Hi, I have built gcc 4.8 successfully with the configuration: ../gcc-trunk/configure -v --with-pkgversion='ubuntu12.04-64' --enable-languages=c,c++,fortran,objc,obj-c++ --prefix=/usr --program-suffix=-4.8 --enable-shared --enable-linker-build-id --with-system-zlib --libexecdir=/usr/lib --without-included-gettext --enable-threads=posix --with-gxx-include-dir=/usr/include/c++/4.8 --libdir=/usr/lib --enable-nls --with-sysroot=/ --enable-clocale=gnu --enable-libstdcxx-debug --enable-libstdcxx-time=yes --enable-gnu-unique-object --enable-plugin --enable-objc-gc --disable-werror --with-arch-32=native --with-tune=native --enable-checking=release --build=x86_64-linux-gnu --host=x86_64-linux-gnu --target=x86_64-linux-gnu However, when I try to compile a test file, the search path is really strange: ignoring nonexistent directory“usr/include/c++/4.8”******************************************There is no slash! ignoring nonexistent directory“usr/include/c++/4.8/x86_64-linux-gnu/.”********************There is no slash! ignoring nonexistent directory“usr/include/c++/4.8/backward”******************************There is no slash! ignoring nonexistent directory“/usr/local/include/x86_64-linux-gnu” ignoring nonexistent directory“/usr/lib/gcc/x86_64-linux-gnu/4.8.0/../../../../x86_64-linux-gnu/include” Any one can help? Thank you! Regards, Yao Yuan.