util: set the name for the 'main' thread on Windows

The default main thread name is undefined, so use a constructor to
explicitly set it to 'main'. This constructor is marked to run early
as the thread name is intended to be used in error reporting / logs
which may be triggered very early in QEMU execution.

This is only done on Windows platforms, because on Linux (and possibly
other POSIX platforms) changing the main thread name has a side effect
of changing the process name reported by tools like 'ps' which fetch
from the file /proc/self/task/tid/comm, expecting it to be the binary
name.

The subsequent patch will address POSIX platforms in a different way.

Reviewed-by: Richard Henderson <richard.henderson@linaro.org>
Reviewed-by: Dr. David Alan Gilbert <dave@treblig.org>
Signed-off-by: Daniel P. Berrangé <berrange@redhat.com>

util/qemu-thread-win32.c

@@ -22,6 +22,12 @@ typedef HRESULT (WINAPI *pSetThreadDescription) (HANDLE hThread,
 static pSetThreadDescription SetThreadDescriptionFunc;
 static HMODULE kernel32_module;
 
+static void __attribute__((__constructor__(QEMU_CONSTRUCTOR_EARLY)))
+qemu_thread_init(void)
+{
+    qemu_thread_set_name("main");
+}
+
 static bool load_set_thread_description(void)
 {
     static gsize _init_once = 0;