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C++ Modules Are Here to Stay

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Re: C++ Modules Are Here to Stay

#31

Post by TimorousBestie »

juliangmp wrote: post #26
bluGill wrote: post #15

Earlier quoted context omitted.

If you tools are not updated that isn't the fault of C++. You will feel the same about Rust when forced to used a 15 year old version too (as I write this Rust 1.0 is only 10 years old). Don't whine to me about these problems, whine to your vendors until they give you the new stuff.

My experience with vendor toolchains is that they generally suck anyway. In a recent bare metal project I chose not to use the vendor's IDE and toolchain (which is just an old version of GCC with some questionable cmake scripts around it) and instead just cross compile with rust manually. And so far its been a really good decision.

Yep, this aligns with my experience. I’ve yet to take the plunge into cross compiling with rust though, might have to try that.

Re: C++ Modules Are Here to Stay

#32

Post by yunnpp »

cpburns2009 wrote: post #30
on_the_train wrote: post #3

Earlier quoted context omitted.

It's been the go-to syntax for 15 years now

Now I haven't touched C++ in probably 15 years but the definition of main() looks confused: > auto main() -> int Isn't that declaring the return type twice, once as auto and the other as int?

No. The auto there is doing some lifting so that you can declare the type afterwards. The return type is only defined once.

There is, however, a return type auto-deduction in recent standards iirc, which is especially useful for lambdas.

https://en.cppreference.com/w/cpp/language/auto.html

auto f() -> int; // OK: f returns int

auto g() { return 0.0; } // OK since C++14: g returns double

auto h(); // OK since C++14: h’s return type will be deduced when it is defined

Re: C++ Modules Are Here to Stay

#33

Post by yunnpp »

I recently started a pet project using modules in MSVC, the compiler that at present has best support for modules, and ran into a compiler bug where it didn't know how to compile and asked me to "change the code around this line".

So no, modules aren't even here, let alone to stay.

Never mind using modules in an actual project when I could repro a bug so easily. The people preaching modules must not be using them seriously, or otherwise I simply do not understand what weed they are smoking. I would very much appreciate to stand corrected, however.

Re: C++ Modules Are Here to Stay

#35

Post by pjmlp »

fooker wrote: post #29

C++ templates and metaprogramming is fundamentally incompatible with the idea of your code being treated in modules. The current solution chosen by compilers is to basically have a copy of your code for every dependency that wants to specialize something. For template heavy code, this is a combinatorial explosion.

It has worked perfectly fine while using VC++, minus the usual ICE that still come up.

Re: C++ Modules Are Here to Stay

#36

Post by pjmlp »

reactjs_ wrote: post #7

Here’s the thing I don’t get about module partitions: They only seem to allow one level of encapsulation. Program - Module - Module Partition whereas in module systems that support module visibility, like Rust’s, you can decompose your program at multiple abstraction levels: Program - Private Module - Private Module - Private Module - Public Module - Public Module Maybe I am missing something. It seems like you will…

Like most languages with modules.

Rust, Modula-2 and Ada are probably the only ones with module nesting.

Re: C++ Modules Are Here to Stay

#38

Post by jcranmer »

bluGill wrote: post #15
TimorousBestie wrote: post #12

I can’t deploy C++ modules to any of the hardware I use in the shop. Probably won’t change in the near-to-mid future. It seems likely I’ll have to move away from C++, or perhaps more accurately it’s moving away from me.

If you tools are not updated that isn't the fault of C++. You will feel the same about Rust when forced to used a 15 year old version too (as I write this Rust 1.0 is only 10 years old). Don't whine to me about these problems, whine to your vendors until they give you the new stuff.

> If you tools are not updated that isn't the fault of C++.

It kinda is. The C++ committee has been getting into a bad habit of dumping lots of not-entirely-working features into the standard and ignoring implementer feedback along the way. See https://wg21.link/p3962r0 for the incipient implementer revolt going on.

Re: C++ Modules Are Here to Stay

#40

Post by WalterBright »

fooker wrote: post #29

C++ templates and metaprogramming is fundamentally incompatible with the idea of your code being treated in modules. The current solution chosen by compilers is to basically have a copy of your code for every dependency that wants to specialize something. For template heavy code, this is a combinatorial explosion.

D has best-in-class templates and metaprogramming, and modules. It works fine.
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