8 Jul
2011
8 Jul
'11
8:12 p.m.
On Friday, July 08, 2011 12:17:34 pm Fons Adriaensen wrote:
Take for instance jack_ringbuffer_read(), which has this
line:
rb->read_ptr = (rb->read_ptr + n) & rb->size_mask;
There's a remote possibility that the compiler could
optimize this as:
rb->read_ptr += n;
rb->read_ptr &= rb->size_mask;
...and this would break the ringbuffer. I don't know if the
`volatile` keyword prevents this or not.
-gabriel
On Fri, Jul 08, 2011 at 09:21:55AM -0400, Paul Davis
wrote:
the one
wrinkle in this is that in theory a compiler
could so completely reorder instructions that even the
basic assumptions that make the single
reader/single-writer ringbuffer safe would break down.
AFAIK nothing fatal can happen if the variables involved
are declared volatile. A compiler is not allowed to
omit, repeat, or re-order instructions involving them.