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Re: Meeting on February 4th at 9AM Pacific

From: Tom Honermann <tom_at_[hidden]>
Date: Fri, 4 Feb 2022 12:57:58 -0500
On 2/4/22 12:08 PM, Gabriel Dos Reis via SG15 wrote:
>
> [Tom]
>
> * I'm struggling with this one though. Modules are needed at parse
> time. Placing them in link-time artifacts seems too late in the
> tooling pipeline; a compiler may not know how to extract them from
> archives or shared objects.
>
> I donít follow.† At install time (or when the modules is built and
> distributed), exactly why putting the needed information in the
> distributed artifact matters where its use it at compile-time?† All
> you need is that the toolset gives you the mean to extract the
> information you need.† For example, GCC already provides some of
> that.† MSVC has always been planned to be doing that too.
>
My (possibly incorrect) understanding of your statement was that the
compiler would have the ability to extract module artifacts directly
from the link-time artifacts. That would create friction with other
tools by imposing on them a requirement to be able to do such extraction
themselves, or to use an implementor specific tool to extract the
information. In either case, that imposes implementation specific
requirements on such tools. I'd prefer a solution that allows tools to
perform module artifact discovery without having to be customized for
every implementation.

> * It also complicates the search for module artifacts by adding more
> sources;
>
> Why is that an additional source if the information is embedded in the
> needed artifact (.a or .so or whatever)?
>
Because those module artifacts may be present in multiple such artifacts
or also be present in a .bmi or .ifc file specified on the command line
or present in a search path. Which one wins?
>
> Is the .d.json the additional source youíre worried about?
>
No.

Tom.

> -- Gaby
>
> *From:* Tom Honermann <tom_at_[hidden]>
> *Sent:* Friday, February 4, 2022 9:03 AM
> *To:* sg15_at_[hidden]; Olga Arkhipova <olgaark_at_[hidden]>
> *Cc:* Gabriel Dos Reis <gdr_at_[hidden]>
> *Subject:* Re: [SG15] Meeting on February 4th at 9AM Pacific
>
> On 2/4/22 11:39 AM, Gabriel Dos Reis via SG15 wrote:
>
> We also need to account for scenarios where one single container
> hosts several BMIs (for several modules),
>
> That seems reasonable.
>
> or where the BMI is embedded either in the .a or the .so (or
> equivalent) to provide self-describing artifacts less disconnected
> (your header units arenít out-of-sync with the object files
> anymore).† I donít think that does violence to the unixy world.
>
> I'm struggling with this one though. Modules are needed at parse time.
> Placing them in link-time artifacts seems too late in the tooling
> pipeline; a compiler may not know how to extract them from archives or
> shared objects. It also complicates the search for module artifacts by
> adding more sources; do you search for matching modules by BMIs named
> on the command line first, then in linker artifacts? Or perhaps in the
> order that they appear on the command line? If so, that has
> implications for '-lmylib' vs '-Wl,-lmylib'.
>
> Tom.
>
> -- Gaby
>
> *From:* SG15 <sg15-bounces_at_[hidden]>
> <mailto:sg15-bounces_at_[hidden]> *On Behalf Of *Steve Downey
> via SG15
> *Sent:* Thursday, February 3, 2022 5:44 PM
> *To:* Olga Arkhipova <olgaark_at_[hidden]>
> <mailto:olgaark_at_[hidden]>
> *Cc:* Steve Downey <sdowney_at_[hidden]> <mailto:sdowney_at_[hidden]>;
> ISO C++ Tooling Study Group <sg15_at_[hidden]>
> <mailto:sg15_at_[hidden]>
> *Subject:* Re: [SG15] Meeting on February 4th at 9AM Pacific
>
> On Thu, Feb 3, 2022 at 8:07 PM Olga Arkhipova
> <olgaark_at_[hidden] <mailto:olgaark_at_[hidden]>> wrote:
>
> The compiler will have to find all BMIs so their locations
> should be defined by some command line options.
>
> My point is that the same options can be used to find the
> .d.json files.
>
> Thanks,
>
> Olga
>
> I agree that if the build system can figure out how to do one, it
> can do the other, as long as there is some discernible
> relationship between the bmi and the .d.json file. But in a
> typical unixy environment, libraries and other artifacts to be
> consumed are not separated out. Perhaps, though the bmi and
> .d.json both live together in an isolated filesystem-like thing
> based on the module name? E.g. a directory or zip file, or some
> such. On the other hand, since .d.json is intended to be portable,
> I would expect to find it in something like
> /usr/share/module_${name} in an FHS style system? Or if a library
> provides multiple modules, underneath /usr/share/lib${name}/?
>
> Replace /usr with /usr/local/, ~, ${etcetera}, etc above.
>
> (sorry I sent this only to Olga, now replying on list, Olga if you
> reply, either here or add the list back?)
>
>
>
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Received on 2022-02-04 17:57:59