Use pthread_testcancel from musl (#16134)

Author: kleisauke

system/lib/libc/musl/src/thread/pthread_cancel.c

@@ -3,7 +3,6 @@
 #include "pthread_impl.h"
 #include "syscall.h"
 
-#ifndef __EMSCRIPTEN__
 hidden long __cancel(), __syscall_cp_asm(), __syscall_cp_c();
 
 long __cancel()
@@ -15,6 +14,7 @@ long __cancel()
 	return -ECANCELED;
 }
 
+#ifndef __EMSCRIPTEN__
 long __syscall_cp_asm(volatile void *, syscall_arg_t,
                       syscall_arg_t, syscall_arg_t, syscall_arg_t,
                       syscall_arg_t, syscall_arg_t, syscall_arg_t);
@@ -67,6 +67,7 @@ static void cancel_handler(int sig, siginfo_t *si, void *ctx)
 
 	__syscall(SYS_tkill, self->tid, SIGCANCEL);
 }
+#endif
 
 void __testcancel()
 {
@@ -75,6 +76,7 @@ void __testcancel()
 		__cancel();
 }
 
+#ifndef __EMSCRIPTEN__
 static void init_cancellation()
 {
 	struct sigaction sa = {

system/lib/pthread/library_pthread.c

@@ -36,8 +36,6 @@
 
 #include "threading_internal.h"
 
-void __pthread_testcancel();
-
 int emscripten_pthread_attr_gettransferredcanvases(const pthread_attr_t* a, const char** str) {
   *str = a->_a_transferredcanvases;
   return 0;

system/lib/pthread/library_pthread_stub.c

@@ -206,6 +206,8 @@ int pthread_cancel(pthread_t thread) {
   return 0;
 }
 
+void pthread_testcancel() {}
+
 _Noreturn void __pthread_exit(void* status) {
    exit(0);
 }

system/lib/pthread/pthread_testcancel.c

@@ -10,7 +10,7 @@ $__pthread_setcancelstate
 $__set_thread_state
 $__stdio_write
 $__timedwait
-$__wake
+$__wake.2
 $__wasi_syscall_ret
 $__wasm_call_ctors
 $__wasm_init_memory
@@ -22,7 +22,7 @@ $_emscripten_thread_init
 $_main_thread
 $a_cas
 $a_dec
-$a_fetch_add
+$a_fetch_add.1
 $a_inc
 $a_swap
 $add

tests/other/metadce/minimal_main_Oz_USE_PTHREADS_PROXY_TO_PTHREAD.funcs

@@ -827,15 +827,12 @@ def get_files(self):
         'syscall_cp.c', 'tls.c',
         # TODO: Support this. See #12216.
         'pthread_setname_np.c',
-        # TODO: Prefer to use the musl implementation.
-        'pthread_testcancel.c',
       ]
       libc_files += files_in_path(
         path='system/lib/pthread',
         filenames=[
           'library_pthread.c',
           'pthread_create.c',
-          'pthread_testcancel.c',
           'emscripten_proxy_main.c',
           'emscripten_thread_init.c',
           'emscripten_thread_state.S',