Adds macros to annotate variables and functions used from same thread or queue.

Adds macros to annotate variables and functions used from same thread or queue.
ACCESS_ON is an alias of GUARDED_BY but should take thread-like object instead of mutex,
RUN_ON is an alias of EXCLUSIVE_LOCKS_REQUIRED to annotate function always run on same
thread/task_queue
RTC_DCHECK_RUN_ON - creates an object that allows use of annotated variables and functions, and adds a run-time DCHECK given thread/queue is current.

R=tommi@webrtc.org

Committed: https://crrev.com/8e572f030ff5c4c695da5d40d3b617d4f6741d4f
Cr-Commit-Position: refs/heads/master@{#12812}

[danilchap, 2016-05-16 12:51:21]

prettified version of idea shown in https://codereview.webrtc.org/1967193002/

Wonder if this macros good enough to help avoid synchronization errors and so
encourage model where posting to other threads/queues is preferable over locking
variables.

[tommi, 2016-05-16 13:01:04]

Description was changed from

==========
Adds macros to annotate variabes and functions used from same thread or queue.
ACCESS_ON is an alias of GUARDED_BY but should take thread-like object instead
of mutex,
RUN_ON is an alias of EXCLUSIVE_LOCKS_REQUIRED to annotate function always run
on same
thread/task_queue
RTC_DCHECK_RUN_ON - creates a object that allows to use annotated
variables and functions, and adds a run-time DCHECK given thread/queue is
current.

R=tommi@webrtc.org
==========

to

==========
Adds macros to annotate variables and functions used from same thread or queue.
ACCESS_ON is an alias of GUARDED_BY but should take thread-like object instead
of mutex,
RUN_ON is an alias of EXCLUSIVE_LOCKS_REQUIRED to annotate function always run
on same
thread/task_queue
RTC_DCHECK_RUN_ON - creates an object that allows use of annotated variables and
functions, and adds a run-time DCHECK given thread/queue is current.

R=tommi@webrtc.org
==========

[tommi, 2016-05-16 13:06:48]

Can we include some test code?

https://codereview.webrtc.org/1981893002/diff/1/webrtc/base/thread_checker.h
File webrtc/base/thread_checker.h (right):

https://codereview.webrtc.org/1981893002/diff/1/webrtc/base/thread_checker.h#...
webrtc/base/thread_checker.h:130: //     encoder_queue_->PostTask([this] {
Encode(); });
nit: I don't think we want to encourage using lambdas that reference 'this', so
if we can avoid that in an example that would be good.  Examples tend to get
copied and make it into actual code.

[danilchap, 2016-05-16 15:19:28]

danilchap@webrtc.org changed reviewers:
- tommi@webrtc.org

[danilchap, 2016-05-16 15:22:58]

On 2016/05/16 13:06:48, tommi-webrtc wrote:
> Can we include some test code?
> 
> https://codereview.webrtc.org/1981893002/diff/1/webrtc/base/thread_checker.h
> File webrtc/base/thread_checker.h (right):
> 
>
https://codereview.webrtc.org/1981893002/diff/1/webrtc/base/thread_checker.h#...
> webrtc/base/thread_checker.h:130: //     encoder_queue_->PostTask([this] {
> Encode(); });
> nit: I don't think we want to encourage using lambdas that reference 'this',
so
> if we can avoid that in an example that would be good.  Examples tend to get
> copied and make it into actual code.

Failed to create meaninfull test code (while can test that code with proper
annotation can compile,
have no idea how to test that code without proper annotation doesn't: template
trick doesn't work
because template specialized way before clang run annotation checks.

Failed to rewrite examples to be more realistic too. Take this as an indication
this macros doesn't help
with annotating good code.

[danilchap, 2016-05-18 15:17:37]

danilchap@webrtc.org changed reviewers:
+ tommi@webrtc.org

[danilchap, 2016-05-18 15:28:53]

examples rewritten, using ref_ptr for lambda capture now.
Tests are partially written since has no idea how to test checks are enforced:
checks are done after compilation and various templates type checks (so can't
use template meta-programming), but before runtime (so can't use normal test
macros)

[tommi, 2016-05-19 08:26:14]

lgtm % a couple of requests.

https://codereview.webrtc.org/1981893002/diff/20001/webrtc/base/thread_checker.h
File webrtc/base/thread_checker.h (right):

https://codereview.webrtc.org/1981893002/diff/20001/webrtc/base/thread_checke...
webrtc/base/thread_checker.h:92: class SCOPED_LOCKABLE AnnounceOnThread {
Since this class is not meant to be used directly, can we move it into a sub
namespace, e.g. rtc::internal?

https://codereview.webrtc.org/1981893002/diff/20001/webrtc/base/thread_checke...
webrtc/base/thread_checker.h:114: // access from same thread/queue.
s/access from same/accessed on the same

https://codereview.webrtc.org/1981893002/diff/20001/webrtc/base/thread_checke...
webrtc/base/thread_checker.h:166: #define RTC_DCHECK_RUN_ON(thread_like_object)
\
have you checked if this produces zero code in non-DCHECK enabled builds? (I
think it should)

https://codereview.webrtc.org/1981893002/diff/20001/webrtc/base/thread_checke...
File webrtc/base/thread_checker_unittest.cc (right):

https://codereview.webrtc.org/1981893002/diff/20001/webrtc/base/thread_checke...
webrtc/base/thread_checker_unittest.cc:200: rtc::Thread* thread;
move these member variables to the bottom of the class, add the postfix _ and
make them private.

