问题描述
这是C ++ code正确吗？
Is this C++ code correct?
const size_t tabsize = 50;
int tab[tabsize];
问题是，我已经看到了这个问题很多不同意见。即使人## C ++的IRC频道和编程论坛声称根本不同的两回事。
The problem is that I've already seen numerous conflicting opinions on that matter. Even people at ##c++ IRC channel and programming forums claim radically different things.
有人说上面的code是正确的。
Some people say the above code is correct.
其他人则认为它不是，它应该一定是这样的：
Others argue that it is not, and that it should necessarily be like this:
constexpr size_t tabsize = 50;
int tab[tabsize];
因为我已经糊涂了足够的相互冲突的C ++专家的意见，我能请向一个合理的备份的答案？非常感谢！
Since I'm already confused enough by conflicting opinions of "C++ experts", could I please ask for a reasonably backed up answer? Many thanks!
推荐答案
在C ++中恒整数比其他类型不变区别对待。如果它们与编译时间常数前pression初始化它们可以在编译时前pression使用。这样做（在 C ++ ，当 constexpr 不存在的开始），使数组的大小可能是一个 const int的而不是的#define D（就像你不得不在C）：
In C++ constant integers are treated differently than other constant types. If they are initialized with a compile-time constant expression they can be used in a compile time expression. This was done (in the beginning of C++, when constexpr didn't exist) so that array size could be a const int instead of #defined (like you were forced in C):
的（假设没有VLA扩展）的
const int s = 10;
int a[s]; // OK in C++
const int s2 = read(); // assume `read` gets a value at run-time
int a2[s2]; // Not OK
int x = 10;
const int s3 = x;
int a3[s3]; // Not OK
因此，答案是肯定的，你可以使用一个const整型变量作为数组的大小如果它是由编译时间常数前pression初始化
So the answer is yes, you can use a const integer variable as the size of an array if it was initialized by a compile time constant expression
这是另外一个问题。这个问题是关于 INT VS 浮动 常量和 constexpr ，所以不完全重复，但答案适用于这里非常漂亮。
This is my answer from another question. That question is about int vs float const and constexpr, so not exactly a duplicate, but the answer applies here very nicely.
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