Revert "[clang] Diagnose dangling issues for the "Container<GSLPointer>" case. (#107213)"

This reverts commit e50131a.

It introduces a new false positive, see comment #107213 (comment)

Author: hokein

clang/docs/ReleaseNotes.rst

@@ -301,8 +301,6 @@ Improvements to Clang's diagnostics
 
 - Clang now warns for u8 character literals used in C23 with ``-Wpre-c23-compat`` instead of ``-Wpre-c++17-compat``.
 
-- Clang now diagnoses cases where a dangling ``GSLOwner<GSLPointer>`` object is constructed, e.g. ``std::vector<string_view> v = {std::string()};`` (#GH100526).
-
 Improvements to Clang's time-trace
 ----------------------------------
 

clang/include/clang/Basic/AttrDocs.td

@@ -6690,20 +6690,6 @@ When the Owner's lifetime ends, it will consider the Pointer to be dangling.
     P.getInt(); // P is dangling
   }
 
-If a template class is annotated with ``[[gsl::Owner]]``, and the first
-instantiated template argument is a pointer type (raw pointer, or ``[[gsl::Pointer]]``),
-the analysis will consider the instantiated class as a container of the pointer.
-When constructing such an object from a GSL owner object, the analysis will
-assume that the container holds a pointer to the owner object. Consequently,
-when the owner object is destroyed, the pointer will be considered dangling.
-
-.. code-block:: c++
-
-   int f() {
-     std::vector<std::string_view> v = {std::string()}; // v holds a dangling pointer.
-     std::optional<std::string_view> o = std::string(); // o holds a dangling pointer.
-   }
-
 }];
 }
 

clang/lib/Sema/CheckExprLifetime.cpp

@@ -267,26 +267,6 @@ static bool isInStlNamespace(const Decl *D) {
   return DC->isStdNamespace();
 }
 
-// Returns true if the given Record decl is a form of `GSLOwner<Pointer>`
-// type, e.g. std::vector<string_view>, std::optional<string_view>.
-static bool isContainerOfPointer(const RecordDecl *Container) {
-  if (const auto *CTSD =
-          dyn_cast_if_present<ClassTemplateSpecializationDecl>(Container)) {
-    if (!CTSD->hasAttr<OwnerAttr>()) // Container must be a GSL owner type.
-      return false;
-    const auto &TAs = CTSD->getTemplateArgs();
-    return TAs.size() > 0 && TAs[0].getKind() == TemplateArgument::Type &&
-           (isRecordWithAttr<PointerAttr>(TAs[0].getAsType()) ||
-            TAs[0].getAsType()->isPointerType());
-  }
-  return false;
-}
-
-static bool isGSLOwner(QualType T) {
-  return isRecordWithAttr<OwnerAttr>(T) &&
-         !isContainerOfPointer(T->getAsRecordDecl());
-}
-
 static bool shouldTrackImplicitObjectArg(const CXXMethodDecl *Callee) {
   if (auto *Conv = dyn_cast_or_null<CXXConversionDecl>(Callee))
     if (isRecordWithAttr<PointerAttr>(Conv->getConversionType()))
@@ -295,7 +275,7 @@ static bool shouldTrackImplicitObjectArg(const CXXMethodDecl *Callee) {
     return false;
   if (!isRecordWithAttr<PointerAttr>(
           Callee->getFunctionObjectParameterType()) &&
-      !isGSLOwner(Callee->getFunctionObjectParameterType()))
+      !isRecordWithAttr<OwnerAttr>(Callee->getFunctionObjectParameterType()))
     return false;
   if (Callee->getReturnType()->isPointerType() ||
       isRecordWithAttr<PointerAttr>(Callee->getReturnType())) {
@@ -433,7 +413,7 @@ static void visitFunctionCallArguments(IndirectLocalPath &Path, Expr *Call,
     // Once we initialized a value with a non gsl-owner reference, it can no
     // longer dangle.
     if (ReturnType->isReferenceType() &&
-        !isGSLOwner(ReturnType->getPointeeType())) {
+        !isRecordWithAttr<OwnerAttr>(ReturnType->getPointeeType())) {
       for (const IndirectLocalPathEntry &PE : llvm::reverse(Path)) {
         if (PE.Kind == IndirectLocalPathEntry::GslReferenceInit ||
             PE.Kind == IndirectLocalPathEntry::LifetimeBoundCall)
@@ -488,17 +468,12 @@ static void visitFunctionCallArguments(IndirectLocalPath &Path, Expr *Call,
     if (CheckCoroCall || Callee->getParamDecl(I)->hasAttr<LifetimeBoundAttr>())
       VisitLifetimeBoundArg(Callee->getParamDecl(I), Args[I]);
     else if (EnableGSLAnalysis && I == 0) {
-      // Perform GSL analysis for the first argument
       if (shouldTrackFirstArgument(Callee)) {
         VisitGSLPointerArg(Callee, Args[0]);
-      } else if (auto *Ctor = dyn_cast<CXXConstructExpr>(Call)) {
-        const auto *ClassD = Ctor->getConstructor()->getParent();
-        // Two cases:
-        //  a GSL pointer, e.g. std::string_view
-        //  a container of GSL pointer, e.g. std::vector<string_view>
-        if (ClassD->hasAttr<PointerAttr>() ||
-            (isContainerOfPointer(ClassD) && Callee->getNumParams() == 1))
-          VisitGSLPointerArg(Ctor->getConstructor(), Args[0]);
+      } else if (auto *CCE = dyn_cast<CXXConstructExpr>(Call);
+                 CCE &&
+                 CCE->getConstructor()->getParent()->hasAttr<PointerAttr>()) {
+        VisitGSLPointerArg(CCE->getConstructor(), Args[0]);
       }
     }
   }
@@ -1010,12 +985,13 @@ static void checkExprLifetimeImpl(Sema &SemaRef,
         //   int &p = *localUniquePtr;
         //   someContainer.add(std::move(localUniquePtr));
         //   return p;
-        IsLocalGslOwner = isGSLOwner(L->getType());
+        IsLocalGslOwner = isRecordWithAttr<OwnerAttr>(L->getType());
         if (pathContainsInit(Path) || !IsLocalGslOwner)
           return false;
       } else {
         IsGslPtrValueFromGslTempOwner =
-            MTE && !MTE->getExtendingDecl() && isGSLOwner(MTE->getType());
+            MTE && !MTE->getExtendingDecl() &&
+            isRecordWithAttr<OwnerAttr>(MTE->getType());
         // Skipping a chain of initializing gsl::Pointer annotated objects.
         // We are looking only for the final source to find out if it was
         // a local or temporary owner or the address of a local variable/param.

