Eric Blake-1 <[EMAIL PROTECTED]> wrote: > The yesno module has a problem on platforms where exit() > does not implicitly flush seekable input streams (this behavior > of exit() is contrary to POSIX, but glibc behaves this way, > and Ulrich was unwilling to fix the glibc bug [1]). Basically, > because the yesno module consumes input from stdin, if > the application does not restore the offset of the underlying > fd to the next unread byte prior to a successful exit, then > data is lost from subsequent applications that also read > from the file descriptor. > > For an example of the bug, try this on Linux (tested > with glibc 2.3): > > $ touch a b > $ echo 'n > y' > blah > $ (export LC_ALL=C; mv -vi a b; mv -vi a b) < blah > mv: overwrite `b'? mv: overwrite `b'? > $ echo $? > 0 > $ ls ? > a b > > contrasted to Solaris or cygwin (where exit() already > takes care of flushing seekable stdin): > > $ touch a b > $ echo 'n > y' > blah > $ (export LC_ALL=C; mv -vi a b; mv -vi a b) < blah > mv: overwrite `b'? mv: overwrite `b'? `a' -> `b' > $ echo $? > 0 > $ ls ? > b > > Basically, on buggy platforms, the first mv did not reset > the file pointer to the unread line "y", so the second mv > saw EOF instead of the affirmative response. The end > result was a violation of POSIX semantics on Linux. > > The closein module is capable of resolving this problem. > However, rather than fix all of the affected applications > one-by-one (the list includes, but is not limited to, > coreutils' cp, ln, mv, rm, and remove; and findutils' find), > it would be nicer to fix this just once in yesno. OK to > apply the patch below? > > [1] http://sources.redhat.com/bugzilla/show_bug.cgi?id=3746 > > > 2007-08-17 Eric Blake <[EMAIL PROTECTED]> > > Don't consume too much input when stdin is seekable. > * lib/yesno.c (yesno): Flush seekable stdin. > * modules/yesno (Depends-on): Add fflush.
That looks fine to me. However, a change like this requires at least one test, either in gnulib or in coreutils (or both!) to exercise it. You're welcome to commit it, but please also add a test or two.
