c - How to find the 'sizeof' (a pointer pointing to an array)? -


first off, here code:

int main()  {     int days[] = {1,2,3,4,5};     int *ptr = days;     printf("%u\n", sizeof(days));     printf("%u\n", sizeof(ptr));      return 0; }

is there way find out size of array ptr pointing (instead of giving size, 4 bytes on 32-bit system)?

no, can't. compiler doesn't know pointer pointing to. there tricks, ending array known out-of-band value , counting size until value, that's not using sizeof.

another trick 1 mentioned zan, stash size somewhere. example, if you're dynamically allocating array, allocate block 1 int bigger 1 need, stash size in first int, , return ptr+1 pointer array. when need size, decrement pointer , peek @ stashed value. remember free whole block starting beginning, , not array.


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