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>Often, it is code that does a ton of unnecessary copies. Often, code written in C / C++ does unnecessary copies precisely because the risk of avoiding those c

>Often, it is code that does a ton of unnecessary copies. Often, code written in C / C++ does unnecessary copies precisely because the risk of avoiding those copies is hours of debugging, crashes in production, or security flaws. So this is a legitimate benefit of Rust. Being able to code more aggressively up front, without fear of something blowing up in your face later, or much later when the intern touches the wrong line. >I haven't seen any examples where C or C++ code written with performance in mind gets a rewrite to Rust and goes faster, and I have seen the opposite. Here's one from Bryan Cantrill http://dtrace.org/blogs/bmc/2018/09/28/the-relative-performance-of-c-and-rust/ http://dtrace.org/blogs/bmc/2018/09/28/the-relative-performa... The point he makes is that while Rust is not strictly faster than C in most cases, it gives you the comfort of being able to use more highly optimized libraries and data structures without needing to have the extreme level of trust in the author that you do in C / C++. This is basically the same argument.

pclmulqdq 4y ago
This is a comparison with C that I am familiar with. It illustrates the reasons why C++ won for many applications (compared to C). The author also is on record as someone who hates C++, and is very careful about not making any claims in that blog post about C++ because that's not his area of expertise. Compared to C, where a data structure library is at best a heap of cobbled-together macros that make a lot of assumptions about the underlying types, C++ has well-developed libraries for all of the data structures mentioned. And you need to trust the author plenty to make a btree that works - that is a very complicated data structure. It's not just about memory safety, there can be a lot of functional bugs, too. The author of the C++ one is Google/Facebook, who I trust to write a solid library, while the author of the Rust one is someone who was inspired by the C++ version. At this point, both are well-tested, but there are a lot of Rust libs that are in the same position, but relatively untested.
- bcantrill 4y ago
  True: not my area of expertise as I have only written ~100,000 lines of C++ -- and that that is insufficient for C++ to be an area of expertise is itself very revealing...
  - pclmulqdq 4y ago
    It's true, and it is a big problem with C++. I'm not sure if you were being sarcastic here, but if those 100,000 lines are not heavily back-weighted towards 2014 and later, that amount of code probably doesn't make you a C++ expert unless you were doing things like writing parts of boost (or another template library) or you happened to decide to read a few hundred pages of the spec recently. The language-change whiplash that people accuse Rust of happens to C++ folks who leave the language for several years, since "idiomatic" C++ has changed substantially over the last 20 years. EDIT - Just to clarify, there are SO MANY different ways to do things in C++ that the way to really learn C++ is by reading (both good code and the spec), not by writing. It's very easy to write a ton of code and not actually do it in the fastest/best/most idiomatic way. This is complicated by the fact that a ton of C++ examples out there are wrong. It's really an electrical engineer's language at this point - read all the datasheets if you want to avoid getting shot in the foot (and still get shot in the foot anyway).

pclmulqdq 4y ago

This is a comparison with C that I am familiar with. It illustrates the reasons why C++ won for many applications (compared to C). The author also is on record as someone who hates C++, and is very careful about not making any claims in that blog post about C++ because that's not his area of expertise. Compared to C, where a data structure library is at best a heap of cobbled-together macros that make a lot of assumptions about the underlying types, C++ has well-developed libraries for all of the data structures mentioned. And you need to trust the author plenty to make a btree that works - that is a very complicated data structure. It's not just about memory safety, there can be a lot of functional bugs, too. The author of the C++ one is Google/Facebook, who I trust to write a solid library, while the author of the Rust one is someone who was inspired by the C++ version. At this point, both are well-tested, but there are a lot of Rust libs that are in the same position, but relatively untested.

bcantrill 4y ago
True: not my area of expertise as I have only written ~100,000 lines of C++ -- and that that is insufficient for C++ to be an area of expertise is itself very revealing...
- pclmulqdq 4y ago
  It's true, and it is a big problem with C++. I'm not sure if you were being sarcastic here, but if those 100,000 lines are not heavily back-weighted towards 2014 and later, that amount of code probably doesn't make you a C++ expert unless you were doing things like writing parts of boost (or another template library) or you happened to decide to read a few hundred pages of the spec recently. The language-change whiplash that people accuse Rust of happens to C++ folks who leave the language for several years, since "idiomatic" C++ has changed substantially over the last 20 years. EDIT - Just to clarify, there are SO MANY different ways to do things in C++ that the way to really learn C++ is by reading (both good code and the spec), not by writing. It's very easy to write a ton of code and not actually do it in the fastest/best/most idiomatic way. This is complicated by the fact that a ton of C++ examples out there are wrong. It's really an electrical engineer's language at this point - read all the datasheets if you want to avoid getting shot in the foot (and still get shot in the foot anyway).