C++核心準(zhǔn)則C.151:使用make_shared構(gòu)建shared_ptr管理的對(duì)象

C.151: Use?make_shared()?to construct objects owned by shared_ptrs

C.151:使用make_shared構(gòu)建shared_ptr管理的對(duì)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為構(gòu)造動(dòng)作提供了更加簡(jiǎn)明的表達(dá)。由于它將shared_ptr的計(jì)數(shù)置于對(duì)象之后，使用它還可以提供減少另外一次的增加計(jì)數(shù)的機(jī)會(huì)。

Example(示例)

void test() {
    // OK: but repetitive; and separate allocations for the Bar and shared_ptr's use count
    shared_ptr p {new Bar{7}};

    auto q = make_shared(7);   // Better: no repetition of Bar; one object
}

Enforcement(實(shí)施建議)

• Flag the repetitive usage of template specialization list

• 提示重復(fù)使用模板特化參數(shù)列表的情況

• Flag variables declared to be?shared_ptr

• 提示使用shared_ptr直接定義變量的情況。

原文鏈接：

https://github.com/isocpp/CppCoreGuidelines/blob/master/CppCoreGuidelines.md#c151-use-make_shared-to-construct-objects-owned-by-shared_ptrs

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