Newbie Questions

Newbie Questions

[Clemens Eisserer]

Hello!

I'm still a very newbie at gjc so plaese dont be angry about my stupid 
questions ;-)....

When I heard first time about gjc and libgjc a was very excited about 
it. But I dont know what I can really do with it.
I heard it is nearly compatible with Java-1.1.8 (without Gui-Stuff...), 
but can I really make native apps with it, like any C++ app.
Is there nothing like a runtime, everything nativly? That would be sooo 
cool....

Is it possible to link static with libgjc , so that the user dont need 
to install it.(Of cource there will be choice...)

Is there a garbage-collector avaible? And how is that realized, I thing 
there is no runtime-enviroment...

I heard that there are already some AWT-Classes. Are they ready to use 
and how does they look on linux? (I heard something like GTK)...

Will all java-classes that are included in my file (e.g. java.io.*) 
 compiled nativly?

Is gjc a "dead" or lacy project, or is there much traffic on it?




Thank you very much for answering my questions and sorry for my bad 
english ;-).....

Re: Newbie Questions

[Tom Tromey]

>>>>> "Clemens" == Clemens Eisserer <linuxhippy@freemail.de> writes:

Clemens> I'm still a very newbie at gjc so plaese dont be angry about
Clemens> my stupid questions ;-)....

Don't worry.  But it is called "gcj".

Clemens> I heard it is nearly compatible with Java-1.1.8 (without
Clemens> Gui-Stuff...), but can I really make native apps with it,
Clemens> like any C++ app.  Is there nothing like a runtime,
Clemens> everything nativly? That would be sooo cool....

No, you still need a runtime.  The runtime contains the garbage
collector, various low-level bits, the class library, and other
things.  On many platforms it even includes a bytecode interpreter.

The difference is that our runtime is a shared library.

Clemens> Is it possible to link static with libgjc , so that the user
Clemens> dont need to install it.(Of cource there will be choice...)

Yes, though static linking isn't as well tested as dynamic linking.
You might have to do strange things to make some code work, for
instance if your code is using reflection.

Clemens> I heard that there are already some AWT-Classes. Are they
Clemens> ready to use and how does they look on linux? (I heard
Clemens> something like GTK)...

AWT exists but is not yet ready to use.  Some parts are missing.  The
native side has not been written.

Actually, to be precise, a lot of the native code does exist in
Classpath.  It uses JNI (not CNI) and has not been merged into libgcj
yet.  The current native peers use Gtk.  They are still quite buggy
and incomplete.

Clemens> Will all java-classes that are included in my file
Clemens> (e.g. java.io.*) compiled nativly?

Yes.

Clemens> Is gjc a "dead" or lacy project, or is there much traffic on it?

Read the mailing list archives or the web page.  There is a lot of
traffic.  It is probably the most active free software java project by
an order of magnitude.

Tom

Re: Re: Newbie Questions

[Clemens Eisserer]

Wow! Thanks for that much and fast feedback! I never expected that ;-))

>Don't worry.  But it is called "gcj".
>
I'm very sorry. I knew that there was something wrong ;-)  ....

>The difference is that our runtime is a shared library.
>
Hmm, maybe i didnt ask right... Is the code-output of gcj native code or 
is it just "tarned" as executable and interpreted by libgcj?
Are also all imported java-classes (java.io.*.....) nativly compiled or 
will they be "linked" by the libgcj and interpreted (.clss-Files).

>
>Clemens> Will all java-classes that are included in my file
>Clemens> (e.g. java.io.*) compiled nativly?
>
>Yes.
>
Cooooooooooooool!

>
>Clemens> Is gjc a "dead" or lacy project, or is there much traffic on it?
>
>Read the mailing list archives or the web page.  There is a lot of
>traffic.  It is probably the most active free software java project by
>an order of magnitude.
>  
>

Thx Tom for your afst answer!

Thx Clemens

Re: Newbie Questions

[Tom Tromey]

>>>>> "Clemens" == Clemens Eisserer <linuxhippy@freemail.de> writes:

Clemens> Hmm, maybe i didnt ask right... Is the code-output of gcj
Clemens> native code or is it just "tarned" as executable and
Clemens> interpreted by libgcj?  Are also all imported java-classes
Clemens> (java.io.*.....) nativly compiled or will they be "linked" by
Clemens> the libgcj and interpreted (.clss-Files).

You can compile either to bytecode or object code, it's up to you.

Tom

Re: Re: Newbie Questions

[Andrew Haley]

Clemens Eisserer writes:
 > Wow! Thanks for that much and fast feedback! I never expected that ;-))
 > 
 > >Don't worry.  But it is called "gcj".
 > >
 > I'm very sorry. I knew that there was something wrong ;-)  ....
 > 
 > >The difference is that our runtime is a shared library.
 > >
 > Hmm, maybe i didnt ask right... Is the code-output of gcj native code or 
 > is it just "tarned" as executable and interpreted by libgcj?
 > Are also all imported java-classes (java.io.*.....) nativly compiled or 
 > will they be "linked" by the libgcj and interpreted (.clss-Files).

We compile Java source (or bytecode if you prefer) to native code and
execute that.  Our Java runtime library, libgcj, is also native code.
If you want to, libgcj can also load bytecode and interpret it[*].  We
don't usually do that, but it is sometimes useful and the Java
standard requires it.

Andrew.

[*] Not all targets support interpreted code.

Re: Newbie Questions

[Jeff Sturm]

On Wed, 5 Jan 2000, Clemens Eisserer wrote:
> When I heard first time about gjc and libgjc a was very excited about 
> it. But I dont know what I can really do with it.

You mean "gcj" and "libgcj".

