Fix null pointer arithmetic, re-enable -Wnull-pointer-arithmetic

Bug: 766891
Change-Id: Ib8cf38fb63d9494f21462ab55ce361775b107322
Reviewed-on: https://chromium-review.googlesource.com/c/1390003Reviewed-by: Antoine Labour <piman@chromium.org>
Reviewed-by: Bill Budge <bbudge@chromium.org>
Reviewed-by: Lambros Lambrou <lambroslambrou@chromium.org>
Reviewed-by: Nico Weber <thakis@chromium.org>
Commit-Queue: Nico Weber <thakis@chromium.org>
Cr-Commit-Position: refs/heads/master@{#619731}

build/config/compiler/BUILD.gn

@@ -1483,9 +1483,6 @@ config("default_warnings") {
       cflags += [
         # TODO(thakis): https://crbug.com/604888
         "-Wno-undefined-var-template",
-
-        # TODO(hans): https://crbug.com/766891
-        "-Wno-null-pointer-arithmetic",
       ]
 
       if (is_win) {

gpu/command_buffer/service/gles2_cmd_decoder_unittest_base.h

@@ -531,9 +531,7 @@ class GLES2DecoderTestBase : public ::testing::TestWithParam<bool>,
   void DoLockDiscardableTextureCHROMIUM(GLuint texture_id);
   bool IsDiscardableTextureUnlocked(GLuint texture_id);
 
-  GLvoid* BufferOffset(unsigned i) {
-    return static_cast<int8_t*>(nullptr) + (i);
-  }
+  GLvoid* BufferOffset(unsigned i) { return reinterpret_cast<GLvoid*>(i); }
 
   template <typename Command, typename Result>
   bool IsObjectHelper(GLuint client_id) {

gpu/command_buffer/service/raster_decoder_unittest_base.h

@@ -212,9 +212,7 @@ class RasterDecoderTestBase : public ::testing::TestWithParam<bool>,
                                      GLsizei height,
                                      GLuint bound_pixel_unpack_buffer);
 
-  GLvoid* BufferOffset(unsigned i) {
-    return static_cast<int8_t*>(nullptr) + (i);
-  }
+  GLvoid* BufferOffset(unsigned i) { return reinterpret_cast<GLvoid*>(i); }
 
  protected:
   static const GLint kMaxTextureSize = 2048;

ppapi/examples/media_stream_video/media_stream_video.cc

@@ -244,8 +244,10 @@ void MediaStreamVideoDemoInstance::DrawYUV() {
   glEnableVertexAttribArray(pos_location);
   glVertexAttribPointer(pos_location, 2, GL_FLOAT, GL_FALSE, 0, 0);
   glEnableVertexAttribArray(tc_location);
-  glVertexAttribPointer(tc_location, 2, GL_FLOAT, GL_FALSE, 0,
-      static_cast<float*>(0) + 16);  // Skip position coordinates.
+  glVertexAttribPointer(
+      tc_location, 2, GL_FLOAT, GL_FALSE, 0,
+      reinterpret_cast<void*>(16 *
+                              sizeof(GLfloat)));  // Skip position coordinates.
   AssertNoGLError();
 
   glDrawArrays(GL_TRIANGLE_STRIP, 0, 4);
@@ -263,8 +265,10 @@ void MediaStreamVideoDemoInstance::DrawRGB() {
   glEnableVertexAttribArray(pos_location);
   glVertexAttribPointer(pos_location, 2, GL_FLOAT, GL_FALSE, 0, 0);
   glEnableVertexAttribArray(tc_location);
-  glVertexAttribPointer(tc_location, 2, GL_FLOAT, GL_FALSE, 0,
-      static_cast<float*>(0) + 16);  // Skip position coordinates.
+  glVertexAttribPointer(
+      tc_location, 2, GL_FLOAT, GL_FALSE, 0,
+      reinterpret_cast<void*>(16 *
+                              sizeof(GLfloat)));  // Skip position coordinates.
   AssertNoGLError();
 
