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Date: 2008-05-29 16:38:27

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Author: bemandawes
Date: 2008-05-29 16:38:26 EDT (Thu, 29 May 2008)
New Revision: 45922
URL: http://svn.boost.org/trac/boost/changeset/45922

Log:
N2636
Added:
sandbox/committee/LWG/proposals/
sandbox/committee/LWG/proposals/n2636.html (contents, props changed)

Added: sandbox/committee/LWG/proposals/n2636.html
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+
+
+<html xmlns:gdoc="">
+
+<head>
+<meta http-equiv="Content-Type" content="text/html; charset=UTF-8">
+<style type="text/css">
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+<body
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+ revision="dc2632k9_2g9w3qtvw:454">
+
+
+
+ 
+Error Handling
+Specification for Chapter 30
+(Threads) 
+ 
+
+<div id=wx2g6>
+ 
+ Document: N2636=08-0146
+ 
+ 
+ Date: 2008-05-16
+ 
+ 
+ Authors: Jeff
+ Garland
+ <jeff_at_[hidden]> 
+ 
+ 
+ 
+               Nick
+ Stoughton <nick_at_[hidden]> 
+ 
+ 
+ 
+               Benjamin
+ Kosnik <bkoz_at_[hidden]>
+ 
+ 
+              
+ Beman Dawes <bdawes_at_[hidden]>
+ 
+ 
+ 
+ 
+ 
+ 
+ 
+ 
+ Motivation
+ 
+ 
+ New facilities have recently been added to C++0x working draft in the
+ diagnostics library to provide mechanisms for the reporting of system errors
+ as part of the C++ library.  These facilities include both portable error
+ codes as well as operating system specific error reporting capabilities, thus
+ enabling implementations to provide a full range of error information. 
+ 
+ This paper provides error condition
+ specifications for the recently added threading API (ie, Chapter 30), as
+ suggested during discussions at the Bellevue meeting. 
+ 
+ For programmers that want
+ to write portable code that does detailed error handling, knowing the specific
+ error codes an implementation may produce for a particular method is
+ vital.  Without these specifications a programmer must be prepared for
+ any possible error code in the entire set of portable codes
+ (over 70 total). 
+ 
+ Note that this type of specification has precedent in other
+ international standards.  The POSIX specification provides the specific
+ error codes that can occur for each function and a description of the
+ condition that would cause them. 
+ 
+ Overview of Changes 
+ 
+ In Chapter 17, introduce an Error Condition clause, with specification and
+ description. 
+ 
+ In Chapter 30, add error condition clauses where appropriate. 
+ 
+ 
+ Proposed Wording
+ 
+ 
+ 
+ 
+ 
+ 
+ Change
+ <a href=http://17.3.1.3/ id=o1702 target=_blank>17.3.1.3</a> Specifications
+ [structure.specifications], paragraph 3, as indicated: 
+ 
+ 
+ 
+ 
+ 
+ 
+ 
+ Descriptions of function semantics contain the
+ following elements (as appropriate):153) 
+ 
+ â€” Requires: the preconditions for calling the function 
+ 
+ â€” Effects: the actions performed by the function 
+ 
+ â€” Postconditions: the observable results established by the
+ function 
+ 
+ â€” Returns: a description of the value(s) returned by the
+ function 
+ 
+ â€” Throws: any exceptions thrown by the function, and the
+ conditions that would cause the exception 
+ 
+ â€” Complexity: the time and/or space complexity of the
+ function 
+ 
+ â€” Remarks: additional semantic constraints on the function 
+ 
+ â€” Error
+ conditions: the default error conditions for error codes reported by the
+ function. 
+ 
+ 
+ 
+ 
+ 
+ 
+ 
+ For non-reserved replacement and handler functions,
+ clause 18 specifies two behaviors for the functions in question: their
+ required and default behavior. The default behavior describes a function
+ definition provided by the implementation. The required behavior describes
+ the semantics of a function definition provided by either the implementation
+ or a C++ program. Where no distinction is explicitly made in the
+ description, the behavior described is the required behavior.
+ 
+ 
+ 
+ 
+ 
+ 
+ Complexity requirements specified in the library
+ clauses are upper bounds, and implementations that provide better 
+ complexity guarantees satisfy the requirements. 
+ 
+ 
+ 
+ 
+ 
+ 
+ 
+ Error conditions
+ specify two types of failure: conditions where a function shall fail, and
+ conditions where a function may fail. The conditions are listed, together
+ with a suitable explanation, as the <code id=o17036>enum class errc</code> constants ([syserr]) that could be
+ used as an argument to function <code id=o17037>make_error_condition</code>([syserr.errcondition.nonmembers]). 
