Making sense of TSD

[Mike Hommey]

On Wed, Apr 11, 2012 at 12:05:05PM -0700, Jason Evans wrote:
> On Apr 11, 2012, at 10:22 AM, Mike Hommey wrote:
> > I'm trying to make sense of the tsd implementation without __thread,
> > which would seem to fit the tls model on windows. But I don't see
> > why the wrapper struct is needed at all. The first thing that
> > bothers me is that the isstatic == true case is set to abort on
> > opt_abort, yet is supported. And it doesn't seem very obvious why
> > initialized is needed.
> 
> The wrapper struct is needed with pthreads TSD because
> pthread_[gs]etspecific() only operate on (void *) pointers.  Thus it's
> impossible to store more than a pointer-sized item with pthreads TSD
> unless that pointer refers to an allocated structure.  I don't
> remember the details of Windows's TLS/TSD API; if it can store any
> type/structure, then no wrapper struct is needed.

Well, the void* pointer could just point to whatever structure you want
to store, instead of having a struct containing two bools which
usefulness I'm doubtful about, and a pointer to that allocated structure.
At least it seems so. That was my question.

Mike