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### 2887. Revert the changes from P0156R0: variadic `lock_guard`

Section: 33.6.5.2 [thread.lock.guard] Status: Resolved Submitter: Finland, Great Britain Opened: 2017-02-03 Last modified: 2017-04-22

Priority: Not Prioritized

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Discussion:

Addresses FI 8, GB 61

The class template `lock_guard` was made variadic. This is abi-breaking, and confusing because one-argument `lock_guard`s have a typedef `mutex_type` but `lock_guard`s with more than one argument don't. There's no need to try to shoehorn this functionality into one type.

Proposed change: Revert the changes to `lock_guard`, and introduce a new variadic class template `vlock_guard` that doesn't have the `mutex_type` typedef at all.

[2017-02-02, Marshall notes]

This was the subject of intense discussion in Issaquah, and a joint LEG/LEWG session agreed on this approach.

[2017-03-12, post-Kona]

Resolved by P0156R2.

Proposed resolution: