When attempting to emerge gtkmm from the latest rsync, I get the following error while 'configure' is running: ---snip--- checking what warning flags to pass to the C++ compiler... -Wall -Wno-unused checking what language compliance flags to pass to the C++ compiler... checking for sigc-config... /usr/bin/sigc-config checking for libsigc++ - version >= 0.8.5... 1.0.4 checking if libsigc++ sane... no configure: error: Libsigc++ is required to compile Gtk--. If libsigc++ was installed but no found to be sane, most likely you have not placed the /usr/local/lib path in the library config file and run ldconfig. !!! ERROR: The ebuild did not complete successfully. !!! Function src_compile, Line 18, Exitcode 1 !!! (no error message) ---snip--- Libsigc++ is installed on the system. I re-emerged it just to be sure, no errors at all.
after you remerged libsigc++, did you try to remerge gtkmm again?
My bad, didn't realize it was some type of incompatibility with IBM's NGPS.
