My texture is not displayed in SDL

What happens is that I define code to show a texture part in C ++ with the SDL libraries. Something like this:

 #include <SDL.h>
 #include <stdio.h>

SDL_Window * ventana;
SDL_Renderer * render;
SDL_Texture * textura;

SDL_Rect tRect1, tRectD1; // Uno selecciona el área de la textura y el otro dónde se va a mostrar.

int main()
{
    // ... omitimos la inicialización, crear ventana, contexto y establecer color
    while(!salir) // Variable que cuando se vuelva verdad saldrá del bucle 
    {
        while(SDL_PollEvent(&evento)){
            // Insertense los eventos que quiera...
        }

        SDL_RenderClear() // Limpia la pantalla
        SDL_RenderCopy(render, textura, &tRect1, &tRectD1); // Función de render
        SDL_RenderPresent() // Actualiza la pantalla
    }
    // Insertese código de cierre
    return 0;
}

The problem arises when initializing the structures rect "tRect1" and "tRectD1"; if I initialize them out of the main while -while (! exit) -, the image is not displayed, but, when initializing them inside the loop, if it shows it. Does anyone know why and how can I solve it?

Thanks I remain attentive to any suggestions.