[aarch64-port-dev ] aarch64: jdk9: 8078245: fails to build from source

[Magnus Ihse Bursie]

Why not just for the library that needs it?

/Magnus

> 4 maj 2015 kl. 11:05 skrev Erik Joelsson <erik.joelsson at oracle.com>:
> 
> Hello,
> 
> I think this looks good enough. The flags handling is still a big mess so even if there were a better place for this, I couldn't say where.
> 
> /Erik
> 
>> On 2015-04-30 07:26, David Holmes wrote:
>> Hi Nevill,
>> 
>> Just realized this was sent to hotspot-dev (attempting bcc) but is not a hotspot issue. With your new approach this is a build issue so cc'ing build-dev.
>> 
>> The new approach seems better to me but build folk need to confirm the placement.
>> 
>> Thanks,
>> David
>> 
>>> On 29/04/2015 8:52 PM, Edward Nevill wrote:
>>>> On Fri, 2015-04-24 at 17:11 +1000, David Holmes wrote:
>>>> Hi Ed,
>>>> 
>>>>> On 21/04/2015 7:16 PM, Edward Nevill wrote:
>>>>> Hi,
>>>>> 
>>>>> The current jdk9 tip fails to build from source on aarch64 with the following error message
>>>>> 
>>>>> /home/ed/build/1504/dev/build/linux-aarch64-normal-server-release/support/native/java.desktop/libsplashscreen/pngrutil.o: In function `png_init_filter_functions':
>>>>> /home/ed/build/1504/dev/jdk/src/java.desktop/share/native/libsplashscreen/libpng/pngrutil.c:3947: undefined reference to `png_init_filter_functions_neon'
>>>>> collect2: error: ld returned 1 exit status
>>>>> 
>>>>> The following webrev gets it building again.
>>>>> 
>>>>> http://cr.openjdk.java.net/~enevill/8078245/webrev.00/
>>>> 
>>>> Shouldn't the guard be Aarch64 specific rather than just __arm__ ? I'm
>>>> also wondering how we would get __ARM_NEON defined but not __arm__?
>>> 
>>> On arm 32 bit gcc defines the symbol __ARM_NEON if the flag -mfpu=neon is specified. Since this is not specified as part of the OpenJDK build the symbol is not defined and the build succeeds.
>>> 
>>> On aarch64 the symbol __ARM_NEON is always defined (the theory being that aarch64 always supports Neon). Personally I think this is borken as it causes builds to fail (and not just OpenJDK, several other projects have had the same build failure - try googling the above error message). But we are stuck with gcc as it is.
>>> 
>>> However, I don't like the above fix because it not only modifies the jdk, it modifies an external component which is pulled into jdk, which means every time a new revision of linpng is pulled in, the patch will have to be applied again.
>>> 
>>> A better approach I think is to define the symbol PNG_ARM_NEON_OPT=0 in the build (only if aarch64).
>>> 
>>> The failing code in pngpriv.h reads
>>> 
>>> #ifndef PNG_ARM_NEON_OPT
>>> 
>>> ...
>>> 
>>> #  if (defined(__ARM_NEON__) || defined(__ARM_NEON)) && \
>>>    defined(PNG_ALIGNED_MEMORY_SUPPORTED)
>>> #     define PNG_ARM_NEON_OPT 2
>>> #  else
>>> #     define PNG_ARM_NEON_OPT 0
>>> #  endif
>>> #endif
>>> 
>>> So, if we just predefine PNG_ARM_NEON=0 in the build this will have the same effect as adding defined(__arm__) or !defined(__aarch64__) above.
>>> 
>>> The following patch webrev does this:-
>>> 
>>> http://cr.openjdk.java.net/~enevill/8078245/webrev.01/
>>> 
>>> If you are happy with this and if I could have another reviewer I will push this.
>>> 
>>> All the best,
>>> Ed.
>