How to detect target architecture using CMake?

Question

I\'ve done a lot of research and been unable to find an answer to this... how can I reliably find the target architecture I\'m compiling for, using CMake? Basically, the equ

Answer 1

This post is old, so sorry if resurrecting the dead here but I just thought I'd share the solution I made.

I didn't want to use any external application and unfortunately the toolchain.cmake file we're using doesn't have the arch set in another variable so I detect it by looking at the CMAKE_C_FLAGS and CMAKE_CXX_FLAGS variables looking for the -march argument to GCC. If there isn't one, it falls back to CMAKE_HOST_SYSTEM_PROCESSOR.

A quick look at the Clang documentation seems to indicate that this wouldn't work for that one but it would just need a second regex step to match its expected argument.

set(TARGET_ARCH_REGEX "^.*-march[= ]([^ ]+).*$")
string(REGEX MATCH "${TARGET_ARCH_REGEX}" TARGET_ARCH_MATCH ${CMAKE_C_FLAGS} ${CMAKE_CXX_FLAGS})
if (TARGET_ARCH_MATCH)
    string(REGEX REPLACE "${TARGET_ARCH_REGEX}" "\\1" TARGET_ARCH ${CMAKE_C_FLAGS} ${CMAKE_CXX_FLAGS})
else()
    set(TARGET_ARCH ${CMAKE_HOST_SYSTEM_PROCESSOR})
endif()

Answer 2

I've a Solution for the Case where the Host and Target System are the same.

First you need to call "uname -m" to get the "machine hardware name". Afterwards you need to cut off the trailing "Carriage Return" to get the actual Value back into the provided Variable.

EXECUTE_PROCESS( COMMAND uname -m COMMAND tr -d '\n' OUTPUT_VARIABLE ARCHITECTURE )

Now you can print out the Variable ${ARCHITECTURE}:

message( STATUS "Architecture: ${ARCHITECTURE}" )

or do some Canonisation to map, e.g. "x86_64", "amd64", ... to e.g. "64Bit". Same goes for 32Bit. With this you can execute archtecture dependend Compilation like:

if( ${ARCHITECTURE} STREQUAL "64Bit" )
    set( BLA_LIBRARY "/opt/lib/libBla.so" )
else()
    set( BLA_LIBRARY "/opt/lib32/libBla.so" )
endif()