From 1bebc22bd94d44214bbd8a2dad10736c7c5e205b Mon Sep 17 00:00:00 2001
From: Matthias Gehre <M.Gehre@gmx.de>
Date: Wed, 14 Aug 2019 21:55:57 +0000
Subject: [PATCH] [LifetimeAnalysis] Support std::stack::top() and
 std::optional::value()

Summary: Diagnose dangling pointers that come from std::stack::top() and std::optional::value().

Reviewers: gribozavr

Subscribers: cfe-commits, xazax.hun

Tags: #clang

Differential Revision: https://reviews.llvm.org/D66164

llvm-svn: 368929
---
 clang/lib/Sema/SemaInit.cpp                      |  2 +-
 clang/test/Sema/warn-lifetime-analysis-nocfg.cpp | 27 ++++++++++++++++++++----
 2 files changed, 24 insertions(+), 5 deletions(-)

diff --git a/clang/lib/Sema/SemaInit.cpp b/clang/lib/Sema/SemaInit.cpp
index 0811d3f..e11cc92 100644
--- a/clang/lib/Sema/SemaInit.cpp
+++ b/clang/lib/Sema/SemaInit.cpp
@@ -6610,7 +6610,7 @@ static bool shouldTrackImplicitObjectArg(const CXXMethodDecl *Callee) {
              OO == OverloadedOperatorKind::OO_Star;
     }
     return llvm::StringSwitch<bool>(Callee->getName())
-        .Cases("front", "back", "at", true)
+        .Cases("front", "back", "at", "top", "value", true)
         .Default(false);
   }
   return false;
diff --git a/clang/test/Sema/warn-lifetime-analysis-nocfg.cpp b/clang/test/Sema/warn-lifetime-analysis-nocfg.cpp
index ba3cc1f..c8016bf 100644
--- a/clang/test/Sema/warn-lifetime-analysis-nocfg.cpp
+++ b/clang/test/Sema/warn-lifetime-analysis-nocfg.cpp
@@ -170,7 +170,15 @@ template<typename T>
 struct optional {
   optional();
   optional(const T&);
-  T &operator*();
+  T &operator*() &;
+  T &&operator*() &&;
+  T &value() &;
+  T &&value() &&;
+};
+
+template<typename T>
+struct stack {
+  T &top();
 };
 }
 
@@ -188,6 +196,16 @@ const char *danglingRawPtrFromLocal() {
   return s.c_str(); // expected-warning {{address of stack memory associated with local variable 's' returned}}
 }
 
+int &danglingRawPtrFromLocal2() {
+  std::optional<int> o;
+  return o.value(); // expected-warning {{reference to stack memory associated with local variable 'o' returned}}
+}
+
+int &danglingRawPtrFromLocal3() {
+  std::optional<int> o;
+  return *o; // expected-warning {{reference to stack memory associated with local variable 'o' returned}}
+}
+
 const char *danglingRawPtrFromTemp() {
   return std::basic_string<char>().c_str(); // expected-warning {{returning address of local temporary object}}
 }
@@ -203,9 +221,10 @@ int *danglingUniquePtrFromTemp2() {
 }
 
 void danglingReferenceFromTempOwner() {
-  int &r = *std::optional<int>(); // expected-warning {{object backing the pointer will be destroyed at the end of the full-expression}}
-  int &r2 = *std::optional<int>(5); // expected-warning {{object backing the pointer will be destroyed at the end of the full-expression}}
-  int &r3 = std::vector<int>().at(3); // expected-warning {{object backing the pointer will be destroyed at the end of the full-expression}}
+  int &&r = *std::optional<int>();          // expected-warning {{object backing the pointer will be destroyed at the end of the full-expression}}
+  int &&r2 = *std::optional<int>(5);        // expected-warning {{object backing the pointer will be destroyed at the end of the full-expression}}
+  int &&r3 = std::optional<int>(5).value(); // expected-warning {{object backing the pointer will be destroyed at the end of the full-expression}}
+  int &r4 = std::vector<int>().at(3);       // expected-warning {{object backing the pointer will be destroyed at the end of the full-expression}}
 }
 
 std::vector<int> getTempVec();
-- 
2.7.4