Add support for statically linking Jansi JNI library

[rsenden]

We have a picocli-based application for which we build native images for Windows, Linux & MacOS using GraalVM. For various reasons, we build a statically linked executable for Linux, and dynamically linked executables for Windows/MacOS.

We would like to add Jansi (and JLine) to our application. Jansi 2.4.0 works just fine for our dynamically linked executables, however it fails to load the native jansi library in the statically linked executable because musl apparently doesn't support dynamic library loading (see https://github.com/oracle/graal/issues/4028#issue-1055983935):

open("/tmp", O_RDONLY|O_LARGEFILE|O_CLOEXEC|O_DIRECTORY) = 4
open("/tmp/jansi-2.4.0-83026643492bd4eb-libjansi.so.lck", O_WRONLY|O_CREAT|O_TRUNC|O_LARGEFILE, 0666) = 4
open("/tmp/jansi-2.4.0-83026643492bd4eb-libjansi.so", O_WRONLY|O_CREAT|O_TRUNC|O_LARGEFILE, 0666) = 4
open("/tmp/jansi-2.4.0-83026643492bd4eb-libjansi.so", O_RDONLY|O_LARGEFILE) = 4
Failed to load native library:jansi-2.4.0-83026643492bd4eb-libjansi.so. osinfo: Linux/x86_64
java.lang.UnsatisfiedLinkError: Can't load library: /tmp/jansi-2.4.0-83026643492bd4eb-libjansi.so

Apart from this issue, it's also just more logical to statically link the Jansi library when building native images, to avoid dynamic extraction of the library to a temporary directory and then loading it.

Based on what I've read so far, I think the following would be needed:

• jansi.c: Export either JNI_OnLoad (for dynamic linking) or JNI_OnLoad_jansi (for static linking)
• Update Makefile to add support for building libJansi.a/jansi.lib files
• Optional: publish pre-built .a/.lib files, to avoid users having to build these themselves
• Update JansiLoader to (also) try System.loadLibrary("jansi") (either always try, or use a system property to decide between this and the original System.load(path)-based approach)
• Document how to statically link Jansi:
  • Add org.graalvm.nativeimage:svm dependency
  • Add the required GraalVM @AutomaticFeature (alternatively, publish a new jansi-<version>-static-feature.jar artifact that readily includes this feature, such that users can simply add this as a dependency)
  • Add -H:CLibraryPath=/path/to/dir/containing/libJansi.a option to native-image invocation
  • Add a resource exclude to prevent dynamic Jansi libraries being added to the native image, basically making GraalVM ignore: https://github.com/fusesource/jansi/blob/00e15cb1fab9117790580a412f7d54f2c08d2f11/src/main/resources/META-INF/native-image/jansi/resource-config.json#L5

For reference, some links related to statically linking JNI libraries:

• https://www.blog.akhil.cc/static-jni
• https://github.com/oracle/graal/issues/3359#issuecomment-822070278
• https://github.com/oracle/graal/issues/3359#issuecomment-1031482202

[xtaixe]

+1. We are also facing this issue.

[gnodet]

A PR would be welcomed @rsenden

[Glavo]

Let me give it a try, I'm doing some work on this.

[rsenden]

Thanks for looking into this!

On Thu, Sep 28, 2023, 19:58 Glavo @.***> wrote:

Let me give it a try, I'm doing some work on this.

— Reply to this email directly, view it on GitHub https://github.com/fusesource/jansi/issues/246#issuecomment-1739777950, or unsubscribe https://github.com/notifications/unsubscribe-auth/ACB4GAQBMK4QAN5UWKDWZXTX4W3EHANCNFSM6AAAAAATDB4VSU . You are receiving this because you were mentioned.Message ID: @.***>

[gnodet]

@Glavo you're still planning to work on this feature ? If that's the case, I can wait a bit before starting a 2.5.0 release.

[Glavo]

@Glavo you're still planning to work on this feature ? If that's the case, I can wait a bit before starting a 2.5.0 release.

I don't think it can be done in a short time. If I don't find a workaround, I need to wait for GraalVM to solve #7507, or give up on what I'm trying and explore something else.

[Glavo]

hmm, I found another easier way. I'll give it a quick try and if it works I'll report the results here.

[Glavo]

@gnodet I think #269 is more promising, please wait for me.