   glDrawArrays(GL_TRIANGLE_STRIP, 4, 4);

ppapi/examples/video_capture/video_capture.cc

@@ -401,7 +401,8 @@ void VCDemoInstance::CreateGLObjects() {
   gles2_if_->EnableVertexAttribArray(context, tc_location);
   gles2_if_->VertexAttribPointer(
       context, tc_location, 2, GL_FLOAT, GL_FALSE, 0,
-      static_cast<float*>(0) + 8);  // Skip position coordinates.
+      reinterpret_cast<void*>(8 *
+                              sizeof(GLfloat)));  // Skip position coordinates.
   AssertNoGLError();
 }
 

ppapi/examples/video_decode/video_decode.cc

@@ -694,13 +694,9 @@ Shader MyInstance::CreateProgram(const char* vertex_shader,
       context_->pp_resource(), pos_location, 2, GL_FLOAT, GL_FALSE, 0, 0);
   gles2_if_->EnableVertexAttribArray(context_->pp_resource(), tc_location);
   gles2_if_->VertexAttribPointer(
-      context_->pp_resource(),
-      tc_location,
-      2,
-      GL_FLOAT,
-      GL_FALSE,
-      0,
-      static_cast<float*>(0) + 8);  // Skip position coordinates.
+      context_->pp_resource(), tc_location, 2, GL_FLOAT, GL_FALSE, 0,
+      reinterpret_cast<void*>(8 *
+                              sizeof(GLfloat)));  // Skip position coordinates.
 
   gles2_if_->UseProgram(context_->pp_resource(), 0);
   assertNoGLError();

ppapi/examples/video_decode/video_decode_dev.cc

@@ -666,7 +666,8 @@ Shader VideoDecodeDemoInstance::CreateProgram(const char* vertex_shader,
   gles2_if_->EnableVertexAttribArray(context_->pp_resource(), tc_location);
   gles2_if_->VertexAttribPointer(
       context_->pp_resource(), tc_location, 2, GL_FLOAT, GL_FALSE, 0,
-      static_cast<float*>(0) + 8);  // Skip position coordinates.
+      reinterpret_cast<void*>(8 *
+                              sizeof(GLfloat)));  // Skip position coordinates.
 
   gles2_if_->UseProgram(context_->pp_resource(), 0);
   assertNoGLError();

remoting/client/display/gl_canvas.cc

@@ -140,8 +140,9 @@ void GlCanvas::DrawTexture(int texture_id,
 
   glVertexAttribPointer(position_location_, kVertexSize, GL_FLOAT, GL_FALSE, 0,
                         0);
-  glVertexAttribPointer(tex_cord_location_, kVertexSize, GL_FLOAT, GL_FALSE, 0,
-                        static_cast<float*>(0) + kVertexSize * kVertexCount);
+  glVertexAttribPointer(
+      tex_cord_location_, kVertexSize, GL_FLOAT, GL_FALSE, 0,
+      reinterpret_cast<void*>(kVertexSize * kVertexCount * sizeof(GLfloat)));
 
   glDrawArrays(GL_TRIANGLE_STRIP, 0, kVertexCount);
   glBindBuffer(GL_ARRAY_BUFFER, 0);

remoting/client/plugin/pepper_video_renderer_3d.cc

@@ -566,7 +566,8 @@ void PepperVideoRenderer3D::CreateProgram(const char* vertex_shader,
   gles2_if_->EnableVertexAttribArray(graphics_3d, tc_location);
   gles2_if_->VertexAttribPointer(
       graphics_3d, tc_location, 2, GL_FLOAT, GL_FALSE, 0,
-      static_cast<float*>(0) + 8);  // Skip position coordinates.
+      reinterpret_cast<void*>(8 *
+                              sizeof(GLfloat)));  // Skip position coordinates.
 
   gles2_if_->UseProgram(graphics_3d, 0);