[clang] 52690db - [clang] Fix -Wdangling false negative regressions caused by 117315 (#118088)

[via cfe-commits]

Author: Haojian Wu
Date: 2024-11-29T23:48:09+01:00
New Revision: 52690db47da36a739ee506d3b3a7457fb918dc1e

URL: https://github.com/llvm/llvm-project/commit/52690db47da36a739ee506d3b3a7457fb918dc1e
DIFF: https://github.com/llvm/llvm-project/commit/52690db47da36a739ee506d3b3a7457fb918dc1e.diff

LOG: [clang] Fix -Wdangling false negative regressions caused by 117315 (#118088)

A specialization declaration can have an attribute even if the primary
template does not, particularly when the specialization is instantiated
from an annotated using-alias declaration.

Fix #118064

Added: 
    

Modified: 
    clang/lib/Sema/CheckExprLifetime.cpp
    clang/test/Sema/warn-lifetime-analysis-nocfg.cpp

Removed: 
    


################################################################################
diff  --git a/clang/lib/Sema/CheckExprLifetime.cpp b/clang/lib/Sema/CheckExprLifetime.cpp
index 15ceff873693a5..868081292bc32c 100644
--- a/clang/lib/Sema/CheckExprLifetime.cpp
+++ b/clang/lib/Sema/CheckExprLifetime.cpp
@@ -258,9 +258,27 @@ template <typename T> static bool isRecordWithAttr(QualType Type) {
   auto *RD = Type->getAsCXXRecordDecl();
   if (!RD)
     return false;
+  // Generally, if a primary template class declaration is annotated with an
+  // attribute, all its specializations generated from template instantiations
+  // should inherit the attribute.
+  //
+  // However, since lifetime analysis occurs during parsing, we may encounter
+  // cases where a full definition of the specialization is not required. In
+  // such cases, the specialization declaration remains incomplete and lacks the
+  // attribute. Therefore, we fall back to checking the primary template class.
+  //
+  // Note: it is possible for a specialization declaration to have an attribute
+  // even if the primary template does not.
+  //
+  // FIXME: What if the primary template and explicit specialization
+  // declarations have conflicting attributes? We should consider diagnosing
+  // this scenario.
+  bool Result = RD->hasAttr<T>();
+
   if (auto *CTSD = dyn_cast<ClassTemplateSpecializationDecl>(RD))
-    RD = CTSD->getSpecializedTemplate()->getTemplatedDecl();
-  return RD->hasAttr<T>();
+    Result |= CTSD->getSpecializedTemplate()->getTemplatedDecl()->hasAttr<T>();
+
+  return Result;
 }
 
 bool isPointerLikeType(QualType QT) {

diff  --git a/clang/test/Sema/warn-lifetime-analysis-nocfg.cpp b/clang/test/Sema/warn-lifetime-analysis-nocfg.cpp
index c18ecd86ad06f0..fc876926ba2e63 100644
--- a/clang/test/Sema/warn-lifetime-analysis-nocfg.cpp
+++ b/clang/test/Sema/warn-lifetime-analysis-nocfg.cpp
@@ -670,3 +670,26 @@ void test13() {
 }
 
 } // namespace GH100526
+
+namespace std {
+template <typename T>
+class __set_iterator {};
+
+template<typename T>
+struct BB {
+  typedef  __set_iterator<T> iterator;
+};
+
+template <typename T>
+class set {
+public:
+  typedef typename BB<T>::iterator iterator;
+  iterator begin() const;
+};
+} // namespace std
+namespace GH118064{
+
+void test() {
+  auto y = std::set<int>{}.begin(); // expected-warning {{object backing the pointer}}
+}
+} // namespace GH118064