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

["Jan Ekström" <jeebjp@gmail.com>]

On Tue, Mar 4, 2025 at 5:14 PM Kacper Michajłow <kasper93@gmail.com> wrote:
>
> Signed-off-by: Kacper Michajłow <kasper93@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
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