GSL VS abseil-cpp

I haven't read much from Bjarne but this is refreshingly self-aware and paints a hopeful path to standardize around "the good parts" of C++.

As a C++ newbie I just don't understand the recommended path I'm supposed to follow, though. It seems to be a mix of "a book of guidelines" and "a package that shows you how you should be using those guidelines via implementation of their principles".

After some digging it looks like the guidebook is the "C++ Core Guidelines":

https://isocpp.github.io/CppCoreGuidelines/CppCoreGuidelines

And that I should read it and then:

> use parts of the standard library and add a tiny library to make use of the guidelines convenient and efficient (the Guidelines Support Library, GSL).

Which seems to be this (at least Microsoft's implementation):

https://github.com/microsoft/GSL

And I'm left wondering, is this just how C++ is? Can't the language provide tooling for me to better adhere to its guidelines, bake in "blessed" features and deprecate what Bjarne calls, "the use of low-level, inefficient, and error-prone features"?

Already showed you how to use ranges and such above, gsl::final_action is here

For span I would recommend the guideline support library - gsl::span

Not sure how things are at this point so you might want to look up with those keywords, but a few years back clang-tidy was one of the suggested tools, or enabling the core guidelines checker in visual studio if you're using that. Maybe using GSL or something similar as well.

When I want safety guarantees, I use the original and run-time checked gsl::span, rather than std::span. https://github.com/microsoft/GSL .

Another solution: use std::span (or some alternative implementations if the codebase doesn't use C++20).

If you ask me, the GSL [1] alone is a fairly radical departure from C++ that delivers a lot of safety. I don't know if it's gotten much popularity, though. Probably because it introduces a similar disruption like you might find from a brand new programming language.

[1] https://github.com/microsoft/GSL

> With Rust, though, one needs to learn entirely new ideas — things like lifetimes, ownership, and the borrow checker. These are not familiar concepts to most people working in other common languages ... Some of those “new” ideas are, of course, present in other languages — especially functional ones.

With C++, lifetime and ownership are just about as important but unfortunately no one's got your back. You can ignore lifetimes and ownership but you do so at your own peril. And the compiler won't tell you you're doing it wrong because the language wasn't designed for it to do so.

If you want a taste of rust's "mindset" (with respect to limitations imposed by some types) without jumping ship to a new language, try C++'s Guidelines Support Library [1]. It introduces some of the same benefits/friction as switching to rust but without a new language. Opting-in to some of these guidelines might be a gentler way to get some of the benefits of Rust. But it comes with a similarly higher bar.

[1] https://github.com/microsoft/GSL

It's also far more verbose than T* or T& (probably intentionally). If you really want a non-nullable pointer, gsl::not_null from the GSL is a good option. Writing your own version is also trivial, if you don't want to add a dependency.

Maybe you’d like ABSL_PREDICT macros?

https://github.com/abseil/abseil-cpp/blob/master/absl/base/o...

Their justification is here https://github.com/abseil/abseil-cpp/issues/720

However, I personally disagree with them since I think it's really important to have _some_ basic reproducibility for things like reproducing the results of a randomized test. In that case, I'm going to avoid changing as much as possible anyways.

abseil.io

From the looks of it Rust [1] uses a constant branching factor based on number of items whereas ABSEIL generally uses a target of 256 bytes for branching and fits however many elements fit within that. Rust’s approach seems to be more primitive as ABSEIL is optimizing for cache line usage (not sure why it’s several multiples of a cache line - maybe to help the prefetcher or to minimize cache line bouncing?)

[1] https://github.com/rust-lang/rust/blob/master/library/alloc/...

[2] https://github.com/abseil/abseil-cpp/blob/74f8c1eae915f90724...

[3] https://github.com/abseil/abseil-cpp/blob/74f8c1eae915f90724...

From the screencast:

> implement also for Days

This fails to recognize that this is a bad feature that the Abseil library would explicitly reject (hence the existence of absl::CivilDay) [0], and instead perpetuates the oversimplification that 1 day is exactly 24 hours (which breaks at least twice every year due to DST).

Which is to say: it'll tell you how to do the thing you ask it to do, but will not tell you that it's a bad idea.

And, of course, that assumes that it even makes the change correctly in the first place (which is nowhere near guaranteed, in my experience). I have seen (and bug-reported!) cases where it incorrectly inverts conditionals, introduces inefficient or outright unsafe code, causes unintended side effects, perpetuates legacy (discouraged) patterns, and more.

It turns out that ML-generated code is only as good as its training data, and a lot of google3 does not adhere to current best practices (in part due to new library developments and adoption of new language versions, but there are also many corners of the codebase with, um, looser standards for code quality).

[0] https://github.com/abseil/abseil-cpp/blob/bde089f/absl/time/...

Yeah, it's nice! And Abseil does it, IFF you use LLVM libc++.

https://github.com/abseil/abseil-cpp/blob/master/absl/string...

The standard adopted it as resize_and_overwrite. Which I think is a little clunky.

This may be confusing to those familiar with Google's libraries. The baseline is the Go BTree, which I personally never heard of until just now, not the C++ absl::btree_set. The benchmarks aren't directly comparable, but the C++ version also comes with good microbenchmark coverage.

https://github.com/google/btree

https://github.com/abseil/abseil-cpp/blob/master/absl/contai...