[llvm-dev] Are C++17 host applications supported?

Chandler Carruth via llvm-dev llvm-dev at lists.llvm.org
Tue Nov 26 10:57:52 PST 2019

On Tue, Nov 26, 2019 at 10:51 AM Reid Kleckner <rnk at google.com> wrote:

> It looks like this was added here:
> https://github.com/llvm/llvm-project/commit/aa60b3fd875c3df1f23b9d4f491c08888e48d823
> IIRC Abseil has a similar problem, and they chose not to support the use
> case of ABI compat between TUs with different standard versions.

FWIW, they did this because it is *hard*.

> Personally, IMO LLVM should support this use case.

FWIW, I think that LLVM should make the same decision as Abseil in general
here. ABI compatibility between TUs with different standard versions is
extremely hard IMO if you care deeply about inlining.

> I think it was a mistake to add inline functions to Compiler.h, which is
> supposed to be all about feature detection and macro definitions.

Sure, happy to see the inline functions moved elsewhere. However, I think
we'll find that will just kick the can down the road. I don't think it will
fully address the underlying issues here.

> Alternatively if people want to keep things the way they are, we should
> change LLVM's CMake to build with C++17 if it is supported. If the user can
> link against LLVM and enable C++17, then the standard library shared by the
> user and LLVM *must* have an aligned allocation function.
> Either way, I don't think the user should have to do anything.
> On Mon, Nov 25, 2019 at 3:04 AM Machiel van Hooren via llvm-dev <
> llvm-dev at lists.llvm.org> wrote:
>> Hi,
>> I am using the llvm libraries compiled with the C++14 standard with a
>> host application that is compiled with the C++17 standard (Both on
>> Windows/MSVC). I am running into an incompatibility for which I filed a
>> bug report: https://bugs.llvm.org/show_bug.cgi?id=44131
>> However, I was wondering if C++17 host applications are even supported?
>> Regards,
>> Machiel van Hooren
>> _______________________________________________
>> LLVM Developers mailing list
>> llvm-dev at lists.llvm.org
>> https://lists.llvm.org/cgi-bin/mailman/listinfo/llvm-dev
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