Accessing Windows thread id

Accessing Windows thread id

[Michael Bieber]

@list

I would like exploit the technique, described here:

http://msdn2.microsoft.com/en-us/library/xcb2z8hs(vs.80).aspx

in order to help my Visual Studio debugger with some more expressive
thread names.

Unfortunately, this is relying on a thread id not being public
accessible for pthreads_win32 clients (It is the last argument to
_beginthreadex, after that call hidden inside the non-public
ptw32_thread_t structure). Windows GetThreadId is no help here, because
it isn't defined for Win XP. Even GetCurrentId is not entirely what I
would like, because the call to SetThreadName (cf. URL above) doesn't
come from the calling thread in my case.

So, is there a way to get the Windows thread id in a way similar to
pthread_getw32threadhandle_np for a handle?

Micha

-- 

Re: Accessing Windows thread id

[Ross Johnson]

Michael Bieber wrote:
> @list
>
> I would like exploit the technique, described here:
>
> http://msdn2.microsoft.com/en-us/library/xcb2z8hs(vs.80).aspx
>
> in order to help my Visual Studio debugger with some more expressive
> thread names.
>
> Unfortunately, this is relying on a thread id not being public
> accessible for pthreads_win32 clients (It is the last argument to
> _beginthreadex, after that call hidden inside the non-public
> ptw32_thread_t structure). Windows GetThreadId is no help here, because
> it isn't defined for Win XP. Even GetCurrentId is not entirely what I
> would like, because the call to SetThreadName (cf. URL above) doesn't
> come from the calling thread in my case.
>
> So, is there a way to get the Windows thread id in a way similar to
> pthread_getw32threadhandle_np for a handle?
>   
Not nicely but otherwise, yes.

As you've found, the win32 thread ID returned by the last arg of 
_beginthreadex() is stored at offset zero in the opaque pthw32_thread_t_ 
struct, which is pointed to by the first element (offset zero) of the 
pthread_t struct, a pointer to which is the first arg passed to 
pthread_create(). So the code below should get you close if not all the 
way there:-

DWORD w32threadID;
pthread_t tid;
pthread_create(&tid, ...);
w32threadID = (DWORD) ((void *)tid)[0][0];

I'll add another function to the library to return this nicely - called, 
say, pthread_getw32threadid_np().

Regards.
Ross

Re: Accessing Windows thread id

[Michael Bieber]

RJ> I'll add another function to the library to return this nicely - called,
RJ> say, pthread_getw32threadid_np().

Hallo Ross,

I was able to circumvent my particular problem, but the new function
should be helpful for some other cases too.

Thank you,
Micha

p.s. The library did a great job during a Linux->Windows port of 100
kLOC, saving a *lot* of time here. Additionally, it is very helpful in
maintaining a common source tree for both OS variants of our software.
Keep up the good work and thank you again!