C.151: Use make_shared() to construct objects owned by shared_ptrs
C.151:使用make_shared构建shared_ptr管理的对象
Reason(原因)
make_shared gives a more concise statement of the construction. It also gives an opportunity to eliminate a separate allocation for the reference counts, by placing the shared_ptr's use counts next to its object.
make_shared为构造动作提供了更加简明的表达。由于它将shared_ptr的计数置于对象之后，使用它还可以提供减少另外一次的增加计数的机会。
Example(示例)
void test() {
// OK: but repetitive; and separate allocations for the Bar and shared_ptr's use count
shared_ptr<Bar> p {new Bar{7}};
auto q = make_shared<Bar>(7); // Better: no repetition of Bar; one object
}
Enforcement(实施建议)
- Flag the repetitive usage of template specialization list<Bar>
- 提示重复使用模板特化参数列表的情况
- Flag variables declared to be shared_ptr<Bar>
- 提示使用shared_ptr直接定义变量的情况。
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