Memoize to a file

ruby-talk
1

I guess I'm once bitten, twice shy as a result of the transition from 1.6.8 to 1.8.0 not too long ago. Thanks for the correction.

Dan

···

-----Original Message-----
From: Mauricio Julio Fernández Pradier
[mailto:ferferse@telefonica.net] On Behalf Of Mauricio Fernandez
Sent: Wednesday, February 01, 2006 4:48 PM
To: ruby-talk ML
Subject: Re: memoize to a file

On Thu, Feb 02, 2006 at 06:49:49AM +0900, Daniel Berger wrote:
> > and it instead of silently failing I now see the error
message: "in
> > `load': marshal data too short (ArgumentError)"
> >
> > My questions:
> > 1 What is causing this error? (possibly Windows related?)
>
> That is odd. I've run it on Windows with no trouble in the past.

(FTR: file not opened in binary mode, [177651])
> Is it possible you ran this program using 1.8.2, downloaded 1.8.4,
> then re-ran the same code using the same cache? It would fail with
> that error if such is the case, since Marshal is not compatible
> between versions of Ruby - not even minor versions.

The Marshal format hasn't changed for a while:

batsman@tux-chan:~/Anime$ ruby182 -v -e 'p
[Marshal::MAJOR_VERSION, Marshal::MINOR_VERSION]' ruby 1.8.2
(2004-12-25) [i686-linux] [4, 8] batsman@tux-chan:~/Anime$
ruby -v -e 'p [Marshal::MAJOR_VERSION,
Marshal::MINOR_VERSION]' ruby 1.8.4 (2005-12-24) [i686-linux] [4, 8]

Also note that ruby can read Marshal data in older formats if
the MAJOR_VERSION hasn't changed (i.e. if only the
MINOR_VERSION was increased):

    if (major != MARSHAL_MAJOR || minor > MARSHAL_MINOR) {
  rb_raise(rb_eTypeError, "incompatible marshal file
format (can't be read)\n\ \tformat version %d.%d required;
%d.%d given",
     MARSHAL_MAJOR, MARSHAL_MINOR, major, minor);
    }
    if (RTEST(ruby_verbose) && minor != MARSHAL_MINOR) {
  rb_warn("incompatible marshal file format (can be
read)\n\ \tformat version %d.%d required; %d.%d given",
    MARSHAL_MAJOR, MARSHAL_MINOR, major, minor);
    }

(after some searching...)

Back in Apr. 2001, matz said that "Marshal should not change
too much (unless in upper compatible way)" [14063]. The last
minor change happened after 1.6.8 (6 -> 8), and MARSHAL_MAJOR
was already 4 in v1_0_1, 7 years, 2 months ago (at which
point I got tired of CVSweb).

Marshal's format is more stable than we think.