Constructability of trivial types-CodePudding

In regards to C 17; GCC, Clang, and MSVC consider a trival class type not to be constructible by any of its data member types. Since C 20, GCC and MSVC changed this, allowing the example below to compile.

#include <type_traits>

struct t {
    int a;
};

static_assert(std::is_constructible<t, int>{});

Unfortunately, Clang seems to disagree and rejects this code when compiling with -std=c 20 as well. Is this a compiler bug of Clang? And why do all compilers not consider a type like t to be constructible with an int when compiling with -std=c 17? After all, t{0} seems to be pretty constructible that way.

CodePudding user response：

Constructibility is based on the ability to use constructor syntax (T(values)). In C 20, aggregates can be initialized using constructor syntax, but in C 17 and before, they must use {} syntax.

Clang's C 20 implementation is simply not up to the standard yet.

CodePudding user response：

Clang will compile this if you add a constructor that can construct a t from an int. I'm not sure why this would not work without it in clang.