[pulseaudio-discuss] Is this a pulseaudio bug or a vala bug?

[Sean McNamara]

Replying to myself:

On Fri, Mar 25, 2011 at 1:08 AM, Sean McNamara <smcnam at gmail.com> wrote:
> Hi,
>
> On Thu, Mar 24, 2011 at 10:37 PM, Alexander Kurtz
> <kurtz.alex at googlemail.com> wrote:
>> Hi,
>>
>> I have a problem with Pulseaudio (0.9.21) + Vala (0.10.4). I've written
>> this small demonstration program:
>>
>>        $ cat test.vala
>>        class MyClass : Object {
>>                static void main(){
>>                        PulseAudio.SampleSpec spec = PulseAudio.SampleSpec() {
>>                                format = PulseAudio.SampleFormat.S32NE,
>>                                channels = 2,
>>                                rate = 44100
>>                        };
>>                        PulseAudio.MainLoop loop =
>>                                new PulseAudio.MainLoop();
>>                        PulseAudio.Context context =
>>                                new PulseAudio.Context(loop.get_api(), null);
>>                        PulseAudio.Stream stream =
>>                                new PulseAudio.Stream(context, "", spec);
>>                        int32[] data = new int32[10];
>>                        stream.write(data, sizeof(int32) * data.length);
>>                }
>>        }
>>        $
>>
>> I know that this program won't work (i.e. "run") but it should compile
>> just fine. However, I get this:
>>
>>        $ valac --vapidir=. --pkg=libpulse --pkg=posix test.vala
>>        /home/alexander/test/test.vala.c: In function ‘myclass_main’:
>>        /home/alexander/test/test.vala.c:61: warning: passing argument 5 of ‘pa_stream_write’ makes integer from pointer without a cast
>>        /usr/include/pulse/stream.h:503: note: expected ‘int64_t’ but argument is of type ‘void *’
>>        /home/alexander/test/test.vala.c:61: error: too many arguments to function ‘pa_stream_write’
>>        error: cc exited with status 256
>>        Compilation failed: 1 error(s), 0 warning(s)
>>        $
>>
>> Looking at the generated C-Code reveals this:
>>
>>        $ valac --vapidir=. --pkg=libpulse --pkg=posix --ccode test.vala
>>        $ cat test.c
>>        [...]
>>                pa_stream_write (stream, data, (gsize) (sizeof (gint32) * data_length1), NULL, NULL, 0, PA_SEEK_RELATIVE);
>>        [...]
>>        $
>>
>> This is obviously wrong, since pa_stream_write takes 6 arguments not 7, see[1].
>>
>> Is this a bug in PA's Vala bindings or in Vala itself?
>
> Look at the PulseAudio bindings in
> /usr/share/vala*/vapi/pulseaudio.vapi, or in git:
> http://git.0pointer.de/?p=pulseaudio.git;a=blob_plain;f=vala/libpulse.vapi;hb=refs/heads/master-tx
>
> [Vala]:
> public int write(void *data, size_t bytes, FreeCb? free_cb = null,
> int64 offset = 0, SeekMode mode = SeekMode.RELATIVE);
>
> Compared to [C]:
> int     pa_stream_write (pa_stream *p, const void *data, size_t nbytes,
> pa_free_cb_t free_cb, int64_t offset, pa_seek_mode_t seek)
>
> It seems that the parameters match up in the vapi, but it compiles
> down to two NULLs instead of just one for the FreeCb. But if you look
> at the signature of FreeCb, it tries to accept a void* as a parameter:
>
> [Vala]
> public delegate void FreeCb(void *p);
>
> Maybe the extra parameter that Vala compiles in is supposed to be the
> void* that the callback would then get passed? I think this is the
> default behavior of a delegate. Maybe there is an annotation to tell
> the Vala compiler not to supply a parameter to the call for the formal
> parameters of the delegate?
>
> Try the following
>
> [CCode (has_target = false)]
> public delegate void FreeCb(void *p);

Yep, this works!

$ valac --pkg=libpulse --pkg=posix test.vala
$ file test
test: ELF 64-bit LSB executable, x86-64, version 1 (SYSV), dynamically
linked (uses shared libs), for GNU/Linux 2.6.15, not stripped

Attached is a patch

HTH,

Sean

>
> Just a guess though -- it may not work as intended! There's virtually
> no documentation on this attribute; I'm just guessing from the Vala
> sources.
>
> HTH,
>
> Sean
>
>>
>> Best regards
>>
>> Alexander Kurtz
>>
>> [1] http://0pointer.de/lennart/projects/pulseaudio/doxygen/stream_8h.html#a4fc69dec0cc202fcc174125dc88dada7
>>
>> _______________________________________________
>> pulseaudio-discuss mailing list
>> pulseaudio-discuss at mail.0pointer.de
>> https://tango.0pointer.de/mailman/listinfo/pulseaudio-discuss
>>
>>
>
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