Who's building this Docker image? https://hub.docker.com/_/jruby/ says this is "official", but maybe you should report to https://github.com/cpuguy83/docker-jruby/issues instead, because I don't see the problem on our release.

$ curl -LO https://repo1.maven.org/maven2/org/jruby/jruby-dist/9.1.16.0/jruby-dist-9.1.16.0-bin.tar.gz
  % Total    % Received % Xferd  Average Speed   Time    Time     Time  Current
                                 Dload  Upload   Total   Spent    Left  Speed
100 20.4M  100 20.4M    0     0  9365k      0  0:00:02  0:00:02 --:--:-- 9364k
$ tar zxf jruby-dist-9.1.16.0-bin.tar.gz
$ cd jruby-9.1.16.0
$ ./bin/jruby -Xjit.max=16384 -v
jruby 9.1.16.0 (2.3.3) 2018-02-21 8f3f95a Java HotSpot(TM) 64-Bit Server VM 25.144-b01 on 1.8.0_144-b01 +jit [darwin-x86_64]

I can reproduce the problem with the Alpine docker image, but not with the jruby image.

This leads me to believe that the problem stems from the difference between Debian and Alpine distros; namely,

expr -- jit.max=16384 : '.*[.]'

works on the former, and fails on the latter. Since Alpine's expr does not respond to --version, it is not a GNU one.

Oops, I was under impression the image is official indeed. If it's not, but claims so – isn't it a problem?

Thank you.

Well, if Alpine's expr does not behave the way expect, perhaps that should be fixed, whether or not this Docker image is "official."

I hate to say it but I am thinking we should start pushing an official image with our releases. Issues like this that we can't fix directly will impact people disproportionately.

Both 9.1.15 and 9.1.16 images inherit from the same Alpine 3.7.0 and jruby script in the former works fine.

The only change to the shell scripts in bin between 9.1.15 and 9.1.16 is this one b617d55 and it was exactly about how expr is being used.

Anyone who would try to pack JRuby 9.1.16 into Alpine (including openjdk:8-jre-alpine) is going to face the same issue.

@alaz Are you saying it worked ok in 9.1.15?

A workaround may be to install the native launcher (gem install jruby-launcher) since it uses standard C/++ to parse out these properties.

We'll need a patch for the bash launcher that doesn't regress the FreeBSD fix.

@headius yes, 9.1.15 accepts arguments w/o problems:

$ docker run --rm jruby:9.1.15-alpine jruby -Xjit.max=16384 --version 
jruby 9.1.15.0 (2.3.3) 2017-12-07 929fde8 OpenJDK 64-Bit Server VM 25.151-b12 on 1.8.0_151-b12 +jit [linux-x86_64]

Reproduced locally.

This patch appears to work on both Darwin and Alpine for me. I'll test Ubuntu shortly.

Edit: wrong patch

diff --git a/bin/jruby.bash b/bin/jruby.bash
index 5c841fedb6..fb090a8818 100755
--- a/bin/jruby.bash
+++ b/bin/jruby.bash
@@ -20,6 +20,14 @@ case "`uname`" in
   MINGW*) jruby.exe "$@"; exit $?;;
 esac
 
+# ----- Determine how to call expr (jruby/jruby#5091) -------------------------
+# On Alpine linux, expr takes no -- arguments, and 'expr --' echoes '--'.
+_expr_dashed=$(expr -- 2>/dev/null)
+if [ "$_expr_dashed" != '--' ] ; then
+  alias expr="expr --"
+fi
+unset _expr_dashed
+
 # ----- Verify and Set Required Environment Variables -------------------------
 if [ -z "$JAVA_VM" ]; then
   JAVA_VM=-client
@@ -244,7 +252,7 @@ do
      # Match -Xa.b.c=d to translate to -Da.b.c=d as a java option
      -X*)
         val=${1:2}
-        if expr -- "$val" : '.*[.]' > /dev/null; then
+        if expr "$val" : '.*[.]' > /dev/null; then
           java_args=("${java_args[@]}" "-Djruby.${val}")
         else
           ruby_args=("${ruby_args[@]}" "-X${val}")

The fix appears to work on Darwin, Ubuntu, and Alpine. I have committed it and it will be in 9.1.17.