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Re: Scheduling a virtual meeting to discuss where the std module source file should live

From: Jayesh Badwaik <jayesh_at_[hidden]>
Date: Mon, 11 Dec 2023 15:04:04 +0100
In my experience, it is not rare to get compiler from library package
manager and would be an important use case. This is how a large community
of HPC developers for example get their compilers (spack and easy build for

On Mon, 11 Dec 2023, 12:26 Mathias Stearn, <redbeard0531+isocpp_at_[hidden]>

> Can we please be explicit about which kind of "package manager" is being
> referred to whenever we use that term? Are we talking about a system
> package manager (yum, apt, pacman, brew, winget etc) or a C++/library
> package manager (conan, vcpkg, cpm, etc)? This whole thread seems very
> ambiguous. I _think_ most people are talking about library package
> managers, but references to the FHS imply otherwise.
> Right now it is very common to get a compiler and stdlib from the system
> package manager on linux. I think it is fairly rare right now to get the
> stdlib from a library package manager, although it would be nice if it were
> simple and easy to do so. To support std modules with the status quo
> environment, we need to work with system package managers. We will probably
> need to support other modules through them eventually, but it seems a both
> harder and a bit less urgent. The opposite seems to be the case for library
> package managers, where supporting non-std modules is probably a higher
> priority than the std module.
> On Mon, Dec 11, 2023 at 7:27 AM Jayesh Badwaik via SG15 <
> sg15_at_[hidden]> wrote:
>> I am not sure I get where this is coming from. The question is about
>> being able to distribute and find a c++ compiler through a package manager.
>> In order to make things uniform, the posts also want system compiler to
>> provide the same CPS interface.
>> Dependency would have been when it would have been necessary to install
>> system compiler with a package manager.
>> On Mon, 11 Dec 2023, 00:57 Gabriel Dos Reis via SG15, <
>> sg15_at_[hidden]> wrote:
>>> Are we establishing a package manager as a dependency for a C++ compiler
>>> (which typically is also the system compiler)?
>>> -- Gaby
>>> ------------------------------
>>> *From:* SG15 <sg15-bounces_at_[hidden]> on behalf of Steve Downey
>>> via SG15 <sg15_at_[hidden]>
>>> *Sent:* Sunday, December 10, 2023 12:01:12 PM
>>> *To:* Mark de Wever <koraq_at_[hidden]>
>>> *Cc:* Steve Downey <sdowney_at_[hidden]>; ISO C++ Tooling Study Group <
>>> sg15_at_[hidden]>
>>> *Subject:* Re: [SG15] Scheduling a virtual meeting to discuss where the
>>> std module source file should live
>>> All the flags that make the BMI unusable make binaries unusable, in the
>>> general case. That standard libraries manage to avoid that is exceptional.
>>> Package managers ought to be able to do this, and an install $prefix is
>>> the purview of a package manager. This is, of course, slightly to the side
>>> of where the interface is source lives.
>>> But if a hello world project has to build the standard library, modules
>>> as a normal feature are DOA as a practical matter.
>>> On Sun, Dec 10, 2023, 14:44 Mark de Wever <koraq_at_[hidden]> wrote:
>>> On Sun, Dec 10, 2023 at 11:40:59AM -0500, Steve Downey wrote:
>>> > Does the std module use the same .a/.so as as headers?
>>> Yes this is the library shipped by the vendor.
>>> > How does that work with headers and -fno-exception, or does that have
>>> > to be taken care of today by the user?
>>> I'm not sure, I've no experience with systems where exceptions are
>>> disabled. Most of libc++'s configuration options do not modify the
>>> compilation flags.
>>> > The other question is if the interface goes in include/ or
>>> share/libc++ for
>>> > FHS like layout, and then is it possible to deploy a commonly used BMI
>>> into
>>> > lib or libexec.
>>> We don't want to deploy BMI files. In Clang BMI's have the same
>>> limitations as precomiled headers; almost all compilation flags makes
>>> BMIs incompatible. The build system needs to build the BMIs from the
>>> module source files. For example, std.cppm.
>>> > FHS implicitly assumes a coherent installation within a $prefix, which
>>> also
>>> > means that ABI affecting flags are fixed, so system compilers ought to
>>> be
>>> > able to at least pre build the system std modules.
>>> At least for now that's not possible with Clang. I'm not sure whether it
>>> ever be possible. For example, changing -std=c++xx flag changes the
>>> exported named declarations of the module.
>>> Cheers,
>>> Mark
>>> _______________________________________________
>>> SG15 mailing list
>>> SG15_at_[hidden]
>>> https://lists.isocpp.org/mailman/listinfo.cgi/sg15
>> _______________________________________________
>> SG15 mailing list
>> SG15_at_[hidden]
>> https://lists.isocpp.org/mailman/listinfo.cgi/sg15

Received on 2023-12-11 14:04:17