C++核心準(zhǔn)則ES.26: 不要將一個(gè)變量用于兩個(gè)無關(guān)的用途

ES.26: Don't use a variable for two unrelated purposes

ES.26: 不要將一個(gè)變量用于兩個(gè)無關(guān)的用途

Reason（原因）

Readability and safety.

可讀性和安全性。

Example, bad（反面示例）

void use()
{
    int i;
    for (i = 0; i < 20; ++i) { /* ... */ }
    for (i = 0; i < 200; ++i) { /* ... */ } // bad: i recycled
}

Note（注意）

As an optimization, you may want to reuse a buffer as a scratch pad, but even then prefer to limit the variable's scope as much as possible and be careful not to cause bugs from data left in a recycled buffer as this is a common source of security bugs.

作為一種優(yōu)化，你可能將buffer用作告訴暫存區(qū)，即使是這種用情況最好還是盡可能限定變量的作用域，而且注意不要因?yàn)榱粼谘h(huán)使用的buffer中的數(shù)據(jù)引發(fā)錯(cuò)誤。這是安全錯(cuò)誤的一個(gè)常見來源。

void write_to_file() {
    std::string buffer;             // to avoid reallocations on every loop iteration
    for (auto& o : objects)
    {
        // First part of the work.
        generate_first_string(buffer, o);
        write_to_file(buffer);

        // Second part of the work.
        generate_second_string(buffer, o);
        write_to_file(buffer);

        // etc...
    }
}

Enforcement（實(shí)施建議）

Flag recycled variables.

標(biāo)記循環(huán)使用的變量。

原文鏈接

https://github.com/isocpp/CppCoreGuidelines/blob/master/CppCoreGuidelines.md#es26-dont-use-a-variable-for-two-unrelated-purposes

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