Fix glGetActiveUniform/Attrib crashes due to state inconsistency

gpu/blink/webgraphicscontext3d_impl.cc

 // Copyright (c) 2012 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.
 
 #include "gpu/blink/webgraphicscontext3d_impl.h"
 
 #include "base/atomicops.h"
 #include "base/lazy_instance.h"
 #include "base/logging.h"
 #include "gpu/GLES2/gl2extchromium.h"
@@ skipping 343 matching lines @@
     WebGLId program, WGC3Duint index, ActiveInfo& info) {
   if (!program) {
     synthesizeGLError(GL_INVALID_VALUE);
     return false;
   }
   GLint max_name_length = -1;
   gl_->GetProgramiv(
       program, GL_ACTIVE_ATTRIBUTE_MAX_LENGTH, &max_name_length);
   if (max_name_length < 0)
     return false;
-  scoped_ptr<GLchar[]> name(new GLchar[max_name_length]);
-  if (!name) {
-    synthesizeGLError(GL_OUT_OF_MEMORY);

[Zhenyao Mo, 2015/03/07 01:00:08]

This is unnecessary because we always crash when "new" fails.

+  if (max_name_length == 0) {
+    // No active attributes exist.
+    synthesizeGLError(GL_INVALID_VALUE);

[no sievers, 2015/03/09 19:10:08]

This seems correct if the program is not valid. But what if the linked shader is
valid but does not reference any attributes or uniforms?

[no sievers, 2015/03/09 19:13:54]

nm, we do call getProgramiv() but this is obviously the right error for
getActiveAttrib/Uniform then too.

lgtm

[Zhenyao Mo, 2015/03/09 19:58:28]

If the linked program has zero attribs or uniforms, then no matter what the
index value is, it is wrong, so an INVALID_VALUE is guaranteed.

     return false;
   }
+  scoped_ptr<GLchar[]> name(new GLchar[max_name_length]);
   GLsizei length = 0;
   GLint size = -1;
   GLenum type = 0;
   gl_->GetActiveAttrib(
       program, index, max_name_length, &length, &size, &type, name.get());
   if (size < 0) {
     return false;
   }
   info.name = blink::WebString::fromUTF8(name.get(), length);
   info.type = type;
   info.size = size;
   return true;
 }
 
 bool WebGraphicsContext3DImpl::getActiveUniform(
     WebGLId program, WGC3Duint index, ActiveInfo& info) {
   GLint max_name_length = -1;
   gl_->GetProgramiv(
       program, GL_ACTIVE_UNIFORM_MAX_LENGTH, &max_name_length);
   if (max_name_length < 0)
     return false;
-  scoped_ptr<GLchar[]> name(new GLchar[max_name_length]);
-  if (!name) {
-    synthesizeGLError(GL_OUT_OF_MEMORY);
+  if (max_name_length == 0) {
+    // No active uniforms exist.
+    synthesizeGLError(GL_INVALID_VALUE);
     return false;
   }
+  scoped_ptr<GLchar[]> name(new GLchar[max_name_length]);
   GLsizei length = 0;
   GLint size = -1;
   GLenum type = 0;
   gl_->GetActiveUniform(
       program, index, max_name_length, &length, &size, &type, name.get());
   if (size < 0) {
     return false;
   }
   info.name = blink::WebString::fromUTF8(name.get(), length);
   info.type = type;
@@ skipping 807 matching lines @@
   output_attribs->samples = attributes.antialias ? 4 : 0;
   output_attribs->sample_buffers = attributes.antialias ? 1 : 0;
   output_attribs->fail_if_major_perf_caveat =
       attributes.failIfMajorPerformanceCaveat;
   output_attribs->bind_generates_resource = false;
   output_attribs->es3_context_required =
       (attributes.webGL && attributes.webGLVersion == 2);
 }
 
 }  // namespace gpu_blink