Thread: Size of an object/variable from its pointer?

Does anyone know if its possible to find the size of an variable from a pointer to the said object. I have the below code (and similar code in my_malloc, which for obvouse reasons is simpler to implement) ovcourse the below returns the size of the pointer not the object, can anyone help?

Code:

void my_free(void *ptr){
	div_t temp;
	
	if (memmoryusage == NULL){
		memmoryusage = 0;
	}
	
	memmoryusage = memmoryusage - sizeof(&ptr);

	temp = div( memmoryusage, 100 );
	printf("(F) MEMORY = %d, %d, %d%\n", memmoryusage, sizeof(&ptr), temp.quot);
	free(ptr);
	
}