+ 
+ 
+ 
+ [Note: the class 
+ <code id=o17040>error_condition</code> ([syserr.errcondition.overview]) object is reported via
+ the <code id=o17042>default_error_condition</code> function ([syserr.errcode.observers])  of the class <code id=o17043>error_code</code>
+ object representing the error. --end note.
+ 
+ 
+ 
+ 
+ 
+ 
+ 
+ 
+</div>
+Change
+30.1.2 Exceptions [thread.req.exception] paragraph 2, as
+indicated: 
+ 
+The error_category (19.4.1.1) of the error_code reported by such an exceptionâ€™s
+code() member function is
+<strike id=znik1>implementation-defined.
+</strike> 
+<strike id=znik2> [Note: The category is typically
+system_category (19.4.1.1) since these error codes usually
+originate</strike> 
+<strike id=znik3>  from the underlying operating system
+application program interface (API). â€” end note ]</strike> 
+as specified in the error
+condition clause. 
+ 
+Change 30.2.1.2 thread constructors
+[thread.thread.constr], paragraph 9, as indicated: 
+ 
+Throws: std::system_error <strike id=znik5>or
+std::bad_alloc</strike> if unable to start the new thread. 
+
+
+ Error
+ conditions:<code id=c2mk8> </code>
+
+
+ <code id=c2mk8>    * resource_unavailable_try_again - </code> The
+ system lacked the necessary resources to create another thread, or the
+ system-imposed     limit on the total number of threads in
+ a process would be exceeded.
+
+
+ 
+ 
+
+Change
+30.2.1.5 thread members [thread.thread.member] paragraph 8 of the joint
+description as
+follows: 
+ 
+Throws: std::system_error when the
+postconditions cannot be achieved. 
+Error
+conditions: 
+    * resource_deadlock_would_occur - If deadlock is
+detected or this->get_id() ==
+std::this_thread::get_id() 
+   
+* no_such_process - If the thread is not valid. 
+    * invalid_argument - If the thread is not joinable. 
+ 
+Change paragraph 12 of the
+detach description 
+ 
+Throws: std::system_error when the
+effects or postconditions cannot be achieved. 
+Error
+conditions: 
+    * no_such_process: Not a valid thread. 
+    * invalid_argument: Not a detachable thread. 
+ 
+Change
+30.3.1 Mutex requirements [thread.mutex.requirements] change paragraph 3 on
+construction 
+ 
+If initialization of an object of a Mutex type fails, an exception of type
+std::system_error shall be thrown. 
+Error
+conditions: 
+   
+* not_enough_memory: If there is not enough memory to construct the mutex
+object. 
+    *
+resource_unavailable_try_again:
+If
+any native_handle_type manipulated is not
+available. 
+    * operation_not_permitted:
+If
+the thread does not have the necessary permission to change state of the
+mutex. 
+   
+* device_or_resource_busy:
+If
+any native_handle_type manipulated is already
+locked. 
+   
+* invalid_argument: If any native_handle_type manipulated as part of mutex
+construction is incorrect. 
+ 
+Append
+after paragraph 10 on m.lock() 
+ 
+Throws: std::system_error when the
+effects or postcondition cannot be
+achieved. 
+Error
+conditions: 
+    * operation_not_permitted: If the thread does not have the
+necessary permission to change state of the mutex. 
+    * resource_deadlock_would_occur: If the current thread
+already owns the mutex, and is able to detect it. 
+    * device_or_resource_busy: If the mutex is already locked and
+blocking is not possible. 
+ 
+Change
+30.3.3 paragraph 3: 
+ 
+<strike>An exception class lock_error is derived from
+std::exception and is used to indicate improper usage of locks such as locking a
+mutex that the lock already owns or unlocking a mutex that the lock does not
+own.</strike> 
+<strike>    namespace std
+{</strike> 
+<strike>       class lock_error :
+public std::exception
+{</strike> 
+<strike>      
+public:</strike> 
+<strike>         virtual
+const char* what() const
+throw();</strike> 
+<strike>      
+};</strike> 
+<strike>   
+}</strike> 
+ 
+Change
+30.3.3.2.2 unique_lock locking [thread.lock.unique.locking] paragraph 3 lock()
+description 
+ 
+Throws:
+<strike id=znik11>lock_error if on entry owns is true or pm is
+null. </strike> 
+std::system_error
+when the postcondition cannot be achieved. 
+Error
+conditions: 
+    * operation_not_permitted: If pm is null. 
+    * resource_deadlock_would_occur: If the current thread
+already owns the mutex (on entry owns is
+true). 
+ 
+Change
+30.3.3.2.2 unique_lock locking [thread.lock.unique.locking] paragraph 7
+try_lock() description 
+ 
+Throws:
+<strike id=znik13>lock_error if on entry owns is true or pm is
+null. </strike> 
+std::system_error
+when the postcondition cannot be achieved. 
+Error
+conditions: 
+    * operation_not_permitted: If pm is null. 
