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

From: Mathias Stearn <redbeard0531+isocpp_at_[hidden]>
Date: Mon, 11 Dec 2023 12:26:10 +0100
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
> _______________________________________________
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> https://lists.isocpp.org/mailman/listinfo.cgi/sg15

Received on 2023-12-11 11:26:23