I read on some blog that "sparc64" was needed to be specified, and so tried: ../../orig/configure --build=sparc64-sun-solaris2.10 ... (our build environment has some pretty deep directory paths involved so we can compile for multiple systems, and it's a really old technique we use.) also specified: ABI=64 CPPFLAGS="-m64" CC="/usr/soft/home/gcc/bin/gcc.pl $CPPFLAGS" CXX="/usr/soft/home/gcc/bin/g++.pl $CPPFLAGS" CFLAGS=$CPPFLAGS CCFLAGS=$CPPFLAGS CXXFLAGS=$CPPFLAGS export ABI CPPFLAGS CFLAGS CCFLAGS CXXFLAGS CC CXX (the *.pl commands referenced above are simply wrappers that replace any "-m32" with "-m64", just to be sure!) and yet it still blows up because some part insists on compiling with "-m32". Why??!!! checking for sparc64-sun-solaris2.10-gcc... /usr/soft/that/gcc-4.8.1/src/default/sparc_sun_solaris2.10/./gcc/xgcc -B/usr/soft/that/gcc-4.8.1/src/default/sparc_sun_solaris2.10/./gcc/ -B/usr/local/sparc64-sun-solaris2.10/bin/ -B/usr/local/sparc64-sun-solaris2.10/lib/ -isystem /usr/local/sparc64-sun-solaris2.10/include -isystem /usr/local/sparc64-sun-solaris2.10/sys-include -m32 checking for suffix of object files... configure: error: in `/usr/soft/that/gcc-4.8.1/src/default/sparc_sun_solaris2.10/sparc64-sun-solaris2.10/sparcv8plus/libgcc': configure: error: cannot compute suffix of object files: cannot compile See `config.log' for more details. gmake[2]: *** [configure-stage1-target-libgcc] Error 1 gmake[2]: Leaving directory `/usr/soft/that/gcc-4.8.1/src/default/sparc_sun_solaris2.10' gmake[1]: *** [stage1-bubble] Error 2 gmake[1]: Leaving directory `/usr/soft/that/gcc-4.8.1/src/default/sparc_sun_solaris2.10' gmake: *** [bootstrap-lean] Error 2 and this is why the configure blows-up: ./sparc64-sun-solaris2.10/sparcv8plus/libgcc/config.log: configure:3565: checking for suffix of object files configure:3587: /usr/soft/that/gcc-4.8.1/src/default/sparc_sun_solaris2.10/./gcc/xgcc -B/usr/soft/that/gcc-4.8.1/src/default/sparc_sun_solaris2.10/./gcc/ -B/usr/local/sparc64-sun-solaris2.10/bin/ -B/usr/local/sparc64-sun-solaris2.10/lib/ -isystem /usr/local/sparc64-sun-solaris2.10/include -isystem /usr/local/sparc64-sun-solaris2.10/sys-include -m32 -c -g -O2 -m64 conftest.c >&5 xgcc: error: may not use both -m32 and -m64 I'm getting the impression that the actual source probably supports 64-bit compile, but it's all the configure stuff that's getting in the way. Amos