It looks to me like this is the dyld start code https://github.com/apple-opensource/dyld/blob/e3f88907bebb8421f50f0943595f6874de70ebe0/src/dyldInitialization.cpp#L130 As one might expect it just walks over the env pointers plus one NULL to get to the apple pointer.

Code merged, now working on macOS 11. The next "big thing" will be arm64 support.

If all goes well I'll push the code for 10.15 tonight and then move on to macOS 11.

I've mostly fixed the issue. It is a problem related to _DATA_CONST. Valgrind needs to be updated so that when the __DATA_CONST load command is handled it shouldn't trigger debuginfo reading. That should happen on the next load command (normally __DATA).

Missed a zero from the end of the link https://bugs.kde.org/show_bug.cgi?id=437790

It's about a year since I wrote this, time for a bit of an update, especially in the light of macOS 11. Short version: If you want Valgrind on macOS, then your best bet is to go here Louis Brunner's github repo - https://github.com/LouisBrunner/valgrind-macos/ Louis seems to be working on improving support on macOS 11 Intel. If you are using macOS on ARM, then you are out of luck. Valgrind is supported on ARM/Linux, but not on ARM for any other platform. It should be possible to make Valgrind work on ARM, but this would be a fairly substantial effort. For my part, I'm not actively working on macOS, and have been working more on FreeBSD. I am now the port maintainer on FreeBSD and also contribute to upstream Valgrind. (FreeBSD is not officially supported, I hope that some time in 2021 I'll get the FreeBSD code added upstream).