Initialize destinations variables before calling GL functions...

gpu/command_buffer/client/gles2_c_lib.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.
 
 // These functions emluate GLES2 over command buffers for C.
 
+#include <assert.h>
 #include "../client/gles2_lib.h"
 
+// Check that destination pointers point to initialized memory.
+// When the context is lost, calling GL function has no effect so if destination
+// pointers point to initialized memory it can often lead to crash bugs. eg.
+//
+// GLsizei len;
+// glGetShaderSource(shader, max_size, &len, buffer);
+// std::string src(buffer, buffer + len);  // len can be uninitialized here!!!
+//
+// Because this check is not official GL this check happens only on Chrome code,
+// not Pepper.
+//
+// If it was up to us we'd just always write to the destination but the OpenGL
+// spec defines the behavior of OpenGL function, not us. :-(
+#if defined(__native_client__)
+  #define GL_CLIENT_VALIDATE_DESTINATION_INITALIZATION_ASSERT(v)
+#elif defined(GPU_DCHECK)
+  #define GL_CLIENT_VALIDATE_DESTINATION_INITALIZATION_ASSERT(v) GPU_DCHECK(v)
+#elif defined(DCHECK)
+  #define GL_CLIENT_VALIDATE_DESTINATION_INITALIZATION_ASSERT(v) DCHECK(v)
+#else
+  #define GL_CLIENT_VALIDATE_DESTINATION_INITALIZATION_ASSERT(v) ASSERT(v)
+#endif
+
+#define GL_CLIENT_VALIDATE_DESTINATION_INITALIZATION(type, ptr) \
+    GL_CLIENT_VALIDATE_DESTINATION_INITALIZATION_ASSERT(ptr && \
+        (ptr[0] == static_cast<type>(0) || ptr[0] == static_cast<type>(-1)));
+
 extern "C" {
 // Include the auto-generated part of this file. We split this because it means
 // we can easily edit the non-auto generated parts right here in this file
 // instead of having to edit some template or the code generator.
 #include "../client/gles2_c_lib_autogen.h"
 }  // extern "C"