In ftello.c, it intentionally skipped fflush for read mode: https://github.com/openunix/cygwin/blob/master/newlib/libc/stdio/ftello.c#L121
/* Find offset of underlying I/O object, then adjust for buffered bytes. Flush a write stream, since the offset may be altered if the stream is appending. Do not flush a read stream, since we must not lose the ungetc buffer. */ if (fp->_flags & __SWR) _fflush_r (ptr, fp); But in fseeko.c, when fseek(..., SEEK_CUR) requires to get the current position first. But it calls _fflush_r(ptr, fp) in read mode, which screwed up the current position after fflush. https://github.com/openunix/cygwin/blob/master/newlib/libc/stdio/fseeko.c#L174 For my job, if I skip _fflush_r for read only mode in fseek(..., SEEK_CUR), the job runs OK. Considering fseek(..., SEEK_CUR) is a basic call, could my understanding be wrong? Thanks. Xiaofeng Liu -- Problem reports: http://cygwin.com/problems.html FAQ: http://cygwin.com/faq/ Documentation: http://cygwin.com/docs.html Unsubscribe info: http://cygwin.com/ml/#unsubscribe-simple
