Compiling Java with GCJ

Hi,

is it possible to pass parameters to an executable file? Or do I need to pass it somehow when I compile the Java code into the exe file using gcj? If so, how do I do that?
I need something replacing this sort of command-line:
java app 12 4 25 56 file.out

Thank you. :)

I could suggest a GCJ alternative - JCGO (developed by IvMaiSoft LLC) which is a Java source to C translator. The tool translates all the classes of your java program at once and produces C files (one .c and .h for each class), which could, further, be compiled (by third-party tools like GCC or VC++) into highly-optimized native code for the target platform (eg., for Windows, Linux, Solaris or embedded).
The produced native code is quite compact unless you are translating a GUI application (you can see a number of sample applications of the JCGO demo page; HelloWorld executable size is only 12 KiB (UPX'ed)). Also, JCGO automatically identifies some immutable static Java objects (like strings) and they go into read-only data program section (an application on an embedded platform with its code in ROM might benefit from this feature). Memory management is performed by BoehmGC (like GNU GCJ does).

Excuse for the stupid question, please!

Can you tell me how to compile an operating system with gcj?

GCJ is great, I just need to understand how to achieve "post deployment" dynamic loading.
I mean, doing something like plugins for the eclipse IDE. You can add plugins (mainly jar files) to the eclipse IDE that is already deployed! As long as the plugin implements some Interface, it can be dynamically loaded by eclipse IDE and the functionality provided by that plugin is available to Eclipse users. This is just classic Java.
As far as I can understand, it is perfectly possible to do that with GCJ. However I had a problem.

I tried to use Class.forName("myC"); which worked fine. However the program doesn't see all classes, but only the ones that where there when the main was compiled. If I add some more classes in the right folder that implement the right interface, and re-run the program it doesn't accept those new class files at all (I raise an exception when the object cannot be created).

Has anyone succeeded in making EXE produced by GCJ accept some new classes/jars (either .class, or preferably in some dll,...) after the EXE was deployed.
Anything I should be aware of? any special flag??

Thanks in advance

gcj --main=HelloWorld -o HelloWorld.exe obj\HelloWorld.o -Lf:\swt

(this instruction get automatic this)
f:\gcj\thisiscool-gcc\gcc-4.0\bin\..\lib\gcc\i686-pc-mingw32\4.0.0\..\..\..\..\i
686-pc-mingw32\bin\ld.exe: cannot find -lgdi32
and the exe is not there

I ran into a few problems while trying to make this work. First of all, I'm using MingW's gcj, not Cygwin. (Cuz I don't like carrying cygwin1.dll around with me.) MingW doesn't come with an iconv implementation, so you have to download the 'binaries' and 'developer files' from here: http://gnuwin32.sourceforge.net/packages/libiconv.htm.

Second problem was the fact that I created my first app with a package. The article doesn't tell you what happens when you do that. Let me try to explain.

You create a Java source file, called Main.java, with the package test.foo. A sample:
package test.foo;

public class Main {
public static void main(String[] args) {
System.out.println("The world says hi!");
}
}

Using GCJ, you turn it into an object using:
gcj -c -g -O Main.java
This step will work without a problem.

However, when you go to turn the object into an executable, the problems will begin. If you try to use the following command:
gcj --main=Main -o Test Main.o
It'll chuck some obnoxious error.

Turns out that you have to tell it the package for the main class:
gcj --main=test.foo.Main -o Test Main.o

Should work fine now.

There are official comparisons with 1.4.2 when it comes to GNU Classpath. But none for GCJ. Is there a way to make that available? Also, why aren't GNU Classpath APIs distributed as native code using GCJ?

V
Java Technologies

I can't find out how to get this gcj stuff!

My application needs to set the memory usage. I use
java -jar -Xms256m -Xmx384m myapplication.jar

Is there any way to set these parameters when I compile my application using GCJ?

Hi, I'm interested in this utility. But...there seems to be much to do with the libgcj, which provide the gcj version of java libraries.

See, I've used both method String.replaceAll and the java.util.regex package in my project, but found neither is supported by gcj now. I'm using gcj version 3.3.1 under cygwin, on Windows 2000. Though the simplest HelloWorld works well, my real project failed. That's sad news for me.

Are there any available supports for both of these features?

Some questions:

* how well does getClass() work?
ie given an object, o, is this supported?
Class c = o.getClass();

* is instanceof supported?
if (o instanceof MyWidget) {...}

* how well does gcj handle run-time class loading?
eg Class c = Class.forName("com.acme.Widget");

* how well does gcj handle run-time reflection?
eg can code query the methods available on class C?
can they be dynamically invoked?

* are multiple class-loaders supported?
eg: if a class has a static member, and it is explicitly loaded
via two different class-loaders, are there two separate
instances of the static member variable? (there should be).

* is dynamic class generation supported?
Java 1.4 provides "dynamic adapters" as an alternative
to using inner classes as adapters. I believe these
generate (simple) new classes on the fly.

Thanks,

Simon

Hi all-,
Am I the only one largely unimpressed by GCJ?
Most of the assumptions (like "not many OS projects") in the
begining of the article are hard to comprehend.
Start up time will improve when the JVM becomes part of the OS (like in Mac OS X) . This will happen in JDK1.5 and there is
no need for compilation to native code.
Speaking of which, how do you plan to transport classes over (let's) RMI in a JINI environment, between different CPUs?

C'mon ... no serious developer should by this! Get real.