0000452: fflush changes need counterpart unget[w]c changes

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Category

Severity

Type

Date Submitted

Last Update

0000452

[2008-TC1] System Interfaces

Objection

Omission

2011-05-23 16:53

2011-06-15 14:58

Reporter

eblake

View Status

public

Assigned To

ajosey

Priority

normal

Resolution

Duplicate

Status

Closed

Product Version

Draft 1

Name

Eric Blake

Organization

Red Hat

User Reference

ebb.unget

Section

XSH/TC1/D1/0083

Page Number

Line Number

2099

Interp Status

---

Final Accepted Text

Summary

0000452: fflush changes need counterpart unget[w]c changes

Description

The proposed changes to fflush:

... the file offset of the underlying open file description shall be set
to the file position of the stream, and any characters pushed back onto
the stream by ungetc() or ungetwc() that have not subsequently been read
from the stream shall be discarded.

have clear rationale presented in bug 87 (that is, for proper behavior
of { app1; app2; } < seekable, if app1 reads one byte too many then uses
ungetc() to push it back before exiting, then app2 must start at the
offset unused by app1). However, that wording is in conflict with
existing wording in ungetc:

[XSH 67927] The value of the file-position indicator for the stream after
reading or discarding all pushed-back bytes shall be the same as it was
before the bytes were pushed back.

For the change to be complete, we also need to modify the wording of
ungetc and ungetwc to make it clear that discarded push-back characters
reset the file offset to the same offset in use while the push-back
characters were pending, and not the offset that was reached prior to
the push-back operation.

Desired Action

At page 141 of draft 1, insert new change actions in the appropriate positions:

On Page: 2151 Line: 67927 Section: ungetc()
In the DESCRIPTION section, change from:
The value of the file-position indicator for the stream after reading
or discarding all pushed-back bytes shall be the same as it was before
the bytes were pushed back.
to:
The value of the file-position indicator for the stream after reading
all pushed-back bytes shall be the same as it was before the bytes were
pushed back.
Rationale: Pushed-back bytes discarded by fflush() are re-read from a
seekable underlying file, rather than skipped.

On Page: 2152 Line: 67971 Section: ungetwc()
In the DESCRIPTION section, change from:
The value of the file-position indicator for the stream after reading
or discarding all pushed-back characters shall be the same as it was
before the characters were pushed back.
to:
The value of the file-position indicator for the stream after reading
all pushed-back characters shall be the same as it was before the
characters were pushed back.
Rationale: Pushed-back characters discarded by fflush() are re-read
from a seekable underlying file, rather than skipped.

Tags

No tags attached.

Attached Files

Relationships

related to	0000087	Closed	ajosey	1003.1(2008)/Issue 7	fflush and ungetc
related to	0000093	Closed	ajosey	1003.1(2008)/Issue 7	ungetc fseeko

Notes
(0000790) eblake (manager) 2011-05-23 19:45	Additionally: At line 4853 [XSH/TC1/D1/0331 ungetc], change: fseek(), [CX]fseeko()[/CX] fsetpos(), or rewind() to: [CX]fflush()[/CX], fseek(), [CX]fseeko()[/CX] fsetpos(), or rewind() At line 4864 [XSH/TC1/D1/0332 ungetwc], change: fseek(), [CX]fseeko()[/CX] fsetpos(), or rewind() to: [CX]fflush()[/CX], fseek(), [CX]fseeko()[/CX] fsetpos(), or rewind()

(0000835) Don Cragun (manager) 2011-06-15 14:58	This bug affects the changes instituted for an approved interpretation 0000087 so this bug is closed as a duplicate of it and it is being reopened.

Issue History
Date Modified	Username	Field	Change
2011-05-23 16:53	eblake	New Issue
2011-05-23 16:53	eblake	Status	New => Under Review
2011-05-23 16:53	eblake	Assigned To	=> ajosey
2011-05-23 16:53	eblake	Name	=> Eric Blake
2011-05-23 16:53	eblake	Organization	=> Red Hat
2011-05-23 16:53	eblake	User Reference	=> ebb.unget
2011-05-23 16:53	eblake	Section	=> XSH/TC1/D1/0083
2011-05-23 16:53	eblake	Page Number	=> 60
2011-05-23 16:53	eblake	Line Number	=> 2099
2011-05-23 16:53	eblake	Interp Status	=> ---
2011-05-23 16:57	eblake	Relationship added	related to 0000087
2011-05-23 19:45	eblake	Note Added: 0000790
2011-05-23 19:45	eblake	Relationship added	related to 0000093
2011-06-15 14:58	Don Cragun	Note Added: 0000835
2011-06-15 14:58	Don Cragun	Status	Under Review => Closed
2011-06-15 14:58	Don Cragun	Resolution	Open => Duplicate

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