STL VS gcc

I believe the impl you link to is not fully standards compliant, so just calls back to

MSFT's one is totally standards compliant and it is a very different beast: https://github.com/microsoft/STL/blob/main/stl/inc/charconv

Apart from various nuts and bolts optimizations (eg not using locales, better cache friendless, etc...) it also uses a novel algorithm which is an order of magnitude quicker for many floating points tasks (https://github.com/ulfjack/ryu).

If you actually want to learn about this, then watch the video I linked earlier.

SRWLocks are a Windows feature, not a Rust feature, so you're looking in the wrong place.

Here's STL's (nominative determinism at work) GitHub issue for Microsoft's C++ stdlib implementation about this https://github.com/microsoft/STL/issues/4448

Here's the C++ Reddit thread where the bug was shown: https://www.reddit.com/r/cpp/comments/1b55686/maybe_possible...

Here's the Rust change which was merged for 1.78: https://github.com/rust-lang/rust/pull/121956/

Interesting thanks. Seems the reason I couldn't find anything on that is because it's not really documented?

https://github.com/microsoft/STL/issues/586

> We talked about this at the weekly maintainer meeting and decided that we're not comfortable enough with the (lack of) design of this feature to begin documenting it for wide usage.

Microsoft does officially call their implementation of the C++ Standard Library in MSVC "The STL." This is due to historical confusion, of course, but it persists to this very day in official materials. Check the name of this repository.

https://github.com/microsoft/STL

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.

> (and of course eventually dropping support for Motorola 68010 on which the Tektronix 4404 is built)

I don't think it ever did? Looking here[1] it still seems to be supported

[1]https://github.com/gcc-mirror/gcc/blob/master/gcc/config/m68...

There are some open source C compilers such as the GNU C compilers (https://github.com/gcc-mirror/gcc) and Clang (https://clang.llvm.org/get_started.html).

There are also proprietary C compilers such as the Microsoft's C compiler (https://visualstudio.microsoft.com/vs/features/cplusplus/) and the Intel C compiler (https://www.intel.com/content/www/us/en/developer/tools/onea...).

There are many others: https://en.m.wikipedia.org/wiki/List_of_compilers#C_compiler...

Most mature C compilers will specify what version(s) of the C standard they implement so developer users can know what features are available. Many C compilers also implement non-standard extensions to the C language and libraries to be more competitive, overcome language shortcomings, or provide for specialized needs or development targets (e.g. features for embedded targets).

But I'm still sure that there are several UB's in my code :)

[1] https://tunglevo.com/note/an-optimization-thats-impossible-i...

[2] https://github.com/gcc-mirror/gcc/blob/d09131eea083e80ccad60...

[3] https://github.com/llvm/llvm-project/blob/4468d58080d0502a05...

I was hoping GCC would do the same, leaving the decision about the value of '\n' to GCC's compiler, but apparently it hardcodes the numeric values for escapes[1], with options for ASCII or EBCDIC systems.

[1] https://github.com/gcc-mirror/gcc/blob/8a4a967a77cb937a2df45...

GCC github-mirror GCC Documentation GCC Internals Mannual Installing GCC

As far as I know, libstdc++'s representation has two advantages:

First, it simplifies the implementation of `s.data()`, because you hold a pointer that invariably points to the first character of the data. The pointer-less version needs to do a branch there. Compare libstdc++ [1] to libc++ [2].

[1]: https://github.com/gcc-mirror/gcc/blob/065dddc/libstdc++-v3/...

[2]: https://github.com/llvm/llvm-project/blob/1a96179/libcxx/inc...

Basically libstdc++ is paying an extra 8 bytes of storage, and losing trivial relocatability, in exchange for one fewer branch every time you access the string's characters. I imagine that the performance impact of that extra branch is tiny, and massively confounded in practice by unrelated factors that are clearly on libc++'s side (e.g. libc++'s SSO buffer is 7 bytes bigger, despite libc++'s string object itself being smaller). But it's there.

The second advantage is that libstdc++ already did it that way, and to change it would be an ABI break; so now they're stuck with it. I mean, obviously that's not an "advantage" in the intuitive sense; but it's functionally equivalent to an advantage, in that it's a very strong technical answer to the question "Why doesn't libstdc++ just switch to doing it libc++'s way?"

Upd: searching in the github mirror by the commit hash from the issue, found that https://github.com/gcc-mirror/gcc/commit/1e3312a25a7b34d6e3f... is in fact in the 'releases/gcc-14.1.0' tag.

Even weirder that this one got swept under the changelog rug, it's a pretty major issue.

> It's true, this was a CVE in Rust and not a CVE in C++, but only because C++ doesn't regard the issue as a problem at all. The problem definitely exists in C++, but it's not acknowledged as a problem, let alone fixed.

Can you find a link that substantiates your claim? You're throwing out some heavy accusations here that don't seem to match reality at all.

Case in point, this was fixed in both major C++ libraries:

https://github.com/gcc-mirror/gcc/commit/ebf6175464768983a2d...

https://github.com/llvm/llvm-project/commit/4f67a909902d8ab9...

So what C++ community refused to regard this as an issue and refused to fix it? Where is your supporting evidence for your claims?