jni.h problem

[Gordon Beaton]

My g++ compiler doesn't know where my jni.h file is. I don't know
how to explicit tell to g++ that jni.h is in the include folder of
java.

The standard compiler flag for extending the header search path is -I.
You need to add two directories, like this:

-I $JAVA_HOME/include -I $JAVA_HOME/include/linux

(assuming an appropriately set JAVA_HOME)

/gordon

 

[Gordon Beaton]

I would like to avoid the command -I
How can I do it? Should I add my /usr/local/.../java.../include in the
path variable, or should I create a new variable?

Your PATH has nothing to do with this.

What are your reasons for wanting to avoid using -I, when it is
clearly the correct solution?

Write a Makefile, and add the -I options to your CFLAGS variable.

/gordon

 

[Marcelo]

Hi,

My g++ compiler doesn't know where my jni.h file is.
I don't know how to explicit tell to g++ that jni.h is in the include
folder of java.

I get the error

HelloWorld.c:1:17: error: jni.h: No such file or directory

What should I do ? (I am working on Linux)

thanks

MArcelo

 

[Stefan Schulz]

Hi,

My g++ compiler doesn't know where my jni.h file is.
I don't know how to explicit tell to g++ that jni.h is in the include
folder of java.

I get the error

HelloWorld.c:1:17: error: jni.h: No such file or directory

What should I do ? (I am working on Linux)

man gcc helps

If you ask again in comp.lang.c, you will probably be flamed to death,
then told about the magic -I switches to gcc (and most other C compilers),
which add directories to the search path.

Since i am in a good mood right now: -I<path/to/your/java/install>/include
and -I<path/to/your/java/install>/include/linux

 

[Marcelo]

thanks,

I would like to avoid the command -I
How can I do it? Should I add my /usr/local/.../java.../include in the
path variable, or should I create a new variable?

thanks a lot

Marcelo

 

[Gordon Beaton]

thanks for the make file,

now i am getting another problem , a little bit strange

~/docs/jni/jniexamples/chap2/HelloWorld$
gcc -I/usr/local/share/jdk1.5.0_05/include
-I/usr/local/share/jdk1.5.0_05/include/linux HelloWorld.c
/usr/lib/gcc/i486-linux-gnu/4.0.2/../../../../lib/crt1.o: In function
`_start':
../sysdeps/i386/elf/start.S:115: undefined reference to `main'
collect2: ld returned 1 exit status

the program is the HelloWorld application the Sun Tutorials.

Because you didn't tell the compiler you wanted a shared library it
tried to compile a program, which needs a main().

Compile your code like this:

gcc -fPIC -D_REENTRANT
-I $JAVA_HOME/include
-I $JAVA_HOME/include/linux
-c HelloWorld.c

Then link the shared library like this:

gcc -shared HelloWorld.o -o libhello.so

Or compile and link with a single command:

gcc -fPIC -shared -D_REENTRANT
-I $JAVA_HOME/include
-I $JAVA_HOME/include/linux
HelloWorld.c
-o libhello.so

(note that each command should be a single line)

/gordon

 

[Marcelo]

thanks for the make file,

now i am getting another problem , a little bit strange

~/docs/jni/jniexamples/chap2/HelloWorld$
gcc -I/usr/local/share/jdk1.5.0_05/include
-I/usr/local/share/jdk1.5.0_05/include/linux HelloWorld.c
/usr/lib/gcc/i486-linux-gnu/4.0.2/../../../../lib/crt1.o: In function
`_start':
.../sysdeps/i386/elf/start.S:115: undefined reference to `main'
collect2: ld returned 1 exit status

the program is the HelloWorld application the Sun Tutorials.

thanks a lot,

Marcelo

 

[Gordon Beaton]

and that is deliberate, you use the same gcc for linking as compiling?

Yes.

/gordon

 

[Marcelo]

thanks for the make file,

now i am getting another problem , a little bit strange

~/docs/jni/jniexamples/chap2/HelloWorld$
gcc -I/usr/local/share/jdk1.5.0_05/include
-I/usr/local/share/jdk1.5.0_05/include/linux HelloWorld.c
/usr/lib/gcc/i486-linux-gnu/4.0.2/../../../../lib/crt1.o: In function
`_start':
../sysdeps/i386/elf/start.S:115: undefined reference to `main'
collect2: ld returned 1 exit status

the program is the HelloWorld application the Sun Tutorials.

thanks a lot,

Marcelo

got the solution

I should use the -shared option in the compilator
thanks

Marcelo

 

[Roedy Green]

gcc -shared HelloWorld.o -o libhello.so

and that is deliberate, you use the same gcc for linking as compiling?