Re: GUILE_PTHREAD_COMPAT

[Marius Vollmer]

NIIBE Yutaka <address@hidden> writes:

> Some GNU C library functions use thread specific data, when it is
> linked with libpthread (and to be thread safe).  Say, let's call the
> function FUNC.  On some architectures (or implementations), that data
> is allocated on thread specific stack.
> 
> When COOP is used, the stack pointer is changed to malloc-ed area.
> The function FUNC will be confused when de-references stack pointer.
> 
> Hence, with GUILE_PTHREAD_COMPAT, Guile uses the stack of the pthread
> for COOP, which is a kind of kludge.  You see, we have a kernel thread
> per a user thread, just for this purpose.

Aha, I see!  Thanks.  To put it into my own words: on some pthread
implementations, thread-specific data is found by looking at the stack
pointer.  This doesn't work, however, when COOP tweaks the stack
pointer as well.  Right?

> IMNSHO, it's somewhat ugly hack with little benefit.

Hmm, the benefit being that Guile runs in a pthread environment.  Is
that a small benefit?  I don't think so.