I am not really getting any smarter from these error messages.
Minimal (not) Working Example on godbolt
#include <initializer_list>
#include <memory>
#include <vector>
struct S
{
int j;
double y;
std::vector<int> data;
S(int i, double x, std::initializer_list<int> list)
: j(i)
, y(x)
, data(list)
{
}
};
int main()
{
auto ptr = std::make_shared<S>(1, 1.2, {1,2,3}); // I want this to work
// auto ptr = std::make_shared<S>(1, 1.2, std::initializer_list<int>({1,2,3})); // works
}
Errors:
<source>:22:35: error: too many arguments to function 'std::shared_ptr<_Tp> std::make_shared(_Args&& ...) [with _Tp = S; _Args = {}]'
22 | auto ptr = std::make_shared<S>(1, 1.2, {1,2,3});
<source>:11:5: note: candidate: 'S::S(int, double, std::initializer_list<int>)'
11 | S(int i, double x, std::initializer_list<int> list)
| ^
<source>:11:5: note: candidate expects 3 arguments, 0 provided
It compiles fine, when I call the explicit constructor for std::initializer_list<int> in front of {1,2,3}. Is there a way to circumvent this, so my std::make_shared does not bloat so much?
CodePudding user response：
{1,2,3} can be multiple things, and make_shared has no possibility of knowing what it is at the time parameter pack is expanded.
If you don't want to state the long std::initializer_list<int>{1,2,3} explicitly, the easiest solutions would be:
a. shortening the type's name: using ints=std::initializer_list<int>;
b. wrapping the call:
auto make_shared_S(int x, double y, std::initializer_list<int> l)
{
return std::make_shared<S>(x, y, l);
}