Hi,

I am having trouble building a dll that java can use jni on, seems to build fine, but then just hangs and hangs and hangs...

Here's the c:
--
-- hello.c
--
#include <jni.h>
#include "HelloWorld.h"
#include <stdio.h>

JNIEXPORT void JNICALL
Java_HelloWorld_displayHelloWorld(JNIEnv *env, jobject obj)
{
printf("Hello world!\n");
return;
}

--
-- HelloWorld.h is a generated file (java gen's it)
--
#include <jni.h>
/* Header for class HelloWorld */

#ifndef _Included_HelloWorld
#define _Included_HelloWorld
#ifdef __cplusplus
extern "C" {
#endif
/*
* Class:     HelloWorld
* Method:    displayHelloWorld
* Signature: ()V
*/
JNIEXPORT void JNICALL Java_HelloWorld_displayHelloWorld
(JNIEnv *, jobject);

#ifdef __cplusplus
}
#endif
#endif

Here is the compile command that I gave dmc:
dmc -I C:\jdk1.5.0_07\include;C:\jdk1.5.0_07\include\win32 -mn -WD hello.c
kernel32.lib

There are no errors displayed and a dll is created. However, when I try to do the java trick (which works with ms compiler created dll's), it hangs. Here's th e java stuff, in case you want to see :)

--HelloWorld.java
class HelloWorld {
public native void displayHelloWorld();

static {
System.loadLibrary("hello");
}

public static void main(String[] args) {
new HelloWorld().displayHelloWorld();
}
}

compile the java byte code: javac -classpath . HelloWorld.java
generate the HelloWorld.h file: javah -jni -classpath . HelloWorld
compile the dll: dmc -I C:\jdk1.5.0_07\include;C:\jdk1.5.0_07\include\win32 -mn
-WD hello.c kernel32.lib
execute the java app: java -classpath . HelloWorld

Any help would be greatly appreciated.

Thanks,

Will

Wouldn't happen to be doing iostream calls, would you?

Will Senn wrote:
> Hi,
> 
> I am having trouble building a dll that java can use jni on, seems to build fine, but then just hangs and hangs and hangs...
> 
> Here's the c:
> --
> -- hello.c
> --
> #include <jni.h>
> #include "HelloWorld.h"
> #include <stdio.h>
> 
> JNIEXPORT void JNICALL
> Java_HelloWorld_displayHelloWorld(JNIEnv *env, jobject obj)
> {
> printf("Hello world!\n");
> return;
> }
> 
> --
> -- HelloWorld.h is a generated file (java gen's it)
> --
> #include <jni.h>
> /* Header for class HelloWorld */
> 
> #ifndef _Included_HelloWorld
> #define _Included_HelloWorld
> #ifdef __cplusplus
> extern "C" {
> #endif
> /*
> * Class:     HelloWorld
> * Method:    displayHelloWorld
> * Signature: ()V
> */
> JNIEXPORT void JNICALL Java_HelloWorld_displayHelloWorld
> (JNIEnv *, jobject);
> 
> #ifdef __cplusplus
> }
> #endif
> #endif
> 
> Here is the compile command that I gave dmc:
> dmc -I C:\jdk1.5.0_07\include;C:\jdk1.5.0_07\include\win32 -mn -WD hello.c
> kernel32.lib
> 
> There are no errors displayed and a dll is created. However, when I try to do the java trick (which works with ms compiler created dll's), it hangs. Here's th e java stuff, in case you want to see :)
> 
> --HelloWorld.java
> class HelloWorld {
> public native void displayHelloWorld();
> 
> static {
> System.loadLibrary("hello");
> }
> 
> public static void main(String[] args) {
> new HelloWorld().displayHelloWorld();
> }
> }
> 
> compile the java byte code: javac -classpath . HelloWorld.java
> generate the HelloWorld.h file: javah -jni -classpath . HelloWorld
> compile the dll: dmc -I C:\jdk1.5.0_07\include;C:\jdk1.5.0_07\include\win32 -mn
> -WD hello.c kernel32.lib
> execute the java app: java -classpath . HelloWorld
> 
> Any help would be greatly appreciated.
> 
> Thanks,
> 
> Will
> 
> 

printf("Hello world!\n");
return;

is the only code in the called dll.


