mojo: Fix the size of several platform-specific structs

Having SerializedPlatformHandleDispatcher::platform_handle_index (and
other platform-specific structs) be a size_t causes 64-bit processes
communicating with 32-bit processes to fail the size check. This change
fixes the size of |platform_handle_index| (and similar ones) so it is
fixed across platforms (to uint32_t) so that the error goes away.

BUG=574945
TEST=32-bit ARC communication works in 64-bit Chrome OS

Review URL: https://codereview.chromium.org/1568693002

Cr-Commit-Position: refs/heads/master@{#368488}

1 files changed, 12 insertions, 5 deletions

diff --git a/mojo/edk/system/data_pipe.cc b/mojo/edk/system/data_pipe.cc
index 3f53798..54a6df4 100644
--- a/mojo/edk/system/data_pipe.cc
+++ b/mojo/edk/system/data_pipe.cc
@@ -8,6 +8,9 @@
 #include <stdint.h>
 #include <string.h>
 
+#include <algorithm>
+#include <limits>
+
 #include "mojo/edk/system/configuration.h"
 #include "mojo/edk/system/options_validation.h"
 #include "mojo/edk/system/raw_channel.h"
@@ -18,17 +21,17 @@ namespace edk {
 
 namespace {
 
-const size_t kInvalidDataPipeHandleIndex = static_cast<size_t>(-1);
+const uint32_t kInvalidDataPipeHandleIndex = static_cast<uint32_t>(-1);
 
 struct MOJO_ALIGNAS(8) SerializedDataPipeHandleDispatcher {
-  size_t platform_handle_index;  // (Or |kInvalidDataPipeHandleIndex|.)
+  uint32_t platform_handle_index;  // (Or |kInvalidDataPipeHandleIndex|.)
 
   // These are from MojoCreateDataPipeOptions
   MojoCreateDataPipeOptionsFlags flags;
   uint32_t element_num_bytes;
   uint32_t capacity_num_bytes;
 
-  size_t shared_memory_handle_index;  // (Or |kInvalidDataPipeHandleIndex|.)
+  uint32_t shared_memory_handle_index;  // (Or |kInvalidDataPipeHandleIndex|.)
   uint32_t shared_memory_size;
 };
 
@@ -119,7 +122,9 @@ void DataPipe::EndSerialize(const MojoCreateDataPipeOptions& options,
   SerializedDataPipeHandleDispatcher* serialization =
       static_cast<SerializedDataPipeHandleDispatcher*>(destination);
   if (channel_handle.is_valid()) {
-    serialization->platform_handle_index = platform_handles->size();
+    DCHECK(platform_handles->size() < std::numeric_limits<uint32_t>::max());
+    serialization->platform_handle_index =
+        static_cast<uint32_t>(platform_handles->size());
     platform_handles->push_back(channel_handle.release());
   } else {
     serialization->platform_handle_index = kInvalidDataPipeHandleIndex;
@@ -131,7 +136,9 @@ void DataPipe::EndSerialize(const MojoCreateDataPipeOptions& options,
 
   serialization->shared_memory_size = static_cast<uint32_t>(shared_memory_size);
   if (serialization->shared_memory_size) {
-    serialization->shared_memory_handle_index = platform_handles->size();
+    DCHECK(platform_handles->size() < std::numeric_limits<uint32_t>::max());
+    serialization->shared_memory_handle_index =
+        static_cast<uint32_t>(platform_handles->size());
     platform_handles->push_back(shared_memory_handle.release());
   } else {
     serialization->shared_memory_handle_index = kInvalidDataPipeHandleIndex;