C ++ SDL中的SIGSEGV错误

Question

This code is making SIGSEGV error and I couldn't puzzle out why.

#include<SDL.h>

SDL_Window* g_pWindow = 0;
SDL_Renderer* g_pRenderer = 0;
int main(int argc, char* args[])
{
    // initialize SDL
    if(SDL_Init(SDL_INIT_EVERYTHING) >= 0)
    {
       // if succeeded create our window
       g_pWindow = SDL_CreateWindow("Chapter 1: Setting up SDL",
       SDL_WINDOWPOS_CENTERED, SDL_WINDOWPOS_CENTERED,640, 480,SDL_WINDOW_SHOWN);
       // if the window creation succeeded create our renderer
       if(g_pWindow != 0)
       {
           g_pRenderer = SDL_CreateRenderer(g_pWindow, -1, 0);
       }
    }
    else
    {
            return 1; // sdl could not initialize
    }
    // everything succeeded lets draw the window
    // set to black // This function expects Red, Green, Blue and
    // Alpha as color values
    SDL_SetRenderDrawColor(g_pRenderer, 0, 0, 0, 255);
    // clear the window to black
    SDL_RenderClear(g_pRenderer);
    // show the window
    SDL_RenderPresent(g_pRenderer);
    // set a delay before quitting
    SDL_Delay(5000);
    // clean up SDL
    SDL_Quit();
    return 0;
}

This code is from "SDL game development" book by Sean Mitchell. But instead of Visual Studio as suggested in the book I'm using mingw. I've configured everything as described in lazyfoo's tutorials: http://lazyfoo.net/tutorials/SDL/01_hello_SDL/windows/mingw/index.php Btw his "Hello SDL" works fine. Here is my Makefile:

#OBJS specifies which files to compile as part of the project
OBJS = main.cpp

#OBJ_NAME specifies the name of our exectuable
OBJ_NAME = hello

#This is the target that compiles our executable
all : $(OBJS)
    g++ $(OBJS) -IC:\Artur\Projects\SDL\include\SDL2 -LC:\Artur\Projects\SDL\lib -w  -lmingw32 -lSDL2main -lSDL2 -o $(OBJ_NAME) -g

And what I've found with gdb:

(gdb) run
Starting program: C:\Artur\Projects\CPP\Snake/hello.exe
[New Thread 4800.0x45c]
[New Thread 4800.0xc7c]
[New Thread 4800.0xc48]
[New Thread 4800.0xa8c]
[New Thread 4800.0xbc0]
[New Thread 4800.0x1350]

Breakpoint 1, SDL_main (argc=argc@entry=1, args=args@entry=0x3b0008)
    at main.cpp:17
17      g_pRenderer = SDL_CreateRenderer(g_pWindow, -1, 0);
(gdb) s
[New Thread 4800.0xf98]

Program received signal SIGSEGV, Segmentation fault.
0x00000000 in ?? <>

So I know that the problem in SDL_CreateRenderer function but I don't know what's wrong.

Answer 1

You are getting Segmentation fault because of this line -

g_pRenderer = SDL_CreateRenderer(g_pWindow, -1, 0);

The reason is g_pWindow is NULL . As you have initialized it with NULL in this line -

SDL_Window* g_pWindow = 0;

You need to provide valid pointer of SDL_Window .

For details, please check this.