I tried to do a compareGradleBuilds by adding

if (gradle.gradleVersion == '1.2') {
   apply plugin: 'compare-gradle-builds'
   compareGradleBuilds {
      sourceBuild {
         gradleVersion = '1.0'
      }
   }
}

to my Gradle 1.0 build and changing the gradle-wrapper.properties to 1.2.

After executing './gradlew cGB' it completed the targetBuild. After that it wanted to execute the sourceBuild. But there during the clean phase there was the following exception:

:cache:clean

FAILURE: Build failed with an exception.

* What went wrong:
Execution failed for task ':cache:clean'.
> java.io.IOException: Unable to delete file: censored\cache\build\libs\cache-shared-server-5.0.RC0.jar

I then looked at the process list and found a dozen or so gradle processes that eat memory and lock files like the one above.
I guess this has not completely to do with compareGradleBuilds as a colleague also regularly has to kill dozens of Gradle processes that hang around and eat memory.

Nevertheless I killed all those processes and tried again, but I still get the same error message and I'm left with two Daemon processes, one for 1.0, one for 1.2 where the 1.2 one locks that file that the 1.0 one wants to delete during clean.

Then I executed it again without killing anything and now get the message already with the target build. I then killed the 1.2 Daemon process and run it again, then the target build succeeded again. Right after the target build being finished during buildSrc compilation of the source build I then killed the 1.2 Daemon process and thus released the file lock. Then the 1.0 Daemon process was able to delete the file during clean phase and the source build succeeded.
To make the timing easier I tried to add "System.console().readLine('Press ENTER to continue ')" to the master build at configuration time so that I don't have to manually watch and get the right time to kill the 1.2 Daemon process manually, but unfortunately this didn't work when executing cGB, only when doing a normal execution as there is no System Console when running through the Daemon. "if (gradle.gradleVersion == '1.0')

" also did not work, it printed the prompt, but continued without waiting for input. I ended up doing just "if (gradle.gradleVersion == '1.0') { 100.times

; sleep 60000 }" and hoping to see it within that minute.