Implement single_threaded pthread_exit

Performs all the cancellation actions and then calls exit()

Makefile

@@ -289,6 +289,7 @@ LIBC_TOP_HALF_MUSL_SOURCES += \
         thread/pthread_barrierattr_init.c \
         thread/pthread_barrierattr_setpshared.c \
         thread/pthread_cancel.c \
+        thread/pthread_cleanup_push.c \
         thread/pthread_condattr_destroy.c \
         thread/pthread_condattr_init.c \
         thread/pthread_condattr_setclock.c \
@@ -332,7 +333,6 @@ LIBC_TOP_HALF_MUSL_SOURCES += \
         thread/pthread_barrier_destroy.c \
         thread/pthread_barrier_init.c \
         thread/pthread_barrier_wait.c \
-        thread/pthread_cleanup_push.c \
         thread/pthread_cond_broadcast.c \
         thread/pthread_cond_destroy.c \
         thread/pthread_cond_init.c \

expected/wasm32-wasip1/defined-symbols.txt

@@ -38,6 +38,8 @@ __cxa_finalize
 __default_guardsize
 __default_stacksize
 __des_setkey
+__do_cleanup_pop
+__do_cleanup_push
 __do_des
 __duplocale
 __env_rm_add
@@ -383,6 +385,8 @@ _environ
 _exit
 _flushlbf
 _initialize
+_pthread_cleanup_pop
+_pthread_cleanup_push
 _start
 a64l
 abort
@@ -982,6 +986,7 @@ pthread_condattr_setpshared
 pthread_create
 pthread_detach
 pthread_equal
+pthread_exit
 pthread_getspecific
 pthread_join
 pthread_key_create

libc-top-half/stub-pthreads/stub-pthreads.c

@@ -5,6 +5,7 @@ static void dummy_0()
 }
 weak_alias(dummy_0, __acquire_ptc);
 weak_alias(dummy_0, __release_ptc);
+weak_alias(dummy_0, __pthread_tsd_run_dtors);
 
 int __pthread_create(pthread_t *restrict res, const pthread_attr_t *restrict attrp, void *(*entry)(void *), void *restrict arg)
 {
@@ -51,3 +52,27 @@ int pthread_once(pthread_once_t *control, void (*init)(void))
 	}
 	return 0;
 }
+
+_Noreturn void pthread_exit(void *result)
+{
+	/*
+		We are the only thread, so when we exit the whole process exits.
+		But we still have to run cancellation handlers...
+	*/
+	pthread_t self = __pthread_self();
+
+	self->canceldisable = 1;
+	self->cancelasync = 0;
+	self->result = result;
+
+	while (self->cancelbuf) {
+		void (*f)(void *) = self->cancelbuf->__f;
+		void *x = self->cancelbuf->__x;
+		self->cancelbuf = self->cancelbuf->__next;
+		f(x);
+	}
+
+	__pthread_tsd_run_dtors();
+
+	exit(0);
+}