SDL，OpenGL：分段錯誤

Question

當我嘗試使用openGL生成紋理時，在此方法中出現了分割錯誤：

 void RendererGL::create_gl(SDL_Surface * surf, GLuint * tex ) {
   GLenum format;   GLint  colors_amount = surf->format->BytesPerPixel;

   if (colors_amount == 4) {
           if (surf->format->Rmask == 0x000000ff)
                   format = GL_RGBA;
           else
                   format = GL_BGRA;
   }
   else if (colors_amount == 3) {
           if (surf->format->Rmask == 0x000000ff)
                   format = GL_RGB;
           else
                   format = GL_BGR;
   }
   else {
       gCritical("Image is not truecolor");
   }
   glGenTextures( 1, tex );

   glBindTexture( GL_TEXTURE_2D, *tex );

   glTexParameteri( GL_TEXTURE_2D, GL_TEXTURE_MIN_FILTER, GL_LINEAR );
   glTexParameteri( GL_TEXTURE_2D, GL_TEXTURE_MAG_FILTER, GL_LINEAR );

   glTexParameteri(GL_TEXTURE_2D, GL_TEXTURE_WRAP_S, GL_CLAMP_TO_EDGE);
   glTexParameteri(GL_TEXTURE_2D, GL_TEXTURE_WRAP_T, GL_CLAMP_TO_EDGE);

   glTexImage2D( GL_TEXTURE_2D, 0, colors_amount, surf->w, surf->h, 0, format,
                 GL_UNSIGNED_BYTE, surf->pixels ); }

我只有在使用nvidia驅動程序的debian上才有這個問題。 使用開源驅動程序，應用程序可以正常運行。 Valgrind測試返回：

[ Info ] RendererGL::Init GL
==13033== Thread 3:
==13033== Invalid read of size 8
==13033==    at 0x51293C9: ??? (in /usr/lib/x86_64-linux-gnu/nvidia/current/libGL.so.304.64)
==13033==    by 0x419B0F: RendererGL::initGL() (RendererGL.cpp:12)
==13033==    by 0x41036C: Renderer::Renderer() (Renderer.cpp:27)
==13033==    by 0x4058EA: Renderer::getInstance() (Renderer.hpp:17)
==13033==    by 0x40B648: StandardReferences::StandardReferences() (StandardReferences.hpp:13)
==13033==    by 0x414C26: Map::Map(short**, unsigned short, unsigned int, unsigned int) (Map.cpp:8)
==13033==    by 0x4136E4: MapManager::loadMapFromFile(std::string, short) (MapManager.cpp:82)
==13033==    by 0x4138A0: MapManager::load() (MapManager.cpp:97)
==13033==    by 0x4084BA: Resource::load() (Resource.cpp:36)
==13033==    by 0x4196AF: Splash::initThread(void*) (Splash.cpp:99)
==13033==    by 0x53D0405: ??? (in /usr/lib/x86_64-linux-gnu/libSDL-1.2.so.0.11.4)
==13033==    by 0x5413898: ??? (in /usr/lib/x86_64-linux-gnu/libSDL-1.2.so.0.11.4)
==13033==  Address 0x658 is not stack'd, malloc'd or (recently) free'd
==13033== 
==13033== 
==13033== HEAP SUMMARY:
==13033==     in use at exit: 22,104,451 bytes in 31,729 blocks
==13033==   total heap usage: 47,499 allocs, 15,770 frees, 54,869,707 bytes allocated
==13033== 
==13033== LEAK SUMMARY:
==13033==    definitely lost: 833 bytes in 8 blocks
==13033==    indirectly lost: 1,728 bytes in 38 blocks
==13033==      possibly lost: 269,732 bytes in 99 blocks
==13033==    still reachable: 21,832,158 bytes in 31,584 blocks
==13033==         suppressed: 0 bytes in 0 blocks
==13033== Rerun with --leak-check=full to see details of leaked memory
==13033== 
==13033== For counts of detected and suppressed errors, rerun with: -v
==13033== Use --track-origins=yes to see where uninitialised values come from
==13033== ERROR SUMMARY: 12 errors from 2 contexts (suppressed: 6 from 6)

Answer 1

我敢打賭，它是在RGB曲面上進行隔離，而不是RGBA曲面。

嘗試glPixelStorei(GL_UNPACK_ALIGNMENT, 1)​你之前glTexImage2D()調用。

GL_UNPACK_ALIGNMENT默認值為4，這對於RGBA數據來說效果很好，但是會導致OpenGL讀取RGB表面的surf->pixels的末端。

你將不得不使用GL_UNPACK_ROW_LENGTH​如果surf->pitch不為零。