Modern C++ for C Programmers: part 5

#1

Post by ahubert » Wed, Jul 25, 2018, 12:47 PM UTC

Modern C++ for C Programmers: part 5
ds9a.nl

Re: Modern C++ for C Programmers: part 5

#2

Post by stephencanon » Wed, Jul 25, 2018, 1:50 PM UTC

Return value optimization is absolutely allowed in C, and ~all compilers do it. It's not commonly talked about because in C, there can be no side-effects when constructing or copying a struct, so there's nothing to discuss. It just happens automatically and there's no observable change in program behavior.

Re: Modern C++ for C Programmers: part 5

#3

Post by jwilk » Wed, Jul 25, 2018, 2:12 PM UTC

Previous parts:

https://news.ycombinator.com/item?id=17309654

https://ds9a.nl/articles/posts/cpp-2/

https://ds9a.nl/articles/posts/cpp-3/

https://ds9a.nl/articles/posts/cpp-4/

Re: Modern C++ for C Programmers: part 5

#4

Post by jcelerier » Wed, Jul 25, 2018, 2:25 PM UTC

stephencanon wrote: post #2

Return value optimization is absolutely allowed in C, and ~all compilers do it. It's not commonly talked about because in C, there can be no side-effects when constructing or copying a struct, so there's nothing to discuss. It just happens automatically and there's no observable change in program behavior.

No, C has much less RVO allowed than C++. I provided an example of this here the last time : https://news.ycombinator.com/item?id=17216250

Re: Modern C++ for C Programmers: part 5

#5

Post by 52-6F-62 » Wed, Jul 25, 2018, 2:37 PM UTC

jwilk wrote: post #3

Previous parts: https://news.ycombinator.com/item?id=17309654 https://ds9a.nl/articles/posts/cpp-2/ https://ds9a.nl/articles/posts/cpp-3/ https://ds9a.nl/articles/posts/cpp-4/

Thanks! I missed this the first time through

Re: Modern C++ for C Programmers: part 5

#6

Post by ttul » Wed, Jul 25, 2018, 2:48 PM UTC

I wish I had a project that warranted C++ right now. It’s a magnificent language.

Re: Modern C++ for C Programmers: part 5

#7

Post by rrmm » Wed, Jul 25, 2018, 2:58 PM UTC

Please please please can we get rid of headers and have modules? I find it super annoying having to specify things half in one place and half in another. Unfortunately, there still seems to be a bit of disagreement on the implementation among the standards committee.

Re: Modern C++ for C Programmers: part 5

#8

Post by ajross » Wed, Jul 25, 2018, 2:59 PM UTC

stephencanon wrote: post #2

Return value optimization is absolutely allowed in C, and ~all compilers do it. It's not commonly talked about because in C, there can be no side-effects when constructing or copying a struct, so there's nothing to discuss. It just happens automatically and there's no observable change in program behavior.

C compilers can do copy ellision when inlining code as long as the result is identical. That's not quite the same thing as RVO, which deliberately relaxes the notion of "identical result" such that it's possible to write C++ code to detect whether or not RVO was actually performed. That's not possible in C (or shouldn't be).

Re: Modern C++ for C Programmers: part 5

#9

Post by mlevental » Wed, Jul 25, 2018, 3:03 PM UTC

is there a modern C++ for python programmers? i have ~5 years programming in dynamic/interpreted (python/js) and compiled/gc'd(java/go) languages and i'd like to learn a systems language. i'm reading the rust programming book (and it's really good/easy to grok) but i'd also like to learn C++. the problem is that most books are either too easy (C++ as your first language) or too hard (straight into RAII and templates). any suggestions for learning resources? modern being key here (stuff like auto ptrs etc.)

Re: Modern C++ for C Programmers: part 5

#10

Post by mikec3010 » Wed, Jul 25, 2018, 3:08 PM UTC

> The move constructor is the important bit. Its presence tells C++ that this class can not be copied, only moved

Is that true? I thought move ctor enabled move semantics, but if you pass by value the copy ctor was still called (except in places where RVO makes sense). And I thought to disable copying you made the copy ctor = delete.