stb_vorbis: Unchecked return value from stb_vorbis_get_frame_float

[weirddan455]

Hello, I am a developer of Dosbox Staging. As part of our CI, we have Coverity static analyzer which detected the following issue:

dosbox-staging/dosbox-staging#2996

https://user-images.githubusercontent.com/1557255/274740089-0bc591db-a476-4b6b-8a0e-d49ea08d30ac.png

Every other time stb_vorbis_get_frame_float is called, the return value is checked.

We've done some modification of the source but the function it is alerting on is unchanged:

stb/stb_vorbis.c

Lines 4919 to 4934 in beebb24

	int stb_vorbis_seek(stb_vorbis *f, unsigned int sample_number)
	{
	if (!stb_vorbis_seek_frame(f, sample_number))
	return 0;
	if (sample_number != f->current_loc) {
	int n;
	uint32 frame_start = f->current_loc;
	stb_vorbis_get_frame_float(f, &n, NULL);
	assert(sample_number > frame_start);
	assert(f->channel_buffer_start + (int) (sample_number-frame_start) <= f->channel_buffer_end);
	f->channel_buffer_start += (sample_number - frame_start);
	}
	return 1;
	}

I just wanted to raise this issue here in case this is a bug. Does the return value need to be checked here? It appears to be length of some sort but I was having a bit of hard time following the logic as I'm not very familiar with this code.

Thanks!

[nothings]

I would guess it's not a bug; since it's part of the seeking logic, it's intentionally consuming a frame and expecting particular behavior based on knowledge of the internals. (I didn't actually write the seeking logic though.)