After switching from Apple Python to the python.org version this is the first time I tried to build scipy. I see the same problem when building scipy trunk against numpy trunk or 0.7.x against numpy 1.3. Compilers: $ gcc --version i686-apple-darwin10-gcc-4.2.1 (GCC) 4.2.1 (Apple Inc. build 5646) (dot 1) $ gcc-4.0 --version i686-apple-darwin10-gcc-4.0.1 (GCC) 4.0.1 (Apple Inc. build 5493) $ gfortran --version GNU Fortran (GCC) 4.2.3 (obtained from http://r.research.att.com/tools/) Python: $ python Python 2.6.4 (r264:75821M, Oct 27 2009, 19:48:32) [GCC 4.0.1 (Apple Inc. build 5493)] on darwin Below is the relevant part (I think) of the build output. The "missing required architecture x86_64 in file" complaints happen for numpy builds as well, and seem to be harmless there. Any ideas? Thanks, Ralf $ LDFLAGS="-lgfortran -arch x86_64" FFLAGS="-arch x86_64" python setup.py build Warning: No configuration returned, assuming unavailable.blas_opt_info: FOUND: extra_link_args = ['-Wl,-framework', '-Wl,Accelerate'] define_macros = [('NO_ATLAS_INFO', 3)] extra_compile_args = ['-faltivec', '-I/System/Library/Frameworks/vecLib.framework/Headers'] lapack_opt_info: FOUND: extra_link_args = ['-Wl,-framework', '-Wl,Accelerate'] define_macros = [('NO_ATLAS_INFO', 3)] extra_compile_args = ['-faltivec'] umfpack_info: libraries umfpack not found in /Library/Frameworks/Python.framework/Versions/2.6/lib libraries umfpack not found in /usr/local/lib libraries umfpack not found in /usr/lib /Users/rgommers/Code/numpy/numpy/distutils/system_info.py:459: UserWarning: UMFPACK sparse solver (http://www.cise.ufl.edu/research/sparse/umfpack/) not found. Directories to search for the libraries can be specified in the numpy/distutils/site.cfg file (section [umfpack]) or by setting the UMFPACK environment variable. warnings.warn(self.notfounderror.__doc__) NOT AVAILABLE running build <SNIP> building 'scipy.fftpack._fftpack' extension compiling C sources C compiler: gcc-4.0 -arch ppc -arch i386 -isysroot /Developer/SDKs/MacOSX10.4u.sdk -fno-strict-aliasing -fno-common -dynamic -DNDEBUG -g -O3 creating build/temp.macosx-10.3-fat-2.6/build creating build/temp.macosx-10.3-fat-2.6/build/src.macosx-10.3-fat-2.6 creating build/temp.macosx-10.3-fat-2.6/build/src.macosx-10.3-fat-2.6/scipy creating build/temp.macosx-10.3-fat-2.6/build/src.macosx-10.3-fat-2.6/scipy/fftpack creating build/temp.macosx-10.3-fat-2.6/build/src.macosx-10.3-fat-2.6/scipy/fftpack/src compile options: '-Iscipy/fftpack/src -Ibuild/src.macosx-10.3-fat-2.6 -I/Users/rgommers/Code/numpy/numpy/core/include -I/Library/Frameworks/Python.framework/Versions/2.6/include/python2.6 -c' gcc-4.0: scipy/fftpack/src/zrfft.c gcc-4.0: build/src.macosx-10.3-fat-2.6/scipy/fftpack/src/dct.c gcc-4.0: scipy/fftpack/src/zfftnd.c gcc-4.0: build/src.macosx-10.3-fat-2.6/fortranobject.c gcc-4.0: build/src.macosx-10.3-fat-2.6/scipy/fftpack/_fftpackmodule.c gcc-4.0: scipy/fftpack/src/drfft.c gcc-4.0: scipy/fftpack/src/zfft.c /usr/local/bin/gfortran -Wall -lgfortran -arch x86_64 build/temp.macosx-10.3-fat-2.6/build/src.macosx-10.3-fat-2.6/scipy/fftpack/_fftpackmodule.o build/temp.macosx-10.3-fat-2.6/scipy/fftpack/src/zfft.o build/temp.macosx-10.3-fat-2.6/scipy/fftpack/src/drfft.o build/temp.macosx-10.3-fat-2.6/scipy/fftpack/src/zrfft.o