[armedbear-devel] Several ABCL/Java questions

[Didier Verna]

       Hi Alessio, thanks for your reply.


Alessio Stalla <alessiostalla at gmail.com> wrote:

>> 1/ Is it possible to create standalone ABCL executables and how ?

> I'd say no, but it really depends on what you mean. You can't create
> standalone executables in Java, the equivalent is a bunch of Jar files
> (for console or GUI applications). It is possible to package ABCL +
> your software as a bunch of Jar files, but ABCL doesn't provide
> facilities of its own for that, though it's not hard to do (you can
> look at ABCL's own build script to get an idea). ABCL has no
> facilities for dumping a memory image, either (memory being controlled
> by the JVM makes this hard).

  OK, so here's where I am right now: Clon is a command-line option
parser library so it's essentially targetted at standalone executables. 
However, I see that you can do something like that:

java -jar myapp.jar --myapp-opt-1 --myapp-other-opt ...

and get the command-line arguments from *command-line-argument-list* so
it probably still makes sense to port Clon to ABCL. The next question
is: how do I hook an initial "main" function into myapp.jar. I seem to
remember that you need a Main class in Java, but I'm not sure about the
Lisp level.


>> 2/ ABCL doesn't seem to provide a [set|put]env function.

> I'd say yes, it's correct. But what are you trying to achieve? If you
> want to provide an environment for a subprocess, the ProcessBuilder
> class supports it. If you want to modify your own environment, you
> can't (without resorting to FFI, as far as I know), but why do you
> want to do that?

  In Clon, command-line options may be associated with environment
variables providing implicit values. In case such a variable contains a
typo (for instance DEBUG=ys instead of DEBUG=yes), Clon provides a
restart for fixing that interactively, which can benefit to the current
process but also subsequent ones launched from the same terminal. I
guess I can just disable this restart in the ABCL version.


>> 3/ It seems that ABCL does not have a complete MOP.

> It doesn't have a complete MOP. I think that validation is performed
> on an ad-hoc basis (e.g. you can't extend structure classes), so every
> other case is implicitly validated.

  OK.


>> 4/ There is a place where I need to access low-level information
>> about a stream

> I don't know. ABCL streams wrap java.io streams and readers/writers
> and I don't think there's a mean of accessing their low-level
> implementation. Perhaps with a dedicated library that uses JNI/JNA and
> provides custom streams, but I don't know any. Terminal handling is
> not common in Java (as most OS-specific stuff).

  OK :-/


Thanks again.

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