You receive this bug because this package does not respect my system's CC ( x86_64-pc-linux-gnu-gcc - /usr/bin/x86_64-pc-linux-gnu-gcc ) and calls directly gcc -/usr/bin/gcc The possible solutions to fix this issue are: 1)Fix the buildsystem, if you can 2)inherit toolchain-funcs and use tc-export CC 3)inherit toolchain-funcs and use emake CC="$(tc-getCC)" gcc -c -march=native -O2 -g0 -pipe -march=native -O2 -g0 -pipe -I.. -W -Wall -D_LARGEFILE_SOURCE -D_FILE_OFFSET_BITS=64 -D_REENTRANT -D_GNU_SOURCE -O3 -DHAVE_LOCALE_H -DHAVE_SETLOCALE -DHAVE_IFADDRS_H -DHAVE_LANGINFO_H -DHAVE_LANGINFO_CODESET -DHAVE_ICONV -pthread -I/usr/include/upnp -o cds.o cds.c
+ 15 Feb 2013; Markos Chandras <hwoarang@gentoo.org> + +files/07_all_drop_optimizations.patch, ushare-1.1a-r5.ebuild: + Respect CC (#457612). Drop -O3 (#457614) +