Had a bit of a problem with re-emerging app-arch/rpm-4.4.6-r3 after an update of libexpat: the emerge failed with a whole bunch of compiler messages.
After a quick search on Gentoo Forums, I found a post about someone who has had the same problem, and was able to solve it.

The problem

About halfway the merge, the compile failed. At the beginning of a long list, I found these error messages:

Quote

i686-pc-linux-gnu-gcc -DHAVE_CONFIG_H -I. -I.. -I. -I.. -I/usr/include/beecrypt -I../lua/include -I../lua/local -I../misc -march=pentium4 -O3 -pipe -fomit-frame-pointer -fPIC -DPIC -D_GNU_SOURCE -D_REENTRANT -Wall -Wpointer-arith -Wstrict-prototypes -Wmissing-prototypes -Wno-char-subscripts -MT rpmdav.lo -MD -MP -MF .deps/rpmdav.Tpo -c rpmdav.c -fPIC -DPIC -o .libs/rpmdav.o
rpmdav.c:12:22: error: ne_alloc.h: No such file or directory
rpmdav.c:13:21: error: ne_auth.h: No such file or directory
rpmdav.c:14:22: error: ne_basic.h: No such file or directory
rpmdav.c:15:22: error: ne_dates.h: No such file or directory
rpmdav.c:16:22: error: ne_locks.h: No such file or directory
rpmdav.c:24:22: error: ne_props.h: No such file or directory
rpmdav.c:25:24: error: ne_request.h: No such file or directory
rpmdav.c:26:23: error: ne_socket.h: No such file or directory
rpmdav.c:27:23: error: ne_string.h: No such file or directory
rpmdav.c:28:22: error: ne_utils.h: No such file or directory

Because of this error, rpm2cpio did not work because of the upgrade to libexpat-2 (which causes a whole bunch of dependency issues when not taken care of). And because of that, I was unable to install a bunch of other packages - netscape-flash was one of them.

The solution

The thread I found talked about re-emerging net-misc/neon, to which the .h files seem to belong to:

emerge -av net-misc/neon

After that was merged, the merge of app-arch/rpm-4.4.6-r3 went like a charm, and with it, I was back on track with my mega-upgrade of my workstation at work (running Gentoo, of course).