RFR(XS) 8218029 [TESTBUG] Use -Djava.class.path= to specify empty -cp in CDS tests

[Ioi Lam]

On 1/29/19 8:35 PM, David Holmes wrote:
> Hi Ioi,
>
> On 30/01/2019 1:51 pm, Ioi Lam wrote:
>> https://bugs.openjdk.java.net/browse/JDK-8218029
>> http://cr.openjdk.java.net/~iklam/jdk13/8218029-testbug-empty-classpath.v01/ 
>>
>>
>> Please review this simple fix. For portability,
>>
>>       "-cp", "\"\"",
>>
>> in the JVM command-line is replaced with
>>
>>       "-Djava.class.path="
>
> Not sure I see how this works. ProcessTools will add:
>
> -cp <value of java.class.path>
>
> but you are setting java.class.path to be empty so to me that means 
> ProcessTools will set
>
> -cp
>
> which is an error? Or does it somehow become
>
> -cp ""
>
> ??
>
> And does that mean the actual command-line ends up with:
>
> -cp "" -Djava.library.path=
>
> ?


Each CDS test typically consists of 2 processes. The "main" test would 
run in the parent process. It will call 
ProcessTools.createJavaProcessBuilder to launch a child process.

     public static ProcessBuilder createJavaProcessBuilder(...., 
String... command) {
         ..
         args.add("-cp");
         args.add(System.getProperty("java.class.path"));
         ..
         Collections.addAll(args, command);

Here, the java.class.path property is from the parent process, so it 
won't be empty.

For the tests I touched, the child process's command-line will end up 
looking like this

        java -cp  <some long jtreg stuff> -Djava.library.path= Foo

and the -Djava.library.path= argument overrides the earlier -cp argument.

Does this answer your question?

========

BTW, ProcessTools.createJavaProcessBuilder actually is buggy. If the 
parent process's java.class.path is indeed empty, on Windows, the child 
process will get

        java -cp Hello

I.e., Windows throws away the empty argument. I could fix it as

String cp = System.getProperty("java.class.path");
if (cp != null) {
     args.add("-cp");
     args.add(cp);
} else {
     args.add("-Djava.library.path=");
}

What do you think?

Thanks

- Ioi



>
> Thanks,
> David
>
>>
>> Thanks!
>>
>> Ioi
>>