RFR: JDK-8159047: Disable redundant build steps when creating buildjdk

[Erik Joelsson]

On 2016-06-09 02:54, David Holmes wrote:
> Hi Erik,
>
> This seems good. Though it does seem to me that whole BUILJDK things 
> is rather complex!
>
Thanks!

I definitely agree. Every time I find an issue like this I feel like I 
went about the buildjdk business the wrong way, but I haven't been able 
to figure out a cleaner solution. In the meantime I just try to be very 
explicit about it in comments.

/Erik
> Great to see that truncated classfile problem tracked down though!
>
> Thanks,
> David
>
> On 8/06/2016 10:01 PM, Erik Joelsson wrote:
>> Hello,
>>
>> When creating the buildjdk (when cross compiling), the idea is to only
>> rebuild the parts that actually need to be rebuilt for the build
>> platform and reuse as much as possible from the normal build. Currently,
>> the interim-langtools step is rebuilt when it shouldn't be.
>>
>> The reason interim-langtools gets rebuilt is that the gensrc steps for
>> those modules get rebuilt. They in turn get rebuilt because the buildjdk
>> redefines the support outputdir, so for the buildjdk makefiles, it looks
>> like the gensrc steps for those modules have not happened. The
>> buildtools outputdir is not redefined however, so when the
>> interim-langtools get rebuilt, it overwrites the old build of it.
>>
>> While this is bad from an efficiency standpoint, it also causes
>> intermittent failures due to a race. When building the test lib, the
>> compilation of the test lib may happen at the same time as the
>> interim-langtools being rebuilt for the buildjdk. This means that the
>> class files being run for the interim javac compiler can be overwritten
>> while they are running. The failure can look like this:
>>
>> BuildTestLib.gmk:49: recipe for target
>> '/scratch/opt/jprt/T/P1/220139.ssteuck/s/build/linux-arm64/support/test/lib/test-lib_classes/_the.BUILD_TEST_LIB_JAR_batch' 
>>
>> failed
>> make[3]: Leaving directory
>> '/scratch/opt/jprt/T/P1/220139.ssteuck/s/make/test'
>> make/Main.gmk:413: recipe for target 'build-test-lib' failed
>> Exception in thread "main" java.lang.ClassFormatError: Truncated 
>> class file
>>     at com.sun.tools.javac.main.CommandLine.parse(CommandLine.java:58)
>>     at
>> com.sun.tools.sjavac.options.OptionHelper.traverse(OptionHelper.java:121) 
>>
>>     at com.sun.tools.sjavac.options.Options.parseArgs(Options.java:187)
>>     at com.sun.tools.sjavac.client.ClientMain.run(ClientMain.java:60)
>>     at com.sun.tools.sjavac.client.ClientMain.run(ClientMain.java:49)
>>     at com.sun.tools.sjavac.Main.go(Main.java:56)
>>     at com.sun.tools.sjavac.Main.main(Main.java:46)
>> make[3]: ***
>> [/scratch/opt/jprt/T/P1/220139.ssteuck/s/build/linux-arm64/support/test/lib/test-lib_classes/_the.BUILD_TEST_LIB_JAR_batch] 
>>
>> Error 1
>> make[2]: *** [build-test-lib] Error 1
>>
>>
>> My proposed fix for this problem is to add more guards in make/Main.gmk
>> that disables the interim and gensrc targets completely when the
>> buildjdk is being built.
>>
>> Bug: https://bugs.openjdk.java.net/browse/JDK-8159047
>> Webrev: http://cr.openjdk.java.net/~erikj/8159047/webrev.01/
>>
>> /Erik