How to get the C pointer array length? [duplicate]

Question

Possible Duplicate:
length of array in function argument

Is there any method like the Java can .length from a C point array? Thank you.

Answer 1

No, given a C pointer you cannot determine it's length in a platform agnostic manner.

For an actual C array though see dirkgently's answer

Answer 2

You could get it using a macro:

#define sizeofa(array) sizeof array / sizeof array[ 0 ]

if and only if the array is automatic and you access it in the scope of its definition as:

#include <stdio.h>
int main() {
   int x[] = { 1, 2, 3 };
   printf("%zd\n", sizeofa( x ));
   return 0;
}

However, if you only have a (decayed) pointer you cannot get the array length without resorting to some non-portable implementation specific hack.