Re: Dynamic loading progress

[Paul Eggert]

Philipp Stephani wrote:
> > Many modules will have needs similar to Emacs itself in
> > >that
> > >respect, and it would be better if they didn't have to reinvent this
> > >so-common
> > >wheel.
> > >
> But what should the interface be? There are only three possibilities in C:
> return a sentinel value, crash, longjmp.

There's a fourth possibility: do what Emacs does. Emacs defines its own 
throw-catch mechanism built atop C. C modules that need to cleanup when unwound 
can do so by registering via the equivalent of record_unwind_protect, and Emacs 
won't longjmp through them without cleaning up.  This already works for xmalloc 
memory-exhaustion failures, and modules can just use the already-existing mechanism.