a question about directory structure of libjava

majia gm gmmajia@gmail.com
Thu Jan 20 12:42:00 GMT 2011


2011/1/20 Bryce McKinlay <bmckinlay@gmail.com>:
> On Thu, Jan 20, 2011 at 8:50 AM, majia gm <gmmajia@gmail.com> wrote:
>>
>> I'm new to gcj. And I'm reading the source code in the directory of
>> libjava. I'm a little confused by the structure of the directory.
>>
>> I found that there often exists two java files, which have much
>> differnce in content, having the same name in different directories.
>> Such as,
>>
>> libjava/java/lang/Class.java
>> libjava/classpath/java/lang/Class.java
>>
>> Will both of them be used?
>
> The files in libjava/classpath are directly imported from the GNU
> Classpath project. In some cases, such as this one, libjava overrides
> classpath's classes with its own.
>
>> I also found C++ files libjava/java/lang/Class.h, which declares the
>> class Class in C++ corresponding to Class.java.
>> And libjava/java/lang/natClass.cc, which implements the native methods.
>
> Right, the .h files are generated by the gcjh tool.
>
>>  But there's often no implementation of methods in C++.
>>  Dose the method code come from the Java file? How dose this happen?
>
> In some cases the native methods are implemented by the GNU Classpath
> code in JNI (C), rather than CNI (C++). These implementations can be
> found under libjava/classpath/native/jni.
>
> Bryce
>

Hi, Bryce.

Thanks for your reply. It's very kind of you.

I'v read a little document of JNI and CNI.

CNI seems to layout data such as classes and objects conforming to
C++, so there comes the header file.

 What I'm really curious about is how the non-native methods in
library being executed in runtime. One way I can imagine is to
interpret the byte codes.

But when I use GDB to track gij,  I found native codes,  source lines
of which is in Java files of the library.

Dose it mean the byte codes in library may be translated into native codes?
 If it is the truth, then when dose it happen?

Thank you.

Gmmajia



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