RFR: 8214796: Create a jlink plugin for stripping debug info symbols from native libraries

[Alan Bateman]

On 07/02/2019 17:09, Severin Gehwolf wrote:
> Hi,
>
> Could I please get reviews for this enhancement? It adds a debug
> symbols stripping plug-in to jlink for Linux and Unix platforms. It's
> the first platform specific jlink plugin and the approach taken for
> keeping it contained is to use a plugin specific ResourceBundle.
> Discussion for this happened in [1].
>
> The test uses a native library which should never get debug symbols
> stripped during the test library build. As such, tiny modifications
> were needed to make/common/TestFilesCompilation.gmk. Hence, build-dev
> being on the list for this RFR. The test currently only runs on Linux
> and requires objcopy to be available. Otherwise the test is being
> skipped.
>
> Example usage of this plugin is described in the bug.
>
> webrev: http://cr.openjdk.java.net/~sgehwolf/webrevs/JDK-8214796/04/webrev/
> Bug: https://bugs.openjdk.java.net/browse/JDK-8214796
>
I agree with Mandy that the CLI options need examination. The proposed 
`--strip-native-debug-symbols` seems reasonable but it will be 
inconsistent with the existing `--strip-debug` option. Mandy - what you 
would think about renaming the existing option to something that makes 
it clear that it strips the debug attribute from class files? (we would 
of course need to do something to keep the existing option working).

The need to specify the argument as "defaults" or "options" is a bit 
annoying. It might be time to replace hasArguments in the plugin 
interface to allow for optional arguments. The plugin interface is not 
exported/documented/supported so we have flexibility to change it. If we 
do this then it should mean the usages reduce down to:

--strip-native-debug-symbols
--strip-native-debug-symbols objcopy=<path-to-objcopy>:...

I see the plugin has moved to src/jdk.jlink/unix in this iteration. It 
might be better to start out in src/jdk.jlink/linux - we can always move 
to the unix tree in the event that there is interest/support on other 
platforms.

Mandy points out the issue with wrapping in the usage output. I agree 
that the`jlink --list-plugins` needs to be readable/tidy esp. in this 
case as there are many sub-options to read about.

The implementation will need a bit of a tidy up too. The readFileBytes 
method can be replaced with Files.readAllBytes. The BAIS usage can be 
replaced with Files.write. Ignoring exceptions thrown in stripBinary 
will also need consideration.

-Alan