darwin: call pthread_setname_np() if available

When setting the process title, also call pthread_setname_np() when
supported (OS X >= 10.6 and iOS >= 3.2.)

src/unix/darwin-proctitle.c

@@ -19,6 +19,7 @@
  */
 
 #include <TargetConditionals.h>
+#include <dlfcn.h>
 
 #if !TARGET_OS_IPHONE
 # include <CoreFoundation/CoreFoundation.h>
@@ -26,9 +27,30 @@
 #endif
 
 
+static int uv__pthread_setname_np(const char* name) {
+  int (*dynamic_pthread_setname_np)(const char* name);
+  char namebuf[64];  /* MAXTHREADNAMESIZE */
+  int err;
+
+  /* pthread_setname_np() first appeared in OS X 10.6 and iOS 3.2. */
+  dynamic_pthread_setname_np = dlsym(RTLD_DEFAULT, "pthread_setname_np");
+  if (dynamic_pthread_setname_np == NULL)
+    return -ENOSYS;
+
+  strncpy(namebuf, name, sizeof(namebuf) - 1);
+  namebuf[sizeof(namebuf) - 1] = '\0';
+
+  err = dynamic_pthread_setname_np(namebuf);
+  if (err)
+    return -err;
+
+  return 0;
+}
+
+
 int uv__set_process_title(const char* title) {
 #if TARGET_OS_IPHONE
-  return -ENOSYS;
+  return uv__pthread_setname_np(title);
 #else
   typedef CFTypeRef (*LSGetCurrentApplicationASNType)(void);
   typedef OSStatus (*LSSetApplicationInformationItemType)(int,
@@ -84,6 +106,8 @@ int uv__set_process_title(const char* title) {
   if (err != noErr)
     return -ENOENT;
 
+  uv__pthread_setname_np(title);  /* Don't care if it fails. */
+
   return 0;
 #endif  /* !TARGET_OS_IPHONE */
 }