> I heard it is nearly compatible with Java-1.1.8 (without Gui-Stuff...), 

Right.  In fact much of 1.2 and later are there, but AWT is not yet
supported (volunteers to test/implement are needed).

> but can I really make native apps with it, like any C++ app.

gcj compiles to native object code, like gcc/g++.  It also produces
bytecode like javac.

> Is there nothing like a runtime, everything nativly? That would be sooo 
> cool....

Of course there is a runtime, consisting of the core java.* classes,
garbage collector and so forth.  However unlike Sun's VM, the bytecode
interpreter is optional.

> Is it possible to link static with libgjc , so that the user dont need 
> to install it.(Of cource there will be choice...)

Yes, with caveats.  Some gcj users are doing that, for the reason you
gave.  However, static builds tend to be large, because they include most
of the runtime.

> Is there a garbage-collector avaible? And how is that realized, I thing 
> there is no runtime-enviroment...

The included GC library is the Boehm-Demers-Weiser conservative collector.
(See http://www.hpl.hp.com/personal/Hans_Boehm/gc/ for details on the GC
library.)

> Will all java-classes that are included in my file (e.g. java.io.*) 
>  compiled nativly?

Yes, most of java.* is included in libgcj and compiled natively.  If you
give it a try, feel free to report problems to this list.

> Is gjc a "dead" or lacy project, or is there much traffic on it?

It's actively maintained.   All releases of the GNU Compiler Collection
(GCC) since 3.0 include gcj.  Your best bet is the 3.1 release, due out
shortly.

Jeff

Newbie questions

[Maury Markowitz]

Hi,

  I'm an Obj-C developer (using gcc) over on the OS-X platform and  
I'm looking for migration and exit strategies for both myself and  
other developers in our market space.  Apple's "commitment" to Obj-C  
is, well, let's call it "unclear".  I'm both a compiler tech and Java  
newbie, so I'll ask for your forgiveness in advance if some of these  
questions are complete no-brainers.

  First and foremost I'm curious about the ability for gcj's  
compiled code to be used as libraries for Obj-C code on top.  IE, if  
I were to use gcj and it's associated libs, what sort of work effort  
would it be to have them work as Obj-C libraries?  Is library format  
an issue at all? (I'm assuming not, but I'll ask to be sure) Is the  
main issue going to be supplying a selection of wrappers in the form  
of .h files?  It "feels" like there is a runtime changed needed to  
Obj-C, and I'm curious if anyone could comment on the level of change  
needed, if any?

  The other question I have relates to extensions and the legality  
thereof.  We Obj-C developers have come to love the language's  
flexibility in terms of "weak" typing and notably in the form of  
categorization.  It seems to me that if you're going to  
native-compile code anyway, extensions like this to Java would no  
longer break it's security orientation.  Would it be possible to  
create a sub-standard, say "Obj-J", that would add in these features  
without ending up on someone's (like Sun's) *&%# list?

  This isn't quite as important to me, if I could use Obj-C over  
gcj's libs this may be a non-issue anyway.  I ask simply because  
there may be uses who wish to stay completely in the Java syntax (for  
good reasons) but sill have access to some of the power of  
categorization, proxies, etc.

  BTW, kudos to all involved in this project.  This is exactly the  
sort of practical response to the Java hype that I think the market  
needs.  I'm still experimenting, but I think gcj's potential for  
mixing my compiled code against bytecode and compiled libs may be  
just the solution I'm (and I think many others) are looking for.

Maury

Re: Newbie questions

[Tom Tromey]

>>>>> "Maury" == Maury Markowitz <maury@oaai.com> writes:

Maury> First and foremost I'm curious about the ability for gcj's
Maury> compiled code to be used as libraries for Obj-C code on top.
Maury> IE, if I were to use gcj and it's associated libs, what sort of
Maury> work effort would it be to have them work as Obj-C libraries?
Maury> Is library format an issue at all? (I'm assuming not, but I'll
Maury> ask to be sure) Is the main issue going to be supplying a
Maury> selection of wrappers in the form of .h files?  It "feels" like
Maury> there is a runtime changed needed to Obj-C, and I'm curious if
Maury> anyone could comment on the level of change needed, if any?

I'm not entirely sure I know what you are asking.

libgcj is just a library like any other library.  It just happens to
be implemented in a miaxture of C++ and Java.  However, it has some
requirements that other libraries probably don't have.  For instance,
it relies on the existence of a garbage collector (this isn't the only
requirement, but it is one of the big ones).

You can use this library from C++ right now.  Using it from ObjC would
require knowing how to make the library bootstrap (not too hard), plus
a knowledge of how to call C++ from ObjC (we've purposely made
compiled Java mostly compatible with compiled C++; I don't know
anything about ObjC so I can't help you there).

Maury> The other question I have relates to extensions and the
Maury> legality thereof.  We Obj-C developers have come to love the
Maury> language's flexibility in terms of "weak" typing and notably in
Maury> the form of categorization.  It seems to me that if you're
Maury> going to native-compile code anyway, extensions like this to
Maury> Java would no longer break it's security orientation.

I think we can do whatever we want, basically.  Of course we'd always
want to provide a way to make the compiler pedantic, just as we do
with C and C++.

However, that doesn't mean I'm necessarily in favor of making any
extensions to the Java language.  I'm pretty sure you'd be on your own
in terms of implementing the changes; there are too many pieces still
missing for us (meaning those of us at Cygnus hacking gcj, or at the
very least just me) to do this sort of thing.  Another factor is that
every extension makes the compiler more difficult to understand and
modify.  I'm told the C++ compiler hackers have found random g++
extensions to be a real pain over time, so this is something to be
wary of.

When you say "weak" typing, what do you mean?
What is categorization?
When you say "proxies", what do you mean?

Tom