#include <iostream>
class Foo {
public:
    Foo()
    {
        throw std::runtime_error("Oops!");
    }
};
struct Arena {
    bool touched = false;
};
void* operator new(std::size_t, Arena& arena)
{
    std::cout << "new has called.\n";
    return ::operator new(sizeof(Foo));
}
void operator delete(void*, Arena& arena)
{
    std::cout << "delete has called.\n";
    arena.touched = true;
}
int main(int argc, char** argv)
{
    Arena arena;
    try {
        new(arena) Foo;
    }
    catch(...) {
        std::cout << "exception was thrown.\n";
    }
    // This differs for different type of builds.
    std::cout << std::boolalpha << "arena.touched == " << arena.touched << '\n';
    return 0;
}
 

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