RFR: [XS] 8184338 : switch minimum supported gcc version to 4.8 - was : RE: jdk10 build : usage of -fno-var-tracking-assignments g++ flag in hotspot build

Wed Jul 19 05:29:21 UTC 2017

Hi Tim , Thanks !

-----Original Message-----
From: Tim Bell [mailto:tim.bell at oracle.com] 
Sent: Mittwoch, 19. Juli 2017 03:29
To: Baesken, Matthias <matthias.baesken at sap.com>; Erik Joelsson <erik.joelsson at oracle.com>; Simon Nash <simon at cjnash.com>; Simonis, Volker <volker.simonis at sap.com>
Cc: 'build-dev at openjdk.java.net' <build-dev at openjdk.java.net>; 'hotspot-dev at openjdk.java.net' <hotspot-dev at openjdk.java.net>; Zeller, Arno <arno.zeller at sap.com>
Subject: Re: RFR: [XS] 8184338 : switch minimum supported gcc version to 4.8 - was : RE: jdk10 build : usage of -fno-var-tracking-assignments g++ flag in hotspot build

Hello -

This fix has been pushed to OpenJDK jdk10/jdk10:

    http://hg.openjdk.java.net/jdk10/jdk10/rev/49a15c503104

Tim

On 07/18/17 03:36, Baesken, Matthias wrote:
> Ping :  could someone from oracle please push it ?
> (reason is that it touches the generated-configure.sh   files )
>
> Thanks, Matthias
>
>
> -----Original Message-----
> From: Baesken, Matthias
> Sent: Freitag, 14. Juli 2017 17:05
> To: 'Erik Joelsson' <erik.joelsson at oracle.com>; Simon Nash <simon at cjnash.com>
> Cc: 'build-dev at openjdk.java.net' <build-dev at openjdk.java.net>; 'hotspot-dev at openjdk.java.net' <hotspot-dev at openjdk.java.net>; Zeller, Arno <arno.zeller at sap.com>
> Subject: RE: RFR: [XS] 8184338 : switch minimum supported gcc version to 4.8 - was : RE: jdk10 build : usage of -fno-var-tracking-assignments g++ flag in hotspot build
>
> Thanks , can you push it ( as far as I know someone from Oracle needs to push it because generated-configure.sh  is changed ) ?
>
> Best regards, Matthias
>
>
>
> -----Original Message-----
> From: Erik Joelsson [mailto:erik.joelsson at oracle.com]
> Sent: Freitag, 14. Juli 2017 14:43
> To: Baesken, Matthias <matthias.baesken at sap.com>; Simon Nash <simon at cjnash.com>
> Cc: 'build-dev at openjdk.java.net' <build-dev at openjdk.java.net>; 'hotspot-dev at openjdk.java.net' <hotspot-dev at openjdk.java.net>; Zeller, Arno <arno.zeller at sap.com>
> Subject: Re: RFR: [XS] 8184338 : switch minimum supported gcc version to 4.8 - was : RE: jdk10 build : usage of -fno-var-tracking-assignments g++ flag in hotspot build
>
> This looks good to me.
>
> /Erik
>
>
> On 2017-07-14 13:47, Baesken, Matthias wrote:
>> After Simons question , I checked   that  the jdk10 builds  still works  with gcc 4.7 on linux x86_64 as well .
>> And created a new webrev  :
>>
>> http://cr.openjdk.java.net/~mbaesken/webrevs/8184338.1/
>>
>> - check adjusted to minimum gcc 4.7
>> - common/doc/building.md    adjusted  (the part talking about gcc versions)
>>
>>
>> Best regards, Matthias
>>
>>
>>
>> -----Original Message-----
>> From: Baesken, Matthias
>> Sent: Freitag, 14. Juli 2017 08:36
>> To: 'Simon Nash' <simon at cjnash.com>
>> Cc: Erik Joelsson <erik.joelsson at oracle.com>; 'build-dev at openjdk.java.net' <build-dev at openjdk.java.net>; 'hotspot-dev at openjdk.java.net' <hotspot-dev at openjdk.java.net>; Zeller, Arno <arno.zeller at sap.com>
>> Subject: RE: RFR: [XS] 8184338 : switch minimum supported gcc version to 4.8 - was : RE: jdk10 build : usage of -fno-var-tracking-assignments g++ flag in hotspot build
