Compiling and Executing the Program

I've saved the C program we wrote as invoke.c.

In order to compile the program to a .exe file, we'll need:

• The JNI headers,
• The import library we built earlier.

The JNI headers come with the JDK, in its /include and /include/win32 directories. We add them to the gcc command line with -I. We can also specify libraries with the -L argument, and name libraries with -l (that's lowercase L). My command line looks like this (where the jdk environment points to my Java installation):

gcc -mno-cygwin -o invoke.exe -I$jdk/include -I$jdk/include/win32 invoke.c -L. -ljvm

Recall that I said I was putting everything in one directory. So my libjvm.dll.a is sitting in my current working directory (hence -L.), and I can refer to it by name as jvm.

In order to execute the program, we must have the JVM's jvm.dll in our Windows PATH variable. So, to run our program using the "Classic" VM, my command line looks like:

PATH=$jdk/jre/bin/classic:$PATH; invoke

If you want to use HotSpot, it will look something like:

PATH=$jdk/jre/bin/hotspot:$PATH; invoke

If you have everything set up correctly, you should see:

$ PATH=$jdk/jre/bin/hotspot:$PATH; invoke
Hello, World!
Arguments sent to this program:
From-C-program

As long as you manage the PATH variable properly, you should be able to execute the Java program from inside or outside Cygwin, since we used the -mno-cygwin option on gcc.

Please let me know if you find errors or omissions in this walkthrough, or have general comments or questions.