[Merged] [MachO] Don't add symbols when processing bind fixups

[bdash]

The target of the bind opcode has its symbol applied when the dynamic symbol table is parsed.

This was previously adding a symbol at the fixed-up address with the name of the symbol being bound. This was resulting in dozens of _OBJC_CLASS_$_NSObject, _OBJC_METACLASS_$_NSObject, and __objc_empty_cache symbols being created: one for each objc_class that referenced those symbols.

Fixes #5351.

[0cyn]

I am largely in favor of this landing, however we do lose some symbols in IL because of this. The current code is a long-standing holdover for this reason.

Occasionally it is able to resolve the pointers although that is analysis based. I think a good solution here may be to instead define a '__ptr_'+name symbol at this location? That way we can avoid IL quality degrading while making things more accurate.

[bdash]

The current IL is wrong so IMO the change shown in the screenshot is an improvement. The argument to dispatch_once isn't __NSConcreteGlobalBlock, it's a pointer to a static struct whose first member is __NSConcreteGlobalBlock.

[0cyn]

I picked a bad example 😄 but your point stands.

Still diffing ILs on several binaries for this in different conditions, but assuming that's the only case of this I can find, this should be able to land. Most other cases (e.g. dyld_stub_binder) seem to resolve in HLIL which is fine.

[0cyn]

Merged with 3e7c1b6.

I missed the git push --force while rebasing this for a few changes that got pushed to dev, so github is marking it as closed/unmerged, however it has landed.

Available in versions >= dev 5.1.7565