problem with JNI( compiling .C file)

[zius oram]

am binding java with C, problem is in compiling hello.c file. where and how to compile ?.C file, i m using win-XP command prompt and tried with command 'cl', and also 'gcc' with cygwin both gives error ' command not found' ..

[Ernest Friedman-Hill]

Well, first question: do you have CL (Visual C++, a commercial product) or gcc (available in Cygwin as an optional install) actually installed? Neither will come with Windows itself.

[zius oram]

first of all thanks for your reply,
i dont have CL but i used intall now link on cygwin.com to download. it is installed.. i typed gcc command in cygwin's bash.

[Ernest Friedman-Hill]

The default cygwin install doesn't include gcc and the other tools you'll need. You have to run the setup.exe program again, find gcc under the "Development" category, and install it -- it should install the other things automatically.

[zius oram]

i have downloaded the appropriate enviorment supporting 'gcc'. i tried to compile .C file as
gcc --mno-cygwin -D __int64="long long" -I jdk/include/ -I jdk/include/win32 -shared -Wl,--stdcall-alias -o HelloNative.dll Hellonative.c
where jdk is directory containing jdk, it is giving error no such file or directory.
refrence-- core java2 volume2 advanced features.. page 854

[Ernest Friedman-Hill]

WHat file or directory is not being found? The JDK includes directory?

In Cygwin you have to use Cygwin paths; if your Windows JDK is at

c:\Program Files\Java\jdk1.5.0_11

then in Cygwin you'd call that

/cygdrive/c/Program\ Files/Java/jdk1.5.0_11

Note how I've "escaped" the space with a backslash.

[zius oram]

thank you,
now the only error is gcc: HelloNative.C : no such file or directory.
i have HelloNative.java, HelloNativeTest.java, HelloNative.C(written in notepad), HelloNative.h in different directory(e:\).

[Ernest Friedman-Hill]

Hmmm. Are you sure that HelloNative.C is not actually named HelloNative.C.txt ? NotePad will do that sometimes!

If you use cygwin's "ls" command to list the files in a directory, you'll see the true name of the file. If it's got that .txt on the end you could say

mv HelloNative.C.txt HelloNative.C

and then try again.

[zius oram]

i checked it is HelloNative.c , i am confused how gcc will come to know about my C file? as no where i am mentioning its location.

[Ernest Friedman-Hill]

zius oram wrote:i checked it is HelloNative.c , i am confused how gcc will come to know about my C file? as no where i am mentioning its location.

Ah. The command you showed assumes that the .c and .h files are both in the same place -- the current directory -- when you type the command. Put the files in the same directory if they're not, and then use "cd" to change to that directory.

[zius oram]

i did it, now error has changed to
cc1: error:unrecogniszed command line option "-fmno-cygwin"

when i removed one hifen (-) shown above(--mno)and now (-mno) it gives me error
HelloNative.c :1:24: HelloNative.h: no such File or Directory
HelloNative.c:4:error: syntax error before "void"
HelloNative.c:4:error: parse error before '*' token
my HelloNative.c file is as...

#include<HelloNative.h>
#include<stdio.h>

JNIEXPORT void JNICALL Java_HelloNative_greeting(JNIEnv *, jclass)
{
	printf("HELLO NATIVE WORLD................");
}

HelloNative.H file is....

/* DO NOT EDIT THIS FILE - it is machine generated */
#include <jni.h>
/* Header for class HelloNative */

#ifndef _Included_HelloNative
#define _Included_HelloNative
#ifdef __cplusplus
extern "C" {
#endif
/*
 * Class:     HelloNative
 * Method:    greeting
 * Signature: ()V
 */
JNIEXPORT void JNICALL Java_HelloNative_greeting
  (JNIEnv *, jclass);

#ifdef __cplusplus
}
#endif
#endif

[Ernest Friedman-Hill]

I think you need to change the include in the C file to

#include "HelloNative.h"

otherwise the compiler won't look in the current directory for the header, but rather in the system include directories.

[zius oram]

did it, now it is
In file included from HelloNative.c:1:
HelloNative.h:2:17: jni.h:no such file or directory
In file included from HelloNative.c:1:
HelloNative.h:15:error: syntax error before "void"
HelloNative.h:16:error: parse error before '*' token
HelloNative.h:16:warning: data defination has no type or storage class
HelloNative.c:4:error: syntax error before "void"
HelloNative.c:4:error: parse error before '*' token

[Ernest Friedman-Hill]

jni.h should be in that "jdk/include" directory. You might not have the path quite right. Make sure you can use "ls" to see the contents of the path you include there.

[zius oram]

Thank You its working........
i followed all the steps specified by you, but the mistake i made was, I Omitted The Space in " \ Files", from the command you gave above.

$gcc -mno-cygwin -D __int64="long long" -I /cygdrive/c/Program\ File/java/jdk1.6.0/include/
-I /cygdrive/c/Program\ Files/java/jdk1.6.0/include/win32 -shared -Wl, --add-stdcall-alias -o HelloNative.dll HelloNative.c

Thank you once again.

[Ernest Friedman-Hill]

Great!