From 8fa7dd0fe0ba6c8b576ce2a9e7fb3ba0bb71fa64 Mon Sep 17 00:00:00 2001
From: Paul Fultz II <pfultz2@yahoo.com>
Date: Mon, 10 Feb 2020 11:01:11 -0600
Subject: [PATCH] Fix issue 9595: False positive: Using pointer to temporary
 doesn't account for const ref extended temporary lifetimes (#2525)

---
 lib/astutils.cpp           | 4 ++--
 lib/astutils.h             | 2 +-
 lib/valueflow.cpp          | 2 +-
 test/testautovariables.cpp | 7 +++++++
 4 files changed, 11 insertions(+), 4 deletions(-)

diff --git a/lib/astutils.cpp b/lib/astutils.cpp
index c0f17766b..a1bce083e 100644
--- a/lib/astutils.cpp
+++ b/lib/astutils.cpp
@@ -220,7 +220,7 @@ const Token * astIsVariableComparison(const Token *tok, const std::string &comp,
     return ret;
 }
 
-bool isTemporary(bool cpp, const Token* tok, const Library* library)
+bool isTemporary(bool cpp, const Token* tok, const Library* library, bool unknown)
 {
     if (!tok)
         return false;
@@ -251,7 +251,7 @@ bool isTemporary(bool cpp, const Token* tok, const Library* library)
             std::string returnType = library->returnValueType(ftok);
             return !returnType.empty() && returnType.back() != '&';
         } else {
-            return false;
+            return unknown;
         }
     }
     return true;
diff --git a/lib/astutils.h b/lib/astutils.h
index 9b9b11fed..990e42357 100644
--- a/lib/astutils.h
+++ b/lib/astutils.h
@@ -87,7 +87,7 @@ std::string astCanonicalType(const Token *expr);
 /** Is given syntax tree a variable comparison against value */
 const Token * astIsVariableComparison(const Token *tok, const std::string &comp, const std::string &rhs, const Token **vartok=nullptr);
 
-bool isTemporary(bool cpp, const Token* tok, const Library* library);
+bool isTemporary(bool cpp, const Token* tok, const Library* library, bool unknown = false);
 
 const Token * nextAfterAstRightmostLeaf(const Token * tok);
 
diff --git a/lib/valueflow.cpp b/lib/valueflow.cpp
index cf54603ae..68608f769 100644
--- a/lib/valueflow.cpp
+++ b/lib/valueflow.cpp
@@ -3231,7 +3231,7 @@ std::vector<LifetimeToken> getLifetimeTokens(const Token* tok, ValueFlow::Value:
             } else if (Token::simpleMatch(var->declEndToken(), "=")) {
                 errorPath.emplace_back(var->declEndToken(), "Assigned to reference.");
                 const Token *vartok = var->declEndToken()->astOperand2();
-                if (vartok == tok || (var->isConst() && isTemporary(true, vartok, nullptr)))
+                if (vartok == tok || (var->isConst() && isTemporary(true, vartok, nullptr, true)))
                     return {{tok, true, std::move(errorPath)}};
                 if (vartok)
                     return getLifetimeTokens(vartok, std::move(errorPath), depth - 1);
diff --git a/test/testautovariables.cpp b/test/testautovariables.cpp
index ebc1897c2..88fee3eb8 100644
--- a/test/testautovariables.cpp
+++ b/test/testautovariables.cpp
@@ -2501,6 +2501,13 @@ private:
         ASSERT_EQUALS(
             "[test.cpp:3] -> [test.cpp:4]: (error) Using iterator to temporary.\n",
             errout.str());
+
+        check("std::string f() {\n"
+              "    std::stringstream tmp;\n"
+              "    const std::string &str = tmp.str();\n"
+              "    return std::string(str.c_str(), 1);\n"
+              "}\n");
+        ASSERT_EQUALS("", errout.str());
     }
 
     void invalidLifetime() {