stupid small GC allocator

gc.cpp

#include <cstdio>
#include <cstdint>
#include <iostream>
#include <algorithm>
using namespace std;

template<typename T>
T * gcalloc(uintptr_t * buf, size_t qty, size_t max) {
    if (buf == nullptr) { 
        buf = new uintptr_t[max]; *buf = (uintptr_t)&buf[1]; }
	auto p = *buf;
	*buf += (qty * sizeof(T) / 8 + 1) * 8;
	return (T *)p;
}

int main(int argc, char ** argv) {
	const int max_gc = 2 * 1024 * 1024;
	uintptr_t * gc = nullptr;
	auto item1 = gcalloc<float>(gc, 2, max_gc);
	auto item2 = gcalloc<int>(gc, 1, max_gc);
	auto item3 = gcalloc<char>(gc, 5, max_gc);
	item1[0] = 6.66; item1[1] = 3.33;
	item2[0] = 1;
    string sitem3(item3);
    sitem3.replace(0, 2, "ok");
    //bonus functional programming
    auto compose = [] (auto f1, auto f2) { 
        return [f1, f2] (auto i) { 
            f2(f1(i)); }; };
    auto lcast = [] (auto i) { return (float) i; };
    auto lcout = [] (auto i) { cout << i << endl; };
    for_each(item1, item1 + 2, lcout);
    for_each(item2, item2 + 1, compose(lcast, lcout));
    cout << item3 << endl;
    //throw everything away
	delete gc;
    return 0;
}