id	summary	reporter	owner	description	type	status	priority	milestone	component	version	resolution	keywords	cc	difficulty
1824	Change locatives representation	sjamaan	sjamaan	"As pointed out [https://lists.nongnu.org/archive/html/chicken-hackers/2023-06/msg00029.html here], we can change the representation of locatives such that they take up less space, and we only have to traverse the live '''weak''' locatives for update during GC.

The idea is to drop the extra ""object"" slot, and store it in the pointer slot instead. When the locative is weak, set {{{C_SPECIALBLOCK_BIT}}}.  When it is strong, do not set it (so that the object is referenced normally). For weak locatives, we traverse the live ones using the ""chained"" approach and update the object.

We don't need to do the pointer recalculation on every GC.  Instead, we calculate the pointer on-the-fly during {{{locative_ref}}}.

NOTE: Perhaps we also want to expose a version of locative-ref that doesn't error out when the object has been collected, but returns {{{bwp-object}}} instead? This means handling of such locatives is a bit simpler and doesn't require exception handling."	enhancement	assigned	minor	6.0.0	core libraries	5.3.0				medium