STL VS STL

As a reminder (you've probably seen this, but maybe not everyone), I am still accepting bug bash reports, if anyone is super excited about trying out the code.

There are indeed bugs, but it's getting close to handling the entire Standard Library. I'm still accepting STL Modules Bug Bash reports, if you can find novel bugs (see the tracking issue microsoft/STL#1694 for known bugs).

Standard Library Modules are coming soon. You can experiment with them (and report issues) by following the instructions at https://github.com/StephanTLavavej/STL/wiki/Standard-Library-Modules-Bug-Bash .

C++23 Standard Library Modules were just officially accepted into the Working Paper. My bug bash for the implementation-in-progress was successful, with many great bugs reported (and most worked around, to the limit of my ability in the library). VS 2022 17.4 Preview 1, released today, contains more fixes for named modules. I'm now close to having a PR prepared for review - just need to add automated testing and do some setup work (as we need to ship a new directory with new files). I can't promise anything yet, but I am very tentatively hopeful that we'll be able to merge this for 17.5.

Agreed - I'm running the Standard Library Modules Bug Bash until end of day today, but I'll continue to accept bug reports afterwards (and will hopefully have time to create a full PR for modules soon).

They should! If you use MSVC as one of your compilers, can you try my upcoming implementation of Standard Library Modules? My bug bash is running for another week, and getting bug reports will help us fix issues in the compiler and library so modules will be usable sooner. (That is, bugs that affect import std; will likely affect people writing their own named modules too.)

If you use MSVC, can you help me test them in the modules bug bash I'm running for the next 2 weeks?

Again, they are barely functional.

MSVC chokes on many standard-defined constructs: https://github.com/microsoft/STL/issues/1694

clang does not claim to be "mostly usable" at all - most papers are not implemented: https://clang.llvm.org/cxx_status.html#cxx20

And gcc will only start ot be usable with CMake when version 14 is released - that has not happened yet.

And, as I mentioned before, IDE support is either buggy (Visual Studio) or non-existing (any other IDE/OS). So you're off to writing in a text editor and hoping your compiler works to a somewhat usable degree. Yes, at some point people should start using modules, I agree, but to advise library maintainers to ship modularized code... the tooling just isn't there yet.

I mean, the GitHub issue is Microsoft trying to ship their standard library modularized, they employ some of the most capable folks on the planet and pay them big money to get that done, while metaphorically sitting next to the Microsoft compiler devs, and they barely, barely get it done (with bugs, as they themselves mention). This is too much for most other library maintainers.

Notice that there are in practice three distinct implementations of the C++ standard library. They're all awful to read though, here's Microsoft's std::vector https://github.com/microsoft/STL/blob/main/stl/inc/vector

However you're being slightly unfair because Rust's Vec is just defined (opaquely) as a RawVec plus a length value, so let's link RawVec, https://doc.rust-lang.org/src/alloc/raw_vec.rs.html -- RawVec is the part responsible for the messy problem of how to actually implement the growable array type.

Still, the existence of three C++ libraries with slightly different (or sometimes hugely different) quality of implementation means good C++ code can't depend on much beyond what the ISO document promises, and yet it must guard against the nonsense inflicted by all three and by lacks of the larger language. In particular everything must use the reserved prefix so that it's not smashed inadvertently by a macro, and lots of weird C++ idioms that preserve performance by sacrificing clarity of implementation are needed, even where you'd ordinarily sacrifice to get the development throughput win of everybody know what's going on. For example you'll see a lot of "pair" types bought into existence which are there to squirrel away a ZST that in C++ can't exist, using the Empty Base Optimisation. In Rust the language has ZSTs so they can just write what they meant.

Here is Microsoft's implementation of map in the standard library. I think of myself as a competent programmer / computer scientist. I couldn't write this: https://github.com/microsoft/STL/blob/f392449fb72d1a387ac502...

Be careful on Windows, the MSVC STL implementation uses the system time, so it can be badly impacted by clock adjustments: https://github.com/microsoft/STL/issues/718

Can you provide a link? If it affects import std;, I'd like to add it to my tracking issue.

Do you have a list of the bugs you've filed and their current status, like the one I have for the STL? I saw you mentioned 3 bugs 7 months ago, 2 of which were fixed in 17.6 and the third of which was a duplicate of an active bug ("deducing this" is known to not yet work with modules, which is why we don't define the feature-test macro to claim full support).

Yep. And look at our implementation's name: https://github.com/microsoft/STL