SDL_DestroyWindow doesn't free memory

Basically, in my program I have to create and destroy a window. I always use the same window pointer creating and destroying the contents (texture and render).

I notice a memory leak in this process so I wrote a simple program to verify this, here the code

#include <iostream>
#include "SDL.h"


int main(int argc, char *argv[])
{
    SDL_Init(SDL_INIT_VIDEO);

    SDL_Window* mainWindow;
    SDL_Renderer* mainRenderer;
    SDL_Texture* mainTexture;

    for (int i = 0; i < 20; i++)
    {
        mainWindow = SDL_CreateWindow("Memory Leak Test v1.0", SDL_WINDOWPOS_CENTERED, SDL_WINDOWPOS_CENTERED, 320, 240, SDL_WINDOW_SHOWN);
        mainRenderer = SDL_CreateRenderer(mainWindow, -1, SDL_RENDERER_ACCELERATED);
        mainTexture = SDL_CreateTexture(mainRenderer, SDL_PIXELFORMAT_ABGR8888, SDL_TEXTUREACCESS_STREAMING, 320, 240);

        if (i == 0)
        {
            std::cout << "SDL Memory Leak Tester, please check the amount of memory\noccupied by the process, then press Enter\n";
            getchar();
        }

        SDL_Delay(1000);

        if (i == 19)
        {
            std::cout << "SDL Memory Leak Tester, please check the amount of memory\noccupied by the process, then press Enter\n";
            getchar();
        }

        SDL_DestroyTexture(mainTexture);
        SDL_DestroyRenderer(mainRenderer);
        SDL_DestroyWindow(mainWindow);
    }

    std::cout << "Test finished, press Enter to close\n";
    getchar();

    return 0;
}

Any idea?