Work around race condition in MakeArray for ASSERTs and document assumptions.

Work around race condition in MakeArray for ASSERTs and document assumptions.

BUG=dart:22501
Committed: https://code.google.com/p/dart/source/detail?r=43898

[Ivan Posva, 2015-02-19 22:43:56]

LGTMwC -ip

https://codereview.chromium.org/936393003/diff/60001/runtime/vm/raw_object.cc
File runtime/vm/raw_object.cc (right):

https://codereview.chromium.org/936393003/diff/60001/runtime/vm/raw_object.cc...
runtime/vm/raw_object.cc:219: if ((instance_size > tags_size && tags_size > 0)
&& (class_id == kArrayCid)) {
"if ((class_id == kArrayCid) && ...) {"

is a bit more readable to me as it tells me that we are only interested in the
actual size relation if we are looking at an array.

https://codereview.chromium.org/936393003/diff/60001/runtime/vm/raw_object.cc...
runtime/vm/raw_object.cc:227: instance_size = Array::InstanceSize(array_length);
Might need a comment why you are only reloading the instance_size, but not the
tag size.

[koda, 2015-02-19 22:48:49]

https://codereview.chromium.org/936393003/diff/60001/runtime/vm/raw_object.cc
File runtime/vm/raw_object.cc (right):

https://codereview.chromium.org/936393003/diff/60001/runtime/vm/raw_object.cc...
runtime/vm/raw_object.cc:219: if ((instance_size > tags_size && tags_size > 0)
&& (class_id == kArrayCid)) {
On 2015/02/19 22:43:56, Ivan Posva wrote:
> "if ((class_id == kArrayCid) && ...) {"
> 
> is a bit more readable to me as it tells me that we are only interested in the
> actual size relation if we are looking at an array.

Agreed.

Slightly less efficient, but OK since this is DEBUG mode.

https://codereview.chromium.org/936393003/diff/60001/runtime/vm/raw_object.cc...
runtime/vm/raw_object.cc:227: instance_size = Array::InstanceSize(array_length);
On 2015/02/19 22:43:56, Ivan Posva wrote:
> Might need a comment why you are only reloading the instance_size, but not the
> tag size.

Done.

[koda, 2015-02-19 22:55:56]

Committed patchset #5 (id:80001) manually as r43898 (presubmit successful).