new file mode 100644
@@ -0,0 +1,57 @@
+From: Khem Raj <khem.raj@oss.qualcomm.com>
+Date: Wed, 21 Oct 2026 13:00:00 -0700
+Subject: [PATCH] checks.m4: Keep the atomic test program from being optimized
+ away
+
+TORRENT_CHECK_ATOMIC decides whether -latomic is needed by linking a
+program that loads from a local std::atomic<uint64_t>. The atomic never
+escapes, so with -O2 in CXXFLAGS clang folds the load to a constant and
+no __atomic_* call is emitted. The check then reports that -latomic is
+not required even on targets that need it for 64-bit atomics, such as
+riscv32, and linking fails later:
+
+ ld.lld: error: undefined symbol: __atomic_load_8
+
+Make the atomic global and modify it with fetch_add() so the atomic
+operations are emitted at any optimization level.
+
+Upstream-Status: Submitted [https://github.com/rakshasa/libtorrent/pull/1020]
+Signed-off-by: Khem Raj <khem.raj@oss.qualcomm.com>
+---
+ scripts/checks.m4 | 13 +++++++++----
+ 1 file changed, 9 insertions(+), 4 deletions(-)
+
+--- a/scripts/checks.m4
++++ b/scripts/checks.m4
+@@ -99,13 +99,17 @@
+ ])
+
+
++# The atomic is global and modified with a read-modify-write operation,
++# otherwise the compiler can optimize the operations away and the program
++# links without libatomic even on targets that need it.
+ AC_DEFUN([TORRENT_CHECK_ATOMIC], [
+ AC_MSG_CHECKING([whether 64-bit atomic operations require -latomic])
+ AC_LANG_PUSH(C++)
+
+ AC_LINK_IFELSE([AC_LANG_PROGRAM([[#include <cstdint>
+- #include <atomic>]],
+- [[std::atomic<uint64_t> x(0);
++ #include <atomic>
++ std::atomic<uint64_t> x(0);]],
++ [[x.fetch_add(1);
+ return x.load();]])],
+ [
+ AC_MSG_RESULT([no])
+@@ -116,8 +120,9 @@
+ LIBS="$LIBS -latomic"
+
+ AC_LINK_IFELSE([AC_LANG_PROGRAM([[#include <cstdint>
+- #include <atomic>]],
+- [[std::atomic<uint64_t> x(0);
++ #include <atomic>
++ std::atomic<uint64_t> x(0);]],
++ [[x.fetch_add(1);
+ return x.load();]])],
+ [
+ AC_MSG_RESULT([yes])
@@ -6,7 +6,9 @@ LIC_FILES_CHKSUM = "file://COPYING;md5=393a5ca445f6965873eca0259a17f833"
DEPENDS = "zlib curl libsigc++-2.0 openssl cppunit"
-SRC_URI = "git://github.com/rakshasa/libtorrent;branch=master;protocol=https;tag=v${PV}"
+SRC_URI = "git://github.com/rakshasa/libtorrent;branch=master;protocol=https;tag=v${PV} \
+ file://0001-checks.m4-Keep-the-atomic-test-program-from-being-opt.patch \
+ "
SRCREV = "6ad3fecf3e7e7aa86855445587b532a91256f344"
UPSTREAM_CHECK_GITTAGREGEX = "v(?P<pver>\d+(\.\d+)+)"
The configure check for -latomic links a program that loads from a local std::atomic<uint64_t>, which clang folds away at -O2. On riscv32 it therefore reports that libatomic is not needed, and libtorrent.so is left with undefined __atomic_fetch_add_8, __atomic_fetch_sub_8, __atomic_load_8 and __atomic_store_8 references and no dependency on libatomic. Add a patch that makes the test atomic global and modifies it with fetch_add() so the check cannot be optimized away. AI-Generated: Uses Claude Code Signed-off-by: Khem Raj <khem.raj@oss.qualcomm.com> --- ...e-atomic-test-program-from-being-opt.patch | 57 +++++++++++++++++++ .../libtorrent/libtorrent_0.16.25.bb | 4 +- 2 files changed, 60 insertions(+), 1 deletion(-) create mode 100644 meta-oe/recipes-connectivity/libtorrent/libtorrent/0001-checks.m4-Keep-the-atomic-test-program-from-being-opt.patch