that contain zero-sized payloads, which should resolve a number of issues with
RemoteMirror incorrectly reflecting enum cases and/or measuring the layout of
structures containing enums.
Background: Enum cases that have zero-sized payloads are handled
differently from other payload-bearing cases.
1. For layout purposes, they're treated as
non-payload cases. This can cause an MPE to
actually get represented in memory as a single-payload
or non-payload enum.
2. However, zero-sized payloads are still considered for
extra inhabitant calculations. Since they have no
extra inhabitants, this tends to cause such enums to
also not expose extra inhabitants to containing enums.
This commit makes several change to how RemoteMirror determines
enum layout:
* The various "*EnumTypeInfo" classes now represent
layout mechanisms -- as described in (1) above,
this can differ from the source code concept.
* An Enum "kind" is separately computed to reflect the
source code concept; this ensures that the dumped
type information reflects the source code.
* For single-payload and no-payload _layouts_,
the extra inhabitant calculation has been adjusted
to ensure that zero-sized payloads are correctly
considered.
Resolves: rdar://92945673
Teach RemoteMirror how to project enum values
This adds two new functions to the SwiftRemoteMirror
facility that support inspecting enum values.
Currently, these support non-payload enums and
single-payload enums, including nested enums and
payloads with struct, tuple, and reference payloads.
In particular, it handles nested `Optional` types.
TODO: Multi-payload enums use different strategies for
encoding the cases that aren't yet supported by this
code.
Note: This relies on information from dataLayoutQuery
to correctly decode invalid pointer values that are used
to encode enums. Existing clients will need to augment
their DLQ functions before using these new APIs.
Resolves rdar://59961527
```
/// Projects the value of an enum.
///
/// Takes the address and typeref for an enum and determines the
/// index of the currently-selected case within the enum.
///
/// Returns true iff the enum case could be successfully determined.
/// In particular, note that this code may fail for valid in-memory data
/// if the compiler is using a strategy we do not yet understand.
SWIFT_REMOTE_MIRROR_LINKAGE
int swift_reflection_projectEnumValue(SwiftReflectionContextRef ContextRef,
swift_addr_t EnumAddress,
swift_typeref_t EnumTypeRef,
uint64_t *CaseIndex);
/// Finds information about a particular enum case.
///
/// Given an enum typeref and index of a case, returns:
/// * Typeref of the associated payload or zero if there is no payload
/// * Name of the case if known.
///
/// The Name points to a freshly-allocated C string on the heap. You
/// are responsible for freeing the string (via `free()`) when you are finished.
SWIFT_REMOTE_MIRROR_LINKAGE
int swift_reflection_getEnumCaseTypeRef(SwiftReflectionContextRef ContextRef,
swift_typeref_t EnumTypeRef,
unsigned CaseIndex,
char **CaseName,
swift_typeref_t *PayloadTypeRef);
```
Co-authored-by: Mike Ash <mikeash@apple.com>
In particular, this fixes the size calculation for nested enums,
specifically enums within Optionals. Without this, the
reflection library computes `v` below as requiring two bytes
instead of one.
```
enum E {
case a
case b
}
let v = Optional<E>
```
This also adds a number of test cases for enums alone and
wrapped in optionals, including:
* Zero-case enums are allocated zero size and have zero extra inhabitants
* Zero-case enums in optionals also get zero size
* One-case no-payload enums are allocated zero size and have zero extra inhabitants
* One-case no-payload enums in optionals get one byte allocated and have zero extra inhabitants
* 254-case enums have only two extra inhabitants, so putting them in thrice-nested optionals requires an extra byte
* Various cases where each nested optional gets an extra byte
Resolves rdar://31154770
