Hello Zack!
0) According to your "arewemodulesyet" site, neither GCC nor Clang fully
supports modules yet, so I would suggest that developer effort is
best spent there *first.* Autotools probably *shouldn't* try to do
much of anything with incompletely implemented language features;
we've had bad luck with that in the past.
I think it is implemented so far that projects are asked to give it a
try and provide feedback. Without build system support only tiny proof
of concepts will be done.
1) Autoconf includes logic to probe for various compiler features and
for adequate support for various levels of the C and C++ standards.
These probes have a bunch of problems and they currently don't
include anything newer than about 2017 for either C or C++.
I think the probes have lost their relevance for more recent versions of
C++. Most new features have preprocessor macros corresponding to C++
language features (like __cpp_modules).
However, the biggest problem with them is NOT that they
are out of date, but that they do not allow the package being
configured to declare which edition of the language standard they
want. That needs to be addressed *before* we add any more editions,
because the current behavior of selecting the most recent edition the
compiler supports is known to be troublesome for big important things
like Postgres, and we don't want to make it worse.
Again, can we work with preprocessor macros? __cplusplus together with a
list of possible std= flags?
If you're interested in working on this yourself, or you know someone
who is, I would be happy to go into more detail. As things stand,
if nobody steps up to do the work, it is unlikely to get done soon.
I want to document the status quo. Maybe I can spark interest with others.
2) Besides an "is this feature available" probe, I don't know if any
support for C++ 2020 modules is even *necessary*, because I don't
know how they work. If any other changes are necessary, they would
probably need to happen in Automake and Libtool, not in Autoconf.
I expect different types of work for
1. using external libraries as modules within a Autotools project
2. using C++23 "import std"
3. Exposing modules from a Autotools project for others
Bye
Christoph
--
Most customers will not accept source code with compile errors in it.
Dan Saks, CppCon 2016 (https://youtu.be/D7Sd8A6_fYU)
