From ba5ed99861d836c33e0ebe94fda254a3e050dcba Mon Sep 17 00:00:00 2001
From: Sergei Trofimovich <slyich@gmail.com>
Date: Sun, 11 Aug 2024 22:18:48 +0100
Subject: [PATCH] x265: fix build on x86_64-darwin

Update to 3.6 pulled in local definition of `__rdtsc()` symbol in
the test suite and caused symbol clash:

    /tmp/nix-build-x265-3.6.drv-0/x265_3.6/source/test/testharness.h:78:24: error: static declaration of '__rdtsc' follows non-static declaration
    static inline uint32_t __rdtsc(void)
                           ^
    /tmp/nix-build-x265-3.6.drv-0/x265_3.6/source/test/testharness.h:78:24: note: '__rdtsc' is a builtin with type 2

The change avoids redefinition if the compiler already provides the
builtin.
---
 .../libraries/x265/darwin-__rdtsc.patch       | 29 +++++++++++++++++++
 pkgs/development/libraries/x265/default.nix   |  6 ++++
 2 files changed, 35 insertions(+)
 create mode 100644 pkgs/development/libraries/x265/darwin-__rdtsc.patch

diff --git a/pkgs/development/libraries/x265/darwin-__rdtsc.patch b/pkgs/development/libraries/x265/darwin-__rdtsc.patch
new file mode 100644
index 000000000000..a052f818af10
--- /dev/null
+++ b/pkgs/development/libraries/x265/darwin-__rdtsc.patch
@@ -0,0 +1,29 @@
+From 5ad351f7d271d0be0611797542c831898b2f531c Mon Sep 17 00:00:00 2001
+From: Sergei Trofimovich <slyich@gmail.com>
+Date: Sun, 11 Aug 2024 22:09:34 +0100
+Subject: [PATCH] source/test/testharness.h: don't redefine `__rdtsc()` builtin
+
+On darwin clang-16 provides `__rdtsc()` builtin. As a result the build
+fails in `nixpkgs` as:
+
+    source/test/testharness.h:78:24: error: static declaration of '__rdtsc' follows non-static declaration
+    static inline uint32_t __rdtsc(void)
+                           ^
+    x265_3.6/source/test/testharness.h:78:24: note: '__rdtsc' is a builtin with type 2
+
+The change avoid redefinition on targets that define `__rdtsc()` builtin.
+---
+ source/test/testharness.h | 2 ++
+ 1 file changed, 2 insertions(+)
+
+--- a/test/testharness.h
++++ b/test/testharness.h
+@@ -69,6 +69,8 @@ protected:
+ #include <intrin.h>
+ #elif HAVE_RDTSC
+ #include <intrin.h>
++#elif defined(__has_builtin) && __has_builtin(__rdtsc)
++/* compiler-provided builtin */
+ #elif (!defined(__APPLE__) && (defined (__GNUC__) && (defined(__x86_64__) || defined(__i386__))))
+ #include <x86intrin.h>
+ #elif ( !defined(__APPLE__) && defined (__GNUC__) && defined(__ARM_NEON__))
diff --git a/pkgs/development/libraries/x265/default.nix b/pkgs/development/libraries/x265/default.nix
index e58e910c2bba..3d10538314f0 100644
--- a/pkgs/development/libraries/x265/default.nix
+++ b/pkgs/development/libraries/x265/default.nix
@@ -41,6 +41,12 @@ stdenv.mkDerivation rec {
     hash = "sha256-ZjUx80HFOJ9GDXMOYuEKT8yjQoyiyhCWk4Z7xf4uKAc=";
   };
 
+  # TODO: apply patch unconditionally in staging. It's conditional to
+  # save rebuild on staging-next.
+  patches = lib.optionals (stdenv.isDarwin && stdenv.isx86_64) [
+    ./darwin-__rdtsc.patch
+  ];
+
   sourceRoot = "x265_${version}/source";
 
   postPatch = ''