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SCM_{DEFER,ALLOW}_INTS

Hmm... i'm seriously confused about the use of
SCM_{DEFER,ALLOW}_INTS. Since i couldn't find anything about them
in the documentation i have here, i checked the guile sources,
and found the following in unif.c:

SCM
scm_makflo (float x)
{
  SCM z;
  if (x == 0.0)
    return scm_flo0;
  SCM_NEWCELL (z);
  SCM_DEFER_INTS;
  SCM_SETCAR (z, scm_tc_flo);
  SCM_FLO (z) = x;
  SCM_ALLOW_INTS;
  return z;
}

That is, it creates a new cell with interrupts enabled, and then
disables the interrupts and assigns values to the cell.
Why were the interrupts disabled only after the cell was created?

And more important, where can i find more information about the
*_INTS calls? Especially, what exactly they do and where one
would need them.

In a related context, is there anything special to note for
guile-using C-code? I need to serialze access to functions of a
library that's not thread-safe. Is it sufficient to use pthread
mutex's here?
	-forcer

-- 
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