std::meta::bit_size_of

consteval std::size_t bit_size_of( std::meta::info r );

Returns the size in bits of the type or (sub)object represented by r.

Parameters

Return value

If r represents a bit-field, returns its bit width.

Otherwise, if r represents a data member description whose bit width is not ⊥, returns that bit width.

Otherwise, returns CHAR_BIT * std::meta::size_of(r).

Exceptions

Throws std::meta::exception unless all of the following conditions are met:

• std::meta::dealias(r) represents one of the following:
• type
• object
• (scalar) value
• variable of non-reference type
• non-static data member
• unnamed bit-field
• direct base class relationship
• data member description
• If std::meta::dealias(r) represents a type, std::meta::is_complete_type(r) is true.

Example

#include <climits>
#include <cstdint>
#include <meta>

static_assert(bit_size_of(^^int) == CHAR_BIT * sizeof(int));
static_assert(bit_size_of(^^int) == std::numeric_limits<int>::digits + 1);

int main()
{
    constexpr struct S { std::uint32_t m{}; } o;
    static_assert(bit_size_of(^^S) == 32);
    static_assert(bit_size_of(^^o) == 32);

    struct B { std::uint64_t m : 42{}; };
    static_assert(bit_size_of(^^B) == 64);
    static_assert(bit_size_of(^^B::m) == 42);
}

See also