Enable C++17 on Eclipse to use `std::byte`

Question

I want to use #include <cstddef> and std::byte from c++17 on eclipse photon. I have configured the project to compile using c++17 >> project >> properties >> C/C++ Build >> settings >> GCC C++ Compiler >> Dialect >> Other dialect flags >> -std=c++17 and I have also tried -std=c++1z. My program below can use <cstddef> library, but the line with std::byte does not compile. Eclipse says Type 'std::byte' could not be resolved. How do I make eclipse support C++17?

#include <cstddef>

int main(void) {
    std::byte myByte { 2 };
}

Thanks

Is `Type 'std::byte' could not be resolved` a compiler error or an eclipse message? Which compiler + version? Which eclipse version? — mch, Oct 02 '18 at 08:55
It is an eclipse message. My eclipse version is `Eclipse IDE for C/C++ Developers Version: Photon Release (4.8.0)` — Felipe, Oct 02 '18 at 08:57
Try and invoke gcc directly with that program and tel us if it works. `g++ --version` and `g++ -std=c++17 byte.cpp` or `g++ -std=c++1z byte.cpp`. — YSC, Oct 02 '18 at 09:05
ok, `g++ --version` command output is something that is confusing me. It outputs `g++ (Ubuntu 6.4.0-17ubuntu1~16.04) 6.4.0 20180424`. So, which C++ version I am actually using? — Felipe, Oct 02 '18 at 09:15
I have long suspected that the eclipse indexer is too detached from how a source file is going to be compiled. It's more than likely that your code and compilation is fine, but the indexer chokes because the standard library header defines `std::byte` conditionally, based on language standard. Since you had to specify `-std=C++17` as an "other option", the indexer probably doesn't have a clue, and therefore you get this annoying message. — StoryTeller - Unslander Monica, Oct 02 '18 at 09:16
Possible solution: https://stackoverflow.com/questions/17131744/eclipse-cdt-indexer-does-not-know-c11-containers/24628885#24628885 — Galik, Oct 02 '18 at 10:14
didn't work @Galik. I am using a shared library and When I disable `CDT User Setting Entries` and `CDT GCC Built-in Compiler Settings` the project that test my shared library does not work anymore. — Felipe, Oct 02 '18 at 10:27
@YSC, I compiled on the command line usin `g++ -std=c++17` and I still get the error `‘byte’ is not a member of ‘std’` — Felipe, Oct 02 '18 at 10:41
I have installed gcc-8, but when I execute `sudo update-alternatives --config gcc` it does not show gcc-8 to use. Only shows version 6 and 4.8 — Felipe, Oct 02 '18 at 10:46
Let us [continue this discussion in chat](https://chat.stackoverflow.com/rooms/181146/discussion-between-galik-and-felipe-oliveira-gutierrez). — Galik, Oct 02 '18 at 10:46

score 4 · Answer 1 · edited Sep 14 '19 at 16:27

4

I use (eclipse 4.7.3a and gcc 7.3.0 MinGW-W64). And C++17 works fine with flag --std=c++1z

project >> properties >> C/C++ Build >> settings >> GCC C++ Compiler >> Dialect >> Other dialect flags >> --std=c++1z

edited Sep 14 '19 at 16:27

Simson

3,373
2
24
38

answered Sep 14 '19 at 11:29

Andrey Golovko

41
3

score 1 · Accepted Answer · answered Oct 02 '18 at 09:29

1

According to https://en.cppreference.com/w/cpp/compiler_support,std::byte is only supported since gcc 7.

Try upgrade your gcc version

answered Oct 02 '18 at 09:29

Irda

81
4

I executed `udo apt install gcc-8`, `sudo apt-get install gcc-8`, `sudo apt-get upgrade gcc` with success. But I still cannot see gcc 8 when I type `gcc --version` or `sudo update-alternatives --config gcc` – Felipe Oct 02 '18 at 09:51
The best solution is to configure Eclipse to use your new gcc (which is probably named `gcc-8` and `g++-8`). The other one is to link `gcc` and `g++` program to `gcc-8` and `g++-8` : `sudo ln -sf /usr/bin/gcc-8 /usr/bin/gcc` – Irda Oct 02 '18 at 09:57

Enable C++17 on Eclipse to use `std::byte`

2 Answers2