Cycling74/max-package-template

Build is generating x86_64 external object on arm64 machine

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TimMoore commented

I'm just getting started with building Max externals using max-sdk on an Apple M1 Pro machine. I found that when I followed the instructions in the README for this project, the resulting build created an external compiled for x86_64 only, instead of arm64 or a universal binary.

See build log at https://gist.github.com/TimMoore/00c4009841938a286626b0c13e2182b3

I tried to regenerate the Xcode project file with the command cmake --trace-expand -G Xcode .. to see more details, and saw this warning in the output:

/opt/homebrew/Cellar/cmake/3.24.2/share/cmake/Modules/Platform/Darwin-Initialize.cmake(20):  set(CMAKE_OSX_ARCHITECTURES  CACHE STRING Build architectures for OSX )
CMake Warning (dev) at /opt/homebrew/Cellar/cmake/3.24.2/share/cmake/Modules/Platform/Darwin-Initialize.cmake:20 (set):
  Policy CMP0126 is not set: set(CACHE) does not remove a normal variable of
  the same name.  Run "cmake --help-policy CMP0126" for policy details.  Use
  the cmake_policy command to set the policy and suppress this warning.

  For compatibility with older versions of CMake, normal variable
  "CMAKE_OSX_ARCHITECTURES" will be removed from the current scope.
Call Stack (most recent call first):
  /opt/homebrew/Cellar/cmake/3.24.2/share/cmake/Modules/CMakeSystemSpecificInitialize.cmake:21 (include)
  CMakeLists.txt:6 (project)
This warning is for project developers.  Use -Wno-dev to suppress it.

The full output is very long, but is available at https://gist.github.com/TimMoore/42326a52ccfe8d1103c4172e9b59a458

I believe the issue is in this line of the CMake configuration:

max-package-template/CMakeLists.txt

Line 3 in 14158a5

set(CMAKE_OSX_ARCHITECTURES x86_64;arm64) # Enable Apple silicon builds

According to the CMake documentation for the CMAKE_OSX_ARCHITECTURES variable:

This variable should be set as a CACHE entry (or else CMake may remove it while initializing a cache entry of the same name) unless policy CMP0126 is set to NEW.

Changing that line of CMakeLists.txt to the following fixes the problem and builds a universal binary:

set(CMAKE_OSX_ARCHITECTURES x86_64;arm64 CACHE STRING "Enable Apple Silicon Builds")
isabelgk commented

Thanks for the detailed explanation -- fix looks good!

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