Re: [PATCH 5/7] audio: Let HWVoice write() handlers take a const buffer

[Philippe Mathieu-Daudé]

On 5/6/20 8:22 AM, Volker Rümelin wrote:
> > diff --git a/audio/dsoundaudio.c b/audio/dsoundaudio.c
> > index 4cdf19ab67..bba6bafda4 100644
> > --- a/audio/dsoundaudio.c
> > +++ b/audio/dsoundaudio.c
> > @@ -454,7 +454,7 @@ static void *dsound_get_buffer_out(HWVoiceOut *hw, size_t 
> > *size)
> >       return ret;
> >   }
> >   
> > -static size_t dsound_put_buffer_out(HWVoiceOut *hw, void *buf, size_t len)
> > +static size_t dsound_put_buffer_out(HWVoiceOut *hw, const void *buf, size_t 
> > len)
> >   {
> >       DSoundVoiceOut *ds = (DSoundVoiceOut *) hw;
> >       LPDIRECTSOUNDBUFFER dsb = ds->dsound_buffer;
>
> You forgot to make the buffer const in dsound_put_buffer_in().
>
> I had to cast buf to LPVOID in dsound_get_buffer_in() and 
> dsound_put_buffer_in() because otherwise I see:
>
> C:/usr/msys64/home/ruemelin/git/qemu/audio/dsoundaudio.c: In function 
> 'dsound_put_buffer_out':
> C:/usr/msys64/home/ruemelin/git/qemu/audio/dsoundaudio.c:466:38: error: passing 
> argument 2 of 'dsound_unlock_out' discards 'const' qualifier from pointer 
> target type [-Werror=discarded-qualifiers]
>    466 |     int err = dsound_unlock_out(dsb, buf, NULL, len, 0);
>        |                                      ^~~
> In file included from 
> C:/usr/msys64/home/ruemelin/git/qemu/audio/dsoundaudio.c:266:
> C:/usr/msys64/home/ruemelin/git/qemu/audio/dsound_template.h:48:12: note: 
> expected 'LPVOID' {aka 'void *'} but argument is of type 'const void *'
>     48 |     LPVOID p1,
>        |     ~~~~~~~^~
> C:/usr/msys64/home/ruemelin/git/qemu/audio/dsoundaudio.c: In function 
> 'dsound_put_buffer_in':
> C:/usr/msys64/home/ruemelin/git/qemu/audio/dsoundaudio.c:571:38: error: passing 
> argument 2 of 'dsound_unlock_in' discards 'const' qualifier from pointer target 
> type [-Werror=discarded-qualifiers]
>    571 |     int err = dsound_unlock_in(dscb, buf, NULL, len, 0);
>        |                                      ^~~
> In file included from 
> C:/usr/msys64/home/ruemelin/git/qemu/audio/dsoundaudio.c:268:
> C:/usr/msys64/home/ruemelin/git/qemu/audio/dsound_template.h:48:12: note: 
> expected 'LPVOID' {aka 'void *'} but argument is of type 'const void *'
>     48 |     LPVOID p1,
>        |     ~~~~~~~^~

OK thanks for testing. This is unfortunate, because a single backend 
invalidates the whole series.
I don't understand why the DirectSound API requires a writable buffer 
for locking.

> With best regards,
> Volker