RFR: JDK-8210750 Clean up compare.sh exceptions

[Erik Joelsson]

Looks good. Thanks for going through this.

/Erik


On 2018-09-14 00:58, Magnus Ihse Bursie wrote:
> The file compare_exceptions.sh.incl contains a lot of "known 
> exceptions" to files that we have ignored various aspects of when 
> comparing two builds using compare.sh.
>
> Most of them should be removed. There are several reasons for this:
>
> 1) The script was developed when we compared two completely different 
> build systems (old and new), and some leeway was needed in that 
> comparison. Now we only make incremental changes to an existing 
> system, and we need to sharpen the tool.
>
> 2) We now have continuous testing on build reproducability, where we 
> build twice in a row and compare the two builds. Essentially, I 
> believe only changes that are triggered under these circumstances 
> should be allowed to be on this list. All other changes could not be 
> just deemed as spurious anymore.
>
> 3) We have addressed multiple issues of non-reproducability in the 
> build, but we have been bad at clearing out this file.
>
> Finally, I believe the DIS_DIFF_FILTER does not belong in the 
> exceptions file, since it's more about the core behavior of the 
> compare script.
>
> I have tested this patch by repeatedly running the comparison test. 
> While some of the issues are indeed intermittent, I believe they have 
> at least been absent far enough on my testing to warrant removal at 
> this point. (The only failure I've noticed is due to JDK-8209880. 
> While I could have added a temporary exclude for tzdb.dat, I hope that 
> JDK-8209880 get fixed soon enough that it's not worth a temporary 
> workaround.)
>
> In the fullness of time, it would be interesting to hunt down the 
> remaining unexplained arbitrary changes in the build. But it's not 
> really high priority.
>
> Bug: https://bugs.openjdk.java.net/browse/JDK-8210750
> WebRev: 
> http://cr.openjdk.java.net/~ihse/JDK-8210750-cleanup-compare-exceptions/webrev.01
>
> /Magnus
>