I am trying to build a "cross" compiler for embedded development: hosted on X86-64, targeting X86-64 (but not replacing the system GCC). I am working from the 4.6.1 tarball from the GCC gnu.org site, building with the system's native 4.5.1 (gcc (SUSE Linux) 4.5.1 20101208 [gcc-4_5-branch revision 167585]). I can build this just fine for a powerpc64 target. However, when I build for X86_64 target, I get the following errors: libtool: compile: /space/tools/ppc/build/x86_64-aeroflex-linux-gnu/gcc_phase2/./gcc/xgcc -B/space/tools/ppc/build/x86_64-aeroflex-linux-gnu/gcc_phase2/./gcc/ -B/opt/aeroflex/tools/4.6.1/x86_64-aeroflex-linux-gnu/bin/ -B/opt/aeroflex/tools/4.6.1/x86_64-aeroflex-linux-gnu/lib/ -isystem /opt/aeroflex/tools/4.6.1/x86_64-aeroflex-linux-gnu/include -isystem /opt/aeroflex/tools/4.6.1/x86_64-aeroflex-linux-gnu/sys-include -DHAVE_CONFIG_H -I. -I/space/tools/ppc/src/gcc-4.6.1/libmudflap -Wall -ffunction-sections -fdata-sections -g -pipe -O3 -MT mf-runtime.lo -MD -MP -MF .deps/mf-runtime.Tpo -c /space/tools/ppc/src/gcc-4.6.1/libmudflap/mf-runtime.c -fPIC -DPIC -o .libs/mf-runtime.o /space/tools/ppc/src/gcc-4.6.1/libmudflap/mf-runtime.c:168:11: error: conflicting types for ?__mf_lc_mask? /space/tools/ppc/src/gcc-4.6.1/libmudflap/mf-runtime.h:46:23: note: previous declaration of ?__mf_lc_mask? was here /space/tools/ppc/src/gcc-4.6.1/libmudflap/mf-runtime.c: In function ?__mfu_check?: /space/tools/ppc/src/gcc-4.6.1/libmudflap/mf-runtime.c:833:24: warning: cast from pointer to integer of different size [-Wpointer-to-int-cast] (repeat a bunch of times) The command I am using to configure the compiler is: libc_cv_forced_unwind=yes \ libc_cv_c_cleanup=yes \ CFLAGS="-fPIC -DPIC -pipe -O3" \ CXXFLAGS="-fPIC -DPIC -pipe -O3" \ /space/tools/ppc/src/glibc-2.14/configure \ --with-sysroot=/opt/aeroflex/tools/4.6.1/x86_64-aeroflex-linux-gnu/sys-root \ --with-headers=/opt/aeroflex/tools/4.6.1/x86_64-aeroflex-linux-gnu/sys-root/usr/include \ --build=`/space/tools/ppc/src/glibc-2.14/scripts/config.guess` \ --host=x86_64-aeroflex-linux-gnu \ --target=x86_64-aeroflex-linux-gnu \ --enable-shared \ --enable-static \ --enable-pic \ --prefix=/usr \ \ --enable-shared make make install Why is this building for PPC and not for X86? And how can I correct that?