Re: Dumper problems and a possible solutions

[Dmitry Antipov]

On 06/24/2014 09:19 PM, Rich Felker wrote:

> To solve ALL of the problems with the dumper (which seems to be a
> recurring theme), I have a proposed design to make it fully portable
> -- even moreso than xemacs "portable dumper" which is still an ugly
> hack. The idea is simple: after loading all of the lisp objects that
> need dumping, walk the lisp heap and output a representation for each
> object as a giant static array in C source format, then compile and
> link this new translation unit with the rest of the emacs .o files to
> produce a final emacs binary.

What about non-Lisp objects?

It's not too hard to walk through live (reachable) Lisp objects - this
is exactly what GC mark phase does. It's not too hard to walk through
all allocated Lisp objects - this is exactly what GC sweep phase does.
But what about lower-level stuff allocated with malloc at invisible
from Lisp? Of course, you can do your own serialization for these objects
as well - but only if you know about their internal structure. What about
stuff allocated by some external library? In general, you can't parse heap
(i.e. looking at object, you can't say where the next object is, what is the
type of next object, etc.). IIUC, "totally portable" heap dumper is impossible
without having a description of each possible heap object and ability to
distinguish between different types of objects.

Dmitry