>>
>>> I am currently building JDK 9 for arm32 (hard float and soft float) using
>>> a Linaro GCC 4.7 cross-compiler (binary download).  What is the reason that
>>> this cannot be supported for JDK 10?
>> Hi Simon,
>>      reason was that  we know gcc-4.8 works nicely because we do a lot of builds (+tests) with this compiler .
>> For gcc 4.7 we just do not know  ( but for old 4.3 / 4.4  it was obvious that the current flags do not work any more).
>> If you are using a gcc  compiler < 4.8 only a warning is reported , it does not mean that you cannot build  any more.
>>
>> My first  suggestion was  :
>>
>>>>> ( e.g. change to minimum gcc   4.6 or gcc  4.7  supporting the flags used in the build )
>>    So if you see a benefit to  test for minimum gcc 4.7 and not 4.8  I am fine with this too (Erik what do you think?).
>> We at SAP just cannot tell  that gcc 4.7 still works (because our builds do not use it).
>>
>> Best regards, Matthias
>>
>>
>>
>> -----Original Message-----
>> From: Simon Nash [mailto:simon at cjnash.com]
>> Sent: Donnerstag, 13. Juli 2017 21:56
>> To: Baesken, Matthias <matthias.baesken at sap.com>
>> Cc: Erik Joelsson <erik.joelsson at oracle.com>; 'build-dev at openjdk.java.net' <build-dev at openjdk.java.net>; 'hotspot-dev at openjdk.java.net' <hotspot-dev at openjdk.java.net>; Zeller, Arno <arno.zeller at sap.com>
>> Subject: Re: RFR: [XS] 8184338 : switch minimum supported gcc version to 4.8 - was : RE: jdk10 build : usage of -fno-var-tracking-assignments g++ flag in hotspot build
>>
>> I am currently building JDK 9 for arm32 (hard float and soft float) using
>> a Linaro GCC 4.7 cross-compiler (binary download).  What is the reason that
>> this cannot be supported for JDK 10?
>>
>> Best regards,
>> Simon
>>
>> On 13/07/2017 14:40, Baesken, Matthias wrote:
>>> Hi Erik, I prepared the change :
>>>
>>> http://cr.openjdk.java.net/~mbaesken/webrevs/8184338/
>>>
>>> bug :
>>>
>>> https://bugs.openjdk.java.net/browse/JDK-8184338
>>>
>>> Asking for review(s) ...
>>>
>>>
>>> Best regards, Matthias
>>>
>>>
>>>
>>>
>>> -----Original Message-----
>>> From: Erik Joelsson [mailto:erik.joelsson at oracle.com]
>>> Sent: Donnerstag, 13. Juli 2017 13:34
>>> To: Baesken, Matthias <matthias.baesken at sap.com>; 'build-dev at openjdk.java.net' <build-dev at openjdk.java.net>; 'hotspot-dev at openjdk.java.net' <hotspot-dev at openjdk.java.net>
>>> Subject: Re: jdk10 build : usage of -fno-var-tracking-assignments g++ flag in hotspot build
>>>
>>> Hello,
>>>
>>> That would be the correct place. If you prepare the change and send the
>>> review I can sponsor the push.
>>>
>>> /Erik
>>>
>>> On 2017-07-13 13:16, Baesken, Matthias wrote:
>>>> Hi Erik,
>>>>
>>>>> AFAIK, the only reason we support GCC versions older than 4.9 is for you
>>>>> guys at SAP, so if you would suggest dropping support, that would of
>>>>> course be the simplest solution.
>>>>      for jdk10  it is fine for us to  use  minimum gcc 4.8  . That would be probably the most simple solution to avoid running into the  "-fno-var-tracking-assignments"  issue
>>>>     ( I now and then run into it when I forget to set the PATH to gcc-4.8 one should use for compiling on the SLES11 machine, so I pick up instead the default gcc 4.3.4 from the machine  ,
