https://www.redhat.com/archives/fedora-test-list/2008-December/msg00426.html
(originally bug 476275 and closed duplicate of bug 223642)

  $ rpm -qR glibc-devel|grep ^glib
  glibc = 2.9-2
  glibc-headers = 2.9-2

So, glibc-devel requires glibc-headers.

  $ rpm -q --provides glibc-headers
  glibc-headers(i386)  
  glibc-headers = 2.9-2
  glibc-headers(x86-32) = 2.9-2

  $ rpm -q --whatprovides glibc-headers
  glibc-headers-2.9-2.i386

  $ sudo rpm -e glibc-headers

Uh? That should not have been possible, because now:

  $ rpm -V glibc-devel
  Unsatisfied dependencies for glibc-devel-2.9-2.i386:
          glibc-headers = 2.9-2 is needed by glibc-devel-2.9-2.i386

As Seth's message adds, it's "Requires(pre)" for this dependency
on glibc-headers. That's true according to the glibc.spec file.

Bug 223642 explains the RPM semantics and the suggested fix:
"Requires: glibc-headers" in glibc-devel would need to be added to fix this.