[FFmpeg-devel] [PATCH v2] w32pthreads: add support for setting thread name

[softworkz .]

> -----Original Message-----
> From: ffmpeg-devel <ffmpeg-devel-bounces at ffmpeg.org> On Behalf Of Jan
> Ekström
> Sent: Montag, 31. März 2025 00:05
> To: FFmpeg development discussions and patches <ffmpeg-devel at ffmpeg.org>
> Subject: Re: [FFmpeg-devel] [PATCH v2] w32pthreads: add support for
> setting thread name
> 
> On Tue, Mar 4, 2025 at 5:14 PM Kacper Michajłow <kasper93 at gmail.com>
> wrote:
> >
> > Signed-off-by: Kacper Michajłow <kasper93 at gmail.com>
> > ---
> >  compat/w32pthreads.h | 30 ++++++++++++++++++++++++++++++
> >  libavutil/thread.h   |  2 ++
> >  2 files changed, 32 insertions(+)
> >
> > diff --git a/compat/w32pthreads.h b/compat/w32pthreads.h
> > index fd6428e29f..8d5b4729fa 100644
> > --- a/compat/w32pthreads.h
> > +++ b/compat/w32pthreads.h
> > @@ -44,6 +44,7 @@
> >  #include "libavutil/internal.h"
> >  #include "libavutil/mem.h"
> >  #include "libavutil/time.h"
> > +#include "libavutil/wchar_filename.h"
> >
> >  typedef struct pthread_t {
> >      void *handle;
> > @@ -209,4 +210,33 @@ static inline int pthread_setcancelstate(int
> state, int *oldstate)
> >      return 0;
> >  }
> >
> > +static inline int win32_thread_setname(const char *name)
> > +{
> > +    typedef HRESULT (WINAPI *SetThreadDescriptionFn)(HANDLE, PCWSTR);
> > +    SetThreadDescriptionFn pSetThreadDescription;
> > +    HRESULT hr;
> > +    wchar_t *wname;
> > +
> > +#if !HAVE_UWP
> > +    HMODULE kernel32 = GetModuleHandleW(L"kernel32.dll");
> > +    if (!kernel32)
> > +        return AVERROR(ENOSYS);
> > +    pSetThreadDescription = (SetThreadDescriptionFn)
> > +        GetProcAddress(kernel32, "SetThreadDescription");
> > +    if (!pSetThreadDescription)
> > +        return AVERROR(ENOSYS);
> > +#else
> > +    WINBASEAPI HRESULT WINAPI
> > +    SetThreadDescription(HANDLE hThread, PCWSTR lpThreadDescription);
> > +    pSetThreadDescription = &SetThreadDescription;
> > +#endif
> > +
> > +    if (utf8towchar(name, &wname) < 0)
> > +        return AVERROR(ENOMEM);
> > +
> > +    hr = pSetThreadDescription(GetCurrentThread(), wname);
> > +    av_free(wname);
> > +    return SUCCEEDED(hr) ? 0 : AVERROR(EINVAL);
> > +}
> > +
> 
> I can only comment on the non-UWP side of things, but in general the
> code seems fine. I guess this function definition has not been in
> mingw-w64 etc for long enough to hope it would always be there and
> thus we need to define it (similar to pf_DXGIGetDebugInterface)?
> 
> The only question mark that is left is whether this functionality is
> actually in kernel32 or kernelbase. When I first saw
> https://stackoverflow.com/questions/62243162/how-to-access-
> setthreaddescription-in-windows-2016-server-version-1607
> I more or less thought of it as a possibly fluke or so, but then
> apparently mingw-w64 went for kernelbase as well in winpthreads?
> https://sourceforge.net/p/mingw-w64/mailman/message/58829419/
> 
> What it seems like is that kernel32 works for (at the very least) 20+
> versions of win10+, and older stuff such as the still-supported server
> 2016 requires direct usage of kernelbase?
> 
> Jan
> _______________________________________________

Hi Jan,

the actual implementation is (and has always been) in kernelbase.dll.

It was introduced there with Windows SDK 10.0.14393 (Windows OS 1607).
At some point between SDKs 14393 and 18362 (don't have the in-betweens installed), a forwarding export had been added to kernel32.dll (try: dumpbin /exports c:\windows\system32\kernel32.dll | findstr SetThreadDescription).

So, using kernelbase.dll will cover more Windows versions than with kernel32.dll.

sw