I encountered this problem while initializing a member array variable (c-style). Interestingly converting the member into a std::array<>
solves the problem.
See below:
struct A {
A(int aa) : a(aa) {}
A(const A &a) = delete;
A &operator=(const A &a) = delete;
private:
int a;
std::vector<int> v;
};
struct B1 {
B1() : a1{{{1}, {2}}} {} // -> compiles OK (gcc 9.2)
private:
std::array<A, 2> a1;
};
struct B2 {
B2()
: a2{{1}, {2}} // -> error: use of deleted function 'A::A(const A&)' (gcc 9.2)
{}
private:
A a2[2];
};
My question is why is this difference in (compiler) behavior? I was assuming that functionality-wise they are pretty much the same (I understand std::array<>
is more of an aggregate instead of a pure container, like vector - I might be wrong though).
Additional observation:
vector<>
member in A
Update:
It is a GCC bug:
Brace initialization of array sometimes fails if no copy constructor (reported in 4.9 and resolved in 9.4)
Does it mean it's a GCC bug
Yes, this seems to be a gcc bug that has been fixed in gcc 9.4. Demo.
A bug for the same has been submitted as:
GCC rejects valid program involving initialization of array in member initializer list