RFR: JDK-8072842 Add support for building native JTReg tests

[Staffan Larsen]

> On 10 feb 2015, at 15:23, Magnus Ihse Bursie <magnus.ihse.bursie at oracle.com> wrote:
> 
> Here is an addition to the build system, that will compile native libraries and executables and make them available for JTReg tests written in Java.
> 
> This patch is the result of the work (in serial, mostly) of Staffan Larsen, David Simms and me. (And possible more that I don't know about.)
> 
> In it current form, the patch only provides the framework on which to attach real tests. To prove the concept, some initial dummy tests are present. These are supposed to be removed as soon as real tests starts to propagate into the jdk and hotspot jtreg test suites.
> 
> The behavior is based on the following design: For directories with native jtreg compilation enabled, the build system searches for native files prefixed with either "lib" or "exe", and compiles a free-standing library or an executable, respectively, for each such file. Since all compiled files are placed in a single directory (this is currently a requirement from the jtreg native support), there is the additional requirement that all files have unique names.
> 
> My personal opinion is that a better long-term approach is to compile all tests into a single library, if possible. (I realize some tests need to be separate to test library loading, etc.) For that to work, however, JTReg needs to be changed. The build framework in the patch is designed in such a way that it will be easy to add compilation to a common library in the future, if that restriction is lifted from JTReg.

To clarify: The restriction in jtreg is that all tests are loaded in separate class loaders (when running in samevm mode). A native library can only be loaded in one class loader at a time. So if two tests tries to load the same library we get errors. It would be possible to change this if samevm mode is removed from jtreg.

/Staffan

> 
> This patch also lays the foundation for building additional tests, not only native jtreg tests, by the build system in the future. For instance, it codifies the suggested correspondence between make targets, intermediate test output and test image final build results. With the on-going test co-location project, we expect a stream of tests to be added to the build system in the future, and we hope this project can serve as an example of a suitable way of integration.
> 
> The patch modifies hotspot code, but it's mostly due to the addition of the new dummy tests. My preference would be to integrate this patch via jdk9-dev, since it modifies the build system most of all, but I'm open for discussion.
> 
> Bug: https://bugs.openjdk.java.net/browse/JDK-8072842
> WebRev: http://cr.openjdk.java.net/~ihse/JDK-8072842-build-native-jtreg-tests/webrev.01
> 
> /Magnus