Martin Hořeňovský 28e651f152
Move SFINAE in decomposer into return type
This is needed so that we can use conjunction and other logical
type traits to workaround issue with older GCC versions (8 and
below), when they run into types that have ambiguous constructor
from `0`, see e.g. #2571.

However, using conjunction and friends in the SFINAE constraint
in the template parameter breaks for C++20 and up, due to the new
comparison operator rewriting rules. With C++20, when the compiler
see `a == b`, it also tries `b == a` and collects overload set
for both of these expressions.

In Catch2, this means that e.g. `REQUIRE( 1 == 2 )` would lead
the compiler to check overloads for both `ExprLhs<int> == int`
and `int == ExprLhs<int>`. Since the overload set and SFINAE
constraints assume that `ExprLhs<T>` is always on the left side,
when the compiler tries to resolve the template parameters, all
hell breaks loose and the compilation fails.

By moving the SFINAE constraints to the return type, the compiler
can discard the switched expression without having to resolve
the complex SFINAE constraints, and thus everything works the
way it is supposed to.

Fixes #2571
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2020-11-02 15:37:35 +01:00
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What is Catch2?

Catch2 is mainly a unit testing framework for C++, but it also provides basic micro-benchmarking features, and simple BDD macros.

Catch2's main advantage is that using it is both simple and natural. Test names do not have to be valid identifiers, assertions look like normal C++ boolean expressions, and sections provide a nice and local way to share set-up and tear-down code in tests.

Example unit test

#include <catch2/catch_test_macros.hpp>

#include <cstdint>

uint32_t factorial( uint32_t number ) {
    return number <= 1 ? number : factorial(number-1) * number;
}

TEST_CASE( "Factorials are computed", "[factorial]" ) {
    REQUIRE( factorial( 1) == 1 );
    REQUIRE( factorial( 2) == 2 );
    REQUIRE( factorial( 3) == 6 );
    REQUIRE( factorial(10) == 3'628'800 );
}

Example microbenchmark

#include <catch2/catch_test_macros.hpp>
#include <catch2/benchmark/catch_benchmark.hpp>

#include <cstdint>

uint64_t fibonacci(uint64_t number) {
    return number < 2 ? 1 : fibonacci(number - 1) + fibonacci(number - 2);
}

TEST_CASE("Benchmark Fibonacci", "[!benchmark]") {
    REQUIRE(Fibonacci(5) == 5);

    REQUIRE(Fibonacci(20) == 6'765);
    BENCHMARK("Fibonacci 20") {
        return Fibonacci(20);
    };

    REQUIRE(Fibonacci(25) == 75'025);
    BENCHMARK("Fibonacci 25") {
        return Fibonacci(25);
    };
}

Catch2 v3 has been released!

You are on the devel branch, where the v3 version is being developed. v3 brings a bunch of significant changes, the big one being that Catch2 is no longer a single-header library. Catch2 now behaves as a normal library, with multiple headers and separately compiled implementation.

The documentation is slowly being updated to take these changes into account, but this work is currently still ongoing.

For migrating from the v2 releases to v3, you should look at our documentation. It provides a simple guidelines on getting started, and collects most common migration problems.

For the previous major version of Catch2 look into the v2.x branch here on GitHub.

How to use it

This documentation comprises these three parts:

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Description
A modern, C++-native, test framework for unit-tests, TDD and BDD - using C++14, C++17 and later (C++11 support is in v2.x branch, and C++03 on the Catch1.x branch)
Readme 62 MiB
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