[clang] [LifetimeSafety] Fix use-after-scope from #198784 (PR #199455)

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<!--LLVM PR SUMMARY COMMENT-->

@llvm/pr-subscribers-clang

Author: Thurston Dang (thurstond)

<details>
<summary>Changes</summary>

This fixes a use-after-scope introduced by #<!-- -->198784 (reported in https://github.com/llvm/llvm-project/pull/198784#issuecomment-4530043621), by manually extending the lifetime.

Note that clang is built using C++17, hence C++23 P2718R0's lifetime extension in range-based for loops does not apply.

---
Full diff: https://github.com/llvm/llvm-project/pull/199455.diff


1 Files Affected:

- (modified) clang/lib/Analysis/LifetimeSafety/Checker.cpp (+5-2) 


``````````diff
diff --git a/clang/lib/Analysis/LifetimeSafety/Checker.cpp b/clang/lib/Analysis/LifetimeSafety/Checker.cpp
index 53899251b9643..7eb948373152b 100644
--- a/clang/lib/Analysis/LifetimeSafety/Checker.cpp
+++ b/clang/lib/Analysis/LifetimeSafety/Checker.cpp
@@ -356,8 +356,11 @@ class LifetimeChecker {
 
     // We iterate in reverse order (from most recent to oldest) to find
     // the first declaration in each file.
-    for (const FunctionDecl *Redecl :
-         llvm::reverse(llvm::to_vector(FDef->redecls())))
+
+    // Store in temporary variable to manually extend lifetime
+    auto redecls = llvm::to_vector(FDef->redecls());
+
+    for (const FunctionDecl *Redecl : llvm::reverse(redecls))
       AddCrossTUDecl(Redecl);
 
     return Targets;

``````````

</details>


https://github.com/llvm/llvm-project/pull/199455