What version of py2app are you using? I ask as this is a known issue for py2app - https://bitbucket.org/ronaldoussoren/py2app/issues/219/new-mach-o-header-is-too-large-to-relocate - and updating might fix it.

Thanks for the prompt reply! I have tried with a couple different py2app versions, including the latest versions of both py2app and macholib (0.19 and 1.11, respectively), and the problem still occurs. Note also the last two comments in that thread, from June, saying they still are having the issue, and reporting how they fixed it by recompiling Pillow. It looks like the FAQ on this issue also still recommends recompiling libraries that trigger this issue: https://py2app.readthedocs.io/en/latest/faq.html

I've compiled C++ / Obj-C macOS apps as well, and it's important in those cases too to specify -headerpad_max_install_names, so I was surprised when he said he could fix it in macholib. I don't know if there is a general fix to be had, but in the meantime, I can confirm that re-compiling the homebrew libraries with that flag as described in the ticket fixes the issue. I've just had to go through the Pillow recompile several times at this point (we use virtualenvs extensively) so I thought I would file the issue in case it was not known.

Thanks. If you're willing to go through the process of putting together a reproducible app, that would be interesting - one that works without Pillow, but fails with Pillow. You should be able to upload a zip in a comment on this issue. My other question to help with reproducibility is - how did you install your Python libraries?

Also, while not related to your issue, be aware that in 2020, Pillow will no longer support Python 2.7, Pillow being committed to https://python3statement.org/

Sorry for the delayed reply! My Mac laptop had a swollen battery and it took it about a week to get it fixed and restored, making it difficult to put together a sample Mac app!

Now that I'm up and running again, here is a minimal sample application:

pillow_mac_setup.zip

Please let me know if you have any questions about it, etc. Hopefully the README.md instructions are detailed enough about how to build, or try to build, the app!

Oh, I didn't make a version that works without Pillow, but if you comment out the Pillow usage in main.py and replace it with print("Hello World"), and remove the PIL package requirement in setup.py, it should build and run okay. (If you call ./dist/main.app/Contents/MacOS/main of course, as it will have no actual GUI to present.)

Thanks. I'm able to replicate using TravisCI.

To link the issues, this is the re-emergence of #3297

Testing, I find that Pillow 5.3 works. To check that I am correctly reproducing your situation, could you tell me if it works for you?

Yes, it does! When I use otool -L to check the linked deps paths, everything looks pretty much the same to me, so I'm not sure what has changed between the two versions. My current theory is that something in the latest builds is causing the @loader_path check in macholib to fail and causing it to try and 'fix' the dependency link, but nothing about the libs I've checked so far jumps out at me as causing this.