[PATCH 8/9] Set the worker thread name on Windows

[Tom Tromey <tromey@adacore.com>]

This patch is a bit different from the rest of the series, in that it
is a change to gdb's behavior on the host.  It changes gdb's thread
pool to try to set the thread name on Windows, if SetThreadDescription
is available.

This is part of PR win32/29050.

This patch isn't likely to be useful to many people in the short term,
because the Windows port of the libstdc++ thread code is not upstream.
(AdaCore uses it, and sent it upstream, but it did not land, I don't
know why.)  However, if that patch does ever go in, or presumably if
you build using some other C++ runtime library, then this will be
useful.

Bug: https://sourceware.org/bugzilla/show_bug.cgi?id=29050
---
 gdbsupport/thread-pool.cc | 72 ++++++++++++++++++++++++++++++++++-----
 1 file changed, 64 insertions(+), 8 deletions(-)

diff --git a/gdbsupport/thread-pool.cc b/gdbsupport/thread-pool.cc
index efd8b799713..9d98529231c 100644
--- a/gdbsupport/thread-pool.cc
+++ b/gdbsupport/thread-pool.cc
@@ -46,14 +46,15 @@
    difference.  */
 
 ATTRIBUTE_UNUSED static void
-set_thread_name (int (*set_name) (pthread_t, const char *, void *),
-				  const char *name)
+do_set_thread_name (int (*set_name) (pthread_t, const char *, void *),
+		    const char *name)
 {
   set_name (pthread_self (), "%s", const_cast<char *> (name));
 }
 
 ATTRIBUTE_UNUSED static void
-set_thread_name (int (*set_name) (pthread_t, const char *), const char *name)
+do_set_thread_name (int (*set_name) (pthread_t, const char *),
+		    const char *name)
 {
   set_name (pthread_self (), name);
 }
@@ -61,12 +62,69 @@ set_thread_name (int (*set_name) (pthread_t, const char *), const char *name)
 /* The macOS man page says that pthread_setname_np returns "void", but
    the headers actually declare it returning "int".  */
 ATTRIBUTE_UNUSED static void
-set_thread_name (int (*set_name) (const char *), const char *name)
+do_set_thread_name (int (*set_name) (const char *), const char *name)
 {
   set_name (name);
 }
 
-#endif	/* USE_PTHREAD_SETNAME_NP */
+static void
+set_thread_name (const char *name)
+{
+  do_set_thread_name (pthread_setname_np, name);
+}
+
+#elif defined (USE_WIN32API)
+
+#include <windows.h>
+
+typedef HRESULT WINAPI (SetThreadDescription_ftype) (HANDLE, PCWSTR);
+static SetThreadDescription_ftype *dyn_SetThreadDescription;
+static bool initialized;
+
+static void
+init_windows ()
+{
+  initialized = true;
+
+  HMODULE hm = LoadLibrary (TEXT ("kernel32.dll"));
+  if (hm)
+    dyn_SetThreadDescription
+      = (SetThreadDescription_ftype *) GetProcAddress (hm,
+						       "SetThreadDescription");
+
+  /* On some versions of Windows, this function is only available in
+     KernelBase.dll, not kernel32.dll.  */
+  if (dyn_SetThreadDescription == nullptr)
+    {
+      hm = LoadLibrary (TEXT ("KernelBase.dll"));
+      if (hm)
+	dyn_SetThreadDescription
+	  = (SetThreadDescription_ftype *) GetProcAddress (hm,
+							   "SetThreadDescription");
+    }
+}
+
+static void
+do_set_thread_name (const wchar_t *name)
+{
+  if (!initialized)
+    init_windows ();
+
+  if (dyn_SetThreadDescription != nullptr)
+    dyn_SetThreadDescription (GetCurrentThread (), name);
+}
+
+#define set_thread_name(NAME) do_set_thread_name (L ## NAME)
+
+#else /* USE_WIN32API */
+
+static void
+set_thread_name (const char *name)
+{
+}
+
+#endif
+
 #endif /* CXX_STD_THREAD */
 
 namespace gdb
@@ -159,11 +217,9 @@ thread_pool::do_post_task (std::packaged_task<void ()> &&func)
 void
 thread_pool::thread_function ()
 {
-#ifdef USE_PTHREAD_SETNAME_NP
   /* This must be done here, because on macOS one can only set the
      name of the current thread.  */
-  set_thread_name (pthread_setname_np, "gdb worker");
-#endif
+  set_thread_name ("gdb worker");
 
   /* Ensure that SIGSEGV is delivered to an alternate signal
      stack.  */
-- 
2.34.1