Darwin syscalls calling convention doesn't clobber CF as it should

[mostobriv]

Version and Platform (required):

• Binary Ninja Version: 5.4.9459-dev Personal (b2c37a6b)
• Edition: Non-Commercial

Bug Description:
Actually it's a semi-feature request semi-bug.

Currently when lifting syscalls on Darwin platforms, BN doesn't use CF as one of the return values of a syscall (on darwin platforms system calls return success status in CarryFlag, CF = 0 - success, fail otherwise), which leads to incorrect IL code being generated when the original code takes CF into account.

Here is example of such case:

IL uses cond:0 from earlier comparison instead of using syscalls result.

Steps To Reproduce:
Please provide all steps required to reproduce the behavior:

1. Open sharedcache
2. Navigate to some syscall wrapper (for example getpid)

Expected Behavior:
BN should clobber the CF and count it.

Binary:
I won't upload whole ios sharedcache, but you can check yourself with any of syscall wrappers there

Additional Information:
As @ glenns suggested me in slack, it can be workarounded via tweaking lifting of syscall instruction, but it is still a workaround and not as clean as it desired to be.