[Oilpan] Create UnsafePtr to store on-heap pointers in Vector

Create UnsafePtr to store on-heap pointers in Vector

In basic rule, we cannot store pointers for on-heap objects
in WTF::Vector.  But in some situation like weak processing,
we need it.
In such cases, you can use UnsafePtr to avoid validations.
Please check the pointee is guaranteed to be alive without
UnsafePtr<>.

BUG=515524
Committed: https://crrev.com/fa48e5f45138dc87c5acca59235df098e18c494c
Cr-Commit-Position: refs/heads/master@{#354234}

[peria, 2015-10-10 13:24:20]

Patchset #1 (id:1) has been deleted

[peria, 2015-10-14 05:21:17]

Patchset #1 (id:20001) has been deleted

[peria, 2015-10-14 05:23:37]

peria@chromium.org changed reviewers:
+ haraken@chromium.org, oilpan-reviews@chromium.org

[peria, 2015-10-14 05:23:38]

PTL

[haraken, 2015-10-14 06:00:21]

https://codereview.chromium.org/1397073002/diff/40001/third_party/WebKit/Sour...
File third_party/WebKit/Source/platform/heap/Handle.h (right):

https://codereview.chromium.org/1397073002/diff/40001/third_party/WebKit/Sour...
third_party/WebKit/Source/platform/heap/Handle.h:879: class UnsafePtr {

I'd rename UnsafePtr to UnsafeMember or UntracedMember. What do you think? (I'd
prefer UntracedMember.)

https://codereview.chromium.org/1397073002/diff/40001/third_party/WebKit/Sour...
third_party/WebKit/Source/platform/heap/Handle.h:879: class UnsafePtr {

Add conversions between UnsafePtr <=> Member, Persistent etc. You need to grep
all conversions in Handle.h (e.g., copy constructor, operator=, operator==,
swap= etc) and add the UnsafePtr version to them.

[peria, 2015-10-14 09:36:28]

https://codereview.chromium.org/1397073002/diff/40001/third_party/WebKit/Sour...
File third_party/WebKit/Source/platform/heap/Handle.h (right):

https://codereview.chromium.org/1397073002/diff/40001/third_party/WebKit/Sour...
third_party/WebKit/Source/platform/heap/Handle.h:879: class UnsafePtr {
On 2015/10/14 06:00:21, haraken wrote:
> 
> I'd rename UnsafePtr to UnsafeMember or UntracedMember. What do you think?
(I'd
> prefer UntracedMember.)

OK.  Both names look better than UnsafePtr.

https://codereview.chromium.org/1397073002/diff/40001/third_party/WebKit/Sour...
third_party/WebKit/Source/platform/heap/Handle.h:879: class UnsafePtr {
On 2015/10/14 06:00:21, haraken wrote:
> 
> Add conversions between UnsafePtr <=> Member, Persistent etc. You need to grep
> all conversions in Handle.h (e.g., copy constructor, operator=, operator==,
> swap= etc) and add the UnsafePtr version to them.

Done.

[haraken, 2015-10-14 09:39:53]

https://codereview.chromium.org/1397073002/diff/50004/third_party/WebKit/Sour...
File third_party/WebKit/Source/platform/heap/Handle.h (right):

https://codereview.chromium.org/1397073002/diff/50004/third_party/WebKit/Sour...
third_party/WebKit/Source/platform/heap/Handle.h:950: class UntracedMember {

I'm just curious but would it be possible to make UntracedMember inherit from
Member? Then maybe can we decrease the code duplication? (I should have asked
this earlier... sorry :-/)

[peria, 2015-10-15 01:47:32]

On 2015/10/14 09:39:53, haraken wrote:
>
https://codereview.chromium.org/1397073002/diff/50004/third_party/WebKit/Sour...
> File third_party/WebKit/Source/platform/heap/Handle.h (right):
> 
>
https://codereview.chromium.org/1397073002/diff/50004/third_party/WebKit/Sour...
> third_party/WebKit/Source/platform/heap/Handle.h:950: class UntracedMember {
> 
> I'm just curious but would it be possible to make UntracedMember inherit from
> Member? Then maybe can we decrease the code duplication? (I should have asked
> this earlier... sorry :-/)

Hooo! It should be!
As far as I tested, it seems to go well.  I was thinking that plugins checked
inheritances of Member.
Update this CL soon.

[peria, 2015-10-15 02:13:15]

https://codereview.chromium.org/1397073002/diff/50004/third_party/WebKit/Sour...
File third_party/WebKit/Source/platform/heap/Handle.h (right):

https://codereview.chromium.org/1397073002/diff/50004/third_party/WebKit/Sour...
third_party/WebKit/Source/platform/heap/Handle.h:950: class UntracedMember {
On 2015/10/14 09:39:53, haraken wrote:
> 
> I'm just curious but would it be possible to make UntracedMember inherit from
> Member? Then maybe can we decrease the code duplication? (I should have asked
> this earlier... sorry :-/)

Done.

[haraken, 2015-10-15 03:55:40]

https://codereview.chromium.org/1397073002/diff/170001/third_party/WebKit/Sou...
File third_party/WebKit/Source/platform/heap/Handle.h (right):

https://codereview.chromium.org/1397073002/diff/170001/third_party/WebKit/Sou...
third_party/WebKit/Source/platform/heap/Handle.h:107: PersistentBase(const
UntracedMember<U>& other) : m_raw(other)

Now that UntracedMember inherits from Member, this won't be needed.

