[PATCH v2] win32: set threads name

[marcandre . lureau]

From: Marc-André Lureau <marcandre.lureau@redhat.com>

As described in:
https://learn.microsoft.com/en-us/visualstudio/debugger/how-to-set-a-thread-name-in-native-code?view=vs-2022

SetThreadDescription() is available since Windows 10, version 1607 and
in some versions only by "Run Time Dynamic Linking". Its declaration is
not yet in mingw, so we lookup the function the same way glib does.

Tested with Visual Studio Community 2022 debugger.

Signed-off-by: Marc-André Lureau <marcandre.lureau@redhat.com>
---
 util/qemu-thread-win32.c | 56 ++++++++++++++++++++++++++++++++++++++--
 1 file changed, 54 insertions(+), 2 deletions(-)

diff --git a/util/qemu-thread-win32.c b/util/qemu-thread-win32.c
index a2d5a6e825..e2d681fe7d 100644
--- a/util/qemu-thread-win32.c
+++ b/util/qemu-thread-win32.c
@@ -19,12 +19,40 @@
 
 static bool name_threads;
 
+typedef HRESULT (WINAPI *pSetThreadDescription) (HANDLE hThread,
+                                                 PCWSTR lpThreadDescription);
+static pSetThreadDescription SetThreadDescriptionFunc = NULL;
+static HMODULE kernel32_module = NULL;
+
+static bool
+load_set_thread_description(void)
+{
+  static gsize _init_once = 0;
+
+  if (g_once_init_enter(&_init_once)) {
+      kernel32_module = LoadLibraryW(L"kernel32.dll");
+      if (kernel32_module) {
+          SetThreadDescriptionFunc =
+              (pSetThreadDescription)GetProcAddress(kernel32_module,
+                                                    "SetThreadDescription");
+          if (!SetThreadDescriptionFunc) {
+              FreeLibrary(kernel32_module);
+          }
+      }
+      g_once_init_leave(&_init_once, 1);
+  }
+
+  return !!SetThreadDescriptionFunc;
+}
+
 void qemu_thread_naming(bool enable)
 {
-    /* But note we don't actually name them on Windows yet */
     name_threads = enable;
 
-    fprintf(stderr, "qemu: thread naming not supported on this host\n");
+    if (enable && !load_set_thread_description()) {
+        fprintf(stderr, "qemu: thread naming not supported on this host\n");
+        name_threads = false;
+    }
 }
 
 static void error_exit(int err, const char *msg)
@@ -400,6 +428,26 @@ void *qemu_thread_join(QemuThread *thread)
     return ret;
 }
 
+static bool
+set_thread_description(HANDLE h, const char *name)
+{
+  HRESULT hr;
+  g_autofree wchar_t *namew = NULL;
+
+  if (!load_set_thread_description() || !name) {
+      return false;
+  }
+
+  namew = g_utf8_to_utf16(name, -1, NULL, NULL, NULL);
+  if (!namew) {
+      return false;
+  }
+
+  hr = SetThreadDescriptionFunc(h, namew);
+
+  return SUCCEEDED(hr);
+}
+
 void qemu_thread_create(QemuThread *thread, const char *name,
                        void *(*start_routine)(void *),
                        void *arg, int mode)
@@ -423,7 +471,11 @@ void qemu_thread_create(QemuThread *thread, const char 
*name,
     if (!hThread) {
         error_exit(GetLastError(), __func__);
     }
+    if (name_threads && !set_thread_description(hThread, name)) {
+        fprintf(stderr, "Failed to set thread description: %s\n", name);
+    }
     CloseHandle(hThread);
+
     thread->data = data;
 }
 
-- 
2.37.3