musllvm

commit de7f32a67d127620a640ecc60ec2925fbaf61d6a
parent 48032775acf3e84f4a03a41faf81bb22a9521b5e
Author: cowmonk <cowmonk@based.pt>
Date:   Sat, 10 Oct 2026 15:58:35 -0700

Fix libc++abi thread exit detection for musl

Use the libc++abi fallback for the hook missing in musl.
Check thread_local destruction in the C++ smoke test.

Diffstat:
M
scripts/build.sh
 | 
3
+++
M
tests/hello.cpp
 | 
18
+++++++++++++++++-

2 files changed, 20 insertions(+), 1 deletion(-)
diff --git a/scripts/build.sh b/scripts/build.sh
@@ -193,6 +193,8 @@ atomic()
 runtimes()
 {
 	if ! done_stage runtimes; then
+		# musl lacks __cxa_thread_atexit_impl
+		# compile only probes cannot detect missing symbols
 		target_cmake -S "$LLVM_SOURCE/runtimes" -B "$BUILD_DIR/runtimes" \
 			-DCMAKE_INSTALL_PREFIX=/usr -DLLVM_ENABLE_RUNTIMES='libunwind;libcxxabi;libcxx' \
 			-DLIBCXX_HAS_MUSL_LIBC=ON -DLIBCXX_USE_COMPILER_RT=ON \
@@ -201,6 +203,7 @@ runtimes()
 			-DLIBCXX_STATICALLY_LINK_ABI_IN_SHARED_LIBRARY=OFF -DLIBCXX_ENABLE_ABI_LINKER_SCRIPT=ON \
 			-DLIBCXX_INCLUDE_TESTS=OFF -DLIBCXX_INCLUDE_BENCHMARKS=OFF \
 			-DLIBCXXABI_USE_COMPILER_RT=ON -DLIBCXXABI_USE_LLVM_UNWINDER=ON \
+			-DLIBCXXABI_HAS_CXA_THREAD_ATEXIT_IMPL=OFF \
 			-DLIBCXXABI_ENABLE_SHARED=ON -DLIBCXXABI_ENABLE_STATIC=ON \
 			-DLIBCXXABI_INCLUDE_TESTS=OFF -DLIBUNWIND_USE_COMPILER_RT=ON \
 			-DLIBUNWIND_ENABLE_SHARED=ON -DLIBUNWIND_ENABLE_STATIC=ON \
diff --git a/tests/hello.cpp b/tests/hello.cpp
@@ -5,15 +5,31 @@
 #include <thread>
 #include <vector>
 
+struct thread_state {
+	std::atomic<int> &destroyed;
+
+	~thread_state()
+	{
+		destroyed.fetch_add(1);
+	}
+};
+
 int
 main()
 {
 	std::vector<int> values(128, 2);
 	std::atomic<int> total{0};
+	std::atomic<int> destroyed{0};
 	std::atomic<unsigned __int128> wide{0};
-	std::thread worker([&]() { total.store(std::accumulate(values.begin(), values.end(), 0)); });
+	std::thread worker([&]() {
+		thread_local thread_state state{destroyed};
+
+		total.store(std::accumulate(values.begin(), values.end(), 0));
+	});
 
 	worker.join();
+	if (destroyed.load() != 1)
+		return 1;
 	wide.store((unsigned __int128)1 << 100);
 	if (wide.load() != (unsigned __int128)1 << 100)
 		return 1;