Why do I get cc1plus: error: unrecognized command line option "-arch"?

Question

/usr/bin/make -f nbproject/Makefile-Debug.mk SUBPROJECTS= .build-conf
/usr/bin/make  -f nbproject/Makefile-Debug.mk dist/Debug/GNU-MacOSX/cppapplication_1
mkdir -p build/Debug/GNU-MacOSX
rm -f build/Debug/GNU-MacOSX/main.o.d
g++ -arch i386   -c -g -MMD -MP -MF build/Debug/GNU-MacOSX/main.o.d -o build/Debug/GNU-MacOSX/main.o main.cpp
cc1plus: error: unrecognized command line option "-arch"
make[2]: *** [build/Debug/GNU-MacOSX/main.o] Error 1
make[1]: *** [.build-conf] Error 2
make: *** [.build-impl] Error 2
BUILD FAILED (exit value 2, total time: 311ms)

simpatico$ g++ -v
Using built-in specs.
COLLECT_GCC=g++
COLLECT_LTO_WRAPPER=/opt/local/libexec/gcc/x86_64-apple-darwin10/4.5.1/lto-wrapper
Target: x86_64-apple-darwin10
Configured with: ../gcc-4.5.1/configure --prefix=/opt/local --build=x86_64-apple-darwin10 --enable-languages=c,c++,objc,obj-c++,fortran,java --libdir=/opt/local/lib/gcc45 --includedir=/opt/local/include/gcc45 --infodir=/opt/local/share/info --mandir=/opt/local/share/man --datarootdir=/opt/local/share/gcc-4.5 --with-local-prefix=/opt/local --with-system-zlib --disable-nls --program-suffix=-mp-4.5 --with-gxx-include-dir=/opt/local/include/gcc45/c++/ --with-gmp=/opt/local --with-mpfr=/opt/local --with-mpc=/opt/local --enable-stage1-checking --disable-multilib --enable-fully-dynamic-string
Thread model: posix
gcc version 4.5.1 (GCC) 

This simple of a file:

#include <stdlib.h>

int main(int argc, char** argv) {

    return (EXIT_SUCCESS);
}

Answer 1

The -arch option is part of the Apple extensions to gcc. You need to use the gcc supplied by Apple's Developer Tools, Xcode.

Answer 2

The -arch option is only in the Apple-provided version of gcc. Change CFLAGS (which might be set via your environment, your makefile, or your configure options) so it uses -march or -m32 instead. For example:

configure CFLAGS='-m32 -O2' CC=gcc-4.5

The difference seems to be that you can specify multiple -arch options to generate universal binaries, whereas -march only generates one at a time.