If you could update the example code too to follow the style guide, that would
be good.

[danilchap, 2016-05-19 11:45:30]

https://codereview.webrtc.org/1981893002/diff/20001/webrtc/base/thread_checker.h
File webrtc/base/thread_checker.h (right):

https://codereview.webrtc.org/1981893002/diff/20001/webrtc/base/thread_checke...
webrtc/base/thread_checker.h:92: class SCOPED_LOCKABLE AnnounceOnThread {
On 2016/05/19 08:26:14, tommi-webrtc wrote:
> Since this class is not meant to be used directly, can we move it into a sub
> namespace, e.g. rtc::internal?

Done.

https://codereview.webrtc.org/1981893002/diff/20001/webrtc/base/thread_checke...
webrtc/base/thread_checker.h:114: // access from same thread/queue.
On 2016/05/19 08:26:14, tommi-webrtc wrote:
> s/access from same/accessed on the same

Done.

https://codereview.webrtc.org/1981893002/diff/20001/webrtc/base/thread_checke...
webrtc/base/thread_checker.h:166: #define RTC_DCHECK_RUN_ON(thread_like_object)
\
On 2016/05/19 08:26:14, tommi-webrtc wrote:
> have you checked if this produces zero code in non-DCHECK enabled builds? (I
> think it should)

I wrote it in a way it is easy for compiler to optimize it into noop when DCHECK
is disabled.
To be sure checked with disassembler it compiles to noop in Release.

https://codereview.webrtc.org/1981893002/diff/20001/webrtc/base/thread_checke...
File webrtc/base/thread_checker_unittest.cc (right):

https://codereview.webrtc.org/1981893002/diff/20001/webrtc/base/thread_checke...
webrtc/base/thread_checker_unittest.cc:200: rtc::Thread* thread;
On 2016/05/19 08:26:14, tommi-webrtc wrote:
> move these member variables to the bottom of the class, add the postfix _ and
> make them private.
> 
> If you could update the example code too to follow the style guide, that would
> be good.

Done.

[danilchap, 2016-05-19 13:47:18]

The CQ bit was checked by danilchap@webrtc.org

[danilchap, 2016-05-19 13:47:19]

The patchset sent to the CQ was uploaded after l-g-t-m from tommi@webrtc.org
Link to the patchset: https://codereview.webrtc.org/1981893002/#ps60001 (title:
"Fix example")

[commit-bot: I haz the power, 2016-05-19 13:47:25]

CQ is trying da patch. Follow status at
 https://chromium-cq-status.appspot.com/patch-status/1981893002/60001
View timeline at
 https://chromium-cq-status.appspot.com/patch-timeline/1981893002/60001

[commit-bot: I haz the power, 2016-05-19 13:49:06]

Description was changed from

==========
Adds macros to annotate variables and functions used from same thread or queue.
ACCESS_ON is an alias of GUARDED_BY but should take thread-like object instead
of mutex,
RUN_ON is an alias of EXCLUSIVE_LOCKS_REQUIRED to annotate function always run
on same
thread/task_queue
RTC_DCHECK_RUN_ON - creates an object that allows use of annotated variables and
functions, and adds a run-time DCHECK given thread/queue is current.

R=tommi@webrtc.org
==========

to

==========
Adds macros to annotate variables and functions used from same thread or queue.
ACCESS_ON is an alias of GUARDED_BY but should take thread-like object instead
of mutex,
RUN_ON is an alias of EXCLUSIVE_LOCKS_REQUIRED to annotate function always run
on same
thread/task_queue
RTC_DCHECK_RUN_ON - creates an object that allows use of annotated variables and
functions, and adds a run-time DCHECK given thread/queue is current.

R=tommi@webrtc.org
==========

[commit-bot: I haz the power, 2016-05-19 13:49:07]

Committed patchset #4 (id:60001)

[commit-bot: I haz the power, 2016-05-19 13:49:14]

Description was changed from

==========
Adds macros to annotate variables and functions used from same thread or queue.
ACCESS_ON is an alias of GUARDED_BY but should take thread-like object instead
of mutex,
RUN_ON is an alias of EXCLUSIVE_LOCKS_REQUIRED to annotate function always run
on same
thread/task_queue
RTC_DCHECK_RUN_ON - creates an object that allows use of annotated variables and
functions, and adds a run-time DCHECK given thread/queue is current.

R=tommi@webrtc.org
==========

to

==========
Adds macros to annotate variables and functions used from same thread or queue.
ACCESS_ON is an alias of GUARDED_BY but should take thread-like object instead
of mutex,
RUN_ON is an alias of EXCLUSIVE_LOCKS_REQUIRED to annotate function always run
on same
thread/task_queue
RTC_DCHECK_RUN_ON - creates an object that allows use of annotated variables and
functions, and adds a run-time DCHECK given thread/queue is current.

R=tommi@webrtc.org

Committed: https://crrev.com/8e572f030ff5c4c695da5d40d3b617d4f6741d4f
Cr-Commit-Position: refs/heads/master@{#12812}
==========

[commit-bot: I haz the power, 2016-05-19 13:49:15]

Patchset 4 (id:??) landed as
https://crrev.com/8e572f030ff5c4c695da5d40d3b617d4f6741d4f
Cr-Commit-Position: refs/heads/master@{#12812}