How to determine the length of an array at compile time?

问题

Are there macros or builtins that can return the length of arrays at compile time in GCC?

For example:

int array[10];

For which:

sizeof(array) == 40
???(array) == 10

Update0

I might just point out that doing this in C++ is trivial. One can build a template that returns the number inside []. I was certain that I'd once found a lengthof and dimof macro/builtin in the Visual C++ compiler but cannot find it anymore.

回答1:

(sizeof(array)/sizeof(array[0]))

Or as a macro

#define ARRAY_SIZE(foo) (sizeof(foo)/sizeof(foo[0]))

    int array[10];
    printf("%d %d\n", sizeof(array), ARRAY_SIZE(array));

40 10

Caution: You can apply this ARRAY_SIZE() macro to a pointer to an array and get a garbage value without any compiler warnings or errors.

回答2:

I wouldn't rely on sizeof since aligment stuff could mess up the thing.

#define COUNT 10
int array[COUNT];

And then you could use COUNT as you want.

回答3:

    sizeof(array) / sizeof(int) 

回答4:

im not aware of a builtin that does this, but i recently used:

sizeof(array)/sizeof(array[0])

to do just that

来源：https://stackoverflow.com/questions/3388656/how-to-determine-the-length-of-an-array-at-compile-time