Lock tag types are defined twice, once incorrectly
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Description
https://eel.is/c++draft/thread#lock.general-2 says:
Some lock constructors take tag types which describe what should be done with the lockable object during the lock's construction.
namespace std { struct defer_lock_t { }; // do not acquire ownership of the mutex struct try_to_lock_t { }; // try to acquire ownership of the mutex // without blocking struct adopt_lock_t { }; // assume the calling thread has already // obtained mutex ownership and manage it inline constexpr defer_lock_t defer_lock { }; inline constexpr try_to_lock_t try_to_lock { }; inline constexpr adopt_lock_t adopt_lock { }; }
But this isn't the actual correct definition of defer_lock_t et al.; those are normatively defined further down in
https://eel.is/c++draft/thread#mutex.syn as having explicit default constructors.
struct defer_lock_t { explicit defer_lock_t() = default; }; struct try_to_lock_t { explicit try_to_lock_t() = default; }; struct adopt_lock_t { explicit adopt_lock_t() = default; }; inline constexpr defer_lock_t defer_lock { }; inline constexpr try_to_lock_t try_to_lock { }; inline constexpr adopt_lock_t adopt_lock { };
IMHO we should figure out a way to strike the first (non-normative?) definitions entirely. At worst, the first definitions should be updated to match the correct normative definitions, so that nobody gets confused.
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Research direction
Compare the introductory tag-type definitions in [thread.lock] with the normative definitions in [thread.mutex.syn] using the linked draft sections. Determine whether the first definitions can be removed or should match the explicit constructors in the normative text; done means the draft no longer presents conflicting definitions.
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Assessment
- Tech stack
- cpp
- Domain
- documentation
- Issue type
- Documentation
- Difficulty
- 3/5
- Estimated time
- 1-2 days
- Activity status
- Stale
- Clarity
- Mostly clear
- Newbie friendliness
- 45/100