[llvm-dev] [RFC] Increase minimum supported GCC version for building LLVM to 4.8

[Justin Bogner via llvm-dev]

Yes, Danny's response directly addressed my concerns, thanks. Sorry I wasn't explicit about that.

> On Oct 17, 2016, at 6:56 AM, Teresa Johnson <tejohnson at google.com> wrote:
> 
> Hi Justin,
> 
> Wanted to follow up to see if Danny's response or the other responses addressed your concerns. 
> 
> Rather than specific new features in gcc 4.8+, it is more an issue of 4.7 being stale, as evidenced by some of the issues reported here and in the thread I pointed to, and 4.8 being the version shipped with Linux distros. Gcc is currently at 6.X, so 4.7 is quite a few major releases ago (even taking into account the change in Gcc major release version numbering).
> 
> Thanks,
> Teresa
> 
>> On Wed, Oct 12, 2016 at 9:42 PM, Daniel Berlin via llvm-dev <llvm-dev at lists.llvm.org> wrote:
>> 
>> 
>>> On Wed, Oct 12, 2016 at 9:14 PM, Justin Bogner via llvm-dev <llvm-dev at lists.llvm.org> wrote:
>>> Teresa Johnson via llvm-dev <llvm-dev at lists.llvm.org> writes:
>>> > According to the documentation at
>>> > http://llvm.org/docs/GettingStarted.html#software, compiling LLVM with GCC
>>> > requires at least version 4.7.0. However, there are apparently several
>>> > problems building current LLVM/Clang with gcc 4.7.X. This proposal is to
>>> > increase the minimum required GCC to 4.8.
>>> 
>>> -1 unless it's particularly hard to fix the incompatibilities that have
>>> been introduced or there are strong pain points in supporting 4.7.4. We
>>> should only increase the minimum version of our host compilers if we
>>> have strong motivation to do so.
>> 
>> We do: Everyone we care about has already done so, including not just all developers, but all users anyone can find.
>> 
>> Nobody is testing or ensuring it builds with 4.7, nor is there any compelling reason anyone can give to do so
>> 
>> Testing with 4.7 would actually require people go and install non-default compilers for their long term supported distros in the buildbots, etc (that's a pain point right there).
>>  
>> Last i looked, 3.9 did  not even build with gcc 4.7, and not a single complaint, bug filed, etc.
>> 
>> (note: I haven't double checked this, it was definitely true at one point).
>> 
>> Even the case where someone noticed that Teresa points out is an odd case, and not a normal usage.
>> 
>> I think the above is a pretty strong motivation, even if it's not the typical motivation of "it adds x feature we want".
>> 
>> We can certainly offer support for 4.7  if we want to, but if we are offering 4.7 just because 4.8 doesn't have magical new features that we would upgrade to, that seems wrong.
>> We should offer support for 4.7 because someone actually wants it, and we care about that someone.
>> Otherwise, it fails the very trivial test of "who cares if we support 4.7 or not"
>> 
>> 
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> 
> 
> 
> -- 
> Teresa Johnson |	 Software Engineer |	 tejohnson at google.com |	 408-460-2413
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