Temurin jdk21 classes.jsa CDS non-reproducible depending on folder path length?

[andrew-m-leonard]

Reproducible build tests have shown classes.jsa non-reproducible, and from testing it "seems" related to the path length of the reproducible build directory. eg.https://ci.adoptium.net/job/Grinder/16560/console

00:28:29  Number of files: 107885
00:28:29  00:28:27 : Comparing expanded JDKs from jdk-21.0.11+1 with reproJDK/jdk-21.0.11+1 ...
00:32:16  00:32:05 : diff complete - rc=1. Output written to file: reprotest.diff
00:32:16  Files jdk-21.0.11+1/lib/server/classes.jsa and reproJDK/jdk-21.0.11+1/lib/server/classes.jsa differ
00:32:16  Number of differences: 1
00:32:16  ReproduciblePercent = 99.99 %

A local reproduce seems possible with the following test, eg. on aarch64 mac try:

curl -L -o jdk.tar.gz https://github.com/adoptium/temurin21-binaries/releases/download/jdk-21.0.11%2B1-ea-beta/OpenJDK21U-jdk_aarch64_mac_hotspot_21.0.11_1-ea.tar.gz

mkdir JDK1
tar -xf jdk.tar.gz -C JDK1

mkdir -p JDK2/SUBFOLDER
tar -xf jdk.tar.gz -C JDK2/SUBFOLDER

JDK1/jdk-21.0.11+1/Contents/Home/bin/java -Xshare:dump -XX:SharedArchiveFile=1.jsa

(cd JDK2/SUBFOLDER && ./jdk-21.0.11+1/Contents/Home/bin/java -Xshare:dump -XX:SharedArchiveFile=../../2.jsa)

diff 1.jsa 2.jsa

[andrew-m-leonard]

Trying the same using SAP jdk-21.0.11+1 does not seem to fail
Also jdk-21.0.10+7 Temurin does not seem to fail

[andrew-m-leonard]

A workaround that seems to work consistently for Temurin reproducible jdk-21 builds is to ensure the reproduced build folder is significantly longer than the original build folder. By adding an arbitrary 50 characters in length seems to work !!