clang/test/Sema/warn-lifetime-analysis-nocfg.cpp

@@ -158,30 +158,17 @@ auto begin(C &c) -> decltype(c.begin());
 template<typename T, int N>
 T *begin(T (&array)[N]);
 
-using size_t = decltype(sizeof(0));
-
-template<typename T>
-struct initializer_list {
-  const T* ptr; size_t sz;
-};
 template <typename T>
 struct vector {
   typedef __gnu_cxx::basic_iterator<T> iterator;
   iterator begin();
   iterator end();
   const T *data() const;
-  vector();
-  vector(initializer_list<T> __l);
-  
-  template<typename InputIterator>
-	vector(InputIterator first, InputIterator __last);
-
   T &at(int n);
 };
 
 template<typename T>
 struct basic_string_view {
-  basic_string_view();
   basic_string_view(const T *);
   const T *begin() const;
 };
@@ -216,21 +203,11 @@ template<typename T>
 struct optional {
   optional();
   optional(const T&);
-
-  template<typename U = T>
-	optional(U&& t);
-
-  template<typename U>
-	optional(optional<U>&& __t);
-
   T &operator*() &;
   T &&operator*() &&;
   T &value() &;
   T &&value() &&;
 };
-template<typename T>
-optional<__decay(T)> make_optional(T&&);
-
 
 template<typename T>
 struct stack {
@@ -576,57 +553,3 @@ void test() {
   std::string_view svjkk1 = ReturnStringView(StrCat("bar", "x")); // expected-warning {{object backing the pointer will be destroyed at the end of the full-expression}}
 }
 } // namespace GH100549
-
-namespace GH100526 {
-void test() {
-  std::vector<std::string_view> v1({std::string()}); // expected-warning {{object backing the pointer will be destroyed at the end}}
-  std::vector<std::string_view> v2({
-    std::string(), // expected-warning {{object backing the pointer will be destroyed at the end}}
-    std::string_view()
-  });
-  std::vector<std::string_view> v3({
-    std::string_view(),
-    std::string()  // expected-warning {{object backing the pointer will be destroyed at the end}}
-  });
-
-  std::optional<std::string_view> o1 = std::string(); // expected-warning {{object backing the pointer}}
-
-  std::string s;
-  // This is a tricky use-after-free case, what it does:
-  //   1. make_optional creates a temporary "optional<string>"" object
-  //   2. the temporary object owns the underlying string which is copied from s.
-  //   3. the t3 object holds the view to the underlying string of the temporary object.
-  std::optional<std::string_view> o2 = std::make_optional(s); // expected-warning {{object backing the pointer}}
-  std::optional<std::string_view> o3 = std::optional<std::string>(s); // expected-warning {{object backing the pointer}}
-  std::optional<std::string_view> o4 = std::optional<std::string_view>(s); 
-
-  // FIXME: should work for assignment cases
-  v1 = {std::string()};
-  o1 = std::string();
-
-  // no warning on copying pointers.
-  std::vector<std::string_view> n1 = {std::string_view()};
-  std::optional<std::string_view> n2 = {std::string_view()};
-  std::optional<std::string_view> n3 = std::string_view();
-  std::optional<std::string_view> n4 = std::make_optional(std::string_view());
-  const char* b = "";
-  std::optional<std::string_view> n5 = std::make_optional(b);
-  std::optional<std::string_view> n6 = std::make_optional("test");
-}
-
-std::vector<std::string_view> test2(int i) {
-  std::vector<std::string_view> t;
-  if (i)
-    return t; // this is fine, no dangling
-  return std::vector<std::string_view>(t.begin(), t.end());
-}
-
-std::optional<std::string_view> test3(int i) {
-  std::string s;
-  std::string_view sv;
-  if (i)
-   return s; // expected-warning {{address of stack memory associated}}
-  return sv; // fine
-}
-
-} // namespace GH100526