Fix compile warning [-Wtype-limits]

src/api.cc

 // Copyright 2012 the V8 project 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 "src/api.h"
 
 #include <string.h>  // For memcpy, strlen.
 #ifdef V8_USE_ADDRESS_SANITIZER
 #include <sanitizer/asan_interface.h>
 #endif  // V8_USE_ADDRESS_SANITIZER
@@ skipping 7235 matching lines @@
 
 size_t Isolate::NumberOfHeapSpaces() {
   return i::LAST_SPACE - i::FIRST_SPACE + 1;
 }
 
 
 bool Isolate::GetHeapSpaceStatistics(HeapSpaceStatistics* space_statistics,
                                      size_t index) {
   if (!space_statistics)
     return false;
-  if (index > i::LAST_SPACE || index < i::FIRST_SPACE)
+  COMPILE_ASSERT(i::FIRST_SPACE == 0, first_space_assumed_to_be_zero);

[Sven Panne, 2015/06/09 06:44:46]

Sorry for chiming in so late, but IMHO this is still far too complicated, just
express what you really want to say explicitly:

bool IsValidAllocationSpace(AllocationSpace space) {
  switch (space) {
    case NEW_SPACE:
    case OLD_SPACE:
    case CODE_SPACE:
    case MAP_SPACE:
    case LO_SPACE:
      return true;
    default:
      return false;
  }
}

(Name/namespace/etc. is open for bikeshedding :-) This is crystal clear,
compiles to 2 instructions in a value context and even 1 instruction in a test
context.

More generally: Looking at the usages, AllocationSpace should really be a class,
not an enum...

[sejunho, 2015/06/09 08:22:27]

Thank you for comment sven.
First, I fixed like this:
if (i::Heap::IsValidAllocationSpace(
       static_cast<i::AllocationSpace>(index)))
    return false;

But, this was very bad because if the index is in
the out of range of AllocationSpace, then process crash.
I think casting size_t to AllocationSpace requires
range checking. 
if (i::FIRST_SPACE <= index && index <= i::LAST_SPACE)

Second, I found heap->GetSpaceName which is using the
integer as argument. I think this is better solution.
What do you think?

if (i::Heap::IsValidAllocationSpace(
       static_cast<int>(index)))

const char* Heap::IsValidAllocationSpace(int idx) {
  switch (idx) {
    case NEW_SPACE:
    case OLD_SPACE:
    case MAP_SPACE:
    case CODE_SPACE:
    case LO_SPACE:
      return true;
    default:
      return false;
  }
}

[sejunho, 2015/06/10 03:17:26]

Done.

+  if (index > i::LAST_SPACE)
     return false;
 
   i::Isolate* isolate = reinterpret_cast<i::Isolate*>(this);
   i::Heap* heap = isolate->heap();
   i::Space* space = heap->space(static_cast<int>(index));
 
   space_statistics->space_name_ = heap->GetSpaceName(static_cast<int>(index));
   space_statistics->space_size_ = space->CommittedMemory();
   space_statistics->space_used_size_ = space->SizeOfObjects();
   space_statistics->space_available_size_ = space->Available();
@@ skipping 1161 matching lines @@
   Address callback_address =
       reinterpret_cast<Address>(reinterpret_cast<intptr_t>(callback));
   VMState<EXTERNAL> state(isolate);
   ExternalCallbackScope call_scope(isolate, callback_address);
   callback(info);
 }
 
 
 }  // namespace internal
 }  // namespace v8