diff options
Diffstat (limited to 'lib/fflush.c')
| -rw-r--r-- | lib/fflush.c | 42 |
1 files changed, 41 insertions, 1 deletions
diff --git a/lib/fflush.c b/lib/fflush.c index be97769a4a..dfc1a74abd 100644 --- a/lib/fflush.c +++ b/lib/fflush.c @@ -1,5 +1,5 @@ /* fflush.c -- allow flushing input streams - Copyright (C) 2007 Free Software Foundation, Inc. + Copyright (C) 2007-2008 Free Software Foundation, Inc. This program is free software: you can redistribute it and/or modify it under the terms of the GNU General Public License as published by @@ -59,6 +59,46 @@ rpl_fflush (FILE *stream) if (stream == NULL || ! freading (stream)) return fflush (stream); + /* Clear the ungetc buffer. + + This is needed before fetching the file-position indicator, because + 1) The file position indicator is incremented by fgetc() and decremented + by ungetc(): + <http://www.opengroup.org/susv3/functions/fgetc.html> + "The file-position indicator is decremented by each successful + call to ungetc()..." + <http://www.opengroup.org/susv3/functions/ungetc.html> + "... the fgetc() function shall ... advance the associated file + position indicator for the stream ..." + 2) <http://www.opengroup.org/susv3/functions/ungetc.html> says: + "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." + 3) Here we are discarding all pushed-back bytes. + + Unfortunately it is impossible to implement this on platforms with + _IOERR, because an ungetc() on this platform prepends the pushed-back + bytes to the buffer without an indication of the limit between the + pushed-back bytes and the read-ahead bytes. */ +#if defined __sferror /* FreeBSD, NetBSD, OpenBSD, MacOS X, Cygwin */ + { +# if defined __NetBSD__ || defined __OpenBSD__ + struct __sfileext + { + struct __sbuf _ub; /* ungetc buffer */ + /* More fields, not relevant here. */ + }; + if (((struct __sfileext *) stream->_ext._base)->_ub._base != NULL) +# else + if (stream->_ub._base != NULL) +# endif + { + stream->_p += stream->_r; + stream->_r = 0; + } + } +#endif + /* POSIX does not specify fflush behavior for non-seekable input streams. Some implementations purge unread data, some return EBADF, some do nothing. */ |