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From "Conor MacNeill" <>
Subject RE: Patch: JAVAC dependency tracking and multiple src paths handling
Date Thu, 11 May 2000 14:19:11 GMT

Interestingly I have also been working on dependency tracking and multiple
source paths.

For multiple source paths, I submitted a patch for multiple source paths a
while back. I chose to use a comma to separate the source paths since it
seemed likely to offend the Windows folks and the Unix folks equally :-) The
patch was not applied because of the use of that comma. There was also some
desire to support elements instead of just an attribute, something like
    <srcdir name="xyz">
    <srcdir name="abc">

I have changed my approach now to use the more "forgiving" ways of
Project.translatePath. I have added a method to Project called
translatePathInternal. Whereas translatePath will translate a path to the
local platform conventions, this new method translates paths, whether
specified with ":/" or ";\", to a platform independent format based on ':'
and '/' but supporting DOS drive style paths (C:\...). This path can then be
tokenized on the ':' character to build the source paths vector. So you can
specify the path in either Windows or Unix style and it should work on
either platform. I'm not sure how other platforms react :-) I still haven't
added the element approach yet.

For dependency tracking I took a different approach from you. I separated
dependency analysis into a new task <depend>. The depend task builds a
dependency file by analysing the given set of class files (either a
directory or a jar). Javac uses the dependency file to determine which
classes are affected by classes being recompiled. In theory the dependency
file could be built in some other way but still be used by Javac. The
dependency format is pretty simple and could be changed easily.

Example usage
 <javac srcdir="${src1.dir}:${src2.dir};${src3.dir}"
 <depend src="${build.classes}" depfile="${build.dir}/depfile.txt" />

I also only follow direct relationships. Say you have a scenario of A
depends on B and B depends on C but A does not depend on C. If you change C,
my approach will only compile C and B but not A. My feeling is that if A
does not depend directly on C, changes to C cannot affect A through B. I'm
still thinking about that :-)

I can't really say which approach is better. I include my source code (and a
set of diffs) here to let people see an alternative approach.


Conor MacNeill

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