[Boost-build] Cross-compile for Apple Silicon on an x86 Mac

From: Ian Emmons (ian_at_[hidden])
Date: 2022-04-22 13:27:25

I am trying to build Boost 1.79.0 shared libraries on an x86-based Mac running the latest MacOS (Monterey, 12.3.1) using the latest Xcode (13.3.1, with Apple’s clang 13.1.6).  Everything works great for building shared libraries that run on an x86-based Mac.

My ideal would be to build a single set of universal (a.k.a. “fat”) binaries that include both x86 and ARM code, but Boost.Build does not seem to contain an option to do that.  (Such options existed in the past for Intel/PowerPC combinations and then later for 64-bit/32-bit Intel combinations.)

Second best is to build two sets of binaries, one for x86 and another for ARM.  I tried to do this using the option architecture=x86,arm on the b2 command line, and it does in fact build two sets of binaries with the expected file names.  For instance, for filesystem it builds these two:

libboost_filesystem-clang-darwin13-mt-a64-1_79.dylib
libboost_filesystem-clang-darwin13-mt-x64-1_79.dylib

But when I use the “file” command to inspect the types of these files, they both are reported as "Mach-O 64-bit dynamically linked shared library x86_64”.

Am I doing something wrong, here?  Or is there a bug in Boost.Build regarding cross-compiling?

Thanks,

Ian