Implement unions as members of structs.

mojo/public/tools/bindings/generators/cpp_templates/union_definition.tmpl

Index: mojo/public/tools/bindings/generators/cpp_templates/union_definition.tmpl
diff --git a/mojo/public/tools/bindings/generators/cpp_templates/union_definition.tmpl b/mojo/public/tools/bindings/generators/cpp_templates/union_definition.tmpl
index ad30fb72f4ddfa5633df7ccefb07ffa570c53898..464daf45029708fb89c0c30b18f2b909dcf837db 100644
--- a/mojo/public/tools/bindings/generators/cpp_templates/union_definition.tmpl
+++ b/mojo/public/tools/bindings/generators/cpp_templates/union_definition.tmpl
@@ -7,9 +7,11 @@
   return new (buf->Allocate(sizeof({{class_name}}))) {{class_name}}();
 }
 
+

[yzshen1, 2015/02/17 19:34:35]

unnecessary empty line.

[azani, 2015/02/18 00:27:58]

Done.

 // static
 bool {{class_name}}::Validate(const void* data,
-                              mojo::internal::BoundsChecker* bounds_checker) {
+                              mojo::internal::BoundsChecker* bounds_checker,
+                              bool claim_memory) {
   if (!data) {
     return true;
   }
@@ -19,7 +21,9 @@ bool {{class_name}}::Validate(const void* data,
     return false;
   }
 
-  if (!bounds_checker->ClaimMemory(data, sizeof({{class_name}}))) {
+  // If the union is inlined in another structure its memory was already claimed.

[yzshen1, 2015/02/17 19:34:35]

nit: I understand 80-char limit is not honored in general in .tmpl files, but
usually people stick to 80-char limits for comments.

[azani, 2015/02/18 00:27:57]

Done.

+  // This ONLY applies to the union itself, NOT anything which the union points to.
+  if (claim_memory && !bounds_checker->ClaimMemory(data, sizeof({{class_name}}))) {

[yzshen1, 2015/02/17 19:34:35]

For non-inlined case, we need to check that the first four bytes stores the
value 16. (I wish we could do the same for non-null inlined case, too. Please
see my comment in the declaration.)

     ReportValidationError(
         mojo::internal::VALIDATION_ERROR_ILLEGAL_MEMORY_RANGE);
     return false;