diff mbox series

[meta-oe,09/29] bit7z: Avoid 64-bit atomics in BufferQueue

Message ID 20261023065350.3228996-9-khem.raj@oss.qualcomm.com
State New
Headers show
Series [meta-oe,01/29] castxml: upgrade 0.7.0 -> 0.8.0 | expand

Commit Message

Khem Raj Oct. 23, 2026, 6:53 a.m. UTC 
BufferQueue keeps its memory usage counter in a std::atomic<uint64_t>,
which riscv32 lowers to __atomic_*_8 libcalls, so programs linking the
static libbit7z, such as the ptest binaries, fail to link:

  ld.lld: error: undefined symbol: __atomic_fetch_add_8
  ld.lld: error: undefined symbol: __atomic_fetch_sub_8
  ld.lld: error: undefined symbol: __atomic_load_8

Add a patch that uses a std::size_t counter instead. It sums the sizes
of in-memory buffers, so it always fits, and the atomic is lock-free on
every target, so no libatomic is needed.

AI-Generated: Uses Claude Code
Signed-off-by: Khem Raj <khem.raj@oss.qualcomm.com>
---
 ...-size_t-for-the-memory-usage-counter.patch | 46 +++++++++++++++++++
 meta-oe/recipes-extended/7zip/bit7z_4.1.0.bb  |  1 +
 2 files changed, 47 insertions(+)
 create mode 100644 meta-oe/recipes-extended/7zip/bit7z/0004-bufferqueue-Use-size_t-for-the-memory-usage-counter.patch
diff mbox series

Patch

diff --git a/meta-oe/recipes-extended/7zip/bit7z/0004-bufferqueue-Use-size_t-for-the-memory-usage-counter.patch b/meta-oe/recipes-extended/7zip/bit7z/0004-bufferqueue-Use-size_t-for-the-memory-usage-counter.patch
new file mode 100644
index 0000000000..4dcc24f5b0
--- /dev/null
+++ b/meta-oe/recipes-extended/7zip/bit7z/0004-bufferqueue-Use-size_t-for-the-memory-usage-counter.patch
@@ -0,0 +1,46 @@ 
+From: Khem Raj <khem.raj@oss.qualcomm.com>
+Date: Wed, 21 Oct 2026 12:00:00 -0700
+Subject: [PATCH] bufferqueue: Use size_t for the memory usage counter
+
+BufferQueue::mMemoryUsage is a std::atomic<std::uint64_t>. On 32-bit
+targets without native 64-bit atomic instructions, such as riscv32, its
+operations become __atomic_*_8 libcalls, so every program linking the
+static libbit7z needs libatomic, and the tests fail to link:
+
+  ld.lld: error: undefined symbol: __atomic_fetch_add_8
+  >>> referenced by bufferqueue.cpp:21 (src/internal/bufferqueue.cpp:21)
+  ld.lld: error: undefined symbol: __atomic_fetch_sub_8
+  ld.lld: error: undefined symbol: __atomic_load_8
+
+The counter is the total size of the buffers currently held in the
+queue, i.e. a sum of std::vector::size() values of in-memory objects,
+so it always fits in a std::size_t. Use that type, which keeps the
+atomic lock-free on every target and removes the libatomic dependency.
+
+Upstream-Status: Submitted [https://github.com/rikyoz/bit7z/pull/344]
+Signed-off-by: Khem Raj <khem.raj@oss.qualcomm.com>
+---
+ src/internal/bufferqueue.hpp | 5 ++++-
+ 1 file changed, 4 insertions(+), 1 deletion(-)
+
+--- a/src/internal/bufferqueue.hpp
++++ b/src/internal/bufferqueue.hpp
+@@ -13,6 +13,7 @@
+ #include "bittypes.hpp"
+ 
+ #include <atomic>
++#include <cstddef>
+ #include <condition_variable>
+ #include <queue>
+ #include <mutex>
+@@ -49,7 +50,9 @@
+         std::condition_variable mEmptyCondition;
+         std::condition_variable mFullCondition;
+         std::atomic_bool mFinished{ false };
+-        std::atomic< std::uint64_t > mMemoryUsage;
++        // Size of the queued in-memory buffers, so it always fits in a size_t,
++        // which keeps the atomic lock-free on 32-bit targets as well.
++        std::atomic< std::size_t > mMemoryUsage;
+         std::uint64_t mMaxMemoryUsage;
+ };
+ 
diff --git a/meta-oe/recipes-extended/7zip/bit7z_4.1.0.bb b/meta-oe/recipes-extended/7zip/bit7z_4.1.0.bb
index d0693cc5f1..77f82c743e 100644
--- a/meta-oe/recipes-extended/7zip/bit7z_4.1.0.bb
+++ b/meta-oe/recipes-extended/7zip/bit7z_4.1.0.bb
@@ -6,6 +6,7 @@  LIC_FILES_CHKSUM = "file://LICENSE;md5=48a3fe23ed1353e0995dadfda05ffdb6"
 SRC_URI = " \
     git://github.com/rikyoz/bit7z.git;protocol=https;branch=master;tag=v${PV} \
     file://0003-internal-replace-glibc-LFS64-names-with-portable-PO.patch \
+    file://0004-bufferqueue-Use-size_t-for-the-memory-usage-counter.patch \
     ${@bb.utils.contains('PTEST_ENABLED', '1', d.getVar('SRC_URI_PTEST'), 'file://0001-cmake-disable-dependency-inclusion.patch', d)} \
 "