Enable reproducible builds with SOURCE_DATE_EPOCH

Enable reproducible builds when the SOURCE_DATE_EPOCH environment variable is defined. See the following page for details on defining the variable:

  SOURCE_DATE_EPOCH
  https://reproducible-builds.org/docs/source-date-epoch/

SYSTEM / OS / JAVA RUNTIME INFORMATION

Ubuntu 20.04.2 LTS

  $ uname -srm
  Linux 5.4.0-70-generic x86_64

macOS 11.2.3 (Big Sur)

  $ uname -srm
  Darwin 20.3.0 x86_64

Windows 10 Pro Version 10.0.19042

  $ uname -srm
  CYGWIN_NT-10.0 3.1.7(0.340/5/3) x86_64

Oracle OpenJDK 15.0.2

  $ java --version
  openjdk 15.0.2 2021-01-19
  OpenJDK Runtime Environment (build 15.0.2+7-27)
  OpenJDK 64-Bit Server VM (build 15.0.2+7-27, mixed mode, sharing)

Apache Ant 1.10.9

  $ ant -version
  Apache Ant(TM) version 1.10.9 compiled on September 27 2020

STEPS TO REPRODUCE

1. Build the JavaFX SDK libraries, JMOD archives, and API documentation:

  $ bash gradlew clean sdk jmods javadoc

2. Save the first build and then run another clean build:

  $ mv build build1
  $ bash gradlew clean sdk jmods javadoc

3. Save the second build and then compare it with the first:

  $ mv build build2
  $ diff -qr build1 build2

EXPECTED RESULTS

The two builds are identical:

  $ diff -qr build1 build2 | wc -l
  0

If not, the command 'strip-nondeterminism' removes their differences:

  $ strip-nondeterminism -v build?/jmods/*.jmod
  $ diff -qr build1 build2 | wc -l
  0

ACTUAL RESULT

There are 47 files that are different between the two builds:

  $ diff -qr build1 build2 | wc -l
  47

The files that differ have the following file types:

  23 .jar
  12 .so
   7 .jmod
   2 .properties
   1 .zip
   1 .class
   1 .java
  --------------
  47 Total

Running the command 'strip-nondeterminism' on the JAR, JMOD, and ZIP files does not remove all of their differences:

  $ strip-nondeterminism -v $(find build? -name "*.jar")
  $ strip-nondeterminism -v build?/jmods/*.jmod
  $ strip-nondeterminism -v build?/sdk/lib/src.zip

  $ diff -qr build1 build2 | grep '\.jar'
  Files build1/publications/javafx.base-linux.jar and
        build2/publications/javafx.base-linux.jar differ
  Files build1/publications/javafx.graphics-linux.jar and
        build2/publications/javafx.graphics-linux.jar differ
  Files build1/sdk/lib/javafx.base.jar and
        build2/sdk/lib/javafx.base.jar differ

  $ diff -qr build1 build2 | grep '\.jmod'
  Files build1/jmods/javafx.base.jmod and
        build2/jmods/javafx.base.jmod differ
  Files build1/jmods/javafx.graphics.jmod and
        build2/jmods/javafx.graphics.jmod differ

  $ diff -qr build1 build2 | grep '\.zip'
  Files build1/sdk/lib/src.zip and
        build2/sdk/lib/src.zip differ

In fact, there are still 22 files that are different after running 'strip-nondeterminism' on all of the supported file types:

  $ diff -qr build1 build2 | wc -l
  22

SOURCE CODE FOR AN EXECUTABLE TEST CASE

N/A

WORKAROUND

None