[clang] [clang] Fix false positive regression for lifetime analysis warning. (PR #127460)

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llvmbot wrote:


<!--LLVM PR SUMMARY COMMENT-->

@llvm/pr-subscribers-clang

Author: Haojian Wu (hokein)

<details>
<summary>Changes</summary>

This fixes a false positive caused by #<!-- -->114044.

For `GSLPointer*` types, it's less clear whether the lifetime issue is about the GSLPointer object itself or the owner it points to. To avoid false positives, we take a conservative approach in our heuristic.

Fixes #<!-- -->127195

(This will be backported to release 20).

---
Full diff: https://github.com/llvm/llvm-project/pull/127460.diff


2 Files Affected:

- (modified) clang/lib/Sema/CheckExprLifetime.cpp (+3-2) 
- (modified) clang/test/Sema/warn-lifetime-analysis-nocfg.cpp (+25) 


``````````diff
diff --git a/clang/lib/Sema/CheckExprLifetime.cpp b/clang/lib/Sema/CheckExprLifetime.cpp
index 8963cad86dbca..3e0867343ccee 100644
--- a/clang/lib/Sema/CheckExprLifetime.cpp
+++ b/clang/lib/Sema/CheckExprLifetime.cpp
@@ -1239,11 +1239,12 @@ static AnalysisResult analyzePathForGSLPointer(const IndirectLocalPath &Path,
     }
     // Check the return type, e.g.
     //   const GSLOwner& func(const Foo& foo [[clang::lifetimebound]])
+    //   GSLOwner* func(cosnt Foo& foo [[clang::lifetimebound]])
     //   GSLPointer func(const Foo& foo [[clang::lifetimebound]])
     if (FD &&
-        ((FD->getReturnType()->isReferenceType() &&
+        ((FD->getReturnType()->isPointerOrReferenceType() &&
           isRecordWithAttr<OwnerAttr>(FD->getReturnType()->getPointeeType())) ||
-         isPointerLikeType(FD->getReturnType())))
+          isGLSPointerType(FD->getReturnType())))
       return Report;
 
     return Abandon;
diff --git a/clang/test/Sema/warn-lifetime-analysis-nocfg.cpp b/clang/test/Sema/warn-lifetime-analysis-nocfg.cpp
index 04bb1330ded4c..e2bad643ef012 100644
--- a/clang/test/Sema/warn-lifetime-analysis-nocfg.cpp
+++ b/clang/test/Sema/warn-lifetime-analysis-nocfg.cpp
@@ -852,3 +852,28 @@ struct Test {
 };
 
 } // namespace GH120543
+
+namespace GH127195 {
+template <typename T>
+struct StatusOr {
+  T* operator->() [[clang::lifetimebound]];
+  T* value() [[clang::lifetimebound]];
+};
+
+const char* foo() {
+  StatusOr<std::string> s;
+  return s->data(); // expected-warning {{address of stack memory associated with local variable}}
+  
+  StatusOr<std::string_view> s2;
+  return s2->data();
+
+  StatusOr<StatusOr<std::string_view>> s3;
+  return s3.value()->value()->data();
+
+  // would be nice to support the nested cases.
+  StatusOr<StatusOr<std::string>> s4;
+  return s4.value()->value()->data();
+}
+
+} // namespace GH127195
+  
\ No newline at end of file

``````````

</details>


https://github.com/llvm/llvm-project/pull/127460