- On Intel Macs, the path is /usr/local/opt/llvm@12
- On Silicon Macs, the path is /opt/homebrew/opt/llvm@12
This makes specifying CMAKE_PREFIX_PATH optional for Homebrew LLVM.
This is particularly relevant for x86_64 and C++ when relocating
StaticInit sections containing static initializers machine code.
Then, in case of SIGNED_X relocations, it is necessary to have the
full image of the VM address layout of the sections in the object
file as this is how the addend needs to be adjusted for non-extern
relocations.
OpenBSD doesn't implement EVFILT_USER filter for kqueue(2), so we couldn't use that for event loop.
instead, use a EVFILT_TIMER filter with EV_ONESHOT (trigger only once) and delay 0sec (which trigger immediatly).
it fits the usage of EVFILT_USER which is only used to "wakeup" the kevent(2) call from userland.
Also, calculate non-extern, section offset based addends for SIGNED
and UNSIGNED relocations on x86_64 upfront as an offset wrt to the
target symbol representing position of the section/atom within the
final artifact.
Otherwise, Apple's tooling goes mental and reports that the executable
is malformed/fails strict validation. We absolutely have to get it
right to support tools such `codesign` which are required to
successfully launch an app on an iOS device for instance. When Zig
matures enough so that we can ditch any Apple tooling and still be
able to successfully codesign for iOS and other, we can revisit this
area. Until then however, we are stuck in having to rewrite the LINKEDIT
segment at every update run of the self-hosted.
FYI, the strict layout for the MachO binary apparently is (please,
read this with a pinch of salt as this is inferred by me):
* __TEXT segment
* __DATA_CONST segment
* __DATA segment
* __LINKEDIT segment
* dyld info (rebase, bind, weak bind, lazy bind, export)
* symbol table
* dynamic symbol table
* string table
* code signature (if expected)
I incorrectly assumed that __kernel_timespec was used when not linking
libc, however that is not the case. `std.os.timespec` is used both for
libc and non-libc cases. `__kernel_timespec` is a special struct that is
used only for io_uring.
