[antlr-interest] Re: [antlr-dev] ANT build cruft?

[Martin Probst]

Hi,

> - The new task addresses the shortcomings of the
> existing apache-hosted task.  I don't remember what
> they are actually; having gotten frustrated with that
> task many years ago I have actually used <java
> class="antlr.Tool"> or the commandline since.  Can any
> current users offer input here (except for that silly
> "ANTLR task should create its own output dir" stuff).

The problem is dependency management and time stamps. To ANT it looks  
like ANTLR has one input file, foo.g, and potentially several output  
files, fooLexer.java, FooParser.java, etc. Now if I change the  
grammar, ANT thinks it needs to update all three files. But when it  
runs ANTLR, ANTLR only updates the files it really has to. So there  
can be changes which actually don't change anything in the files, and  
changes which only change some of the files. In any of these, ANT  
keeps running the ANTLR task every time because it doesn't expect  
this behaviour.

For C++ people this careful behaviour about modifying/touching files  
might actually be very nice (less C++ compiling), but for Java it's  
generally a lot more annoying to have ANTLR running every time than  
compiling two Java files once more than absolutely necessary. I think  
anyone with a real build system uses the old "touch file" strategy,  
which actually results in an optimal solution. However I think a  
built-in task can hardly start creating magic "touch" files, so it  
should maybe resort to saying: "one of the output files is newer than  
the grammar" instead of "all of the output files are newer than the  
grammar", if that's possible in ANT?

Martin