Build fails when excluding Serial GC

[Magnus Ihse Bursie]

On 2021-01-29 11:19, Stefan Karlsson wrote:
> On 2021-01-29 10:49, Magnus Ihse Bursie wrote:
>>
>>
>> On 2021-01-29 09:03, Yang Yi wrote:
>>> Hi,
>>>
>>> It's quite easy to reproduce this problem:
>>> ./configure --with-jvm-features=-serialgc ... ; make images
>>>
>>> I got the following output
>>> ```
>>> ...
>>> === Output from failing command(s) repeated here ===
>>> * For target hotspot_variant-server_libjvm_objs_genCollectedHeap.o:
>>> /home/qingfeng.yy/openjdk16_so_warning/jdk/src/hotspot/share/gc/shared/genCollectedHeap.cpp: 
>>> In member function 'virtual void GenCollectedHeap::post_initialize()':
>>> /home/qingfeng.yy/openjdk16_so_warning/jdk/src/hotspot/share/gc/shared/genCollectedHeap.cpp:206:3: 
>>> error: 'MarkSweep' has not been declared
>>>    206 |   MarkSweep::initialize();
>>>        |   ^~~~~~~~~
>>> * All command lines available in 
>>> /home/qingfeng.yy/openjdk16_so_warning/jdk/build/linux-x86_64-server-release/make-support/failure-logs.
>>> === End of repeated output ===
>>> ```
>>> I found current JVM features contain the serial gc, but actually I 
>>> can not
>>> build an image that does not contain serial gc. This problem has 
>>> existed
>>> from jdk 11 to jdk head. I am somewhat surprised, so I haven't filed an
>>> issue on JBS. Is this really a bug? Or actually we should revise the 
>>> building
>>> document and remove all INCLUDE_SERIALGC macros?
>>
>> About a year ago I opened 
>> https://bugs.openjdk.java.net/browse/JDK-8240224, to fix this (and 
>> other things). This caused quite a heated debate [1], and the result 
>> was that I closed the bug again.
>>
>> In summary, my understanding is that hotspot developers view the 
>> serialgc as essential, and that there exists no reason beyond toy 
>> applications to remove it from compilation. But furthermore the 
>> INCLUDE_SERIALGC macros should remain, even though they do not really 
>> work, since they function as markers of intent for the code. I don't  
>> agree 100% with this stance, but it's not my code to complain about. :-)
>
> I think you got push back on some of the changes. To me and many 
> others the gcConfig.* changes were really controversial. It doesn't 
> mean that fixes to clean this up won't be accepted. 

Fair enough. I think the road to make it possible to exclude serial gc 
is to first fix the hotspot code for e.g. JDK-8234502, and then we can 
revisit the build changes needed. But I did get the impression from some 
developers that this was a futile exercise.

/Magnus

> In that mail thread, there was a reference to this bug '8234502: Merge 
> GenCollectedHeap and SerialHeap'. Chipping away at that would be good. 
> Fixing that would not only make it possible to build without Serial 
> GC, but also help with the maintainability of our code.
>
> StefanK
>
>>
>> Possibly, the configure script should be changed so it does not look 
>> like it's possible to exclude the serialgc...
>>
>> /Magnus
>>
>>
>> [1] 
>> https://mail.openjdk.java.net/pipermail/hotspot-gc-dev/2020-March/028779.html
>>
>>>
>>> Cheers,Yang Yi
>>>
>>
>