PRB: JVC: J0029 and J5020 Errors When Using Language Extensions

ID: Q198322

The information in this article applies to:

SDK for Java, version 2.02
Microsoft SDK for Java, versions 2.02, 3.2

SYMPTOMS

One or more of the following warnings/errors may occur when compiling a Java program that uses Microsoft language extensions:

warning J5020: Directive '@security' ignored--extensions are turned off

-or-

warning J5020: Directive '@com' ignored--extensions are turned off

-or-

warning J5020: Directive '@dll' ignored--extensions are turned off

-or-

error J0029: Invalid character

CAUSE

Microsoft SDK for Java 2.02 (Microsoft virtual machine build 2435) includes the Microsoft compiler for Java (Jvc.exe) version 1.02.7318 or later, which disables Microsoft language extensions by default. Previous versions of the Microsoft compiler for Java (Jvc.exe) did not disable Microsoft language extensions by default.

RESOLUTION

To compile code that uses Microsoft extensions, you should use the /x- switch to enable extensions.

Jvc.exe supports the following command-line options for enabling and disabling language extensions:


/x    Disable language extensions (now the default setting)
/x-   Enable language extensions

MORE INFORMATION

Steps to Reproduce Behavior

Create a file named Test.java that contains the following:


      /**
      @dll.import("USER32.DLL")
      */ 
      public class Test {
        public static void main(String args[])
        {
        #if MSGBOX
           MessageBox(0,"HELLO","Hello World",0);
        #else
           System.out.println("Hello World");
        #endif
        }
        #if MSGBOX
        public native static int MessageBox (int hWnd, String lpText,
            String lpCaption, int uType);
        #endif
      }

Compile the file using the following command:
```
jvc Test.java 
```
This produces the following error messages:

Test.java(4,1) : warning J5020: Directive '@dll' ignored -- extensions are turned off

-or-

Test.java(7,1) : error J0029: Invalid character

-or-

Test.java(7,5) : error J0013: Expected '('

-or-

Test.java(8,4) : error J0014: Expected ')'

-or-

Test.java(9,1) : error J0029: Invalid character

The correct way to compile a file that uses Microsoft language extensions is to use the following command-line:


jvc /x- Test.java

This produces the following warning message:

NOTE: Use of the Microsoft language extensions for Java results in compiled code that will run only on Windows systems with the Microsoft virtual machine installed and may not run on other virtual machines. The Microsoft virtual machine is installed with Windows 98, and a freely redistributable version is included with this product. While future versions of Microsoft's Java development tools may be prohibited by court order from incorporating keyword extensions and compiler directives not contained in Sun's Java language specification, any code written and compiled with this version of the product will be unaffected by such a ruling. (Use /nomessage to disable this message.)

If you want to compile the file and define the MSGBOX symbol, you would use the following command:


jvc /x- /D MSGBOX Test.java

When compiling Java code that contains Microsoft language extensions, it is possible to disable the warning message by passing the /nomessage switch to JVC. Older compilers do not support the /nomessage switch and will generate a "warning J5003: Ignoring unknown compiler option '/nomessage'." To use the /nomessage switch, your command-line options would be as follows:


jvc /x- /nomessage /D MSGBOX Test.java

If you upgrade Microsoft Visual J++ to use the compiler from the SDK for Java, it is possible that your Microsoft Visual J++ product will always disable Microsoft extensions, regardless of the check box "Disable Microsoft Language Extensions" being selected or not. In this case, to compile code using language extensions, you will need to add the "/x-" switch (without the quotes) to the Additional compiler options, in the Project Properties/Compile tab.

If you compile code and receive the J5020 warning, the .class file generated may not function properly. You should recompile using the "/x-" switch. Failure to do so may result in the following error message when running your application:

Caught exception: java.lang.UnsatisfiedLinkError: Simple.MessageBox Possible causes: If you are trying to use J/Direct (@dll.import), check your compiler version (for JVC, requires 4336 or greater.) If you are trying to use RNI, there are new requirements: see documentation. Probably wrong version of Java compiler.

REFERENCES

For the latest Knowledge Base articles and other support information on Visual J++ and the SDK for Java, please see the following pages on the Microsoft Technical Support site:

http://support.microsoft.com/support/visualj/

http://support.microsoft.com/support/java/

Additional query words:


Keywords          : kbGrpJava kbSDKJava202 kbCmpiler kbSDKJava320 
Version           : WINDOWS:2.02
Platform          : WINDOWS 
Issue type        : kbprb

Last Reviewed: July 28, 1999