C++ STL design is broken. The language shouldn’t define an API for std, it should provide an implementation. AFAIK no other major language defines the std library the way C++ does. It’s so bad and problematic.
Also, how does providing a concrete/reference implementation prevent the API problems? Hyrum's law [0] means that you would make the situation worse because now people will depend on every detail you can think of. And if you want to improve the implementation in a new version, you now are (most likely) breaking ABI on every platform at once, instead of giving different platforms the ability to find compromises as needed. Just look at the recent "no ABI break in C++23" discussions to see how contentious that topic is.
The STL spec is so over designed that they strongly imply, if not mandate, a particular implementation. But they don’t actually provide an implementation so every platform has to implement one. However those implementations select different trade-offs which means different behaviors so actually developers wind up writing their own version that is consistent. It’s basically the worst outcome.
For example, random number distributions are underspecified. The standard only defines the distributions but not the algorithms. If you need deterministic behavior after choosing the rng and the seed – for example for testing, reproducibility, or procedural content generation – you can't use the standard distributions.
C++ is typically used in applications where performance is important. If you want a "good enough" standard library, it must be good enough for most people who care about performance. A cross-platform implementation is rarely good enough, because performance often depends on platform-specific parameters and instructions.
Data structure APIs are particularly difficult if you care about performance. If you use a generic API, you will often end up using the data structure suboptimally. Your mental model is likely wrong, and the API may not pass through information that could help you avoid redundant work. You want an API that matches the actual implementation closely – but not so closely that every implementation change becomes a breaking API change.
I respectfully disagree with this.
We’re talking about std::unordered_map here. I don’t know of any platform that has done implementation work to make std::unordered_map not mediocre.
Let’s be specific. What platforms are we talking about? How many STL implementations are there? Which ones offer a significant improvement for which platforms?
C++ has been my daily driver for 15 years. I’ve shipped quite a lot of code that uses std::vector and std::unordered_map, amongst others! If I really cared about performance I’d pick a hash map implementation that wasn’t mediocre.
I would definitely not consider any std::unordered_map to be highly tuned for any platform. Quite the opposite. It’s over-specified but still stuck with different implementations. IMHO it would be much better if the C++ committee released C++XX libraries that were considered “pretty good” with support for common platforms. New or proprietary platforms can then add the relatively small bits of code necessary to support their platform (think PS5) or release a completely separate library with different constraints.
Part of the problem here is C++ also really, really sucks to compile. Maybe someday modules will make it easy to drop in new libraries and containers. Jury’s still out on that one though.
std::unordered_map is not a particularly good example of things that need platform-specific optimizations. The implementations I have seen are pretty close to standard C++. std::vector implementations, on the other hand, are often really weird and rely extensively on compiler-specific annotations.
Thus while your parent may have meant that types like std::unordered_map shouldn't be magic, it's true that for example you can't implement atomics from the standard library usefully without help from the vendor.
Just like some people have a pet peeve to correct people on this usage, I have a pet peeve to tell those people to look at the name of the MSVC implementation of the C++ standard library.
https://github.com/microsoft/STL
Yes, historically "the STL" was a subset of what became the C++ standard library. But unless you want to tell one of the big three standard library implementations that you know better than them what the name should be, using "STL" for the entire C++ standard library is simply not incorrect.
(Your point that this may be a misunderstanding between the other poster and me stands though.)
We're talking here about the company that has two very well known products "Active Directory" and "Visual Studio" but decided there was no reason it couldn't call unrelated products "Azure Active Directory" and "Visual Studio Code".
Here's how Sony named their video game consoles: PlayStation, PlayStation 2, PlayStation 3, and PlayStation 4. Makes sense. Microsoft decided to make video game consoles too. It named them (I am not kidding for anyone who doesn't play video games, this is real): Xbox, Xbox 360, Xbox One, Xbox Series. Why ?