[clang] [clang][Sema] Always clear UndefinedButUsed (PR #73955)

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llvmbot wrote:


<!--LLVM PR SUMMARY COMMENT-->

@llvm/pr-subscribers-clang

Author: Jonas Hahnfeld (hahnjo)

<details>
<summary>Changes</summary>

Before, it was only cleared if there were undefined entities. This is important for Clang's incremental parsing as used by `clang-repl` that might receive multiple calls to `Sema.ActOnEndOfTranslationUnit`.

---
Full diff: https://github.com/llvm/llvm-project/pull/73955.diff


1 Files Affected:

- (modified) clang/lib/Sema/Sema.cpp (+1-2) 


``````````diff
diff --git a/clang/lib/Sema/Sema.cpp b/clang/lib/Sema/Sema.cpp
index 9771aaa2f3b0371..d08f8cd56b39bde 100644
--- a/clang/lib/Sema/Sema.cpp
+++ b/clang/lib/Sema/Sema.cpp
@@ -870,6 +870,7 @@ static void checkUndefinedButUsed(Sema &S) {
   // Collect all the still-undefined entities with internal linkage.
   SmallVector<std::pair<NamedDecl *, SourceLocation>, 16> Undefined;
   S.getUndefinedButUsed(Undefined);
+  S.UndefinedButUsed.clear();
   if (Undefined.empty()) return;
 
   for (const auto &Undef : Undefined) {
@@ -923,8 +924,6 @@ static void checkUndefinedButUsed(Sema &S) {
     if (UseLoc.isValid())
       S.Diag(UseLoc, diag::note_used_here);
   }
-
-  S.UndefinedButUsed.clear();
 }
 
 void Sema::LoadExternalWeakUndeclaredIdentifiers() {

``````````

</details>


https://github.com/llvm/llvm-project/pull/73955