* fseek(...,SEEK_CUR) calls _fflush_r(ptr, fp) in read only mode [not found] <1470375482.5430561.1512147734234.ref@mail.yahoo.com> @ 2017-12-01 17:02 ` Xiaofeng Liu via cygwin 2017-12-01 17:19 ` Corinna Vinschen 0 siblings, 1 reply; 2+ messages in thread From: Xiaofeng Liu via cygwin @ 2017-12-01 17:02 UTC (permalink / raw) To: The Cygwin Mailing List 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 ^ permalink raw reply [flat|nested] 2+ messages in thread
* Re: fseek(...,SEEK_CUR) calls _fflush_r(ptr, fp) in read only mode 2017-12-01 17:02 ` fseek(...,SEEK_CUR) calls _fflush_r(ptr, fp) in read only mode Xiaofeng Liu via cygwin @ 2017-12-01 17:19 ` Corinna Vinschen 0 siblings, 0 replies; 2+ messages in thread From: Corinna Vinschen @ 2017-12-01 17:19 UTC (permalink / raw) To: cygwin [-- Attachment #1: Type: text/plain, Size: 1223 bytes --] On Dec 1 17:02, Xiaofeng Liu via cygwin wrote: > 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? Please provide a simple, self-contained testcase. It might clear up the problem. Corinna -- Corinna Vinschen Please, send mails regarding Cygwin to Cygwin Maintainer cygwin AT cygwin DOT com Red Hat [-- Attachment #2: signature.asc --] [-- Type: application/pgp-signature, Size: 819 bytes --] ^ permalink raw reply [flat|nested] 2+ messages in thread
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2017-12-01 17:02 ` fseek(...,SEEK_CUR) calls _fflush_r(ptr, fp) in read only mode Xiaofeng Liu via cygwin
2017-12-01 17:19 ` Corinna Vinschen
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