Support thread names on coop threads

libc-top-half/musl/src/internal/pthread_impl.h

@@ -70,6 +70,7 @@ struct pthread {
 	void *stdio_locks;
 	#ifdef __wasi_cooperative_threads__
 	volatile int joiner_futex;
+	char name[16];
 	#endif
 
 	/* Part 3 -- the positions of these fields relative to

libc-top-half/musl/src/thread/coop-threads/pthread_create.c

@@ -280,6 +280,7 @@ int __pthread_create(pthread_t *restrict res,
   new->robust_list.head = &new->robust_list.head;
   new->canary = self->canary;
   new->sysinfo = self->sysinfo;
+  new->name[0] = 0;
 
   // Setup argument structure for the new thread on its stack.
 

libc-top-half/musl/src/thread/coop-threads/pthread_getname_np.c

@@ -1,6 +1,11 @@
-
+#define _GNU_SOURCE
+#include <string.h>
 #include "pthread_impl.h"
 
 int pthread_getname_np(pthread_t thread, char *name, size_t len) {
-  return ENOTSUP;
+  size_t n = strlen(thread->name);
+  if (n >= len)
+    return ERANGE;
+  strcpy(name, thread->name);
+  return 0;
 }

libc-top-half/musl/src/thread/coop-threads/pthread_setname_np.c

@@ -1,3 +1,11 @@
+#define _GNU_SOURCE
+#include <string.h>
 #include "pthread_impl.h"
 
-int pthread_setname_np(pthread_t thread, const char *name) { return ENOTSUP; }
+int pthread_setname_np(pthread_t thread, const char *name) {
+  size_t len = strlen(name);
+  if (len > 15)
+    return ERANGE;
+  strcpy(thread->name, name);
+  return 0;
+}

test/CMakeLists.txt

@@ -504,6 +504,7 @@ endif()
 
 if (ENABLE_COOP_THREADS)
   add_wasilibc_test(coop_smoke.c)
+  add_wasilibc_test(coop_thread_name.c)
   add_wasilibc_test(coop_sem_multiwaiter.c)
   add_wasilibc_test(coop_cond_signal_wakeup.c)
   add_wasilibc_test(coop_stdio_orphan_lock.c)

test/src/coop_thread_name.c

@@ -0,0 +1,75 @@
+#define _GNU_SOURCE
+#include "test.h"
+#include <errno.h>
+#include <pthread.h>
+#include <semaphore.h>
+#include <string.h>
+
+#define TEST(c)                                                                \
+  do {                                                                         \
+    if (!(c))                                                                  \
+      t_error("%s failed\n", #c);                                              \
+  } while (0)
+
+static sem_t go;
+static sem_t named;
+static sem_t checked;
+
+static void *worker(void *arg) {
+  (void)arg;
+  char buf[16];
+
+  // The name set by the main thread is visible here.
+  TEST(sem_wait(&go) == 0);
+  TEST(pthread_getname_np(pthread_self(), buf, sizeof(buf)) == 0);
+  TEST(strcmp(buf, "from-main") == 0);
+
+  // Rename ourselves and let the main thread observe it.
+  TEST(pthread_setname_np(pthread_self(), "from-worker") == 0);
+  TEST(sem_post(&named) == 0);
+  TEST(sem_wait(&checked) == 0);
+  return NULL;
+}
+
+int main(void) {
+  char buf[32];
+
+  // The main thread starts out with no name.
+  TEST(pthread_getname_np(pthread_self(), buf, sizeof(buf)) == 0);
+  TEST(strcmp(buf, "") == 0);
+
+  TEST(pthread_setname_np(pthread_self(), "main-thread") == 0);
+  TEST(pthread_getname_np(pthread_self(), buf, sizeof(buf)) == 0);
+  TEST(strcmp(buf, "main-thread") == 0);
+
+  // size limits
+  TEST(pthread_setname_np(pthread_self(), "123456789012345") == 0);
+  TEST(pthread_getname_np(pthread_self(), buf, sizeof(buf)) == 0);
+  TEST(strcmp(buf, "123456789012345") == 0);
+  TEST(pthread_setname_np(pthread_self(), "1234567890123456") == ERANGE);
+
+  char small[4];
+  TEST(pthread_getname_np(pthread_self(), small, sizeof(small)) == ERANGE);
+  char exact[16];
+  TEST(pthread_getname_np(pthread_self(), exact, sizeof(exact)) == 0);
+  TEST(strcmp(exact, "123456789012345") == 0);
+
+  // Names can be set and read across threads.
+  TEST(sem_init(&go, 0, 0) == 0);
+  TEST(sem_init(&named, 0, 0) == 0);
+  TEST(sem_init(&checked, 0, 0) == 0);
+  pthread_t t;
+  pthread_attr_t attr;
+  TEST(pthread_attr_init(&attr) == 0);
+  TEST(pthread_create(&t, &attr, worker, NULL) == 0);
+  TEST(pthread_setname_np(t, "from-main") == 0);
+  TEST(sem_post(&go) == 0);
+
+  TEST(sem_wait(&named) == 0);
+  TEST(pthread_getname_np(t, buf, sizeof(buf)) == 0);
+  TEST(strcmp(buf, "from-worker") == 0);
+  TEST(sem_post(&checked) == 0);
+
+  TEST(pthread_join(t, NULL) == 0);
+  return t_status;
+}