Does CDS archive generation work for crossbuilds?

[Magnus Ihse Bursie]

On 2021-10-28 22:56, Ioi Lam wrote:
> How reliable would it be to use qemu to run the cross-compiled 
> binaries? Has anyone tried that recently?
I experimented with qemu and the JDK build some years ago (so not really 
recently). As I remember it, the takeaway was that it probably was 
reliable, but it was slow as h*ll, up to the point of being practically 
unusable.

Add to this the fact that you need to prepare an entire OS image, 
complete with all tools needed to build the JDK... I set up a few such 
images for my own use (I think it was emulating linux-aarch64 on x64) to 
run testing. I had an idea of describing how I did to share the 
knowledge, but in the end it was just too complicated and slow to even 
consider recommending.

/Magnus
>
>
> On 10/23/21 5:48 AM, Thomas Stüfe wrote:
>> Hi Alan,
>>
>> On Sat, Oct 23, 2021 at 9:58 AM Alan Bateman <Alan.Bateman at oracle.com>
>> wrote:
>>
>>>
>>> On 23/10/2021 07:57, Thomas Stüfe wrote:
>>>> Hi,
>>>>
>>>> when I crossbuild (for linux aarch64, using a devkit, building on 
>>>> linux
>>>> x64), for some reason I don't
>>>> get the classes.jsa generated inside the images directory.
>>>>
>>>> My configure options:
>>>>
>>>>
>>> --with-devkit=/shared/projects/openjdk/devkits/x86_64-linux-gnu-to-aarch64-linux-gnu 
>>>
>>>> --openjdk-target=aarch64-linux-gnu
>>>> --with-boot-jdk=/shared/projects/openjdk/jdks/sapmachine17
>>>>
>>> --with-build-jdk=/shared/projects/openjdk/jdk-jdk/output-release/images/jdk 
>>>
>>>> --with-gtest=/shared/projects/openjdk/gtest/googletest
>>>> --with-debug-level=fastdebug
>>>>
>>>> The build jdk is a freshly build x64 release VM from the same source
>>> tree.
>>>> Am I missing something obvious? Is CDS archive generation even 
>>>> supported
>>>> for crossbuilds?
>>> It needs the generate run-time to execute "java -Xshare:dump" so I 
>>> don't
>>> expect so. hotspot-runtime-dev is probably the place to discuss the
>>> details. BTW: this came up recently in the context of the jlink plugin
>>> that generates the CDS archive. The plugin needed a check to ensure 
>>> that
>>> the target platform matched the current platform as it could launch the
>>> target VM to create the dump.
>>>
>>>
>> Thinking for a second, probably it cannot work since we copy binary
>> structures verbatim to the archive; I guess the chance that they are 
>> binary
>> compatible between platforms is very small. But it should be easily
>> rectified by calling Xshare:dump on the target platform.
>>
>> Thank you!
>>
>> ..Thomas
>>
>>
>>> -Alan
>>>
>