RE: externs and thread local storage

["Gary Funck" <gary at intrepid dot com>]

Seongbae Park wrote:
> As I said, you're welcome to implement a new option
> (either a runtime option or a compile time configuration option)
> that will allow mixing TLS vs non-TLS.

In a way, we've already done that -- in an experimental dialact of "C"
called UPC.  When compiled for pthreads, all file scope data not
declared in a system header file is made thread local, and in fact all
data referenced through externs is also made thread local.  There is a new
syntax (a "shared" qualifier) used by the programmer to identify
objects shared across all threads.  Sounds a little scary, but works
amazingly well.  Because the tagging of data as __thread local is done
by the compiler transparently, I tend to think that we probably stress
the TLS feature more than most.

> Whether or not it should be enabled for a particular platform
> should be a matter of discussion, and whether or not that patch will be
> accepted in the mainline will be yet another.

For myself, I've worked around the problem, and don't see any consensus
forming, so see little need to come up with a patch for something that
has no support.  As far as the process goes, I think it is
better to discuss the issues here to develop a consensus (if any)
before developing a patch.