Version Histories (was Whats Happening with 3.10. etc.)
tim at rowledge.org
Thu Jan 11 07:14:09 UTC 2007
Here is my schema, such as it is thus far, for improving the source
referencing. It's not complete. I need some suggestions for ways to
tackle a few items.
The problem we face is that a lot needs to be changed in order to use
anything other than indices into file; so many facilities rely upon
it. Some serious refactoring would be needed in assorted changelist,
version listing etc methods. There are complications in ImageSegment
code too. RemoteString is pretty yucky. Class comments are also mixed
up in file/index encoding assumptions. All the source compression,
tempname-in-method etc code will need altering.
During the writing (and indeed installing later) of the code we need
all our normal tools to keep working so we can stay sane while doing
The basic idea is to add a proper oop for a source reference object
so that we can later implement classes that use a database, a web
search, access multiple files, decompile, guess or whatever.
Initially I propose simply using an integer with a simple encoding
scheme (not the rather covoluted one currently in use - take a look
at StandardSourceFileArray>fileIndexFromSourcePointer: and friends)
and just reusing the files.
First possibly contentious idea
Do this work in a 3.8.1 image to avoid the change in sources/changes
files done during the 3.9 cycle and some issues with the introduction
of Traits. I am *not* suggesting abandoning all the hard work in 3.9
and anyone implying that I did so will get a late night visitation.
You Don't Want That.
*After* incorporating the improved source referencing, add the 3.9
packages but leave out the source condensing step(s). This would
leave the SqueakV3.sources file untouched and could either leave us
with a changes file that is simply appended to (and obviously quite
big) or slightly reformatted (and still pretty big).
Add a new source reference ivar to the method properties object that
all methods now have. Well, except that method properties were added
somewhere during 3.9 - so they'd have to be added early. Drat. Ideas
on the minimum disruptive way to add this?
Add new method creation methods that do not use the trailerBytes
stuff. We are not using them yet...
Change source access method(s) to check the value of the source
reference in the methodProperties and use the 'old' access if it is
nil - which of course it is for now. Also change endPC similarly.
change #generate methods to refer to a global flag to say whether
they use trailerbytes or not. Set the flag *before* that... DAMHIKT!
A big do-it to flip the global flag, recompile all methods and
thereby set the new shiny source pointers. This is where things can
get very complicated. We have to decide what to do about the changes
file and all those historical versions.
a) we could effectively condenseSources so that there is no need to
worry about handling encrypted pointers to older versions. This would
of course mean a new .sources file.
b) we could condenseChanges so that any methods in the changelog that
are also in the old sources file have a correct back pointer, thus
losing most but not all history.
c) we could try to be very clever and copy the entire history chain
for each method across to a new changes file, keeping history.
d) we could be insane and try to make code that works out when a
history pointer is 'old format' and still handle it and then just
append new format sources to the current changes. I'm not going to
write that one myself...
change the #generate methods to ignore trailerbytes completely, drop
the global flag and remove it
remove all the redundant method creation methods etc
rework ImageSegment, source code compression, abandonSources, etc
There is a *lot* needing changing to do this well. I'm horrified how
poorly factored and written some of this core code is and how it has
just accreted more and more crap over the last few years. Yuck. Yuck.
Bad taste in mouth.
tim Rowledge; tim at rowledge.org; http://www.rowledge.org/tim
Strange OpCodes: EFBI: Emulate Five-volt Battery Intermittently
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