Ilya Zakharevich on Tue, 26 Nov 2002 12:31:45 -0800

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Re: Patch for install: allow to change prototype

On Tue, Nov 26, 2002 at 02:55:33PM +0100, Karim BELABAS wrote:
> > BTW, I see no reason to have the warning at all.  How is it different from

> >  ? f() = 12
> >  ? f() = 12
> I don't know how to safely "reload" a symbol from an external library. In
> particular, you cannot recompile an external module, and re-install a
> routine. You can kill() its GP wrapper, then formally re-install it, but
> unless dlclose() is called first, you install the old version (still loaded
> in memory).

If I understand it correct, the *only* information we keep about the
address space of the external library is an entry in entree.  Thus it
should be safe to do dlclose() at the appropriate time.  (Note that
Perl has no notion of unloading a module due to much more flexible
interface, thus uncontrollable "pollution" of data with addresses from
the library.)

Hmm, some results from a call to a library may contain references to
static variables in the library, so maybe it is not so bulletproof...
Otherwise one could keep a hash with a reference count of symbols from
a library; increment it when install(), decrement when kill().  When
the reference count goes to 0, unload the library.  (Or unload/load it
on the next install()...)

Hmm, with this interface the user could keep an extra dummy
install()ed function to keep a DLL from being auto-unloading if the
above scenario of a PARI variable containing a reference to a static
variable is applicable to a particular module...