+    * resource_deadlock_would_occur: If the current thread
+already owns the mutex (on entry owns is
+true). 
+ 
+Change
+30.3.3.2.2 unique_lock locking [thread.lock.unique.locking] paragraph 11
+timed_lock() description 
+ 
+Throws:
+<strike id=znik15>lock_error if on entry owns is true or pm is
+null. </strike> 
+std::system_error
+when the postcondition cannot be achieved. 
+Error
+conditions: 
+    * operation_not_permitted: If pm is null. 
+    * resource_deadlock_would_occur: If the current thread
+already owns the mutex (on entry owns is
+true). 
+ 
+Change
+30.3.3.2.2 unique_lock locking [thread.lock.unique.locking] paragraph 15
+templatized timed_lock()
+description 
+ 
+Throws:
+<strike id=znik17>lock_error if on entry owns is true or pm is
+null. </strike> 
+std::system_error
+when the postcondition cannot be achieved. 
+Error
+conditions: 
+    * operation_not_permitted: If pm is null. 
+    * resource_deadlock_would_occur: If the current thread
+already owns the mutex (on entry owns is
+true). 
+ 
+Change
+30.3.3.2.2 unique_lock locking [thread.lock.unique.locking] paragraph 18
+unlock() description 
+ 
+Throws:
+<strike id=znik19>lock_error if on entry owns is false.
+</strike> 
+std::system_error
+when the postcondition cannot be achieved. 
+Error
+conditions: 
+    * operation_not_permitted: If on entry owns is false. 
+ 
+Change
+30.3.5.1 Struct once_flag append after paragraph 3 
+ 
+Throws:
+Nothing. 
+ 
+<div id=wx2g447 style="TEXT-ALIGN:justify; FONT-FAMILY:Arial">
+ Change 30.3.5.2 Function
+ call_once [thread.once.callonce] paragraph 4 
+ 
+</div>
+ 
+Throws: std::system_error when the effects cannot be achieved, or
+any exception thrown by func. 
+Error
+conditions: 
+   
+* invalid_argument: If once_flag object is no longer valid. 
+ 
+Change
+30.4.1 Class condition_variable [thread.condition.condvar] paragraph 2
+construction 
+ 
+Effects: Constructs an object of type condition_variable. 
+Throws:
+std::system_error when conditions cannot be
+achieved. 
+Error
+conditions: 
+    * not_enough_memory: If a memory limitation prevents
+initialization. 
+    * resource_unavailable_try_again: If some non-memory
+limitation prevents initialization 
+    * device_or_resource_busy: If attempting to initialize a
+previously-initialized but as of yet undestroyed condition_variable. 
+ 
+Change
+30.4.1 Class condition_variable [thread.condition.condvar] paragraph 11 of wait
+description 
+ 
+Throws: std::system_error when the
+effects, 
+pre-conditions,
+or
+postcondition cannot be achieved. 
+Error
+conditions: 
+    * operation_not_permitted: If the thread does not own the
+lock. 
+    * equivalent error_condition from lock.lock() or
+lock.unlock() 
+ 
+
+Change 30.4.1 Class condition_variable [thread.condition.condvar] paragraph 16
+of templatized wait description 
+ 
+Returns:
+true
+<strike>false</strike>
+if the call is returning because the time specified by abs_time was reached,
+otherwise <strike>true</strike>
+false. 
+ 
+ Change 30.4.1 Class
+condition_variable [thread.condition.condvar] paragraph 17 of templatized wait
+description 
+ 
+Throws: std::system_error when the
+<strike id=znik25>returned value, </strike>effects, or
+postcondition cannot be achieved. 
+Error
+conditions: 
+    * operation_not_permitted: If the thread does not own the
+lock. 
+    * equivalent error_condition from lock.lock() or
+lock.unlock() 
+ 
+Change 30.4.2 Class
+condition_variable_any [thread.condition.condvarany] paragraph 10 of wait
+description 
+ 
+Throws: std::system_error when the
+effects or postcondition cannot be achieved. 
+Error
+conditions: 
+    * equivalent error_condition from lock.lock() or
+lock.unlock() 
+ 
+Change
+30.4.2 Class condition_variable_any [thread.condition.condvarany] paragraph 15
+of
+templatized wait description
+ 
+ 
+Throws:
+std::system_error when the returned value, effects, or postcondition cannot be
+achieved. 
+Error
+conditions: 
+    * equivalent error_condition from lock.lock() or
+lock.unlock() 
+ 
+ 
+
+ Acknowedgements
+
+
+ 
+
+
+ Special thanks to
+ Anthony Williams for reviewing
+ drafts and clarifying error specifications.
+
+ 
+ 
+ 
+ 
+ 
+ 
+ 
+ 
+ 
+ 
+ 
+ 
+ 
+ 
+ </body>
+</html>

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