Initialize destinations variables before calling GL functions...

gpu/command_buffer/client/gles2_demo_cc.cc

 // Copyright (c) 2009 The Chromium Authors. All rights reserved.
 // Use of this source code is governed by a BSD-style license that can be
 // found in the LICENSE file.
 
 // This file is here so other GLES2 related files can have a common set of
 // includes where appropriate.
 
 #include "../client/gles2_demo_cc.h"
 #include "../common/logging.h"
 
@@ skipping 29 matching lines @@
   CheckGLError("LoadShader", __LINE__);
   GLuint shader = glCreateShader(type);
   if (shader == 0) {
     return 0;
   }
   // Load the shader source
   glShaderSource(shader, 1, &shaderSrc, NULL);
   // Compile the shader
   glCompileShader(shader);
   // Check the compile status
-  GLint value;
+  GLint value = 0;
   glGetShaderiv(shader, GL_COMPILE_STATUS, &value);
   if (value == 0) {
     char buffer[1024];
     GLsizei length = 0;
     glGetShaderInfoLog(shader, sizeof(buffer), &length, buffer);
     std::string log(buffer, length);
     GPU_DLOG(gpu::ERROR) << "Error compiling shader:" << log;
     glDeleteShader(shader);
     return 0;
   }
@@ skipping 32 matching lines @@
   }
   glAttachShader(programObject, vertexShader);
   glAttachShader(programObject, fragmentShader);
   // Bind g_Position to attribute 0
   // Bind g_TexCoord0 to attribute 1
   glBindAttribLocation(programObject, 0, "g_Position");
   glBindAttribLocation(programObject, 1, "g_TexCoord0");
   // Link the program
   glLinkProgram(programObject);
   // Check the link status
-  GLint linked;
+  GLint linked = 0;
   glGetProgramiv(programObject, GL_LINK_STATUS, &linked);
   if (linked == 0) {
     char buffer[1024];
     GLsizei length = 0;
     glGetProgramInfoLog(programObject, sizeof(buffer), &length, buffer);
     std::string log(buffer, length);
     GPU_DLOG(gpu::ERROR) << "Error linking program:" << log;
     glDeleteProgram(programObject);
     return;
   }
@@ skipping 52 matching lines @@
 }
 
 }  // anonymous namespace.
 
 void GLFromCPPInit() {
   CheckGLError("GLFromCPPInit", __LINE__);
   glClearColor(0.f, 0.f, .7f, 1.f);
   g_texture = CreateCheckerboardTexture();
   InitShaders();
   CheckGLError("GLFromCPPInit", __LINE__);
+
+  char buf[128];
+  glReadPixels(0, 0, 1, 1, 0, 0, buf);
+  CheckGLError("GLFromCPPInit:ReadPixels", __LINE__);
 }
 
 void GLFromCPPDraw() {
   const float kPi = 3.1415926535897932384626433832795f;
 
   CheckGLError("GLFromCPPDraw", __LINE__);
   // TODO(kbr): base the angle on time rather than on ticks
   g_angle = (g_angle + 1) % 360;
   // Rotate about the Z axis
   GLfloat rot_matrix[16];
@@ skipping 41 matching lines @@
   // Bind the texture to texture unit 0
   glBindTexture(GL_TEXTURE_2D, g_texture);
   CheckGLError("GLFromCPPDraw", __LINE__);
   // Point the uniform sampler to texture unit 0
   glUniform1i(g_textureLoc, 0);
   CheckGLError("GLFromCPPDraw", __LINE__);
   glDrawArrays(GL_TRIANGLES, 0, 6);
   CheckGLError("GLFromCPPDraw", __LINE__);
   glFlush();
 }