In article <e76k2s$1hb7$1@digitaldaemon.com>, Scott Michel says...
>
>Wouldn't happen to be doing iostream calls, would you?
>
>Will Senn wrote:
>> Hi,
>> 
>> I am having trouble building a dll that java can use jni on, seems to build fine, but then just hangs and hangs and hangs...
>> 
>> Here's the c:
>> --
>> -- hello.c
>> --
>> #include <jni.h>
>> #include "HelloWorld.h"
>> #include <stdio.h>
>> 
>> JNIEXPORT void JNICALL
>> Java_HelloWorld_displayHelloWorld(JNIEnv *env, jobject obj)
>> {
>> printf("Hello world!\n");
>> return;
>> }
>> 
>> --
>> -- HelloWorld.h is a generated file (java gen's it)
>> --
>> #include <jni.h>
>> /* Header for class HelloWorld */
>> 
>> #ifndef _Included_HelloWorld
>> #define _Included_HelloWorld
>> #ifdef __cplusplus
>> extern "C" {
>> #endif
>> /*
>> * Class:     HelloWorld
>> * Method:    displayHelloWorld
>> * Signature: ()V
>> */
>> JNIEXPORT void JNICALL Java_HelloWorld_displayHelloWorld
>> (JNIEnv *, jobject);
>> 
>> #ifdef __cplusplus
>> }
>> #endif
>> #endif
>> 
>> Here is the compile command that I gave dmc:
>> dmc -I C:\jdk1.5.0_07\include;C:\jdk1.5.0_07\include\win32 -mn -WD hello.c
>> kernel32.lib
>> 
>> There are no errors displayed and a dll is created. However, when I try to do the java trick (which works with ms compiler created dll's), it hangs. Here's th e java stuff, in case you want to see :)
>> 
>> --HelloWorld.java
>> class HelloWorld {
>> public native void displayHelloWorld();
>> 
>> static {
>> System.loadLibrary("hello");
>> }
>> 
>> public static void main(String[] args) {
>> new HelloWorld().displayHelloWorld();
>> }
>> }
>> 
>> compile the java byte code: javac -classpath . HelloWorld.java
>> generate the HelloWorld.h file: javah -jni -classpath . HelloWorld
>> compile the dll: dmc -I C:\jdk1.5.0_07\include;C:\jdk1.5.0_07\include\win32 -mn
>> -WD hello.c kernel32.lib
>> execute the java app: java -classpath . HelloWorld
>> 
>> Any help would be greatly appreciated.
>> 
>> Thanks,
>> 
>> Will
>> 
>> 

Attached some code I wrote some years ago to export the Window Address BooK (WAB) from Java via JNI.

Hope this helps.

Jan



-- 
ManiaC++
Jan Knepper

But as for me and my household, we shall use Mozilla... www.mozilla.org

Will Senn wrote:
> printf("Hello world!\n");
> return;
> 
> is the only code in the called dll.

Ok, so you're only using stdio. Make sure you're using the DLL runtime and not the statically linked DMC runtime. Will require a recompile.

Scott Michel wrote:
> Will Senn wrote:
>> printf("Hello world!\n");
>> return;
>>
>> is the only code in the called dll.
> 
> Ok, so you're only using stdio. Make sure you're using the DLL runtime and not the statically linked DMC runtime. Will require a recompile.

Scott,

What do you mean by "DLL runtime and not he statically linked DMC runtime"? or rather, how do I ensure that this is the case - is it a paramter to the compiler or what?

Thanks,
Will

Will Senn wrote:
> What do you mean by "DLL runtime and not he statically linked DMC runtime"? or rather, how do I ensure that this is the case - is it a paramter to the compiler or what?

"-ND" to the compiler. That causes the compiler to insert a library record into the object file that picks up the DLL version of the compiler runtime.

http://www.digitalmars.com/ctg/ctg.html will always be your friend.

Scott Michel wrote:
> Will Senn wrote:
>> What do you mean by "DLL runtime and not he statically linked DMC runtime"? or rather, how do I ensure that this is the case - is it a paramter to the compiler or what?
> 
> "-ND" to the compiler. That causes the compiler to insert a library record into the object file that picks up the DLL version of the compiler runtime.
> 
> http://www.digitalmars.com/ctg/ctg.html will always be your friend.

Hmmm... Seems like this option needs SND.lib, which is purportedly only available on the CD, which costs 40+ bucks.

I verified that this works in MS. I downloaded VC++ 2005 Express Edition and built the dll using:

cl -IC:\jdk1.5.0_07\include -IC:\jdk1.5.0_07\include\win32 -LD hello.c -Fehello.dll

the dll that resulted worked flawlessly with jni...

I would prefer to use Digital Mars, but I'm not excited about paying for a CD just to 'see' if my program will compile and run.

Is there not a way to build this incredibly simplistic example of a dll using the downloadable version of dmc?

The cl options are:
-I include dir
-LD create dll
-Fe name output executable

That's it, no bizarre options, just build a dll and name it hello.dll.


Thanks,

Will

Will Senn wrote:
> Hmmm... Seems like this option needs SND.lib, which is purportedly only available on the CD, which costs 40+ bucks.

<sarcasm>And this is some incredible hardship?</sarcasm>

> I verified that this works in MS. I downloaded VC++ 2005 Express Edition and built the dll using:
> 
> cl -IC:\jdk1.5.0_07\include -IC:\jdk1.5.0_07\include\win32 -LD hello.c -Fehello.dll
> 
> the dll that resulted worked flawlessly with jni...
> 
> I would prefer to use Digital Mars, but I'm not excited about paying for a CD just to 'see' if my program will compile and run.

Sounds like you use DM for a lot more than just this project.

In the past, '-ND' was the way I went about making JNI work. Static libraries don't work well, esp. stdio or iostreams are involved.