RFR: JDK-8167479: arm 32/64 slowdebug fails to build on unpack200

[Magnus Ihse Bursie]

On 2016-10-12 13:07, David Holmes wrote:
>
>
> On 12/10/2016 7:04 PM, Magnus Ihse Bursie wrote:
>> On 2016-10-12 04:38, David Holmes wrote:
>>> On 11/10/2016 7:41 PM, Erik Joelsson wrote:
>>>> Hello,
>>>>
>>>> After the cleanup of C++ linking with the GCC toolchain. We missed
>>>> updating one instance with the correct TOOLCHAIN configuration. This
>>>> leads to build failures for arm ports with slowdebug. I have no 
>>>> idea why
>>>> it only happens there, but correcting the TOOLCHAIN configuration (so
>>>> that g++ is used to link instead of gcc) makes it build again.
>>>
>>> Unexplained errors raise alarm bells for me. This particular reference
>>> relates to C++ exception handling which raises questions:
>>>
>>> - why only on this platform?
>>> - why only in slowdebug?
>>> - why only in this code? (which seems unrelated to exceptions)
>>>
>>> I agree the fix is to use g++ instead of gcc for linking, assuming the
>>> exception related code should actually be there.
>> The alarm bells ringed for me too. :-) I actually started debugging this
>> one, but Erik beat me to it. :) I did however conclude that this error
>> occured due to static linking (without it, everything went fine) and if
>> I explicitely specified -lstdc++ as well, I got a more informative
>> error, telling me that the static version of libgcc was not found. I
>> didn't go further, since Erik found the (correct) solution, but I assume
>> that the devkit we use to build for the arm platforms are missing some
>> bits, which was only needed for slowdebug builds.
>
> Still too vague for me. What is special about this code?
I have no idea. The question should probably be rephrased: "Why does 
this work on all the other platforms, when it's obviously incorrect?" 
And the answer to that is most likely "*shrug* ... pure luck?".

/Magnus

>
> Thanks,
> David
>
>> /Magnus
>>
>>>
>>> Thanks,
>>> David
>>>
>>>> The build error looks like this:
>>>>
>>>> /localhome/hg/jdk9-dev-CDR/build/linux-arm64-slowdebug/support/native/jdk.pack200/unpackexe/bands.o:(.data.DW.ref.__gxx_personality_v0[DW.ref.__gxx_personality_v0]+0x0): 
>>>>
>>>>
>>>> undefined reference to `__gxx_personality_v0'
>>>> collect2: error: ld returned 1 exit status
>>>>
>>>> Bug: https://bugs.openjdk.java.net/browse/JDK-8167479
>>>>
>>>> Webrev: http://cr.openjdk.java.net/~erikj/8167479/webrev.01/
>>>>
>>>> /Erik
>>>>
>>