cxx_thread: Add __cxa_thread_atexit_impl

Signed-off-by: Samuel Holland <samuel@sholland.org>

3 files changed, 62 insertions, 0 deletions

diff --git a/CHANGELOG.rst b/CHANGELOG.rst
index ee9851d..2902cb3 100644
--- a/CHANGELOG.rst
+++ b/CHANGELOG.rst
@@ -17,6 +17,11 @@ Build system
 
 * Allow building against libucontext.
 
+cxx_thread
+----------
+
+* Add __cxa_thread_atexit_impl.
+
 
 math
 ----
diff --git a/Makefile b/Makefile
index 06af84f..74c25f6 100644
--- a/Makefile
+++ b/Makefile
@@ -1,6 +1,7 @@
 LIBGCOMPAT_INCLUDE = \
 	libgcompat/alias.h
 LIBGCOMPAT_SRC = \
+	libgcompat/cxx_thread.c		\
 	libgcompat/dlfcn.c		\
 	libgcompat/error.c		\
 	libgcompat/execinfo.c		\
diff --git a/libgcompat/cxx_thread.c b/libgcompat/cxx_thread.c
new file mode 100644
index 0000000..105e4c5
--- /dev/null
+++ b/libgcompat/cxx_thread.c
@@ -0,0 +1,56 @@
+#include <pthread.h> /* NULL, pthread_{key,once,{get,set}specific} */
+#include <stdlib.h>  /* malloc, free */
+
+#include "internal.h"
+
+struct dtor_node {
+	struct dtor_node *next;
+	void (*func)(void *);
+	void *obj;
+};
+
+static pthread_key_t key;
+static pthread_once_t once = PTHREAD_ONCE_INIT;
+
+static void run_dtors(void *head)
+{
+	struct dtor_node *next, *node = head;
+
+	while (node != NULL) {
+		next = node->next;
+		node->func(node->obj);
+		free(node);
+		node = next;
+	}
+}
+
+static void create_key(void)
+{
+	int res = pthread_key_create(&key, run_dtors);
+
+	GCOMPAT__assert_with_reason(res, "No key for thread_atexit list");
+}
+
+/**
+ * Register a destructor to run at thread exit.
+ *
+ * See
+ * https://sourceware.org/glibc/wiki/Destructor%20support%20for%20thread_local%20variables
+ */
+int __cxa_thread_atexit_impl(void (*func)(void *), void *obj, void *dso_symbol)
+{
+	struct dtor_node *node;
+
+	pthread_once(&once, create_key);
+
+	node = malloc(sizeof(*node));
+	GCOMPAT__assert_with_reason(node, "No memory for thread_atexit node");
+	node->next = pthread_getspecific(key);
+	node->func = func;
+	node->obj = obj;
+
+	int res = pthread_setspecific(key, node);
+	GCOMPAT__assert_with_reason(!res, "Cannot update thread_atexit list");
+
+	return 0;
+}