0 Replies Latest reply on Oct 17, 2014 2:05 AM by fletcheb

    GL_ARB_shader_storage_buffer_object ".length()" for unsized arrays returns erroneous value


      I am using OpenGL 4.3 core profile to do various things in OpenGL under Linux.  I am having trouble when using shader storage buffers where the last component of a shader storage block is an unsized array.  I do not have this problem when using the NVIDIA driver.  Is this a driver bug, or am I doing something wrong??



      Description of problem:


      It appears that the ".length()" function for unsized arrays at the end of shader storage blocks always returns 0. This is contrary to the specification for GL_ARB_shader_storage_buffer_object where "Issue (19)" describes ".length()" as returning the size of unsized arrays based on the size of the provided buffer object.



      Steps to reproduce:

      1. Include a shader with a shader storage block containing an unsized array as the last component



      layout(std430, binding=0) buffer Test


        float test[];




      2. Bind a shader storage buffer with a size equivalent to the desired shader storage block unsized array size in bytes



      GLuint testBuffer;

      glGenBuffers(1, &testBuffer);

      glBindBufferBase(GL_SHADER_STORAGE_BUFFER, 0, testBuffer);

      glBufferData(GL_SHADER_STORAGE_BUFFER, sizeof(float)*4, NULL, GL_DYNAMIC_DRAW);



      3. In the shader, access the shader storage block unsized array ".length()" function and check that it contains the number of elements we allocated via




      int elements = test.length();




        // the .length() function has returned a value outside the

        // GL_ARB_shader_storage_buffer_object specification





      Actual result:


      elements = 0


      Expected result:


      elements = 4