Question

How to use the VirtualAlloc function using the Win32 API in C++

Answer 1

#include <windows.h>
#include <iostream>

int main() {
    SIZE_T size = 1024;  // allocate 1 KB

    // Allocate memory
    void* mem = VirtualAlloc(
        nullptr,            // let Windows choose the address
        size,               // number of bytes
        MEM_RESERVE | MEM_COMMIT,
        PAGE_READWRITE      // memory protection
    );

    if (!mem) {
        std::cerr << "VirtualAlloc failed: " << GetLastError() << "\n";
        return 1;
    }

    std::cout << "Allocated at: " << mem << "\n";

    // Use the memory
    char* buffer = static_cast<char*>(mem);
    strcpy_s(buffer, size, "VirtualAlloc is a low-level Windows API function used to allocate memory");

    std::cout << buffer << "\n";

    // Free the memory
    BOOL ok = VirtualFree(mem, 0, MEM_RELEASE);
    if (!ok) {
        std::cerr << "VirtualFree failed: " << GetLastError() << "\n";
    }

    return 0;
}



/*
run:

Allocated at: 000002455A430000
VirtualAlloc is a low-level Windows API function used to allocate memory

*/

 

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