RFR 8181299/10, Several jdk tests fail with java.lang.NoClassDefFoundError: jdk/test/lib/process/StreamPumper

Ioi Lam ioi.lam at oracle.com
Thu Jun 1 22:37:58 UTC 2017

On 6/1/17 1:17 PM, Igor Ignatyev wrote:
>> On Jun 1, 2017, at 1:20 AM, Chris Hegarty <chris.hegarty at oracle.com> wrote:
>> Igor,
>>> On 1 Jun 2017, at 04:32, Igor Ignatyev <igor.ignatyev at oracle.com> wrote:
>>> Hi Felix,
>>> I have suggested the exact opposite change[1-3] to fix the same problem.
>> I’m sorry, but this is all just too confusing. After your change, who, or what, is
>> responsible for building/compiling the test library dependencies?
> jtreg is responsible, there is an implicit build for each @run, and jtreg will analyze a test class to get transitive closure for static dependencies, hence you have to have @build only for classes which are not in constant pool, e.g. used only by reflection or whose classnames are only used to spawn a new java instance.

I suspect the problem is caused by a long standing bug in jtreg that 
results in library classes being partially compiled. Please see my 
evaluation in


In the bug report, there is test case that can reliably reproduce the 
NoClassDefFoundError problem.

I think adding all the @build commands in the tests are just band-aids. 
Things will break unless every test explicitly uses @build to build 
every class in every library that they use, including all the private 
classes that are not directly accessible by the test cases.

For example: doing this may be enough for now:

      * @build jdk.test.lib.process.*

But what if in the future, jdk.test.lib.process is restructured to have 
a private package jdk.test.lib.process.hidden? To work around 
CODETOOLS-7901986, all the test cases that must be modified to the 
following, which unnecessarily exposes library implementation details to 
the library users:

      * @build jdk.test.lib.process.* jdk.test.lib.process.hidden.*

Just imagine this -- "in order to use malloc() you must explicitly build 
not only malloc(), but also sbrk() ... and every other function in 
libc". That seems unreasonable to me.

By the way, we made a fix in the HotSpot tests (see 
https://bugs.openjdk.java.net/browse/JDK-8157957) that got rid of many 
(but not all) of the NoClassDefFoundErrors by *removing* the @build 
lines .....

My proposal is, instead of just adding @build for band-aid, we should 
fix CODETOOLS-7901986 instead.

- Ioi

>> Test library code has no @modules tags, so does not explicitly declare its
>> module dependencies. Instead module dependencies, required by test
>> library code, are declared in the test using the library. If we wildcard, or
>> otherwise leave broad build dependencies, from tests then there is no
>> way to know what new module dependencies may be added in the future.
>> That is, one of, the reason(s) I asked Felix to be explicit about the build
>> dependencies.
> having explicit builds does not really help w/ module dependency, if someone change a testlibrary class so it starts to depend on another testlibrary class, jtreg will implicitly build it and if this class has some module dependencies, you will have to reflect them in the test.
> generally speaking, I don't like having explicit build actions because build actions themselves are implicit, so they don't really help, it's still will be hard to spot missed explicit builds. not having (unneeded) explicit builds is an easy rule to follow and we can easily find all places which don't follow this rule by grep.
> -- Igor
>> -Chris.
>>> [1] https://bugs.openjdk.java.net/browse/JDK-8181391
>>> [2] http://mail.openjdk.java.net/pipermail/core-libs-dev/2017-June/048012.html
>>> [3] http://cr.openjdk.java.net/~iignatyev//8181391/webrev.00/index.html

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