0.16.9 --- the ok image exports __cxa_thread_atexit; openkal-musl 0.22.9

README.md

@@ -6,7 +6,7 @@ C library.
 
 ```toml
 [dependencies]
-openkal-llvm-runtime = "0.16.8"
+openkal-llvm-runtime = "0.16.9"
 ```
 
 > **Engine floor (mcpp 2026.9.20.1):** this version of this package pins

examples/image-cxx/mcpp.toml

@@ -1,7 +1,7 @@
 # The C++ runtime inside an ok image (target `<arch>-openkal', openkal SPEC
 # clause 12): one image per architecture, run through okrun on Linux, macOS and
-# Windows. `import std', an exception, a thread, a thread-local variable and the
-# containers, above openkal-musl's image form.
+# Windows. `import std', an exception, a thread, thread-local variables (one
+# with a destructor) and the containers, above openkal-musl's image form.
 [package]
 name    = "image-cxx"
 version = "0.1.0"
@@ -10,7 +10,7 @@ version = "0.1.0"
 openkal-llvm-runtime = { path = "../.." }
 
 [build-dependencies]
-openkal-tools = { version = "0.1.3", tools = ["okld", "okrun"] }
+openkal-tools = { version = "0.1.4", tools = ["okld", "okrun"] }
 
 [targets.image-cxx]
 kind = "bin"

examples/image-cxx/src/main.cpp

@@ -9,6 +9,8 @@ void check(bool held, std::string_view what) {
     if (!held) ++failures;
 }
 thread_local int tl = 7;
+std::atomic<int> tls_dtor_ran{0};
+struct TlsProbe { int v; ~TlsProbe() { tls_dtor_ran.store(v); } };
 }
 
 int main(int argc, char** argv) {
@@ -24,6 +26,12 @@ int main(int argc, char** argv) {
     t.join();
     check(seen == 7 && tl == 7, "a thread has its own thread-local variable");
 
+    // A thread_local with a destructor needs `__cxa_thread_atexit`, which the
+    // image's runtime provides; the image would not link without it.
+    std::thread d([] { thread_local TlsProbe p{7}; (void)p; });
+    d.join();
+    check(tls_dtor_ran.load() == 7, "a thread_local's destructor runs when its thread ends");
+
     std::map<std::string, int> m{{"a", 1}, {"b", 2}};
     std::vector<int> v(100);
     std::iota(v.begin(), v.end(), 1);

llvm/libcxxabi/src/cxa_thread_atexit.cpp

@@ -179,14 +179,19 @@ namespace {
 //
 // THE FALLBACK BELOW WAS ALREADY COMPLETE; only the export was missing. What
 // was NOT complete is where it kept its list --- see `run_dtors` above.
+//
+// THE OK IMAGE IS THE FOURTH SUCH TARGET. Its triple names no operating system,
+// so the guard reads `OPENKAL_TARGET_IMAGE`, which `mcpp.toml` states for
+// `cfg(os = "openkal")` as it states `OPENKAL_TARGET_WINDOWS` for PE.
 #if defined(__linux__) || defined(__Fuchsia__) \
-    || defined(OPENKAL_TARGET_WINDOWS) || defined(__APPLE__)
+    || defined(OPENKAL_TARGET_WINDOWS) || defined(OPENKAL_TARGET_IMAGE) \
+    || defined(__APPLE__)
 extern "C" {
 
   _LIBCXXABI_FUNC_VIS int __cxa_thread_atexit(Dtor dtor, void* obj, void* dso_symbol) throw() {
 #ifdef HAVE___CXA_THREAD_ATEXIT_IMPL
     return __cxa_thread_atexit_impl(dtor, obj, dso_symbol);
-#elif defined(__APPLE__)
+#elif defined(__APPLE__) || defined(OPENKAL_TARGET_IMAGE)
     // NO WEAK PROBE ON MACH-O, AND THE REASON IS THE OBJECT FORMAT.
     //
     // The `else` branch below declares `__cxa_thread_atexit_impl` weak and
@@ -198,7 +203,10 @@ extern "C" {
     //     ld64.lld: error: undefined symbol: __cxa_thread_atexit_impl
     //
     // The test is also pointless here: what would define that symbol is
-    // libSystem, and libSystem is what this stack replaces.
+    // libSystem, and libSystem is what this stack replaces. An ok image takes
+    // the same branch: nothing beneath it defines the symbol either, and an
+    // image may import nothing but `kal_*`, which an unresolved weak reference
+    // would put in question.
     (void)dso_symbol;
     return register_dtor(dtor, obj);
 #else
@@ -229,5 +237,5 @@ extern "C" {
 #endif
 
 } // extern "C"
-#endif // defined(__linux__) || defined(__Fuchsia__)
+#endif // the targets that export __cxa_thread_atexit
 } // namespace __cxxabiv1

mcpp.toml

@@ -1,7 +1,7 @@
 [package]
 namespace   = "mcpplibs"
 name        = "openkal-llvm-runtime"
-version     = "0.16.8"
+version     = "0.16.9"
 description = "LLVM's C++ runtime libraries — libc++, libc++abi and libunwind — configured for openkal-musl rather than for a host C library."
 license     = "Apache-2.0"
 authors     = ["mcpplibs"]
@@ -220,7 +220,7 @@ cflags = ["-DDISABLE_AARCH64_FMV=1"]
 # runtime itself (`mcpp:compiler-runtime=compiler-rt' above), and on an ok image
 # (`<arch>-openkal') that feature would bring a second supplier of the same layer
 # --- which a build refuses rather than picks between.
-openkal-musl = { version = "0.22.8", default-features = false, features = ["posix"] }
+openkal-musl = { version = "0.22.9", default-features = false, features = ["posix"] }
 
 [build]
 
@@ -523,6 +523,18 @@ sources = [
   "!llvm/compiler-rt/lib/builtins/*xc3.c",
 ]
 
+[target.'cfg(os = "openkal")'.build]
+# WHICH TARGET THIS IS, FOR THE ONE FILE THAT MUST KNOW IT IS AN OK IMAGE.
+#
+# An ok image's triple is `<arch>-unknown-none-elf`: no `__linux__`, no
+# `__APPLE__`, nothing a source can read the target off. `cxa_thread_atexit.cpp`
+# exports `__cxa_thread_atexit` on the targets where no other runtime does, and
+# without this define the ok image was not one of them: every image holding a
+# `thread_local` with a destructor was refused by `okld check` for the undefined
+# symbol (measured building clangd as an ok image, 2026-10-29).
+cflags   = ["-DOPENKAL_TARGET_IMAGE=1"]
+cxxflags = ["-DOPENKAL_TARGET_IMAGE=1"]
+
 [target.'cfg(windows)'.build]
 # WHICH TARGET THIS IS, STATED HERE RATHER THAN READ OFF `_WIN32`.
 #