[llvm-dev] Using C++14 code in LLVM

[Bruce Hoult via llvm-dev]

I personally don't have any problem with it if I can use the platform
compiler to build the compiler I use to build the LLVM I'm working on.

I don't need to use the platform compiler directly, and in fact I use the
above process *anyway* because I work on several different machines with
different OS versions and installed gccs, so I always build myself a local
copy of the exact same version of the gnu toolchain and libraries
everywhere and then use that to build LLVM. Although the resulting gnu
binaries are different on different machines this ensures the LLVM ones are
the same (or near enough) everywhere.

On Fri, May 11, 2018 at 9:30 AM, Andrew Kelley via llvm-dev <
llvm-dev at lists.llvm.org> wrote:

> I'll add my considerations as a frontend which depends on LLVM.
>
> It is a goal of Zig to keep the bootstrapping process to a minimum number
> of steps (See https://github.com/zig-lang/zig/issues/853).
>
> However, we will always depend on LLVM, Clang, and LLD. So that means the
> bootstrapping process of these 3 projects are inherently intertwined. From
> the perspective of bootstrapping, ability to build with older compilers is
> better.
>
> On Thu, May 10, 2018 at 5:21 PM, Chandler Carruth via llvm-dev <
> llvm-dev at lists.llvm.org> wrote:
>
>> On Thu, May 10, 2018 at 3:10 PM Zachary Turner <zturner at google.com>
>> wrote:
>>
>>> On Thu, May 10, 2018 at 1:50 PM Chandler Carruth via llvm-dev <
>>> llvm-dev at lists.llvm.org> wrote:
>>>
>>>> Last time this came up, there were a lot of people that were stuck on
>>>> GCC 4.9 due to ABI reasons. I think forcing that upgrade is going to be the
>>>> most disruptive part of this, and I think that will really need a decent
>>>> amount of time. =[
>>>>
>>>
>>> "a decent amount of time" is very vague though, and is a good way of
>>> stalling forward progress.
>>>
>>
>> Let's try to avoid implying bad intent. =/
>>
>>
>>>   How *much* time?  And when can we start the clock?
>>>
>>
>> I don't know. I can only speak to the use cases I'm aware of and care
>> about. Whoever wants to drive this change needs to get a lot more feedback
>> than just from me (IMO) about different users and whether a particular
>> schedule will work.
>>
>> And I already mentioned my schedule, but maybe not explicitly enough: the
>> primary platform I care about is planning to be off of libstdc++4.9 (the
>> tall poll of the tent for us) by the end of 2018. So it seems like right
>> after the branch in January 2019 would be fine for us to bump things up.
>> Anything earlier than this will be somewhere between extremely hard to
>> infeasible for us.
>>
>> At that point, we could probably go for C++17 as easily as C++14.
>>
>> But maybe my group is unique in that timing so we should really ask
>> others for input as well.
>>
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>>
>>
>
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