为什么没有可变大小的数组在栈? [英] Why no variable size array in stack?
问题描述
我真的不明白,为什么我不能在堆栈上的可变大小的数组,所以像
I don't really understand why I can't have a variable size array on the stack, so something like
foo(int n) {
int a[n];
}
据我了解的数据段的一部分堆栈(-segment),因此它不是固定大小的。
As I understand the stack(-segment) of part of the data-segment and thus it is not of "constant size".
推荐答案
变长数组(VLA)是不是在C ++允许按C ++标准。结果
许多编译器包括gcc支持它们作为一个编译器扩展,但要注意的是,使用这样的扩展任何code是非便携式是重要的。
Variable Length Arrays(VLA) are not allowed in C++ as per the C++ standard.
Many compilers including gcc support them as a compiler extension, but it is important to note that any code that uses such an extension is non portable.
C ++提供的 的std ::矢量 执行类似的功能< STRONG> VLA
有一个 建议 在C ++ 11引入变长数组,但最终还是放弃了,因为它需要用C大的变化的类型系统++。是能够不浪费空间,或要求未使用的元素构造函数创建堆栈小数组的好处被认为足以在C ++类型系统大的变化并不显著。
There was a proposal to introduce Variable Length Arrays in C++11, but eventually was dropped, because it would need large changes to the type system in C++. The benefit of being able to create small arrays on stack without wasting space or calling constructors for not used elements was considered not significant enough for large changes in C++ type system.
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