Re: vm status update

[Neil Jerram]

Hi Andy,

A couple of late comments...

Andy Wingo <address@hidden> writes:

>   * Much more source information propagates through the compiler and
>     into the metadata now. In short, whereas before it was "expressions
>     are only marked as coming from a source location if they are eq? to
>     an expression read in by guile", now it is "expressions are marked
>     with the source location of their containing expression, unless they
>     are eq? to an expression read by guile".
>
>     The upshot is that original source information is preserved to a
>     much broader extent than before, as macro-expanded or transformed
>     expressions all have some kind of anchor to the original source.
>
>     Another ramification of this is that procedures have source
>     information corresponding to where they were really defined, in
>     addition to locations of their subexpressions. (program-source foo
>     0) will give you that.

How much of this is compiler-specific?  Does some of it also apply to
old-style reading and interpreting?

>   * The in-bytecode metadata representation has been compressed. Now we
>     associate bytecode offsets with line-column pairs, and only record
>     that information when it changes. The idea is, byte N in the
>     instruction stream corresponds to source info for byte M, where M <=
>     N. Also, we only record the filename when it changes.
>
>     This means that we can have more source information, as mentioned
>     above, but still have objcode files of similar size.

Nice idea.

Regards,
        Neil