[armedbear-devel] Idea to fix ticket 79: identical uninterned symbols coalesced in fasl

[Erik Huelsmann]

Ticket 79 is one of the "correctness" category: we do something which
we shouldn't (although it hasn't been seen in real life yet). When we
compile a file containing 2 *different* -yet similarly named -
uninterned symbols, they are coalesced into the same object when
reading that fasl.

The above behaviour is a consequence of the design choice: the same
uninterned symbol may occur in multiple places in the sources, meaning
that multiple CompiledClosures may need to refer to the same symbol in
their constructor. ABCL solved this problem by interning all unintered
symbols into the same anonymous package. When that happens, all
occurrances of the same uninterned symbols are coalesced into the same
object.

However, the same happens to all equally named uninterned symbols
which are *not* the same symbol.

Here's my idea to resolve this situation, in a simple step-by-step
representation:

0. Install a dispatch macro function (in some unused dispatch macro
character); something like #n#
1. Adjust DUMP-FORM to generate the dispatch output for uninterned symbols
1. Create all uninterned symbols at the start of the FASL (filling a
table with them)
2. Let the reader resolve the uninterned symbols by looking up in the table

This approach has the nice side-effect that we can eliminate the need
for the anonymous package - although we will need to maintain a table.
It will resolve the issues we currently have with the coalesced
symbols. It uses standard Lisp infrastructure; no heavy code changes
required.

Comments?

Bye,

Erik.