Default arm-linux-gnueabihf-gcc Architecture/CPU/fpu Flags

Question

How can I print the used/default options for

• -march
• -mcpu
• -mfpu
• -mtune

for a specific cross compiler (arm-linux-gnueabihf-gcc)?

Answer 1

You can use arm-linux-gnueabihf-gcc -E -v

For instance on Raspberry Pi:

$ arm-linux-gnueabihf-gcc -E -v Using built-in specs. COLLECT_GCC=arm-linux-gnueabihf-gcc Target: arm-linux-gnueabihf Configured with: ../src/configure -v --with-pkgversion='Raspbian 8.3.0-6+rpi1' --with-bugurl=file:///usr/share/doc/gcc-8/README.Bugs --enable-languages=c,ada,c++,go,d,fortran,objc,obj-c++ --prefix=/usr --with-gcc-major-version-only --program-suffix=-8 --program-prefix=arm-linux-gnueabihf- --enable-shared --enable-linker-build-id --libexecdir=/usr/lib --without-included-gettext --enable-threads=posix --libdir=/usr/lib --enable-nls --enable-bootstrap --enable-clocale=gnu --enable-libstdcxx-debug --enable-libstdcxx-time=yes --with-default-libstdcxx-abi=new --enable-gnu-unique-object --disable-libitm --disable-libquadmath --disable-libquadmath-support --enable-plugin --with-system-zlib --with-target-system-zlib --enable-objc-gc=auto --enable-multiarch --disable-sjlj-exceptions --with-arch=armv6 --with-fpu=vfp --with-float=hard --disable-werror --enable-checking=release --build=arm-linux-gnueabihf --host=arm-linux-gnueabihf --target=arm-linux-gnueabihf Thread model: posix gcc version 8.3.0 (Raspbian 8.3.0-6+rpi1)

On my x86 laptop:

$ arm-linux-gnueabihf-gcc -E -v Using built-in specs. COLLECT_GCC=arm-linux-gnueabihf-gcc Target: arm-linux-gnueabihf Configured with: ../src/configure -v --with-pkgversion='Ubuntu/Linaro 7.4.0-1ubuntu1~18.04.1' --with-bugurl=file:///usr/share/doc/gcc-7/README.Bugs --enable-languages=c,ada,c++,go,d,fortran,objc,obj-c++ --prefix=/usr --with-gcc-major-version-only --program-suffix=-7 --enable-shared --enable-linker-build-id --libexecdir=/usr/lib --without-included-gettext --enable-threads=posix --libdir=/usr/lib --enable-nls --with-sysroot=/ --enable-clocale=gnu --enable-libstdcxx-debug --enable-libstdcxx-time=yes --with-default-libstdcxx-abi=new --enable-gnu-unique-object --disable-libitm --disable-libquadmath --disable-libquadmath-support --enable-plugin --enable-default-pie --with-system-zlib --with-target-system-zlib --enable-multiarch --enable-multilib --disable-sjlj-exceptions --with-arch=armv7-a --with-fpu=vfpv3-d16 --with-float=hard --with-mode=thumb --disable-werror --enable-multilib --enable-checking=release --build=x86_64-linux-gnu --host=x86_64-linux-gnu --target=arm-linux-gnueabihf --program-prefix=arm-linux-gnueabihf- --includedir=/usr/arm-linux-gnueabihf/include Thread model: posix gcc version 7.4.0 (Ubuntu/Linaro 7.4.0-1ubuntu1~18.04.1)

As you can notice RaspberryPi builds with armv6 by default (RPI0 uses a ARM11 - based on ARMv6 architecture) while arm-linux-gnueabihf-gcc ships with Ubuntu uses armv7-a - probably the most spread ARM 32bit architecture for Linux.

By default multi-arch GCC does not tune for any processor as its primarily targets are architecture.

Answer 2

after building a sample , run readelf -a command over executable for checking architecuture .