The javah command throws exit code zero even in case of errors. Here, is a sample code that generates it.

package test;
public class JavahTest{
        public static void main(String args){
                System.out.println("Test Message");
        }
        private static native Object nativeTest();
}

To reproduce the problem please do the following.
1. Compile the above program.
2. Run javah JavaTest.
This will throw the following error.
error: cannot access JavahTest
bad class file: ./JavahTest.class
class file contains wrong class: test.JavahTest
Please remove or make sure it appears in the correct subdirectory of the classpath.
com.sun.tools.javac.util.Abort
        at com.sun.tools.javac.comp.Check.completionError(Check.java:173)
        at com.sun.tools.javadoc.DocEnv.loadClass(DocEnv.java:159)
        at com.sun.tools.javadoc.RootDocImpl.<init>(RootDocImpl.java:77)
        at com.sun.tools.javadoc.JavadocTool.getRootDocImpl(JavadocTool.java:157)
        at com.sun.tools.javadoc.Start.parseAndExecute(Start.java:330)
        at com.sun.tools.javadoc.Start.begin(Start.java:128)
        at com.sun.tools.javadoc.Main.execute(Main.java:66)
        at com.sun.tools.javah.Main.main(Main.java:147)
javadoc: error - fatal error
2 errors

But, the exit code of the command is not some non zero value. The command echo $? prints just zero.

There are 2 issues here.
1. The command doesn't throw proper exit code.
2. It throws some javadoc error message which misleads.

The javah command with which this behaviour is observed is bundled with jdk version 1.5.0-beta2-b45.