Add pthread_getname_np and pthread_setname_np

This patch adds pthread_getname_np and pthread_setname_np.

These were added to glibc in 2.12[1] and are also present in some form on
NetBSD and several UNIXes.

The code is based on NetBSD's implementation with changes to better match
Linux behaviour.

Implementation quirks:

* pthread_setname_np with a NULL pointer segfaults (as linux)

* pthread_setname_np returns ERANGE for names longer than 16 characters (as
linux)

* pthread_getname_np with a NULL pointer returns EFAULT (as linux)

* pthread_getname_np with a buffer length of less than 16 returns ERANGE (as
linux)

* pthread_getname_np truncates the thread name to fit the buffer length.
This guarantees success even when the default thread name is longer than 16
characters, but means there is no way to discover the actual length of the
thread name. (Linux always truncates the thread name to 16 characters)

* Changing program_invocation_short_name changes the default thread name (on
linux, it has no effect on the default thread name)

I'll leave it up to you to decide if any of these matter.

This is implemented via class pthread_attr to make it easier to add
pthread_attr_[gs]etname_np (present in NetBSD and some UNIXes) should it
ever be added to Linux (or we decide we want it anyway).

[1] https://sourceware.org/git/?p=glibc.git;a=blob;f=NEWS

winsup/cygwin/common.din

@@ -1046,6 +1046,7 @@ pthread_exit SIGFE
 pthread_getattr_np SIGFE
 pthread_getconcurrency SIGFE
 pthread_getcpuclockid SIGFE
+pthread_getname_np SIGFE
 pthread_getschedparam SIGFE
 pthread_getsequence_np SIGFE
 pthread_getspecific SIGFE
@@ -1086,6 +1087,7 @@ pthread_self SIGFE
 pthread_setcancelstate SIGFE
 pthread_setcanceltype SIGFE
 pthread_setconcurrency SIGFE
+pthread_setname_np SIGFE
 pthread_setschedparam SIGFE
 pthread_setschedprio SIGFE
 pthread_setspecific SIGFE

winsup/cygwin/include/cygwin/version.h

@@ -467,12 +467,13 @@ details. */
        strtoull_l, wcstod_l, wcstof_l, wcstol_l, wcstold_l, wcstoll_l,
        wcstoul_l, wcstoull_l.
   302: Export nl_langinfo_l.
+  303: Export pthread_getname_np, pthread_setname_np.
 
   Note that we forgot to bump the api for ualarm, strtoll, strtoull,
   sigaltstack, sethostname. */
 
 #define CYGWIN_VERSION_API_MAJOR 0
-#define CYGWIN_VERSION_API_MINOR 302
+#define CYGWIN_VERSION_API_MINOR 303
 
 /* There is also a compatibity version number associated with the shared memory
    regions.  It is incremented when incompatible changes are made to the shared

winsup/cygwin/include/pthread.h

@@ -222,6 +222,8 @@ void pthread_testcancel (void);
 
 #if __GNU_VISIBLE
 int pthread_getattr_np (pthread_t, pthread_attr_t *);
+int pthread_getname_np (pthread_t, char *, size_t) __attribute__((nonnull(2)));
+int pthread_setname_np (pthread_t, const char *) __attribute__((nonnull(2)));
 int pthread_sigqueue (pthread_t *, int, const union sigval);
 int pthread_yield (void);
 #endif

winsup/cygwin/release/2.6.0

@@ -20,6 +20,7 @@ What's new:
 - locale(1) now supports a -i/--input option to fetch the current input
   locale (this is basically equivalent to the current keyboard layout setting).
 
+- New API: pthread_getname_np, pthread_setname_np.
 
 What changed:
 -------------

winsup/cygwin/thread.cc

@@ -1106,7 +1106,7 @@ pthread::resume ()
 pthread_attr::pthread_attr ():verifyable_object (PTHREAD_ATTR_MAGIC),
 joinable (PTHREAD_CREATE_JOINABLE), contentionscope (PTHREAD_SCOPE_PROCESS),
 inheritsched (PTHREAD_INHERIT_SCHED), stackaddr (NULL), stacksize (0),
-guardsize (wincap.def_guard_page_size ())
+guardsize (wincap.def_guard_page_size ()), name (NULL)
 {
   schedparam.sched_priority = 0;
 }
@@ -2576,6 +2576,69 @@ pthread_getattr_np (pthread_t thread, pthread_attr_t *attr)
   return 0;
 }
 
+/* For Linux compatibility, the length of a thread name is 16 characters. */
+#define THRNAMELEN 16
+
+extern "C" int
+pthread_getname_np (pthread_t thread, char *buf, size_t buflen)
+{
+  char *name;
+
+  if (!pthread::is_good_object (&thread))
+    return ESRCH;
+
+  if (!thread->attr.name)
+    name = program_invocation_short_name;
+  else
+    name = thread->attr.name;
+
+  /* Return ERANGE if the provided buffer is less than THRNAMELEN.  Truncate
+     and zero-terminate the name to fit in buf.  This means we always return
+     something if the buffer is THRNAMELEN or larger, but there is no way to
+     tell if we have the whole name. */
+  if (buflen < THRNAMELEN)
+    return ERANGE;
+
+  int ret = 0;
+  __try
+    {
+      strlcpy (buf, name, buflen);
+    }
+  __except (NO_ERROR)
+    {
+      ret = EFAULT;
+    }
+  __endtry
+
+  return ret;
+}
+
+extern "C" int
+pthread_setname_np (pthread_t thread, const char *name)
+{
+  char *oldname, *cp;
+
+  if (!pthread::is_good_object (&thread))
+    return ESRCH;
+
+  if (strlen (name) > THRNAMELEN)
+    return ERANGE;
+
+  cp = strdup (name);
+  if (!cp)
+    return ENOMEM;
+
+  oldname = thread->attr.name;
+  thread->attr.name = cp;
+
+  if (oldname)
+    free (oldname);
+
+  return 0;
+}
+
+#undef THRNAMELEN
+
 /* provided for source level compatability.
    See http://www.opengroup.org/onlinepubs/007908799/xsh/pthread_getconcurrency.html
 */

winsup/cygwin/thread.h

@@ -240,6 +240,7 @@ public:
   void *stackaddr;
   size_t stacksize;
   size_t guardsize;
+  char *name;
 
   pthread_attr ();
   ~pthread_attr ();

winsup/doc/new-features.xml

@@ -64,6 +64,10 @@ Support AzureAD accounts.
 "nobody" account support for WinFSP.
 </para></listitem>
 
+<listitem><para>
+New API: pthread_getname_np, pthread_setname_np.
+</para></listitem>
+
 </itemizedlist>
 
 </sect2>

winsup/doc/posix.xml

@@ -1337,6 +1337,8 @@ also IEEE Std 1003.1-2008 (POSIX.1-2008).</para>
     pow10l
     ppoll
     pthread_getattr_np
+    pthread_getname_np
+    pthread_setname_np
     pthread_sigqueue
     ptsname_r
     putwc_unlocked