build/temp.macosx-10.3-fat-2.6/scipy/fftpack/src/zfftnd.o build/temp.macosx-10.3-fat-2.6/build/src.macosx-10.3-fat-2.6/scipy/fftpack/src/dct.o build/temp.macosx-10.3-fat-2.6/build/src.macosx-10.3-fat-2.6/fortranobject.o -L/usr/local/lib/gcc/i686-apple-darwin8/4.2.3/x86_64 -Lbuild/temp.macosx-10.3-fat-2.6 -ldfftpack -lfftpack -lgfortran -o build/lib.macosx-10.3-fat-2.6/scipy/fftpack/_fftpack.so ld: warning: in build/temp.macosx-10.3-fat-2.6/build/src.macosx-10.3-fat-2.6/scipy/fftpack/_fftpackmodule.o, missing required architecture x86_64 in file ld: warning: in build/temp.macosx-10.3-fat-2.6/scipy/fftpack/src/zfft.o, missing required architecture x86_64 in file ld: warning: in build/temp.macosx-10.3-fat-2.6/scipy/fftpack/src/drfft.o, missing required architecture x86_64 in file ld: warning: in build/temp.macosx-10.3-fat-2.6/scipy/fftpack/src/zrfft.o, missing required architecture x86_64 in file ld: warning: in build/temp.macosx-10.3-fat-2.6/scipy/fftpack/src/zfftnd.o, missing required architecture x86_64 in file ld: warning: in build/temp.macosx-10.3-fat-2.6/build/src.macosx-10.3-fat-2.6/scipy/fftpack/src/dct.o, missing required architecture x86_64 in file ld: warning: in build/temp.macosx-10.3-fat-2.6/build/src.macosx-10.3-fat-2.6/fortranobject.o, missing required architecture x86_64 in file Undefined symbols: "_MAIN__", referenced from: _main in libgfortranbegin.a(fmain.o) ld: symbol(s) not found collect2: ld returned 1 exit status ld: warning: in build/temp.macosx-10.3-fat-2.6/build/src.macosx-10.3-fat-2.6/scipy/fftpack/_fftpackmodule.o, missing required architecture x86_64 in file ld: warning: in build/temp.macosx-10.3-fat-2.6/scipy/fftpack/src/zfft.o, missing required architecture x86_64 in file ld: warning: in build/temp.macosx-10.3-fat-2.6/scipy/fftpack/src/drfft.o, missing required architecture x86_64 in file ld: warning: in build/temp.macosx-10.3-fat-2.6/scipy/fftpack/src/zrfft.o, missing required architecture x86_64 in file ld: warning: in build/temp.macosx-10.3-fat-2.6/scipy/fftpack/src/zfftnd.o, missing required architecture x86_64 in file ld: warning: in build/temp.macosx-10.3-fat-2.6/build/src.macosx-10.3-fat-2.6/scipy/fftpack/src/dct.o, missing required architecture x86_64 in file ld: warning: in build/temp.macosx-10.3-fat-2.6/build/src.macosx-10.3-fat-2.6/fortranobject.o, missing required architecture x86_64 in file Undefined symbols: "_MAIN__", referenced from: _main in libgfortranbegin.a(fmain.o) ld: symbol(s) not found collect2: ld returned 1 exit status error: Command "/usr/local/bin/gfortran -Wall -lgfortran -arch x86_64 build/temp.macosx-10.3-fat-2.6/build/src.macosx-10.3-fat-2.6/scipy/fftpack/_fftpackmodule.o build/temp.macosx-10.3-fat-2.6/scipy/fftpack/src/zfft.o build/temp.macosx-10.3-fat-2.6/scipy/fftpack/src/drfft.o build/temp.macosx-10.3-fat-2.6/scipy/fftpack/src/zrfft.o build/temp.macosx-10.3-fat-2.6/scipy/fftpack/src/zfftnd.o build/temp.macosx-10.3-fat-2.6/build/src.macosx-10.3-fat-2.6/scipy/fftpack/src/dct.o build/temp.macosx-10.3-fat-2.6/build/src.macosx-10.3-fat-2.6/fortranobject.o -L/usr/local/lib/gcc/i686-apple-darwin8/4.2.3/x86_64 -Lbuild/temp.macosx-10.3-fat-2.6 -ldfftpack -lfftpack -lgfortran -o build/lib.macosx-10.3-fat-2.6/scipy/fftpack/_fftpack.so" failed with exit status 1