JDK-8275509: (jlink) SystemModulesPlugin generates a jdk.internal.module.SystemModules$all.class which isn't reproducible

[Claes Redestad]

On 2021-10-19 14:31, Jaikiran Pai wrote:
> The other option I experimented with was to make 
> ModuleDescriptor#hashCode() generate the same hashcode across multiple 
> JVM runs. Although I do have a "working" version of that change, I 
> decided not to spend too much time on it because the 
> java.lang.Object#hashCode() contract itself clearly states that this 
> value isn't expected to be same across multiple JVM runs. So whatever 
> I do here is going to be brittle. 

I'm assuming the cause for ModuleDescriptor#hashCode being is due to the 
various enums not having an explicitly defined hashCode? I think this 
should be fixed.

Either way you're going to be brittle since the patch to emit a 0 is 
relying on the ModuleDescriptor#hashCode implementation disallowing 0 as 
a hash value (a 0 will force a recalculation). While it'll only happen 
at most once per module these relatively expensive calculations are 
something we want to avoid on startup if we can do so for free.

/Claes