No worries, thank you for all the answers!

The issue was in libgrcypt libtool.m4. It was an old version which didn't support macOS 11.x properly and thus defaulting to using flat_namespace. I provided a patch to upgrade to a newer libtool.m4: https://lists.gnupg.org/pipermail/gcrypt-devel/2021-September/005173.html I still wonder why RTLD_NOW | RTLD_LOCAL worked... Thanks, Aleix

Thank you so much for your answer, really appreciate it. I believe this makes sense. Just one last question: what would be the difference with RTLD_NOW | RTLD_LOCAL? Shouldn't this cause the same issue? Or would RTLD_NOW also look int the global flat namespace even if RTLD_LOCAL is defined? By the way, I found this issue while using Guile (https://www.gnu.org/software/guile/) and trying to load guile-gcrypt. Newer versions of Guile (>= 3.0.6) use RTLD_LAZY | RTLD_LOCAL and when loading guile-gcrypt the crashed happened. https://lists.gnu.org/archive/html/guile-devel/2021-09/msg00008.html I have also provided a patch to Guile, but probably not going to be accepted since this doesn't seem a Guile issue. https://lists.gnu.org/archive/html/guile-devel/2021-09/msg00024.html So, I will need to go to homebrew and gcrypt and see how libgcrypt is built. Thank you so much again. Aleix

For anyone else reading this thread, I have found this PDF to be very useful to understand what lazy, two-level namespace or flat namespace are. https://www.symbolcrash.com/wp-content/uploads/2019/02/MachORuntime.pdf

Thank you again for your reply. Here's the info you requested: ❯ xcrun dyldinfo -lazy_bind /usr/local/lib/libgcrypt.dylib | grep gcry_check_version __DATA __la_symbol_ptr 0x000A40C8 0x02C7 flat-namespace __gcry_check_version Also, here's the one from before properly formatted: ❯ nm -m /usr/local/lib/libgcrypt.dylib | grep gcry_check_version 0000000000005954 (__TEXT,__text) external __gcry_check_version 0000000000002aa7 (__TEXT,__text) external _gcry_check_version Thanks again, Aleix