Fix #81302: Stream position after stream filter removed

[cmb69]

When flushing the stream filters actually causes data to be written to
the stream, we need to update its position, because that is not done by
the streams' write methods.

[nikic]

Something I'm a bit confused about is this code in write_buffer:

php-src/main/streams/streams.c

Lines 1148 to 1152 in 1c675b9

	/* Only screw with the buffer if we can seek, otherwise we lose data
	* buffered from fifos and sockets */
	if (stream->ops->seek && (stream->flags & PHP_STREAM_FLAG_NO_SEEK) == 0) {
	stream->position += justwrote;
	}

It only changes the position for seekable streams, though I don't really understand the rationale given in the comment.

[nikic]

Looks like the code originally looked like this: f98f27f Possibly the condition around the position update is just a leftover and it should be updated unconditionally?

[cmb69]

I think you're right; 088e269#diff-34c102f51eb0af2504e7d1c1f588a83c6555ae92d2f83602314ea45fc94621b4 looks fishy; not updating the position for non-seekable streams seems to be a bug. I'm going to check that.

[cmb69]

See PR #7356.