[clang] Include [[clang::require_explicit_initialization]] warnings in system headers (PR #141133)

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https://github.com/higher-performance created https://github.com/llvm/llvm-project/pull/141133

Fixes #141103

>From 0bdda2b593167bb7f75bea33da1f3adf4d8b6276 Mon Sep 17 00:00:00 2001
From: higher-performance <higher.performance.github at gmail.com>
Date: Thu, 22 May 2025 16:30:29 -0400
Subject: [PATCH] Include [[clang::require_explicit_initialization]] warnings
 in system headers

Fixes #141103
---
 clang/include/clang/Basic/DiagnosticSemaKinds.td | 3 ++-
 1 file changed, 2 insertions(+), 1 deletion(-)

diff --git a/clang/include/clang/Basic/DiagnosticSemaKinds.td b/clang/include/clang/Basic/DiagnosticSemaKinds.td
index 78b36ceb88125..8a3aafeabdad3 100644
--- a/clang/include/clang/Basic/DiagnosticSemaKinds.td
+++ b/clang/include/clang/Basic/DiagnosticSemaKinds.td
@@ -2423,7 +2423,8 @@ def note_uninit_reference_member : Note<
   "uninitialized reference member is here">;
 def warn_field_requires_explicit_init : Warning<
   "field %select{%1|in %1}0 requires explicit initialization but is not "
-   "explicitly initialized">, InGroup<UninitializedExplicitInit>;
+   "explicitly initialized">, InGroup<UninitializedExplicitInit>,
+   ShowInSystemHeader;
 def warn_field_is_uninit : Warning<"field %0 is uninitialized when used here">,
   InGroup<Uninitialized>;
 def warn_base_class_is_uninit : Warning<