I have a ARM virtual machine on AWS with Ubuntu18.04 installed.
dpkg & uname commands show this,
$ dpkg --print-architecture
arm64
$ uname -m
aarch64
I've got a third-party precompiled static library (.a) built for 32-bit.
I understand that I cannot link 32-bit library to a 64-bit application, so I've created a new application which will link the library and get compiled for 32-bit. This application will communicate with rest of the applications (64-bit) using some IPC mechanism. To compile this application I've added following flag in my cmake file,
set (CMAKE_CXX_FLAGS "-m32")
but the compiler throw this error,
c++: error: unrecognized command line option ‘-m32’
c++ version on my machine is,
$ c++ -v
Using built-in specs.
COLLECT_GCC=c++
COLLECT_LTO_WRAPPER=/usr/lib/gcc/aarch64-linux-gnu/7/lto-wrapper
Target: aarch64-linux-gnu
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 --program-prefix=aarch64-linux-gnu- --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-libquadmath --disable-libquadmath-support --enable-plugin --enable-default-pie --with-system-zlib --enable-multiarch --enable-fix-cortex-a53-843419 --disable-werror --enable-checking=release --build=aarch64-linux-gnu --host=aarch64-linux-gnu --target=aarch64-linux-gnu
Thread model: posix
gcc version 7.4.0 (Ubuntu/Linaro 7.4.0-1ubuntu1~18.04.1)
It shows that it is prepared with configuration option --enable-multiarch which I suppose should allow me to compile for different architecture (32-bit ARM).
On one of the other thread on stackoverflow says that some ARM64 machine's hardware may not support compilation of 32-bit applications.
My question is how to check if my ARM64 machine is capable of building 32-bit application? And if it is capable of building then what is the alternative to -m32 flag?
1 Answer 1
I resolved this issue by using different toolchains for compiling 32bit and 64bit applications - arm-linux-gnueabihf & arm-linux-gnueabi respectively. Not sure if there exist a better way of doing it.
Anyways, I don't need this anymore as the Cavium processor of the ARM64 machine I'm using does not support 32bit libraries. I will have to find a way to get the 64bit version of the library.