I'm starting a project using C++, which I haven't used before outside of a handful of school projects - nowhere near the scope of what I'm tackling now.
My goal is to try my best to follow the C++ Core Guidelines as I work to avoid errors, improve performance, and most importantly: improve maintainability of my code.
I've been running into literally hundreds of issues ranging from my g++ / Clang++ versions not being right to standard libraries not being found to g++ using the wrong version of C++ for compilation to very basic functions not behaving as expected - and I haven't even started to look into autotools, so I expect many more headaches to follow.
This question is specific to one part of the C++ Core Guidelines, though. Interfaces 6: Prefer Expects() for expressing preconditions
I tried writing the following simple code:
#include <iostream>
using namespace std;
int square(int x) {
Expects(x > 0);
return x * x;
}
int main() {
cout << square(3) << endl;
return 0;
}
This threw an error in g++:
$> g++ -std=c++17 main.cpp
main.cpp: In function ‘int square(int)’:
main.cpp:7:2: error: ‘Expects’ was not declared in this scope
Expects(x > 0);
^~~~~~~
-> [1]
I tried using Clang, as well, but it has an entirely different (and unrelated) problem:
$> clang++ -x c++ main.cpp
main.cpp:1:10: fatal error: 'iostream' file not found
#include <iostream>
^~~~~~~~~~
1 error generated.
-> [1]
I haven't figured out how to fix that one yet, so I'm not bothering with it.
Expects is part of the GSL library. You have to use some GSL library implementation, which you can find on Github:
These are the ones I have off the top of my head.
The CPP Guidelines likely allude to the "contracts" proposal which provides the same checks via attributes. It was scheduled for C++20, but later removed for lack of consensus on its scope. See p1823r0 and a standard committee member's Reddit thread on the rationale leading to the removal.