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

[Jonas Hahnfeld via cfe-commits]

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

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`.

>From 9dd0362e1dcffa5475d9f959ce9bfc6a7e83083b Mon Sep 17 00:00:00 2001
From: Jonas Hahnfeld <jonas.hahnfeld at cern.ch>
Date: Thu, 30 Nov 2023 16:51:23 +0100
Subject: [PATCH] [clang][Sema] Always clear UndefinedButUsed

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.
---
 clang/lib/Sema/Sema.cpp | 3 +--
 1 file changed, 1 insertion(+), 2 deletions(-)

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() {