From 90f186d9bfcd60fa9cfa38dc59b3521bd6033f26 Mon Sep 17 00:00:00 2001
From: Victor Stinner <vstinner@python.org>
Date: Thu, 4 Jun 2026 14:21:12 +0200
Subject: [PATCH] gh-150907: Fix dynamic_annotations.h when built with C++ and
 Valgrind

Add extern "C++" scope for the C++ template.
---
 Include/dynamic_annotations.h                                  | 3 +++
 .../next/C_API/2026-06-04-14-26-17.gh-issue-150907.CA91_B.rst  | 2 ++
 2 files changed, 5 insertions(+)
 create mode 100644 Misc/NEWS.d/next/C_API/2026-06-04-14-26-17.gh-issue-150907.CA91_B.rst

diff --git a/Include/dynamic_annotations.h b/Include/dynamic_annotations.h
index 4d4def9bf8983e2..5290319dd762c55 100644
--- a/Include/dynamic_annotations.h
+++ b/Include/dynamic_annotations.h
@@ -461,6 +461,7 @@ int RunningOnValgrind(void);
 
 #if DYNAMIC_ANNOTATIONS_ENABLED != 0 && defined(__cplusplus)
 
+extern "C++" {
   /* _Py_ANNOTATE_UNPROTECTED_READ is the preferred way to annotate racey reads.
 
      Instead of doing
@@ -476,6 +477,8 @@ int RunningOnValgrind(void);
     _Py_ANNOTATE_IGNORE_READS_END();
     return res;
   }
+}
+
   /* Apply _Py_ANNOTATE_BENIGN_RACE_SIZED to a static variable. */
 #define _Py_ANNOTATE_BENIGN_RACE_STATIC(static_var, description)        \
     namespace {                                                       \
diff --git a/Misc/NEWS.d/next/C_API/2026-06-04-14-26-17.gh-issue-150907.CA91_B.rst b/Misc/NEWS.d/next/C_API/2026-06-04-14-26-17.gh-issue-150907.CA91_B.rst
new file mode 100644
index 000000000000000..f58b248f3a0b986
--- /dev/null
+++ b/Misc/NEWS.d/next/C_API/2026-06-04-14-26-17.gh-issue-150907.CA91_B.rst
@@ -0,0 +1,2 @@
+Fix ``dynamic_annotations.h`` header file when built with C++ and Valgrind:
+add ``extern "C++" scope`` for the C++ template. Patch by Victor Stinner.