大小为 0 的数组 [英] Array with size 0
问题描述
今天无意中定义了一个二维数组，一维的大小为0，但是我的编译器没有抱怨.我发现以下内容表明这是合法的，至少在 gcc 的情况下是这样:
Today I incidentally defined a two dimensional array with the size of one dimension being 0, however my compiler did not complain. I found the following which states that this is legal, at least in the case of gcc:
但是，我对这种用法有两个疑问:
However, I have two questions on this usage:
首先，这被认为是良好的编程习惯吗?如果是这样，那么我们什么时候应该在现实世界中使用它?
First, is this considered as good programming practice? If so, then when should we use it in real world?
第二，我定义的数组是二维的，一维大小为0.这和一维情况一样吗?例如，
Second, the array I defined was two dimensional, with 0 size for one dimension. Is this the same as the one dimensional case? For example,
int s[0]
int s[0][100]
int s[100][0]
它们在内存和编译器中都是一样的吗?
Are they all the same in the memory and for the compiler?
回复 Greg:我使用的编译器是 gcc 4.4.5.我对这个问题的意图与编译器无关，但是如果有任何特定于编译器的怪癖也会有帮助:)
Reply to Greg: The compiler I am using is gcc 4.4.5. My intention for this problem is not compiler-dependent, however if there are any compiler specific quirks that would be helpful too:)
提前致谢！
推荐答案
在 C++ 中声明零长度的数组是非法的.因此，当您将代码绑定到特定的编译器扩展时，它通常不被认为是一种好的做法.动态大小数组的许多用途最好用容器类代替，例如 std::vector.
In C++ it is illegal to declare an array of zero length. As such it is not normally considered a good practice as you are tying your code to a particular compiler extension. Many uses of dynamically sized arrays are better replaced with a container class such as std::vector.
ISO/IEC 14882:2003 8.3.4/1:
ISO/IEC 14882:2003 8.3.4/1:
如果constant-expression (5.19) 存在，它应该是一个整数常量表达式并且它的值应该大于零.
If the constant-expression (5.19) is present, it shall be an integral constant expression and its value shall be greater than zero.
但是，您可以使用 new[] 动态分配零长度的数组.
However, you can dynamically allocate an array of zero length with new[].
ISO/IEC 14882:2003 5.3.4/6:
ISO/IEC 14882:2003 5.3.4/6:
direct-new-declarator 中的表达式应具有非负值的整数或枚举类型 (3.9.1).
The expression in a direct-new-declarator shall have integral or enumeration type (3.9.1) with a non-negative value.
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