#include <cstdio>
#include <iostream>
using ll=long long;
constexpr int N=4e5+5;
template<typename T,int max_size,int page_size>
class MemoryPool{
	T pool[max_size*page_size],*stk[max_size],**top;
public:
	MemoryPool():top(stk+max_size){
		std::cerr<<"Start: "<<top<<std::endl;
		int i=0;
		for(T*&x:stk)x=pool+page_size*(i++);
	}
	T*alloc(){
		std::cerr<<"Alloc: "<<top<<std::endl;
		return *--top;
	}
	void free(T*p){*top++=p;}
};
template<int n,int base>
class lll{
	static MemoryPool<int,10,n>mp;
	int *a,len;
public:
	lll():a(mp.alloc()),len(0){}
	~lll(){mp.free(a);}
};
template<int n,int base>
MemoryPool<int,10,n>lll<n,base>::mp;
lll<N,10>a;
int main(){
	return 0;
}

rt，本来想写个高精的，结果a的构造函数比mp的构造函数先调用，导致top还没被初始化就被alloc()调用了