c++ - 如何使用列表初始化对聚合类型进行值初始化

Question

如何使用列表初始化语法对 C++14 中的聚合类型进行值初始化？

Aggregate_t {}; 

这被视为聚合初始化，它会对 Aggregate_t 的未初始化成员产生错误或警告。

这可能吗？

编辑:示例

struct Aggregate_t {
  int x;
};

int main (int, char**)
{
  Aggregate_t {};
  return 0;
}

使用 g++-4.9.2 编译:

main.c++: In function ‘int main(int, char**)’:
main.c++:7:16: warning: missing initializer for member ‘Aggregate_t::x’ [-Wmissing-field-initializers]
   Aggregate_t {};
            ^

Answer 1

[dcl.init.aggr]:

7 - If there are fewer initializer-clauses in the list than there are members in the aggregate, then each member not explicitly initialized shall be initialized [C++14: from its brace-or-equal-initializer or, if there is no brace-or-equal-initializer,] from an empty initializer list (8.5.4).

所以 g++ 的警告过于热心了；我不知道有什么方法可以避免它，同时在警告有效的情况下保留它，当然除了使用带有预期复制省略的复制初始化:

Aggregate_t a = Aggregate_t();