Mac Binary Package (Apple M1 and Mac x86_64)

Macos binary packages are built with the script which, near the end of its operation, involves code signing, package signing, and notarization. The build will be universal2 and work on arm64 and x86_64 architectures (if the pythons used are themselves, universal2). Preparing your Mac development environment for correct functioning of the script requires installing a few extra Dependencies beyond the normal user source build, obtaining an Apple Developer Program membership, and requesting two signing certificates from Apple. Those actions are described in separate sections below. On an Apple M1 or x86_64, the script, by default, creates, e.g., nrn-8.0a-726-gb9a811a32-macosx-11-universal2-py-38-39-310.pkg where the information between nrn and macosx comes from git describe, the number after macos refers to the MACOSX_DEPLOYMENT_TARGET=11 the next item(s) before py indicate the architectures on which the program can run (i.e. arm64, x86_64, or universal2 for both) and the numbers after the py indicate the python versions that are compatible with this package. Those python versions must be installed on the developer machine. The script will build a universal pkg only if all the Python’s are themselves universal. Presently, one must manually make sure that all the python builds used the same MACOSX_DEPLOYMENT_TARGET. You can check both of these with python3 -c 'import sysconfig; print(sysconfig.get_platform())'

A space separated list of python executable arguments can be used in place of the internal default lists. $NRN_SRC is the location of the repository, default $HOME/neuron/nrn. The script makes sure $NRN_SRC/build exists and uses that folder to configure and build the software. The software is installed in /Applications/NEURON.

At time of writing, the cmake command in the script that is used to configure the build is

  -DNRN_PYTHON_DYNAMIC="$pythons" \
  $archs_cmake \

The default variables above will be

pythons="python3.8 python3.9 python3.10"

A universal build is possible with -DCMAKE_OSX_ARCHITECTURES="arm64;x86_64" but the installations of python on your machine must also be universal. The MPI library does not have to be universal if configuring with -DNRN_ENABLE_MPI_DYNAMIC=ON as the library is not linked against during the build.

make -j install is used to build and install in /Applications/NEURON

make macpkg ( see src/mac/CMakeLists.txt ) is used to:

  • activate the apps src/mac/

  • codesign all the binaries src/mac/

    • Codesigning all binaries in the package is a prerequisite for notarization and not necessary if the package is not notarized. In that case it is a bit more trouble for users to install as they must ignore the scary message that pops up before the installer and know to right click on that message, then click Open. Then accept the option to Open the installer.
    • To prevent Notarization failure the binaries need hardened runtime enabled and then some of the binaries need some special entitlements enabled. These entitlements are specified in src/mac/nrn_entitlements.plist and allow use of the Apple Events, Just in time compilation, and disable library validation. The user will be asked to accept the first time these entitlements are invoked.
  • create NEURON.pkg . /usr/bin/packagesbuild uses src/mac/macdist/

  • productsign NEURON.pkg src/mac/

  • request Apple to notarize NEURON.pkg src/

    If notarizaton fails, it is occasionally due to Apple changing the contracts and demanding that “You must first sign the relevant contracts online. (1048)”. In that case, go to to accept the legal docs. For other notarization failures, one must consult the LogFileURL which can be obtained with

    % xcrun altool  --notarization-info $RequestIdentifier \
        --username "" \
        --password "`cat ~/.ssh/notarization-password`"
    No errors getting notarization info.
              Date: 2022-01-02 23:38:12 +0000
              Hash: 7254157952d4f3573c2804879cf6da8d...
       RequestUUID: 152f0f0e-af58-4d22-b291-6a441825dd20
            Status: invalid
       Status Code: 2
    Status Message: Package Invalid

    where RequestIdentifer (the RequestUUID) appears in the email sent back in response to the notarization request.

The script ends by printing:

  Until we figure out how to automatically staple the notarization
  the following two commands must be executed manually.
  xcrun stapler staple $PACKAGE_FILE_NAME

where the variables are filled out and can be copy/pasted to your terminal after Apple sends an email declaring that notarization was successful.

The email from Apple usually takes just a few minutes but can be hours. I’ve been uploading the $PACKAGE_FULL_NAME as an artifact for a Release version from by choosing Releases, choosing the proper Release tag (e.g. Release 8.0a), Edit release, and clicking in the “Attach binaries …” near the bottom of the page.


This uses Apple M1 as the example but mostly the same for an x86_64 mac. lipo tells what architecture a binary must be run on. For example,

lipo -archs `which python3`
x86_64 arm64

which is generally the case for all Big Sur mac software. On the other hand, brew install ... executables and libraries are generally only for the architecture indicated by uname -m. That is ok for openmpi but since the various python libraries are linked against during build to create the version specific neuron modules, those python installers also have to be universal. Fortunately, universal python versions can be found at at least for (as of 2022-01-01) python3.8, python3.9, and python3.10.

  • xcode-select --install:

    • Sadly, notarization requires altool which is not distributed with the command line tools. So one needs to install the full xcode (at least version 12) from the App Store. That is very large and may take an hour or so to download. (should be checked to see if this is still the case.)
  • Install latest XQuartz release. At least XQuartz-2.8.0_rc1

  • Install PackagesBuild

  • brew install coreutils cmake bison flex open-mpi

    • Python 3.8 is already installed as /usr/bin/python3 and is universal2.

    • The normal source build explains how to install brew and add it to the PATH.

      /bin/bash -c "$(curl -fsSL"
      echo 'eval $(/opt/homebrew/bin/brew shellenv)' >> $HOME/.zprofile
      eval $(/opt/homebrew/bin/brew shellenv)
    • Default build uses universal pythons from I also redundantly include their python3.8 as I find it more convenient to be able to explicitly specify the full name as python3.8.

    • All pythons used for building need numpy installed, e.g.

      pip3.9 install --user --upgrade pip
      pip3.9 install --user numpy
    • At least one python3 in your PATH needs cython installed. And, to avoid compile errors, the minimum version is 0.29.26

      python3.10 -m pip install --user cython

Signing and Notarization

Notarization needs a $99/year Apple Developer Program membership. Certificates last 5 years.

The most clearly explained recipe for notarization that I found is Notarizing installers for macOS Catalina .

However it took me while to figure out that it takes two certificates from apple. I.e. A “developerID_application.cer” to sign all the binaries before the pkg is built and a “developerID_installer.cer” to sign the pkg. Certificates can be obtained through Keychain by creating a certificate signing request On receipt of the certificates, I added to my keychain by clicking on them.

And one must manage an App specific password to request notarization from Apple. I put the password in $HOME/.ssh/notarization-password which is where src/mac/ expects it.

Notarization requires that we “enable hardened runtime” which is done during the binary signing, but that results in issues with regard to apple events and mismatched, unsigned, and non-system libraries (as well as preventing JIT compilation). At this point How to add entitlements… was very helpful with regard to picking entitlements to develop a nrn_entitlements.plist to relax the strict hardened runtime.