The same comment for other parts in this CL. Basically, UntracedMember is
similar to WeakMember in that they inherit from Member. You just need to define
the UntracedMember version only in places where the WeakMember version is
defined.

[peria, 2015-10-15 05:11:58]

https://codereview.chromium.org/1397073002/diff/170001/third_party/WebKit/Sou...
File third_party/WebKit/Source/platform/heap/Handle.h (right):

https://codereview.chromium.org/1397073002/diff/170001/third_party/WebKit/Sou...
third_party/WebKit/Source/platform/heap/Handle.h:107: PersistentBase(const
UntracedMember<U>& other) : m_raw(other)
On 2015/10/15 03:55:39, haraken wrote:
> 
> Now that UntracedMember inherits from Member, this won't be needed.
> 
> The same comment for other parts in this CL. Basically, UntracedMember is
> similar to WeakMember in that they inherit from Member. You just need to
define
> the UntracedMember version only in places where the WeakMember version is
> defined.

Done.

[haraken, 2015-10-15 05:26:08]

LGTM with comments.

https://codereview.chromium.org/1397073002/diff/190001/third_party/WebKit/Sou...
File third_party/WebKit/Source/platform/heap/Handle.h (right):

https://codereview.chromium.org/1397073002/diff/190001/third_party/WebKit/Sou...
third_party/WebKit/Source/platform/heap/Handle.h:877: // some reason.

// UntracedMember is a pointer to an on-heap object that is not traced for some
reason. Please don't use this unless you understand what you're doing.
Basically, all pointers to on-heap objects must be stored in either of
Persistent, Member or WeakMember. It is not allowed to leave raw pointers to
on-heap objects. However, there can be scenarios where you have to use raw
pointers for some reason, and in that case you can use UntracedMember. Of
course, it must be guaranteed that the pointing on-heap object is kept alive
while the raw pointer is pointing to the object.

https://codereview.chromium.org/1397073002/diff/190001/third_party/WebKit/Sou...
third_party/WebKit/Source/platform/heap/Handle.h:879: class UntracedMember :
public Member<T> {

Add final.

https://codereview.chromium.org/1397073002/diff/190001/third_party/WebKit/Sou...
third_party/WebKit/Source/platform/heap/Handle.h:896:
UntracedMember(WTF::HashTableDeletedValueType x) : Member<T>(x) { }

Also implement operator=, just like WeakMember's operator=.

[peria, 2015-10-15 06:03:43]

https://codereview.chromium.org/1397073002/diff/190001/third_party/WebKit/Sou...
File third_party/WebKit/Source/platform/heap/Handle.h (right):

https://codereview.chromium.org/1397073002/diff/190001/third_party/WebKit/Sou...
third_party/WebKit/Source/platform/heap/Handle.h:877: // some reason.
On 2015/10/15 05:26:08, haraken wrote:
> 
> // UntracedMember is a pointer to an on-heap object that is not traced for
some
> reason. Please don't use this unless you understand what you're doing.
> Basically, all pointers to on-heap objects must be stored in either of
> Persistent, Member or WeakMember. It is not allowed to leave raw pointers to
> on-heap objects. However, there can be scenarios where you have to use raw
> pointers for some reason, and in that case you can use UntracedMember. Of
> course, it must be guaranteed that the pointing on-heap object is kept alive
> while the raw pointer is pointing to the object.
> 

Done.
Thank you for this description.

https://codereview.chromium.org/1397073002/diff/190001/third_party/WebKit/Sou...
third_party/WebKit/Source/platform/heap/Handle.h:879: class UntracedMember :
public Member<T> {
On 2015/10/15 05:26:08, haraken wrote:
> 
> Add final.

Done.

https://codereview.chromium.org/1397073002/diff/190001/third_party/WebKit/Sou...
third_party/WebKit/Source/platform/heap/Handle.h:896:
UntracedMember(WTF::HashTableDeletedValueType x) : Member<T>(x) { }
On 2015/10/15 05:26:08, haraken wrote:
> 
> Also implement operator=, just like WeakMember's operator=.

Done.

[peria, 2015-10-15 06:03:49]

The CQ bit was checked by peria@chromium.org

[peria, 2015-10-15 06:03:49]

The patchset sent to the CQ was uploaded after l-g-t-m from haraken@chromium.org
Link to the patchset: https://codereview.chromium.org/1397073002/#ps210001
(title: "Work for nits")

[commit-bot: I haz the power, 2015-10-15 06:04:04]

CQ is trying da patch. Follow status at
 https://chromium-cq-status.appspot.com/patch-status/1397073002/210001
View timeline at
 https://chromium-cq-status.appspot.com/patch-timeline/1397073002/210001

[commit-bot: I haz the power, 2015-10-15 07:15:10]

Committed patchset #10 (id:210001)

[commit-bot: I haz the power, 2015-10-15 07:15:52]

Patchset 10 (id:??) landed as
https://crrev.com/fa48e5f45138dc87c5acca59235df098e18c494c
Cr-Commit-Position: refs/heads/master@{#354234}