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.

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senfiaj 3 hours ago | parent | next [-]

I still hope that modules become mature and safe for production code. Initially I coded in C/C++ and this header #include/#ifndef approach seemed OK at that time. But after using other programming languages, this approach started to feel too boilerplate and archaic. No sane programming language should require a duplication in order to export something (for example, the full function and its prototype), you should write something once and easily export.

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kccqzy 3 hours ago | parent | next [-]

> No sane programming language should require a duplication in order to export something (for example, the full function and its prototype)

You are spoiled by the explosive growth of open source and the ease of accessing source code. Lots of closed source commercial libraries provide some .h files and a .so file. And even when open source, when you install a library from a package from a distribution or just a tarball, it usually installs some .h files and a .so file.

The separation between interface and implementation into separate files was a good idea. The idea seemed to be going out of vogue but it’s still a good idea.

	▲	senfiaj 2 hours ago \| parent \| next [-]
		> Lots of closed source commercial libraries provide some .h files and a .so file. I'm mostly talking about modules for internal implementation, which is likely to be the bulk of the exports. Yes, it's understandable that for dll / so files exporting something for external executables is more complicated also because of ABI compatibility concerns (we use things like extern "C"). So, yes header approach might be justified in this case, but as I stated, such exports are probably a fraction of all exports (if they are needed at all). I'll still prefer modules when it's possible to avoid them.
	▲	AgentME 2 hours ago \| parent \| prev \| next [-]
		In most situations, auto-generating the equivalent of .h files for a library based on export statements in the source code would be fine and a useful simplification.
	▲	johannes1234321 2 hours ago \| parent \| prev [-]
		> The separation between interface and implementation into separate files was a good idea. The idea seemed to be going out of vogue but it’s still a good idea. However as soon as you do C++ that goes away. With C++ you need implementation of templates available to the consumer (except cases with limited set of types where you can extern them), wmin many cases you get many small functions (basic operator implementations, begin()/end() for iterators in all variations etc.) which benefit from inking, thus need to be in the header. Oh and did I mention class declarations tonthe the class size ... or more generic and even with plain C: As soon as the client should know about the size of a type (for being able to allocate it, have an array of those etc) you can't provide the size by itself, but you have to provide the full type declaration with all types down the rabbit hole. Till you somewhere introduce a pointer to opaque type indirection. And then there macros ... Modules attempt to do that better, by providing just the interface in a file. But hey, C++ standard doesn't "know" about those, so module interface files aren't a portable thing ...

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Maxatar 3 hours ago | parent | prev [-]

I think everyone hopes/hoped for a sane and useful version of modules, one that would provide substantial improvements to compilation speed and make things like packaging libraries and dealing with dependencies a lot more sane.

The version of modules that got standardized is anything but that. It's an incredibly convoluted mess that requires an enormous amount of effort for little benefit.

	▲	senfiaj 2 hours ago \| parent [-]
		> It's an incredibly convoluted mess that requires an enormous amount of effort for little benefit. I'd say C++ as a whole is a complete mess. While it's powerful (including OOP), it's complicated and inconsistent language with a lot of historical baggage (40+ years). That's why people and companies still search for (or even already use) viable replacements for C++, such as Rust, Zig, etc.

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bluGill 2 hours ago | parent | prev | next [-]

Modules are still in the early adoptor phase - despite 3 years. there are unfortunately bugs, and we still need people to write the "best practices for C++ modules" books. Everyone who has use them overall says they are good things and worth learning, but there is a lot about using them well that we haven't figured out.

	▲	alextingle 2 hours ago \| parent [-]
		Best practice for C++ modules: avoid. (Buy my book)

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malfmalf 3 hours ago | parent | prev | next [-]

They are using modules in the MS Office team:

https://devblogs.microsoft.com/cppblog/integrating-c-header-...

	▲	Maxatar 3 hours ago \| parent [-]
		This is untrue. The MS Office team is using a non-standard MSVC compiler flag that turns standard #include into header units, which treats those header files in a way similar to precompiled header files. This requires no changes to source code, except for some corner cases they mention in that very blog post to work around some compiler quirks. That is not the same as using modules, which they have not done.

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vitaut 2 hours ago | parent | prev | next [-]

Modules have been working reasonably well in clang for a while now but MSVC support is indeed buggy.

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throw_sepples an hour ago | parent | prev [-]

I'm afraid things will continue very much sucking for a long time and will still be less-than even when they become broadly supported since sepples programmers, being real programmers™, are not entitled to have nice things.