Issues with Compiling Constexpr Code

Accelerated Computing HPC Compilers nvc, nvc++ and nvfortran
1

This should compile with C++20 but it doesn’t. (The uninitialized value error is incorrect since the value is only written to while it is uninitialized)


#include <array>

struct vector
{
    std::array<int,3> a_;
};

constexpr auto create(int a, int b, int c) -> vector
{
    vector v;
    v.a_[0] = a;
    v.a_[1] = b;
    v.a_[2] = c;
    return v;
}


auto f()
{
    constexpr vector v = create(3,4,4);
}
2

I talked with engineering, but they believe the compiler error message is correct.

From engineering:

Evaluating v.a_[0] = a; involves calling operator[] on the uninitialized std::array subobject. It’s the call to the member function that is problematic and resulting in the error.

3

Thank you for your reply. I’ll see what can be done about it. For now, I guess initializing it makes sense.