Ask HN: C with Array.size?

Do you know that, for statically defined arrays, you can get the size like this:

   int foo[10];
   int ten = sizeof(foo)/sizeof(foo[0]);

Of course, that doesn’t work if you do that with a function argument because you can’t pass arrays as arguments, only pointers, so a function can’t know whether a passed value is a statically defined array or dynamically allocated.

   int f(int * foo) {
       return sizeof(foo)/sizeof(foo[0]); // 
   }
   int notTen = f(foo);

That even is the case when you do things like these (https://stackoverflow.com/a/2375038):

   int f(int foo[10]) {
       return sizeof(foo)/sizeof(foo[0]);
   }
   int notTen = f(foo);

or

   int f(int foo[static 10]) {
       return sizeof(foo)/sizeof(foo[0]);
   }
   int notTen = f(foo);

> store it in the bytes before the start of the array

Ah, Pascal strings. There is a reason why they have lost the battle.