[Mesa3d-users] offscreen render segmentation fault with mesa 7.7

[Geng, X. (NIH/N. [C] <ge...@ni...>]

Hi,

I'm new to mesa and openGL. I'm trying to do offscreen rendering on a 64bit Suse Linux machine. 

I started from a mesa demo code progs/osdemos/osdemo.c. I copied the main part below:
 
   /* Create an RGBA-mode context */
#if OSMESA_MAJOR_VERSION * 100 + OSMESA_MINOR_VERSION >= 305
   /* specify Z, stencil, accum sizes */
   ctx = OSMesaCreateContextExt( OSMESA_RGBA, 16, 0, 0, NULL );
#else
   ctx = OSMesaCreateContext( OSMESA_RGBA, NULL );
#endif
   if (!ctx) {
      printf("OSMesaCreateContext failed!\n");
      return 0;
   }

   /* Allocate the image buffer */
   buffer = malloc( Width * Height * 4 * sizeof(GLubyte) );
   if (!buffer) {
      printf("Alloc image buffer failed!\n");
      return 0;
   }

   /* Bind the buffer to the context and make it current */
   if (!OSMesaMakeCurrent( ctx, buffer, GL_UNSIGNED_BYTE, Width, Height )) {
      printf("OSMesaMakeCurrent failed!\n");
      return 0;
   }  

   {
      int z, s, a;
      glGetIntegerv(GL_DEPTH_BITS, &z);
      glGetIntegerv(GL_STENCIL_BITS, &s);
      glGetIntegerv(GL_ACCUM_RED_BITS, &a);
      printf("Depth=%d Stencil=%d Accum=%d\n", z, s, a);
   }
   render_image();

I compiled the code with no problem:
gcc osdemo.c  -lglut -lGLU -lOSMesa -lm -o osdemo

But when I run it:
./osdemo output.ppm 400 400

It gave me a seg fault. I used gdb to debug it, and the error message is:

(gdb) run
Starting program: /data/380/gengx/tools/Mesa-7.5.1/progs/osdemos/osdemo output.ppm 400 400
[Thread debugging using libthread_db enabled]

Program received signal SIGSEGV, Segmentation fault.
glGetIntegerv () at ../../../src/mesa/x86-64/glapi_x86-64.S:9444
9444            movq    2104(%rax), %r11
Current language:  auto; currently asm

Our own offscreen code (also using " OSMesaCreateContextExt " and " OSMesaMakeCurrent ") faced the same segmentation problem. Basically it gave a segmentation at whatever gl routine first called in the code. 

We are currently using mesa7.7.

Any suggestion is appreciated! Thanks.

Xiujuan