The mem_limit() function, in libXtTest/avs_func.c, is very hard to comprehend,
and I suspect it may be incorrect on Linux because malloc() is not guaranteed to
return NULL when there is not enough memory.

The code looks like this:

size_t
mem_limit()
{
	char	*ptr;
	size_t	hbit,i,j;

	j = 0;
	for (hbit=(((size_t)-1)>>1)+1;hbit;hbit=(ptr)?(i>>1):(i>>2)){
		for(i=1;
			(ptr=malloc(i|j)) && (free(ptr),1) && (i<hbit);
		i<<=1);
			j |= (ptr) ? i : i >> 1;
	}
	return(j);
}