Submitter: Nick Stoughton (US)
Submission Date: 2013-06-19
Source: Austin Group
Reference Documents: N1719,
Austin Group Defect #701
Version: 1.0
Date: June 2013
Subject: ungetc / ungetwc and file position after discarding push back
problems
Summary
C11 (and C99 before it) state for both ungetc() and ungetwc() that
A successful intervening call (with the stream pointed to by stream) to a file positioning function (fseek, fsetpos, or rewind) discards any pushed-back characters for the stream. ... 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.(7.21.7.10 p2 & p5, with similar at 7.29.3.10 p2 & p5). The "or discarding" phrasing in p5 makes no sense: all of the listed functions which discard the push back also _set_ the file position. The file position will end up as whatever the function sets it to, not "the same as it was before the characters were pushed back".
Suggested Change
ChangeThe 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 all pushed-back characters have been read shall be the same as it was before the characters were pushed back.
Committee Discussion
Proposed Technical Corrigendum