I am a user of Gentoo Linux and I found some warnings on my screen that I could not redirect like stdout or stderr. They appear during execution of configure scripts, like the ones from coreutils or m4 and are caused by glibc. So I wrote a bug report on the Gentoo bug tracker. But the guys there say that everything is as it should be: http://bugs.gentoo.org/show_bug.cgi?id=257279 But I do not think, that this is acceptable. Next, I wrote to the bug-autoconf mailing list: http://lists.gnu.org/archive/html/bug-autoconf/2009-02/msg00006.html and was forwarded to bug-gnulib: http://lists.gnu.org/archive/html/bug-gnulib/2009-02/msg00103.html and from there I was sent here: http://lists.gnu.org/archive/html/bug-gnulib/2009-02/msg00106.html
The message should not be ignored and the code in glibc works hard to always get the message out. It works as it should.
IMO the exact opposite is true. The message can not be logged and will be discarded. It will be ignored, because it will not even be recognized. It is always possible to ignore a warning, no matter how it is announced. But when caring about important warnings, they are expected on stderr. I personally prefer an operating system that cooperates and does not force me to keep a terminal open.
glibc attempts to write to the controlling terminal, in the hopes that it will be noticed at the highest possible level. Especially since a process may have closed its stderr already. To explicitly disable this and try to write to fd 2, you can set the environment variable LIBC_FATAL_STDERR_=1 (yes, there is a trailing underscore in the variable name).