Problem with libomp (was supertux)

[Christopher Jones]

Hi,

c++ standard support in compilers isn’t always black and white. Compilers often claim to support a given standard, but then fail in some corner cases..

That said, in this case looking at

https://build.macports.org/builders/ports-10.8_x86_64-builder/builds/31506/steps/install-port/logs/stdio <https://build.macports.org/builders/ports-10.8_x86_64-builder/builds/31506/steps/install-port/logs/stdio>

I don’t see -std=c++11 in the list of compiler options, so as c++11 is not default for this old OS, it might just be a case of adding this

configure.cxxflags-append -std=c++11

Chris

> On 5 Dec 2020, at 1:03 pm, Ken Cunningham <ken.cunningham.webuse at gmail.com> wrote:
> 
> the std:atomic thing was added in 2018, so something else seems funny... clang-3.4 supports c++11 after all...
> 
> libomp probably should not be a dependency of clang at all
> 
> if it was separate from clang, it can be installed using the current toolchain rathervthan block it
> 
> K
> 
> On Dec 5, 2020, at 04:56, Chris Jones <jonesc at hep.phy.cam.ac.uk <mailto:jonesc at hep.phy.cam.ac.uk>> wrote:
> 
>> Hi,
>> 
>> The problem is simply the latest version uses std::atomic, which requires c++11, and the usual fix of requesting this c++ standard in the port file does not work due to the fact this port is a clang dependency, so using clang as a fallback compiler is not possible.
>> 
>> Note, the port already installs a different version for some systems, those using libstdc++ 
>> 
>> https://github.com/macports/macports-ports/blob/master/lang/libomp/Portfile <https://github.com/macports/macports-ports/blob/master/lang/libomp/Portfile>
>> 
>> So a relatively trivial fix would be to peg macOS 10.9 and older to the last version that builds there, version 10.x. Probably a bit simpler than having to deal with multiple libomp-X ports...
>> 
>> Chris
>> 
>>> On 5 Dec 2020, at 5:57 am, Ken Cunningham <ken.cunningham.webuse at gmail.com <mailto:ken.cunningham.webuse at gmail.com>> wrote:
>>> 
>>> 
>>>> 
>>>> Attempting to install supertux complains on libomp.
>>>> 
>>>> Logfile shows compiler complaints about atomic and variable templates.
>>>> 
>>> I noticed that the recent update to libomp-11 failed on 10.8 and 10.9 (and 10.6 and less).
>>> 
>>> This is not a big surprise — more likely a miracle that libomp up to 10.0 built without trouble on every system.
>>> 
>>> I will see if I can fix it — maybe I can — but even if so, libomp 12, 13, or … will be unbuildable eventually.
>>> 
>>> So we’ll need to come up with a libomp plan. There is really no reason (I think) that we can only have one libomp — we could install the one that comes with each llvm and then it would always work, I think. Eg clang-9 would use libomp-9.
>>> 
>>> Anyway, that is for the future. until libomp is fixed, every clang is dead on 10.8 and 10.9
>>> 
>>> BUT — good news. clang (and most everything else) doesn’t really need libomp anyway. I don’t even know why it is listed as a dependency, to be honest. Just delete from the clang portfile, and you’re good to go again, I think (haven’t tried it… but …).
>>> 
>>> Ken

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