This change set incorporates a number of changes that all needed to
happen together:
* The imp is now the first field of the `objc_method` structure. This
makes it possible to extend the structure without breaking anything
that relies on being able to access the IMP.
* There is no owner in the slot, so we must use other mechanisms for
determining the owner of a method (e.g. whether the same method appears
in the superclass)
* Again, because there is no owner in the slot, we can't use this as a
fast path for finding the C++ construct / destruct methods. These are
now cached in the class structure when they are found.
* The version field is gone from the slot and now we provide a global
version. This is based on the observation that method replacements
are relatively infrequent and the overhead of invalidating all method
caches is cheaper than adding extra state for every (class, method)
pair.
* A number of the runtime functions are simplified because replacing
the IMP in a `Method` now implicitly updates the dtable.
In the legact ABI, superclass pointers are initially set to strings
containing the superclass name and the runtime fixes them up. In the
new ABI, the compiler sets up the linkage directly.
In the new ABI, we use the legacy type encoding in the selector and the
extended type encoding in the types field. We want to only expose the
legacy type encoding through existing APIs.
Extended type encodings add more detailed information to object and
block types:
* Objects are encoded as @"ClassName".
* Blocks are encoded as @?<parameter type signature>
In the new ABI, we use classic type encodings for selectors and extended
type encodings everywhere else.
With the old ABI, we generated a copy of every protocol in every
compilation unit that declared it. We now emit protocols only if they
are referenced (and have the linker deduplicate them).
This test was previously failing with the Apple runtime.
These are currently ignored, because they are only important when the
runtime has upgraded the protocol. The runtime will upgrade legacy
protocols, but they are not referenced by this indirection layer.
We're now using a new class and category structure and auto-upgrading the old ones. Other changes:
- The Ivar structure now points to the ivar offset variable, so we can more easily find it.
- Categories can now add properties.
This probably didn't make a difference, but if we ended up
resolving a class as a result of resolving a subclass, then we'd previously go and explore an unrelated linked list for a bit.
macOS ships with libc++abi, which doesn't provide the hooks required
for interop, so this was causing all of the tests to fail to link in
the Travis macOS test. We're now correctly detecting that it won't
work on macOS and disabling those tests.
Throwing an Objective-C exception through a C++ catch block was broken.
This was because the C++ code inserts a cleanup handler to make sure
that it invokes `__cxa_end_catch`. Unwinding through this catchup
transformed the Objective-C exception into a C++ one. This case should
have been handled, except for two bugs:
1. A typo (`#ifdef` instead of `#ifndef`) meant that we were not
extracting the Objective-C exception from the C++ object.
2. We were skipping everything except catchalls after the search phase,
because we lose some information in the transformation.
Fixes#49
Weak refs were being left as dangling pointers after being deleted. The
load that caused the deallocation would return nil, but then the next
one would dereference a dangling pointer.
David Chisnall
David Chisnall
David Chisnall
David Lobron
David Chisnall