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How to find the size of a variable with out using sizeof

using C, can we somehow find the size of a pointer without using sizeof operator ? though i found this question at lot of places while googling, but i couldn’t find any answer. any help will be greatly appreciated. thanks

Answer 1

Here is a small but legal hack that you can use:

int *unused = NULL;
int **ptr = &unused;
printf("%tu\n", ((char*)(ptr+1))-(char*)ptr);

Here is how it works:

• Recall that adding N to a pointer adds N times the size of the type pointed to; hence (ptr+1) adds sizeof(int*) to the “raw” value of ptr
• sizeof(char) is always 1, so casting to char* lets you subtract “raw” values; the result is the sizeof added by the (ptr+1) operation.