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

[David Holmes]

On 30/01/2019 3:55 pm, Ioi Lam wrote:
> 
> 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.

Ah! Yes of course.

> 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.

s/library/class/ :)

> Does this answer your question?

Yes - thanks. I can't help but think this is working around a problem 
that should be more readily solvable, but I don't have time to delve 
into ProcessTools.

> ========
> 
> 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?

I think it sounds like ProcessTools both needs a fix for that and could 
better handle the "forwarding" of the classpath. Though on the other 
hand do these tests really need to use createJavaProcessBuilder (which 
presumably allows you to pass through runtime args from jtreg etc) and 
just launch the VM under test in a more direct and simple way?

David
-----

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