This makes it a bit easier to diagnose unexpected boxing problems in the debugger, by allowing `po [value _swiftTypeName]` to work, instead of forcing users to know how to call `swift_getTypeName` from lldb themselves.
It has been fairly easy to cause the runtime to crash on multithreaded read-read access to weak references (e.g. https://bugs.swift.org/browse/SR-192). Although weak references are value types, they can get elevated to the heap in multiple ways, such as when captured by a closure or when used as a property in a class object instance. In such cases, race conditions involving weak references could cause the runtime to perform to multiple decrement operations of the unowned reference count for a single increment; this eventually causes early deallocation, leading to use-after-free, modify-after-free and double-free errors.
This commit changes the weak reference operations to use a spinlock rather than assuming thread-exclusive access, when appropriate.
With this change, the crasher discussed in SR-192 no longer encounters crashes due to modify-after-free or double-free errors.
It's to be used by code produced by the ReleaseDevirtualizer.
As the function is only used for non-escaping objects, the deallocating bit is set non-atomically.
- Add RuntimeTarget template This will allow for converting between
metadata structures for native host and remote target architectures.
- Create InProcess and External templates for stored pointers
Add a few more types to abstract pointer access in the runtime
structures but keep native in-process pointer access the same as that
with a plain old pointer type.
There is now a notion of a "stored pointer", which is just the raw value
of the pointer, and the actual pointer type, which is used for loads.
Decoupling these allows us to fork the behavior when looking at metadata
in an external process, but keep things the same for the in-process
case.
There are two basic "runtime targets" that you can use to work with
metadata:
InProcess: Defines the pointer to be trivially a T* and stored as a
uintptr_t. A Metadata * is exactly as it was before, but defined via
AbstractMetadata<InProcess>.
External: A template that requires a target to specify its pointer size.
ExternalPointer: An opaque pointer in another address space that can't
(and shouldn't) be indirected with operator* or operator->. The memory
reader will fetch the data explicitly.
This makes sure that runtime functions use proper calling conventions, get the required visibility, etc.
We annotate the most popular runtime functions in terms of how often they are invoked from Swift code.
- Almost all variants of retain/release functions are annotated to use the new calling convention.
- Some popular non-reference counting functions like swift_getGenericMetadata or swift_dynamicCast are annotated as well.
The set of runtime functions annotated to use the new calling convention should exactly match the definitions in RuntimeFunctions.def!
...and explicitly mark symbols we export, either for use by executables or for runtime-stdlib interaction. Until the stdlib supports resilience we have to allow programs to link to these SPI symbols.
This is a bit of a hodge-podge of related changes that I decided
weren't quite worth teasing apart:
First, rename the weak{Retain,Release} entrypoints to
unowned{Retain,Release} to better reflect their actual use
from generated code.
Second, standardize the names of the rest of the entrypoints around
unowned{operation}.
Third, standardize IRGen's internal naming scheme and API for
reference-counting so that (1) there are generic functions for
emitting operations using a given reference-counting style and
(2) all operations explicitly call out the kind and style of
reference counting.
Finally, implement a number of new entrypoints for unknown unowned
reference-counting. These entrypoints use a completely different
and incompatible scheme for working with ObjC references. The
primary difference is that the new scheme abandons the flawed idea
(which I take responsibility for) that we can simulate an unowned
reference count for ObjC references, and instead moves towards an
address-only scheme when the reference might store an ObjC reference.
(The current implementation is still trivially takable, but that is
not something we should be relying on.) These will be tested in a
follow-up commit. For now, we still rely on the bad assumption of
reference-countability.
Getting the name of a type seems like reasonable core runtime functionality, and something the runtime can cache on its side too. Have the function return a pointer to a raw string in memory owned by the runtime, and have it be wrappen in a Swift.String on the standard library side.
some of the ARC entry points. rdar://22724641. After this commit,
swift_retain_noresult will be completely replaced by swift_retain.
LLVMARCOpts pass is modified NOT to rewrite swift_retain to
swift_retain_noresult which forward no reference.
Swift SVN r32082
After this commit, swift_retain will return no reference and LLVMARCContract pass is modified NOT to rewrite
swift_retain_noresult to old swift_retain which forwarded the reference.
Swift SVN r32075
I asked that the patches were split up so I could do post commit review.
This reverts commit r32059.
This reverts commit r32058.
This reverts commit r32056.
This reverts commit r32055.
Swift SVN r32060
to remove reference forwarding for some of the ARC entry points. rdar://22724641. After this
commit, swift_retain_noresult will be completely replaced by swift_retain and LLVMARCOpts.cpp
will no longer canonicalize swift_retain to swift_retain_noresult as now swift_retain returns no
reference.
Swift SVN r32058
to remove reference forwarding for some of the ARC entry points. rdar://22724641. After this
commit, swift_retain will be the same as swift_retain_noresult, returning no reference.
LLVMARCContract pass is also modified NOT to rewrite swift_retain_noresult to the
old swift_retain which forwards the reference.
Swift SVN r32055
dealloc_ref [destructor] is the existing behavior. It expects the
reference count to have reached zero and the isDeallocating bit to
be set.
The new [constructor] variant first drops the initial strong
reference.
This allows DI to properly free uninitialized instances in
constructors. Previously this would fail with an assertion if the
runtime was built with debugging enabled.
Progress on <rdar://problem/21991742>.
Swift SVN r31142
Provide new swift_{alloc,dealloc,project}Box2 entry points that allocate, project, and deallocate typed boxes using runtime-instantiated metadata. Give these a new metadata kind, so that external tools recognize the difference and can interpret the metadata appropriately.
Swift SVN r29714
The standard library has grown significantly, and we need a new
directory structure that clearly reflects the role of the APIs, and
allows future growth.
See stdlib/{public,internal,private}/README.txt for more information.
Swift SVN r25876
