From 4217b3c12809b070928413f75949a7ddc4f2221c Mon Sep 17 00:00:00 2001
From: Victor Stinner <vstinner@python.org>
Date: Tue, 1 Sep 2020 20:54:37 +0200
Subject: [PATCH] bpo-41617: Fix pycore_byteswap.h to support clang 3.0
 (GH-22042) (GH-22044)

__builtin_bswap16() is not available in LLVM clang 3.0.

(cherry picked from commit e6905e4c82cc05897dc1bf5ab2b5b94b2b043a7f)
---
 Include/internal/pycore_byteswap.h                     | 10 ++++++----
 .../Build/2020-08-24-18-34-01.bpo-41617.sKKXz7.rst     |  2 ++
 2 files changed, 8 insertions(+), 4 deletions(-)
 create mode 100644 Misc/NEWS.d/next/Build/2020-08-24-18-34-01.bpo-41617.sKKXz7.rst

diff --git a/Include/internal/pycore_byteswap.h b/Include/internal/pycore_byteswap.h
index 5e64704a004..975e150dd91 100644
--- a/Include/internal/pycore_byteswap.h
+++ b/Include/internal/pycore_byteswap.h
@@ -15,10 +15,12 @@ extern "C" {
 #  error "this header requires Py_BUILD_CORE define"
 #endif
 
-#if defined(__clang__) || \
-    (defined(__GNUC__) && \
-     ((__GNUC__ >= 5) || (__GNUC__ == 4) && (__GNUC_MINOR__ >= 8)))
-   /* __builtin_bswap16() is available since GCC 4.8,
+#if ((defined(__GNUC__) \
+      && ((__GNUC__ >= 5) || (__GNUC__ == 4) && (__GNUC_MINOR__ >= 8))) \
+     || (defined(__clang__) \
+         && (__clang_major__ >= 4 \
+             || (__clang_major__ == 3 && __clang_minor__ >= 2))))
+   /* __builtin_bswap16() is available since GCC 4.8 and clang 3.2,
       __builtin_bswap32() is available since GCC 4.3,
       __builtin_bswap64() is available since GCC 4.3. */
 #  define _PY_HAVE_BUILTIN_BSWAP
diff --git a/Misc/NEWS.d/next/Build/2020-08-24-18-34-01.bpo-41617.sKKXz7.rst b/Misc/NEWS.d/next/Build/2020-08-24-18-34-01.bpo-41617.sKKXz7.rst
new file mode 100644
index 00000000000..9e4bc60fd85
--- /dev/null
+++ b/Misc/NEWS.d/next/Build/2020-08-24-18-34-01.bpo-41617.sKKXz7.rst
@@ -0,0 +1,2 @@
+Fix ``pycore_byteswap.h`` header file to support old clang versions:
+``__builtin_bswap16()`` is not available in LLVM clang 3.0.