Attachment 39843 Details for Bug 31194 – Example showing the bug

Example showing the bug

test-useprogram.c (text/x-csrc), 2.95 KB, created by Neil Roberts on 2010-10-28 06:00:28 UTC

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Filename:

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Creator: Neil Roberts

Created: 2010-10-28 06:00:28 UTC

Size: 2.95 KB

patch

obsolete

>#include <GL/glew.h>
>#include <GL/freeglut.h>
>#include <GL/gl.h>
>#include <stdio.h>
>#include <string.h>
>
>typedef struct
>{
>  float x, y;
>} Vert;
>
>static GLuint
>create_program (void)
>{
>  static const GLchar source[] =
>    "void main ()\n"
>    "{\n"
>    "  gl_FragColor = vec4 (0.0, 0.0, 1.0, 1.0);\n"
>    "}\n";
>  const GLchar *source_strings[] = { source };
>  GLint source_lengths[] = { sizeof (source) - 1 };
>  GLuint program, shader;
>  GLint compile_status, link_status;
>
>  shader = glCreateShader (GL_FRAGMENT_SHADER);
>  glShaderSource (shader, 1, source_strings, source_lengths);
>  glCompileShader (shader);
>  glGetShaderiv (shader, GL_COMPILE_STATUS, &compile_status);
>
>  if (!compile_status)
>    {
>      fprintf (stderr, "Failed to compile shader\n");
>      exit (1);
>    }
>
>  program = glCreateProgram ();
>  glAttachShader (program, shader);
>  glLinkProgram (program);
>  glGetProgramiv (program, GL_LINK_STATUS, &link_status);
>
>  if (!link_status)
>    {
>      fprintf (stderr, "Failed to link shader\n");
>      exit (1);
>    }
>
>  return program;
>}
>
>static void
>show_error (const char *msg)
>{
>  printf ("%s: 0x%x\n", msg, glGetError ());
>
>  /* Clear any other errors */
>  while (glGetError () != GL_NO_ERROR);
>}
>
>static void
>display_cb (void)
>{
>  GLuint program;
>  static const Vert verts[] =
>    {
>      { -0.5, -0.5 },
>      { 0.0, -0.5 },
>      { -0.5, 0.5 },
>      { 0.0, 0.5 }
>    };
>
>  glClear (GL_COLOR_BUFFER_BIT);
>  glColor3f (1.0, 0.0, 0.0);
>
>  program = create_program ();
>
>  glUseProgram (program);
>  /* We should be able to delete the program immediately. According to
>     the OpenGL docs it will stay alive until another program is
>     selected */
>  glDeleteProgram (program);
>
>  glEnableClientState (GL_VERTEX_ARRAY);
>  glVertexPointer (2, GL_FLOAT, sizeof (Vert), &verts[0].x);
>
>  /* Draw the quad once with the program */
>  glDrawArrays (GL_TRIANGLE_STRIP, 0, 4);
>
>  /* Calling glDrawPixels should invoke the mesa meta save/restore
>     code. We haven't deliberately changed the program so it should
>     still be valid but mesa meta changes the program for us so the
>     program will end up deleted. It also throws a GLerror because it
>     tries to use a deleted program when the old state is restored */
>  show_error ("before glDrawPixels: ");
>  glDrawPixels (1, 1, GL_RGBA, GL_UNSIGNED_BYTE,
>                (GLubyte[]) { 0x00, 0xff, 0x00, 0xff });
>  show_error ("after glDrawPixels: ");
>
>  /* We should still be able to draw the quad again using the shader,
>     but Mesa will have delete it for us so the quad ends up red */
>  glPushMatrix ();
>  glTranslatef (0.5, 0.0, 0.0);
>  glDrawArrays (GL_TRIANGLE_STRIP, 0, 4);
>  glPopMatrix ();
>
>  glDisableClientState (GL_VERTEX_ARRAY);
>  glUseProgram (0);
>
>  glutSwapBuffers ();
>}
>
>int
>main (int argc, char **argv)
>{
>  glutInit (&argc, argv);
>  glutInitDisplayMode (GLUT_RGB | GLUT_DOUBLE);
>  glutInitWindowSize (640, 480);
>  glutCreateWindow ("Test keep program");
>  glutDisplayFunc (display_cb);
>  glewInit ();
>
>  glutMainLoop ();
>
>  return 0;
>}

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Attachments on bug 31194: 39843

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