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|ID||Category||Severity||Type||Date Submitted||Last Update|
|0000613||[1003.1(2008)/Issue 7] System Interfaces||Editorial||Omission||2012-09-24 21:41||2022-09-27 15:22|
|Priority||normal||Resolution||Accepted As Marked|
|Final Accepted Text||Note: 0005944|
|Summary||0000613: Relationship of automatic object lifetimes to cancellation cleanup functions is not specified|
Purportedly it is the intent of the standard to allow implementation of thread cancellation and cleanup functions using language-level exception handling, such as the exception extensions to the C language offered by GCC. However, nowhere is it specified that acting on a cancellation request prematurely terminates execution of any block; thus, by a strict reading of the standard as written, cleanup handlers are permitted to access objects with automatic storage duration whose lifetimes have not ended at the point where cancellation is acted upon, but whose lifetimes would have ended if an otherwise-equivalent exception were thrown from that point.
A manifestation of this issue in the GNU C library can be seen in this issue report, which I filed:
Also, the follow-up on the issue tracker cites language in the rationale for the original 1996 standard, which I cannot find in the current standard, clarifying that such exception-based implementations were intended to be permitted.
Adding language to this effect in the specification of pthread_cleanup_push should be sufficient:
"Invoking a cancellation cleanup function may terminate the execution of any block being executed by the thread whose execution began began after the corresponding invocation of pthread_cleanup_push."
After 2018 edition page 48 line 1520 section 3 Definitions, add a new definition:
3.xxx Code Block
In the context of the System Interfaces Volume of this standard, a block as defined in the ISO C standard.
After 2018 edition page 1605 line 52316 section pthread_cleanup_pop(), add a new paragraph:
Invoking a cancellation cleanup handler may terminate the execution of any code block being executed by the thread whose execution began after the corresponding invocation of pthread_cleanup_push().
|2012-09-24 21:41||dalias||New Issue|
|2012-09-24 21:41||dalias||Status||New => Under Review|
|2012-09-24 21:41||dalias||Assigned To||=> ajosey|
|2012-09-24 21:41||dalias||Name||=> Rich Felker|
|2012-09-24 21:41||dalias||Organization||=> musl libc|
|2012-09-24 21:41||dalias||Section||=> pthread_cleanup_push|
|2012-09-24 21:41||dalias||Page Number||=> unknown|
|2012-09-24 21:41||dalias||Line Number||=> unknown|
|2022-08-25 15:15||geoffclare||Note Added: 0005944|
|2022-08-25 15:15||geoffclare||Interp Status||=> ---|
|2022-08-25 15:15||geoffclare||Final Accepted Text||=> Note: 0005944|
|2022-08-25 15:15||geoffclare||Status||Under Review => Resolved|
|2022-08-25 15:15||geoffclare||Resolution||Open => Accepted As Marked|
|2022-08-25 15:16||geoffclare||Tag Attached: tc3-2008|
|2022-09-27 15:22||geoffclare||Status||Resolved => Applied|
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