Re: scm_gc_unprotect during GC

[Marius Vollmer]

Han-Wen Nienhuys <address@hidden> writes:

> A short term solution is to make sure that LilyPond never does
> scm_gc_unprotect_object() from smobbed destructor. However, I feel
> that this is a kludge.
>
> Either scm_gc_unprotect_object is callable during sweep, or this is
> forbidden. At present, GUILE does not print a warning, but barfs in an
> unrelated location.

Yes, that's unfortunate.  Almost anything is forbidden during sweep,
and we need to document that more clearly.

I'd say that a smob free function should not call
scm_gc_unprotect_object, or any other function that accesses the heap.
The heap might be in an inconsistent state, etc.  We probably should
list all functions that are callable, starting with just scm_gc_free.

Why do you need to call scm_gc_unprotect_object from your smob free
function?  To release a SCM value that was in use by the smob?  The
usual way to do that is to mark that value in the smob mark function.

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