From: Stefan Monnier <monnier@IRO.UMontreal.CA>
To: Alan Mackenzie <acm@muc.de>
Cc: emacs-devel@gnu.org
Subject: Re: Getting the correct line/column numbers on byte compilation error/warning messages
Date: Mon, 17 Jul 2017 16:27:43 -0400 [thread overview]
Message-ID: <jwvd18yx1p5.fsf-monnier+Inbox@gnu.org> (raw)
In-Reply-To: <20170717195654.GB3647@acm> (Alan Mackenzie's message of "Mon, 17 Jul 2017 19:56:54 +0000")
>> Stefan "who'd actually prefer a «real» solution rather than
>> another hack, but beggars can't be choosers"
> I've been thinking about this for nearly a year, and I can't conceive of
> a "real" solution which doesn't involve redesigning the byte compiler
> from scratch (or even one which does).
AFAIK redesign is not needed (in the sense that the code structure
doesn't need to be changed), but a lot of code would need to be
touched, yes.
> Lisp source code doesn't seem to lend itself to keeping track of
> source positions as the forms are manipulated, taken apart, and put
> together again.
All compilers for all languages do that "take-apart-and-put-together"
over and over again. The only difference is the Lisp macros which are
defined to operate on a form of the code which doesn't include
position info.
> Can you conceive of some better scheme by which accurate line/column
> numbers can be output by error messages, and which doesn't involve
> rewriting the byte compiler?
The «real» solution, AFAIC, is to use a representation of the code where
position-info is added to each node:
- provide a new `read` function which provides something similar to
`edebug-read` (and then change Edebug to use that function).
- change macroexp to accept and return such a representation.
- change byte-opt to accept and return such a representation.
- change cconv to accept and return such a representation.
- change bytecomp.el to accept representation.
The changes to macroexp, byte-opt, cconv, and bytecomp aren't
complicated and will be fairly repetitive, but they'll touch most of
the code.
> What I do anticipate about my hack is, assuming I ever get it working,
> it will produce the correct source code positions all the time, not just
> most of the time.
It might work well in practice, yes. Tho using setc[ad]r like you
suggest is risky since macros can return code which is a DAG rather than
a tree (it's fairly unusual but not unheard of), so if you setc[ad]r on
one side it might lead to nasty surprises on the other.
Stefan
prev parent reply other threads:[~2017-07-17 20:27 UTC|newest]
Thread overview: 6+ messages / expand[flat|nested] mbox.gz Atom feed top
2017-07-16 13:44 Getting the correct line/column numbers on byte compilation error/warning messages Alan Mackenzie
2017-07-17 10:27 ` Clément Pit-Claudel
2017-07-17 17:53 ` Alan Mackenzie
2017-07-17 19:42 ` Stefan Monnier
2017-07-17 19:56 ` Alan Mackenzie
2017-07-17 20:27 ` Stefan Monnier [this message]
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