View Issue Details
| ID | Project | Category | View Status | Date Submitted | Last Update |
|---|---|---|---|---|---|
| 0000632 | 1003.1(2008)/Issue 7 | System Interfaces | public | 2012-11-09 13:29 | 2019-06-10 08:55 |
| Reporter | dalias | Assigned To | ajosey | ||
| Priority | normal | Severity | Editorial | Type | Clarification Requested |
| Status | Closed | Resolution | Accepted As Marked | ||
| Name | Rich Felker | ||||
| Organization | musl libc | ||||
| User Reference | |||||
| Section | XSH 2.9.5, pclose | ||||
| Page Number | unknown | ||||
| Line Number | unknown | ||||
| Interp Status | Approved | ||||
| Final Accepted Text | 0000632:0001447 | ||||
| Summary | 0000632: Side effects of pclose on cancellation are not specified | ||||
| Description | pclose is an optional cancellation point, but the text in XSH 2.9.5 regarding side effects on cancellation is insufficient to specify its behavior when cancelled, since pclose is explicitly documented not to return early ("In any case, pclose() shall not return before the child process created by popen() has terminated.") and thus not to fail with EINTR. | ||||
| Desired Action | Either remove pclose from the list of optional cancellation points, or add language specifying what actions are permitted by the implementation when pclose is cancelled. The most important question is whether the stream is closed or not; not closing it would allow the application to attempt to pclose again from its cancellation handlers. However at this point the pipe must already be closed, so the stream would already be non-functional for further use. Lesser issues, but still important, are whether it might leak a pid, kill the child, or continue waiting. | ||||
| Tags | tc2-2008 | ||||
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The minutes from 6 December 2012 recorded: After a lengthy discussion we came to the conclusion that pclose() and cancellation do not mix. We considered leaving the normative text as-is and just adding application usage warning that applications should not cancel a thread that is executing pclose(), but we felt that was not strong enough. The direction we plan to take is for the normative text to state that if a thread is cancelled while it is executing pclose(), the behaviour is undefined. This is being left open for feedback. |
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Interpretation response ------------------------ The standard states pclose is an optional cancellation point, and conforming implementations must conform to this. However, concerns have been raised about this which are being referred to the sponsor. Rationale: ------------- After a lengthy discussion we came to the conclusion that pclose() and cancellation do not mix. We considered leaving the normative text as-is and just adding application usage warning that applications should not cancel a thread that is executing pclose(), but we felt that was not strong enough. The direction we plan to take is for the normative text to state that if a thread is cancelled while it is executing pclose(), the behaviour is undefined. Notes to the Editor (not part of this interpretation): ------------------------------------------------------- We recommend that the following text be placed on P1396 as a new paragraph after line 45712: If a thread is canceled during execution of pclose(), the behavior is undefined. We recommend that in Section XSH 2.9.5: At page 513 line 17758 remove pclose() from the list of functions in which a cancellation point may occur. At page 514 line 17795 append to the paragraph about EINTR: For functions that are explicitly required not to return when interrupted (for example, pclose()), if a thread is canceled while executing the function, the behavior is undefined. |
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Interpretation Proposed 29 Mar 2013 |
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Interpretation approved 3 May 2013 |
| Date Modified | Username | Field | Change |
|---|---|---|---|
| 2012-11-09 13:29 | dalias | New Issue | |
| 2012-11-09 13:29 | dalias | Status | New => Under Review |
| 2012-11-09 13:29 | dalias | Assigned To | => ajosey |
| 2012-11-09 13:29 | dalias | Name | => Rich Felker |
| 2012-11-09 13:29 | dalias | Organization | => musl libc |
| 2012-11-09 13:29 | dalias | Section | => XSH 2.9.5, pclose |
| 2012-11-09 13:29 | dalias | Page Number | => unknown |
| 2012-11-09 13:29 | dalias | Line Number | => unknown |
| 2012-11-28 17:27 | nick | Relationship added | related to 0000529 |
| 2012-11-28 17:37 | nick | Relationship added | related to 0000614 |
| 2013-01-10 16:09 | ajosey | Note Added: 0001440 | |
| 2013-01-17 16:35 | msbrown | Note Added: 0001447 | |
| 2013-01-17 16:36 | msbrown | Interp Status | => Pending |
| 2013-01-17 16:36 | msbrown | Final Accepted Text | => 0000632:0001447 |
| 2013-01-17 16:36 | msbrown | Status | Under Review => Interpretation Required |
| 2013-01-17 16:36 | msbrown | Resolution | Open => Accepted As Marked |
| 2013-01-17 16:42 | msbrown | Tag Attached: tc2-2008 | |
| 2013-03-29 08:04 | ajosey | Interp Status | Pending => Proposed |
| 2013-03-29 08:04 | ajosey | Note Added: 0001518 | |
| 2013-05-03 12:19 | ajosey | Interp Status | Proposed => Approved |
| 2013-05-03 12:19 | ajosey | Note Added: 0001578 | |
| 2019-06-10 08:55 | agadmin | Status | Interpretation Required => Closed |