>>>> configure works nicely and then the build fails in the middle of the HS make )
>>>>
>>>> autoconf/toolchain.m4
>>>>
>>>> TOOLCHAIN_MINIMUM_VERSION_gcc="4.8"
>>>>
>>>> Is there right place to  adjust I think, I guess we need someone for Oracle to regenerate the generated-configure.sh files ?
>>>>
>>>> Best regards, Matthias
>>>>
>>>>
>>>>
>>>>
>>>> -----Original Message-----
>>>> From: Erik Joelsson [mailto:erik.joelsson at oracle.com]
>>>> Sent: Donnerstag, 13. Juli 2017 11:59
>>>> To: Baesken, Matthias <matthias.baesken at sap.com>; 'build-dev at openjdk.java.net' <build-dev at openjdk.java.net>; 'hotspot-dev at openjdk.java.net' <hotspot-dev at openjdk.java.net>
>>>> Subject: Re: jdk10 build : usage of -fno-var-tracking-assignments g++ flag in hotspot build
>>>>
>>>> Hello Matthias,
>>>>
>>>> AFAIK, the only reason we support GCC versions older than 4.9 is for you
>>>> guys at SAP, so if you would suggest dropping support, that would of
>>>> course be the simplest solution.
>>>>
>>>> If you want to keep support but make the use of this flag optional, the
>>>> preferred method is to add a test in flags.m4. We have macros defined
>>>> for this. FLAGS_COMPILER_CHECK_ARGUMENTS or
>>>> FLAGS_CXX_COMPILER_CHECK_ARGUMENTS would be suitable in this case. Use
>>>> it to check if the flag is valid for the current compiler. If so, you
>>>> can define a variable
>>>> "CXXFLAGS_GCC_NO_VAR_TRACKING_ASSIGNMENTS=-fno-var-tracking-assignment"
>>>> and empty otherwise, and in the makefile use this variable in the
>>>> assignement.
>>>>
>>>> We want to avoid static shell expressions in the makefiles if possible
>>>> and keep that kind of logic in configure. It's also better to explicitly
>>>> check for features rather than versions.
>>>>
>>>> /Erik
>>>>
>>>>
>>>> On 2017-07-13 11:21, Baesken, Matthias wrote:
>>>>> Hello,  when building jdk10 on Suse Linux 11 with default gcc/g++  4.3.4 installed, I was running into
>>>>> compilation errors because of the  missing support for  g++ flag -fno-var-tracking-assignments .
>>>>>
>>>>> It seems gcc-4.6  has the -fvar-tracking-assignments / -fnovar-tracking-assignments  flags , see
>>>>>
>>>>> https://gcc.gnu.org/onlinedocs/gcc-4.6.4/gcc/Option-Summary.html#Option-Summary
>>>>>
>>>>> I have no gcc-4.6 at hand but could verify that gcc-4.7 and gcc-4.8 "know" the flag.
>>>>> There are various solutions one could do  to avoid  the  compilation error .
>>>>>
>>>>>
>>>>> 1) disallow usage of old gcc versions here :
>>>>>
>>>>> autoconf/toolchain.m4
>>>>>
>>>>> TOOLCHAIN_MINIMUM_VERSION_gcc="4.3"
>>>>>
>>>>> ( e.g. change to minimum gcc   4.6 or gcc  4.7  supporting the flags used in the build )
>>>>>
>>>>>
>>>>> 2) remove the flag  -fno-var-tracking-assignments for older gcc versions here :
>>>>> (in a similar way it was done :  http://hg.openjdk.java.net/jdk9/jdk9/hotspot/rev/37e693211deb  )
>>>>>
>>>>> hotspot/make/lib/JvmOverrideFiles.gmk-32-ifeq ($(TOOLCHAIN_TYPE), gcc)
>>>>> hotspot/make/lib/JvmOverrideFiles.gmk:33:  BUILD_LIBJVM_vmStructs.cpp_CXXFLAGS := -fno-var-tracking-assignments -O0
>>>>> hotspot/make/lib/JvmOverrideFiles.gmk:34:  BUILD_LIBJVM_jvmciCompilerToVM.cpp_CXXFLAGS := -fno-var-tracking-assignments
>>>>> hotspot/make/lib/JvmOverrideFiles.gmk-35-endif
>>>>>
>>>>> What is your preferred solution ?
>>>>>
>>>>>
>>>>> Thanks, Matthias
>>>>>
>>>>>
>