Question

我正在尝试制作一个程序来根据键盘输入移动一个盒子，但此刻它只是设置为在屏幕上呈现一个绿色矩形。但是，程序似乎初始化窗口，然后在终止之前返回“分段错误（核心转储）”。我根本没有编译错误，相当一部分代码与我在网上发现的教程相匹配。如果它有所不同，我正在使用GCC在Ubuntu上运行Code :: Blocks。

main基本上按顺序调用名为init，drawRect和close的函数（如下所示），根据成功或失败打印语句。

编辑：将其缩小到close，如下所示。特别是，SDL_FreeSurface和SDL_Quit给我带来了问题。我还清理了关于指针处理的close（以及程序的其他部分）并制作了一个新的pastebin文件。

接近：

void close()
{
   // Deallocate gScreenSurface
   SDL_FreeSurface(gScreenSurface);
   gScreenSurface=NULL;

   // Destroy renderer
   SDL_DestroyRenderer(gRenderer);
   gRenderer=NULL;

   // Destroy gWindow
   SDL_DestroyWindow(gWindow);
   gWindow=NULL;

   SDL_Quit();
}

这是 new 完整源代码，包括指针初始化，包含和伪代码：

/* === Includes === */
#include <cstdlib>
#include <stdio.h>
#include "SDL2/SDL.h"

using namespace std;

/* === Constants === */
const int SCREEN_WIDTH = 640;
const int SCREEN_HEIGHT = 480;

/* === Enums === */
/*enum Keys {KEY_DEFAULT,
           KEY_UP,
           KEY_DOWN,
           KEY_LEFT,
           KEY_RIGHT,
           KEY_TOTAL};*/

/* === Prototypes === */

bool init();
bool drawRect(SDL_Renderer* pRenderer, SDL_Rect* pRect, int pX, int pY, int pW, int pH, int pR, int pG, int pB, int pA);
void close();

/* === Pointer Initialization === */
SDL_Window* gWindow = NULL;
SDL_Surface* gScreenSurface = NULL;
SDL_Renderer* gRenderer = NULL;
SDL_Rect* gRect = NULL;

/**==================================================
Box Mover

This was intended to be a learning activity to
teach myself how to use SDL, in particular basic
"block" graphics and keyboard inputs.

Unfortunately, I can't figure out why it's always
returning seg fault. I think it's outside of main,
but I can't be sure.
==================================================**/

int main()
{
   if(!init())
      printf("Failed to initialize!\n");
   else
   {
      if(!drawRect(gRenderer, gRect, 0, 0, SCREEN_WIDTH, SCREEN_HEIGHT, 0, 255, 0, 255))
         printf("Failed to draw rectangle!\n");
      else
      {
         /*SDL_BlitSurface( gImage, NULL, gScreenSurface, NULL);
         SDL_UpdateWindowSurface(gWindow);
         SDL_Delay(2000);*/
         printf("Success in main!\n"); // Placeholder until I figure out why I'm getting a seg fault, then I can fix the contents.
      }
   }
   close();

   return 0;
}

/*=========================
Init

Initializes SDL
Returns true for success, false for failure
Prints error on failure
=========================*/
bool init()
{
   //Initialization flag
   bool success = true;
   if( SDL_Init( SDL_INIT_VIDEO ) < 0 )
   {
      printf( "SDL could not initialize! SDL_Error: %s\n", SDL_GetError() );
      success = false;
   }
   else
   {
      gWindow = SDL_CreateWindow( "Box Mover", 0, 0, SCREEN_WIDTH, SCREEN_HEIGHT, 0 );
      if( gWindow == NULL )
      {
         printf( "Window could not be created! SDL_Error: %s\n", SDL_GetError() );
         success = false;
      }
      else
      {
         gScreenSurface = SDL_GetWindowSurface( gWindow );
      }
   }
   return success;
}

/*=========================
Draw Rectangle

Draws a rectangle of specified color and location

TO DO:
Check to see if renderer needs to be deallocated here.

Inputs:
>> pRenderer:     SDL_Renderer pointer which can be thought of as a drawing tool
>> pRect:         SDL_Rect pointer which holds location and size data
>> pX, pY:        X-Y location of the upper left corner of the rectangle
>> pR, pG, pB:    Color values (technically Uint8, 0-255)
>> pA:            Alpha (transparency) value of the rectangle (also technically Uint8)
=========================*/
bool drawRect(SDL_Renderer* pRenderer, SDL_Rect* pRect, int x, int y, int w, int h, int r, int g, int b, int a)
{
   bool success = true;

   pRenderer=SDL_CreateRenderer(gWindow, -1, SDL_RENDERER_SOFTWARE);
   if(pRenderer==NULL)
   {
      printf("Renderer could not be created! SDL Error: %s\n", SDL_GetError());
      success=false;
   }
   else
   {
      pRect = new SDL_Rect;
      if(pRect == NULL)
      {
         printf("Could not create rectangle! SDL Error: %s\n", SDL_GetError());
         success=false;
      }
      else
      {
            pRect->x = x;
            pRect->y = y;
            pRect->w = w;
            pRect->h = h;

         SDL_SetRenderDrawColor(pRenderer, r, g, b, a);

         if(SDL_RenderDrawRect(pRenderer, pRect) < 0)
         {
            printf("Rectangle could not be rendered! SDL Error: %s\n", SDL_GetError());
            success=false;
         }
      }
   }
   return success;
}

/*=========================
Close

Closes the SDL systems cleanly, deallocating memory.

Found the seg fault! It's this fucker!
In particular, SDL_FreeSurface and SDL_Quit
=========================*/
void close()
{
   // Deallocate gScreenSurface
   SDL_FreeSurface(gScreenSurface);
   gScreenSurface=NULL;
   printf("Surface closed. Working on renderer...\n");

   // Destroy renderer
   SDL_DestroyRenderer(gRenderer);
   gRenderer=NULL;
   printf("Renderer closed. Working on window...\n");

   // Destroy gWindow
   SDL_DestroyWindow(gWindow);
   gWindow=NULL;
   printf("Window closed. Working on SDL...\n");

   SDL_Quit();
   printf("SDL closed.\n");
}

Answer 1

您通过值将SDL_Renderer *renderer指针传递给drawRect函数，并在该函数中初始化它。这并没有初始化你在全局范围内的指针，它会使你在退出函数时丢失的副本初始化。您已经close在全局范围指针SDL_DestroyRenderer上调用NULL。{/ 1}。

如果要初始化drawRect函数内的全局，则需要将指针传递给函数的指针（SDL_Renderer **）。

在drawRect函数中，您正在调用SDL_RenderDrawRect，这会将矩形渲染到后台缓冲区，然后在屏幕上绘制它，您需要调用{{1} }}

Answer 2

不要试图释放从SDL_GetWindowSurface()返回的表面，SDL管理返回指针本身的生命周期：

gScreenSurface = SDL_GetWindowSurface( gWindow );
...
SDL_FreeSurface(gScreenSurface);

请参阅SDL_GetWindowSurface()的文档（强调我的）：

说明

如有必要，将使用窗口的最佳格式创建新曲面。当窗口被破坏时，该表面将被释放。 不要释放此表面。

SDL2分段故障

2 个答案: