# <memory_resource>

**[<memory_resource>](https://en.cppreference.com/w/cpp/header/memory_resource)** provides polymorphic memory allocators: `std::pmr::memory_resource` and standard containers adapted to use them, like `std::pmr::vector`, `std::pmr::string`. This allows switching allocators (stack, arena, monotonic) at runtime without changing container types.

Use it when you need custom allocation strategies; most code just uses the default allocator.

## Example

This example uses a pmr vector with the default new_delete resource, demonstrating polymorphic memory allocation.

```cpp
// compile: g++ -std=c++17 -o memoryresourceexample memoryresourceexample.cpp
// run: ./memoryresourceexample
// description: pmr vector with a memory resource

#include <memory_resource>
#include <vector>
#include <iostream>

int main() {
    std::vector<int, std::pmr::polymorphic_allocator<int>> vec(std::pmr::new_delete_resource());
    vec.push_back(1);
    vec.push_back(2);
    
    std::cout << "vec size: " << vec.size() << "\n";
    
    return 0;
}
```