25. Placement New Static Buffer

#include <iostream>
#include <cstdint>
#include <new>
using namespace std;

// Simple struct representing a data block
struct Block {
    int id;
    int value;
};

int main() {
    int id, value;
    cin >> id >> value;

    // Properly aligned static buffer for one Block
    alignas(Block) uint8_t buffer[sizeof(Block)];

    // Construct Block object inside buffer using placement new
    Block* ptr = new (buffer) Block;

    ptr->id = id;
    ptr->value = value;

    // Output fields
    cout << ptr->id << " " << ptr->value;

    // Explicit destructor call (required for placement new)
    ptr->~Block();

    return 0;
}

Explanation & Logic Summary:

• alignas(Block) guarantees correct alignment for the object
• uint8_t buffer[sizeof(Block)] reserves raw memory only
• new (buffer) Block constructs the object in-place
• Placement new does not allocate memory
• Destructor must be called manually
• This pattern avoids heap usage entirely

Firmware Relevance & Real-World Context:

• Placement new is widely used when:
  • Heap allocation is forbidden
  • Objects must live in static memory
  • Drivers, RTOS objects, or protocol stacks are constructed in-place
• Proper alignment is mandatory on many MCUs
• This pattern is common in safety-critical and real-time firmware systems