had me at What to do with C++
What to do with C++ modules?
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Re: What to do with C++ modules?
#52Back in the 90s, I implemented precompiled headers for my C++ compiler (Symantec C++). They were very much like modules. There were two modes of operation: 1. all the .h files were compiled, and emitted as a binary that could be rolled in all at once 2. each .h file created its own precompiled header. Sounds like modules, right? Anyhow, I learned a lot, mostly that without semantic improvements to C++, while it made…
What has to change in C++ templates for this to work? It seems particularly tricky to define a template in a module and then instantiate it or specialize it somewhere else.
I think modularization of templates is really hard. Best thing I can think of is a cache e.g. for signatures. But then again this is basically what the mangling already does anyways in my understanding.
Re: What to do with C++ modules?
#53Earlier quoted context omitted.
Have a look at any serious job postings. C++ jobs outnumber Rust jobs somewhere around 50:1. Internet hype meets actual industry reality :-).
Or could it be (or to be a bit of devil's advocate) that Rust projects require only 2% (1/50) of manpower, comparing the same project using C++?
I couldn't even tell if you are joking. Rust is weird, its like a programming language people developed a parasocial relationship with. If a Twitch streamer was a programming language it would be Rust. Perhaps its just people being immature I don't know.
Re: What to do with C++ modules?
#54Earlier quoted context omitted.
What has to change in C++ templates for this to work? It seems particularly tricky to define a template in a module and then instantiate it or specialize it somewhere else.
In order to make things work smoothly, the module has to have its own namespace, and a namespace that is closed. D also has an `alias` feature, where you can do things like: alias Q = abc.T; where from then on, `abc.T` can be referred to simply as `Q`. This also eliminates a large chunk of purpose behind the preprocessor.
Neat, closed namespaces sound great!
C++ has adapted the ‘using’ keyword now to seem fairly similar to alias, but can’t completely subsume macros unfortunately.
Re: What to do with C++ modules?
#55Earlier quoted context omitted.
What has to change in C++ templates for this to work? It seems particularly tricky to define a template in a module and then instantiate it or specialize it somewhere else.
I think modularization of templates is really hard. Best thing I can think of is a cache e.g. for signatures. But then again this is basically what the mangling already does anyways in my understanding.
Not just signatures, you need the whole AST more or less.
This seems incredibly wasteful, but of course still marginal better than just #including code which is the alternative.
Re: What to do with C++ modules?
#56Earlier quoted context omitted.
There is a big big difference between C and C++. The article is about C++, which is being replaced by Rust imho. C is different, and far more frequently used for embedded or OS development. Don't know about games, but last I looked, stuff like unity was C#, so something else yet again.
It is a pitty that - GCC switched from C to C++ - CUDA switched from C to C++ But I can understand the decision, and at that time , C++ frontend features and libs were a little bit less horrible.
It's a pity?
Please explain in detail how alternatives would have worked better for GCC and CUDA. Also, if you could share some historical context about how those alternatives could realistically have been implemented at the time, that would be helpful too.
I love to hear all the "would've" and "should've" scenarios.
Re: What to do with C++ modules?
#57All that the C++ committee needed to do was just introduce "import" as "this is the same as include except no context can leak into it". Would have been dirt simple to migrate existing codebases over to using it (find and replace include with import, mostly), and initial implementations of it on the compiler side could have been nearly identical to what's already there, while offering some easy space for optimizing i…
That could be said of every additional c++ feature since c++0x. The committee has taken backwards compatibility, backwards - refusing to introduce any nuance change in favor of a completely new modus operandi. Which never jives with existing ways of doing things because no one wants to fix that 20 year old codebase.
if no one wants to fix this 20yo codebase, why is there someone who wants to push it to the new C++ standard?
Re: What to do with C++ modules?
#58Modules are unusable in real projects with real dependencies. Until that changes there’s no chance I’ll look at them.
how are modules related to dependencies in general? You can use your modules at the same time using dependencies via includes. And this works well.
Re: What to do with C++ modules?
#59I did C++ for over 10 years, and now have been doing rust for about 4. On the whole, I like rust much better, but I really miss header files. Modules are horrible for build times. If you change an implementation (i.e something that would not normally involve editing a header) the amount of rebuilding that happens is crazy, compared to any C++ project that was set up with a minimal amount of care.
What was it about headers?
In terms of rebuild performance in defining the interface vs implementation, there is interest in having rustc handle that automatically, see https://rust-lang.github.io/rust-project-goals/2025h2/relink...
Re: What to do with C++ modules?
#60I did C++ for over 10 years, and now have been doing rust for about 4. On the whole, I like rust much better, but I really miss header files. Modules are horrible for build times. If you change an implementation (i.e something that would not normally involve editing a header) the amount of rebuilding that happens is crazy, compared to any C++ project that was set up with a minimal amount of care.
D modules are very fast. Many of our customers rely on D being way faster than C++ to compile.
I often hear about a lot of advantages of D. So I don't understand why it is so unpopular.
Probably I need to give it a chance, but I'm unsure that I will find a real job with the D stack.