malloc(0)

malloc(0) can either return a null pointer or a pointer to a 0 length region of memory. We can deal with this variation in one of (at least) 3 ways.

• Ignore it.

  
  	#define xnalloc(_t,_n)	((_t*)malloc((_n)*sizeof(_t)))
  

• Have a 0 length region always return 0.

  
  	#define xnalloc(_t,_n)	\
  		( ((_n)==0) ? ((_t*)0) : ((_t*)malloc((_n)*sizeof(_t))) )
  

• Disallow it.

  
  	#define xnalloc(_t,_n)	\
  		( assert((_n) != 0 ), ((_t*)malloc((_n)*sizeof(_t))) )
  

My personal preference is to pick the third. Occasionally it is legitimate to allocate a 0 length object. In that case, we have to write:

	if( n == 0 ) {
	  p = 0;
	}
	else {
	  p = xnalloc(Type, n);
	}

However, fairly often when we are allocating a 0 length object it indicates the presence of a potential bug (n should never have been 0), or a performance optimization (if n is 0, then there is no work to be done, so don't execute the rest of the function).