26. Reinitialize Object In-Place

#include <iostream>
#include <cstdint>
#include <new>

using namespace std;

// Mode struct representing a firmware mode/level
struct Mode {
    int level;
};

int main() {
    int firstLevel, secondLevel;
    cin >> firstLevel >> secondLevel;

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

    // Construct first Mode object in-place
    Mode* modePtr = new (buffer) Mode{firstLevel};

    // Destroy first object
    modePtr->~Mode();

    // Reconstruct Mode object with new level in same buffer
    modePtr = new (buffer) Mode{secondLevel};

    // Print the updated mode level
    cout << modePtr->level;

    // Final destructor call
    modePtr->~Mode();

    return 0;
}

Explanation & Logic Summary:

• The same memory buffer is reused for both object constructions.
• alignas(Mode) ensures correct alignment for placement new.
• Placement new constructs objects without allocating memory.
• Manual destructor calls are required before reuse.
• This models deterministic, heap-free reinitialization common in firmware.

Firmware Relevance & Real-World Context:

• Common in embedded systems with fixed memory layouts
• Used for:
  • In-place reset of control structures
  • State machine reinitialization
  • Driver reconfiguration
  • Avoiding heap fragmentation
• Ensures deterministic behavior and memory safety in firmware environments