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x265: Link with libatomic when 64-bit atomics need it

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The encoder uses atomic operations on 64-bit counters. On riscv32 these
become __atomic_*_8 libcalls, and libx265 is not linked with libatomic,
so linking the x265 CLI fails:

  ld.lld: error: undefined reference: __atomic_fetch_or_8
  >>> referenced by libx265.so.217 (disallowed by --no-allow-shlib-undefined)

Add a patch that checks in CMake whether 64-bit atomics need libatomic
and adds it to the platform libraries only in that case.

AI-Generated: Uses Claude Code
Signed-off-by: Khem Raj <khem.raj@oss.qualcomm.com>
This commit is contained in:
Khem Raj committed 2026-10-22 20:34:22 -07:00
1 parent fa336f784e
commit 07ee40fb83
2 files changed
+56
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meta-multimedia/recipes-multimedia/x265/x265/0004-cmake-Link-with-libatomic-when-64-bit-atomics-need-i.patch
+55
View File
@@ -0,0 +1,55 @@
From: Khem Raj <khem.raj@oss.qualcomm.com>
Date: Wed, 21 Oct 2026 15:00:00 -0700
Subject: [PATCH] cmake: Link with libatomic when 64-bit atomics need it
The encoder uses the ATOMIC_* macros, i.e. the __sync builtins, on
64-bit counters, e.g. the threaded ME sequence number and timing
totals. On 32-bit targets without 64-bit atomic instructions, such as
riscv32, the compiler lowers these to __atomic_*_8 libcalls. libx265 is
not linked with libatomic, so linking the x265 CLI against it fails:
ld.lld: error: undefined reference: __atomic_fetch_or_8
>>> referenced by libx265.so.217 (disallowed by --no-allow-shlib-undefined)
Check whether 64-bit atomics link on their own, and if not, whether they
link with libatomic, and add it to PLATFORM_LIBS only in that case, so
libx265, the CLI and the Libs.private of x265.pc all get it. The test
variable is global so the compiler cannot optimize the atomic
operations away.
Upstream-Status: Pending
Signed-off-by: Khem Raj <khem.raj@oss.qualcomm.com>
---
source/CMakeLists.txt | 21 +++++++++++++++++++++
1 file changed, 21 insertions(+)
--- a/source/CMakeLists.txt
+++ b/source/CMakeLists.txt
@@ -191,6 +191,27 @@
if(NO_ATOMICS)
add_definitions(-DNO_ATOMICS=1)
endif(NO_ATOMICS)
+ if(NOT NO_ATOMICS)
+ # The atomics on 64-bit counters need libatomic on 32-bit targets
+ # without 64-bit atomic instructions, e.g. riscv32. The variable is
+ # global so the compiler cannot optimize the atomic operations away.
+ set(ATOMIC64_TEST "
+#include <stdint.h>
+uint64_t v;
+int main(void) {
+ __sync_fetch_and_add(&v, 1);
+ return (int)__sync_fetch_and_or(&v, 0);
+}")
+ check_c_source_compiles("${ATOMIC64_TEST}" HAVE_ATOMIC64)
+ if(NOT HAVE_ATOMIC64)
+ set(CMAKE_REQUIRED_LIBRARIES atomic)
+ check_c_source_compiles("${ATOMIC64_TEST}" HAVE_ATOMIC64_WITH_LIBATOMIC)
+ unset(CMAKE_REQUIRED_LIBRARIES)
+ if(HAVE_ATOMIC64_WITH_LIBATOMIC)
+ list(APPEND PLATFORM_LIBS atomic)
+ endif()
+ endif()
+ endif()
find_library(VMAF vmaf)
option(ENABLE_LIBVMAF "Enable VMAF" OFF)
if(ENABLE_LIBVMAF)
meta-multimedia/recipes-multimedia/x265/x265_4.3.bb
+1
View File
@@ -13,6 +13,7 @@ SRC_URI = " \
file://0001-fix-dynamicHDR10-undefined-uint8_t.patch;patchdir=.. \
file://0002-x265-fix-build-with-cmake-4.patch;patchdir=.. \
file://0003-riscv64-Fix-case-of-STRIDE_SHIFT-macro-invocation.patch;patchdir=.. \
file://0004-cmake-Link-with-libatomic-when-64-bit-atomics-need-i.patch;patchdir=.. \
"
SRCREV = "e9b88125dc21393b3fd8d68e98083bdfb89778a8"
S = "${UNPACKDIR}/x265-${PV}/source"