Add compile assertions to enforce the sizes of all structs and enums in the C...

ppapi/c/pp_var.h

 // Copyright (c) 2010 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.
 
 #ifndef PPAPI_C_PP_VAR_H_
 #define PPAPI_C_PP_VAR_H_
 
 /**
  * @file
  * Defines the API ...
  *
  * @addtogroup PP
  * @{
  */
 
 #include "ppapi/c/pp_bool.h"
 #include "ppapi/c/pp_macros.h"
 #include "ppapi/c/pp_stdint.h"
 
 typedef enum {
   PP_VARTYPE_UNDEFINED,
   PP_VARTYPE_NULL,
   PP_VARTYPE_BOOL,
   PP_VARTYPE_INT32,
   PP_VARTYPE_DOUBLE,
   PP_VARTYPE_STRING,
   PP_VARTYPE_OBJECT
 } PP_VarType;
-
 PP_COMPILE_ASSERT_SIZE_IN_BYTES(PP_VarType, 4);
 
 /**
  * Do not rely on having a predictable and reproducible
  * int/double differentiation.
  * JavaScript has a "number" type for holding a number, and
  * does not differentiate between floating point and integer numbers. The
  * JavaScript library will try to optimize operations by using integers
  * when possible, but could end up with doubles depending on how the number
  * was arrived at.
  *
  * Your best bet is to have a wrapper for variables
  * that always gets out the type you expect, converting as necessary.
  */
 struct PP_Var {
   PP_VarType type;
+
+  /** Ensures @a value is aligned on an 8-byte boundary relative to the
+   *  start of the struct. Some compilers align doubles on 8-byte boundaries
+   *  for 32-bit x86, and some align on 4-byte boundaries.
+   */
+  int32_t padding;
+
   union {
     PP_Bool as_bool;
     int32_t as_int;
     double as_double;
 
     /**
      * Internal ID for strings and objects. The identifier is an opaque handle
      * assigned by the browser to the plugin. It is guaranteed never to be 0,
      * so a plugin can initialize this ID to 0 to indicate a "NULL handle."
      */
     int64_t as_id;
   } value;
 };
+PP_COMPILE_ASSERT_STRUCT_SIZE_IN_BYTES(PP_Var, 16);
 
 PP_INLINE struct PP_Var PP_MakeUndefined() {
-  struct PP_Var result = { PP_VARTYPE_UNDEFINED, {PP_FALSE} };
+  struct PP_Var result = { PP_VARTYPE_UNDEFINED, 0, {PP_FALSE} };
   return result;
 }
 
 PP_INLINE struct PP_Var PP_MakeNull() {
-  struct PP_Var result = { PP_VARTYPE_NULL, {PP_FALSE} };
+  struct PP_Var result = { PP_VARTYPE_NULL, 0, {PP_FALSE} };
   return result;
 }
 
 PP_INLINE struct PP_Var PP_MakeBool(PP_Bool value) {
-  struct PP_Var result = { PP_VARTYPE_BOOL, {PP_FALSE} };
+  struct PP_Var result = { PP_VARTYPE_BOOL, 0, {PP_FALSE} };
   result.value.as_bool = value;
   return result;
 }
 
 PP_INLINE struct PP_Var PP_MakeInt32(int32_t value) {
-  struct PP_Var result = { PP_VARTYPE_INT32, {PP_FALSE} };
+  struct PP_Var result = { PP_VARTYPE_INT32, 0, {PP_FALSE} };
   result.value.as_int = value;
   return result;
 }
 
 PP_INLINE struct PP_Var PP_MakeDouble(double value) {
-  struct PP_Var result = { PP_VARTYPE_DOUBLE, {PP_FALSE} };
+  struct PP_Var result = { PP_VARTYPE_DOUBLE, 0, {PP_FALSE} };
   result.value.as_double = value;
   return result;
 }
 
 /**
  * @}
  * End addtogroup PP
  */
 #endif  // PPAPI_C_PP_VAR_H_