Reinhold Kainhofer <reinh...@kainhofer.com> writes:
> However, I'm not sure if this will really work out or give us much benefit.
> In particular, we have lots of checks for == SCM_EOL or == SCM_BOOL_T. E.g.
> very deep inside the core of lilypond:
>
> inline bool ly_cheap_is_list (SCM x) {return scm_is_pair (x) || x==SCM_EOL; }
>
> Is this really not allowed?
The Guile documentation is unambiguous about that: it is not allowed.
Guile has scm_is_null which is a macro expanding to the direct
comparison with SCM_EOL if the type debugging is switched off, and to
something that works and compiles if it is on.
I have hit several type bugs (Scheme/integer confusions) so far while
looking randomly for the source of my segmentation fault. If we can get
the source into a state where the compiler can help with the work of
flagging them, that's an advantage.
And I don't think it a good idea to rely on explicitly undefined
behavior of Guile.
--
David Kastrup
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