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| ID | Category | Severity | Type | Date Submitted | Last Update | ||
| 0000508 | [1003.1(2008)/Issue 7] System Interfaces | Objection | Enhancement Request | 2011-11-10 21:26 | 2020-03-05 15:25 | ||
| Reporter | eblake | View Status | public | ||||
| Assigned To | ajosey | ||||||
| Priority | normal | Resolution | Accepted As Marked | ||||
| Status | Applied | ||||||
| Name | Eric Blake | ||||||
| Organization | Red Hat | ||||||
| User Reference | ebb.ptsname_r | ||||||
| Section | ptsname | ||||||
| Page Number | 1712 | ||||||
| Line Number | 54741 | ||||||
| Interp Status | --- | ||||||
| Final Accepted Text | See Note: 0001248 | ||||||
| Summary | 0000508: Add ptsname_r | ||||||
| Description |
The standard lacks any simple thread-safe mechanism for determining the name of the slave of a pseudo-terminal device after obtaining the master side. [A not-so-simple mechanism for a multi-threaded application in possession of a master pseudo-terminal file descriptor would be spawning off a child application that can then use ptsname() in a single-threaded context, and pass information back to the parent process, but that is obviously inefficient and complex.] This proposal is modeled after the ptsname_r() interface present in at least glibc, and using ttyname() vs. ttyname_r() as the reference for how to expand the existing ptsname() interface to also cover a thread-safe alternative. This proposal assumes 0000503 has been applied first. Optionally, since ptsname( ) is very similar to ttyname( ), and ttyname( ) is allowed to be a cancellation point, it would make sense to allow both ptsname( ) and ptsname_r( ) to be cancellation points. |
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| Desired Action |
After line 12013 [XBD <stdlib.h>], add with XSI shading: int ptsname_r(int, char *, size_t); At line 46510 [XSH posix_openpt RATIONALE], change: The posix_openpt( ) function is designed to complement the grantpt( ), ptsname( ), and unlockpt( ) functions. to: The posix_openpt( ) function is designed to complement the grantpt( ), ptsname( ), ptsname_r( ), and unlockpt( ) functions. At line 54738 [XSH ptsname() NAME], change "ptsname" to "ptsname, ptsname_r" After line 54741 [SYNOPSIS], add with XSI shading: int ptsname_r(int fildes, char *name, size_t namesize); After line 54747 [DESCRIPTION], add: The ptsname_r( ) function shall store the name of the slave pseudo-terminal device corresponding to fildes in the character array referenced by name. The array is namesize characters long and should have space for the name and the terminating null character. The maximum length of the terminal name shall be {TTY_NAME_MAX}. After line 54752 [RETURN VALUE], add: If successful, the ptsname_r( ) function shall return zero. Otherwise, an error number shall be returned to indicate the error. At line 54754 [ERRORS], change this text (from 0000503): The ptsname( ) function may fail if: [EBADF] The fildes argument is not a valid file descriptor. [EINVAL] or [ENOTTY] The filedes argument is not associated with a master pseudo-terminal device. to: The ptsname_r( ) function shall fail if: [EBADF] The fildes argument is not a valid file descriptor. [EINVAL] The name argument is a null pointer. [ERANGE] The value of namesize is smaller than the length of the string to be returned including the terminating null character. The ptsname( ) function may fail if: [EBADF] The fildes argument is not a valid file descriptor. The ptsname( ) and ptsname_r( ) functions may fail if: [EINVAL] or [ENOTTY] The filedes argument is not associated with a master pseudo-terminal device. At line 54760 [RATIONALE], change "None." to: The ptsname_r( ) is required to make it possible for a multi-threaded program to safely determine the name of a slave device. Although the name of the device is constrained by {TTY_NAME_MAX}, this value might not be a compile-time constant, so an application can rely on repeated calls with successively larger buffers until the result is no longer ERANGE as an alternative for properly sizing the buffer. Historically, some versions of ptsname( ) did not set errno even when returning NULL. However, ptsname_r( ) is required to either populate the buffer with a valid name or return an error value. After line 126740 [XRAT E.1 Subprofiling Option Groups], add a new sub-profiling group: XSI_GENERAL_TERMINAL_R: XSI Thread-Safe General Terminal ptsname_r( ) Additional editorial changes, such as listing ptsname_r( ) in XRAT B.1.1 Change History, will be needed as appropriate. Optionally: At line 17788 [XSH 2.9.5.2 Cancellation Points], add ptsname( ) and ptsname_r( ) in sorted order into the list of optional cancellation points. |
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| Tags | issue8 | ||||||
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Notes |
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(0001248) nick (manager) 2012-05-31 16:07 |
As described in the Desired Action, with the final "Optionally" required (i.e. add both ptsname() and ptsname_r() to the list of cancellation points). |
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Issue History |
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| Date Modified | Username | Field | Change |
| 2011-11-10 21:26 | eblake | New Issue | |
| 2011-11-10 21:26 | eblake | Status | New => Under Review |
| 2011-11-10 21:26 | eblake | Assigned To | => ajosey |
| 2011-11-10 21:26 | eblake | Name | => Eric Blake |
| 2011-11-10 21:26 | eblake | Organization | => Red Hat |
| 2011-11-10 21:26 | eblake | User Reference | => ebb.ptsname_r |
| 2011-11-10 21:26 | eblake | Section | => ptsname |
| 2011-11-10 21:26 | eblake | Page Number | => 1712 |
| 2011-11-10 21:26 | eblake | Line Number | => 54741 |
| 2011-11-10 21:26 | eblake | Interp Status | => --- |
| 2011-11-10 21:27 | eblake | Tag Attached: issue8 | |
| 2011-11-10 21:27 | eblake | Relationship added | related to 0000503 |
| 2011-11-10 21:28 | eblake | Relationship added | related to 0000075 |
| 2012-05-31 16:03 | eblake | Desired Action Updated | |
| 2012-05-31 16:07 | nick | Final Accepted Text | => See Note: 0001248 |
| 2012-05-31 16:07 | nick | Note Added: 0001248 | |
| 2012-05-31 16:07 | nick | Status | Under Review => Resolved |
| 2012-05-31 16:07 | nick | Resolution | Open => Accepted As Marked |
| 2012-10-03 03:30 | eblake | Relationship added | related to 0000618 |
| 2020-03-05 15:25 | geoffclare | Status | Resolved => Applied |
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