[Bug libc/11161] New: process with closed fd 2 sees no problem on stdout

["kogorman at calpoly dot edu" <sourceware-bugzilla at sourceware dot org>]

When a process is started with file descriptor 2 closed (such as some daemon
processes, or for headless operation), or if fd 2 becomes closed without
explicitly closing stdout, functions on filestream stdout do not report errors.
 I will attach a C program that illustrates this situation.
Run it from bash as "fsbad >&-" to start with a closed STDOUT_FILENO.

I know that processes which expect fd2 to be closed should not be writing to
stdout, but it seems odd for the error not to be reported.  What is even more
odd is that the first attempt to use stdout changes 'errno' to EBADF, but
otherwise gives a normal return.

This was a problem for me because I am teaching systems programming, and I tell
my students to get in the habit of checking all calls for errors, and they hit
on this as a technique to test their code, and thoght they had done something wrong.

-- 
           Summary: process with closed fd 2 sees no problem on stdout
           Product: glibc
           Version: 2.8
            Status: NEW
          Severity: normal
          Priority: P2
         Component: libc
        AssignedTo: drepper at redhat dot com
        ReportedBy: kogorman at calpoly dot edu
                CC: glibc-bugs at sources dot redhat dot com,kogorman at
                    calpoly dot edu


http://sourceware.org/bugzilla/show_bug.cgi?id=11161

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