在循環中聲明變量是否有任何開銷？ (C++) - Is there any overhead to declaring a variable within a loop? (C++)

問題：

I am just wondering if there would be any loss of speed or efficiency if you did something like this:我只是想知道如果你做這樣的事情是否會降低速度或效率：

int i = 0;
while(i < 100)
{
    int var = 4;
    i++;
}

which declares int var one hundred times.它聲明瞭int var一百次。 It seems to me like there would be, but I'm not sure.在我看來好像會有，但我不確定。 would it be more practical/faster to do this instead:這樣做會更實用/更快嗎：

int i = 0;
int var;
while(i < 100)
{
    var = 4;
    i++;
}

or are they the same, speedwise and efficiency-wise?或者它們在速度和效率方面是否相同？

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解決方案：

參考一： https://en.stackoom.com/question/47iF
參考二： https://stackoom.com/question/47iF