Fail to cross compiling jdk12 for mips64el-linux-gnu target

[David Holmes]

On 24/01/2019 1:51 pm, Ao Qi wrote:
> Hi David,
> 
> On Thu, Jan 24, 2019 at 10:47 AM David Holmes <david.holmes at oracle.com> wrote:
>>
>> Hi Leslie,
>>
>> I'm not Erik :) however ....
>>
>> On 24/01/2019 12:28 pm, Leslie Zhai wrote:
>>> Hi Erik,
>>>
>>> Because the flags' macro of MIPS is different from other targets[1], it
>>> will effect the `UnixConstants` of
>>> src/java.base/unix/classes/sun/nio/fs/UnixConstants.java.template, for
>>> example, PREFIX_O_APPEND, so the `Flags` in `FileChannel` is different
>>> from other targets.  Then failed[2] to cross compiling jdk12 for
>>> mips64el-linux-gnu target by following the document[3].
>>
>> It's been quite a while since we built for a platform where the flags
>> had different values, but it is supposed to work. I suspect that the way
>> we build now with the module system may not be quite correct in this
>> regard - but that is just supposition on my part. Because compile-time
>> constants are stored directly into class files that use them, we have to
>> generate UnixConstants.java before compiling any class that needs to use
>> it, then we must compile all classes that do use it. Those classes must
>> only be executed in conjunction with a tool executing on the target
>> platform (javac, jmod etc). My suspicion is that we may be executing a
>> tool on the build platform using the newly compiled classes for the
>> target platform - and that would be wrong.
>>
> 
> Yes. Some variables in UnixConstants.java is defined according to the
> target (fcntl.h of mips in this case), but would be executed on host
> (x86 in this case) during "make images". These variables of ppc64le,
> aarch64 and s390x are the same as x86, but the ones of mips are not.
> However, mips is not an official supported target and I did not find
> other targets have similar issue, I am not sure if this is a bug or if
> this is the right mailing list :)

This is the right mailing list to discuss. :)

So I went back to find when this happened in the past and I 
mis-remembered how we solved it. We previously had a problem with the 
Oracle Java SE Embedded PPC port where some Linux PPC-e500v2 platforms 
defined a different value for the O_NOFOLLOW and O_DIRECT flags. The 
solution then was to commit a platform specific version of 
UnixConstants.java and change the build system to only use the template 
file if there was not a pre-existing .java file. But that platform and 
the SE Embedded support was all removed. (SocketOptions.java had a 
similar problem.) Further that build logic is completely different to 
what we had back then (JDK 6/7).

This is definitely a bug in our build logic IMHO as we specifically use 
the build platform c-pre-processor to process the template file based on 
the target header files, but then use the resulting class when running 
tools on the build platform. This was not something that happened in 6/7 
or even 8 and I think the module system tools are where the issue now lies.

I think Erik and/or Magnus will have to give advice on how this may be 
properly fixed. I can't see any simple solution.

David
-----

>   For example:
> 
> jdk/build$ find . -name UnixConstants.java | xargs grep -A2 O_APPEND
> ./linux-ppc64le-server-release/support/gensrc/java.base/sun/nio/fs/UnixConstants.java:
>     static final int O_APPEND =
> ./linux-ppc64le-server-release/support/gensrc/java.base/sun/nio/fs/UnixConstants.java-
> ./linux-ppc64le-server-release/support/gensrc/java.base/sun/nio/fs/UnixConstants.java-
>                                       02000
> --
> ./linux-x86_64-server-release/support/gensrc/java.base/sun/nio/fs/UnixConstants.java:
>     static final int O_APPEND =
> ./linux-x86_64-server-release/support/gensrc/java.base/sun/nio/fs/UnixConstants.java-
> ./linux-x86_64-server-release/support/gensrc/java.base/sun/nio/fs/UnixConstants.java-
>                                       02000
> --
> ./linux-s390x-server-release/support/gensrc/java.base/sun/nio/fs/UnixConstants.java:
>     static final int O_APPEND =
> ./linux-s390x-server-release/support/gensrc/java.base/sun/nio/fs/UnixConstants.java-
> ./linux-s390x-server-release/support/gensrc/java.base/sun/nio/fs/UnixConstants.java-
>                                       02000
> --
> ./linux-aarch64-server-release/support/gensrc/java.base/sun/nio/fs/UnixConstants.java:
>     static final int O_APPEND =
> ./linux-aarch64-server-release/support/gensrc/java.base/sun/nio/fs/UnixConstants.java-
> ./linux-aarch64-server-release/support/gensrc/java.base/sun/nio/fs/UnixConstants.java-
>                                       02000
> --
> ./linux-x86_64-zero-release/support/gensrc/java.base/sun/nio/fs/UnixConstants.java:
>     static final int O_APPEND =
> ./linux-x86_64-zero-release/support/gensrc/java.base/sun/nio/fs/UnixConstants.java-
> ./linux-x86_64-zero-release/support/gensrc/java.base/sun/nio/fs/UnixConstants.java-
>                                       02000
> --
> ./linux-mips64el-zero-release/support/gensrc/java.base/sun/nio/fs/UnixConstants.java:
>     static final int O_APPEND =
> ./linux-mips64el-zero-release/support/gensrc/java.base/sun/nio/fs/UnixConstants.java-
> ./linux-mips64el-zero-release/support/gensrc/java.base/sun/nio/fs/UnixConstants.java-
>                                       0x0008
> --
> ./linux-ppc64le-zero-release/support/gensrc/java.base/sun/nio/fs/UnixConstants.java:
>     static final int O_APPEND =
> ./linux-ppc64le-zero-release/support/gensrc/java.base/sun/nio/fs/UnixConstants.java-
> ./linux-ppc64le-zero-release/support/gensrc/java.base/sun/nio/fs/UnixConstants.java-
>                                       02000
> 
> log.mips:2of path:
> /home/loongson/aoqi/jdk-mips/build/linux-mips64el-normal-server-release/support/interim-jmods/temp/.java.base.jmod.tmp
> oflags: 769 O_TRUNC:512 O_APPEND:8 O_CREAT:256 O_EXCL:1024
> log.ppc:2of path:
> /home/loongson/aoqi/jdk-mips/build/linux-ppc64le-normal-server-release/support/interim-jmods/temp/.java.base.jmod.tmp
> oflags: 577 O_TRUNC:512 O_APPEND:1024 O_CREAT:64 O_EXCL:128
> 
> Cheers,
> Ao Qi
>