runtime: recover is ineffective in some interface method calls

[alotabits]

What steps will reproduce the problem?

Defer a call to an interface method. A call to recover() within the implementing method
will return nil, even if the goroutine is panicking.

If possible, include a link to a program on play.golang.org.

Defer direct method call:    http://play.golang.org/p/Dkwo66X6me
Defer interface method call: http://play.golang.org/p/Pra5_uu1RZ

What is the expected output?

DON'T PANIC

What do you see instead?

PANIC

Which compiler are you using (5g, 6g, 8g, gccgo)?

6g

Which operating system are you using?

Windows

Which version are you using?  (run 'go version')

Tested in playground and at tip with the same results

[remyoudompheng]

Comment 1:

It works properly only if RecoverImp has the same size as a word. In other cases
(smaller or larger), a wrapper method is needed and the function containing recover is
no longer "called" directly.

[bradfitz]

Comment 2:

Nice find!

Labels changed: added priority-soon, removed priority-triage.

Status changed to Accepted.

[ianlancetaylor]

Comment 3:

Labels changed: added compilerbug.

[rsc]

Comment 4:

Labels changed: added go1.2.

[rsc]

Comment 5:

Status changed to Started.

[rsc]

Comment 6:

This issue was closed by revision 7276c02.

Status changed to Fixed.