlist, SymbolDatabase*, ErrorLogger
             valueFlowLifetimeFunction(tok, tokenlist, errorLogger, settings);
         }
         // Unique pointer lifetimes
-        else if (isUniqueSmartPointer(tok) && astIsLHS(tok) && Token::simpleMatch(tok->astParent(), ". get ( )")) {
+        else if (astIsUniqueSmartPointer(tok) && astIsLHS(tok) && Token::simpleMatch(tok->astParent(), ". get ( )")) {
             Token* ptok = tok->astParent()->tokAt(2);
             ErrorPath errorPath = {{ptok, "Raw pointer to smart pointer created here."}};
             ValueFlow::Value value;

test/testautovariables.cpp

@@ -2482,6 +2482,15 @@ class TestAutoVariables : public TestFixture {
               "    }\n"
               "};\n");
         ASSERT_EQUALS("", errout.str());
+
+        check("struct A {\n"
+              "    std::map<std::string, int> m;\n"
+              "    int* f(std::string s) {\n"
+              "        auto r = m.emplace(name, name);\n"
+              "        return &(r.first->second);\n"
+              "    }\n"
+              "};\n");
+        ASSERT_EQUALS("", errout.str());
     }
 
     void danglingLifetimeContainerView()