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Fix a leak when interpolating optional references.

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The runtime support for casting optionals introduced in 35cb1afa
resulted in a redundant retain.

Fixes SR-459: Weakened optionals don't zero...
rdar://24057977.
This commit is contained in:
Andrew Trick
2016-01-08 13:37:18 -08:00
parent 0948c71988
commit 9cf84c24ca
2 changed files with 76 additions and 30 deletions
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87
stdlib/public/runtime/Casting.cpp
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@@ -1987,15 +1987,59 @@ static id dynamicCastValueToNSError(OpaqueValue *src,
}
#endif
static bool canCastToExistential(OpaqueValue *dest, OpaqueValue *src,
const Metadata *srcType,
const Metadata *targetType) {
if (targetType->getKind() != MetadataKind::Existential)
return false;
static struct OptionalCastResult {
bool success;
const Metadata* payloadType;
};
return _dynamicCastToExistential(dest, src, srcType,
cast<ExistentialTypeMetadata>(targetType),
DynamicCastFlags::Default);
/// Handle optional unwrapping of the cast source.
/// \returns {true, nullptr} if the cast succeeds without unwrapping.
/// \returns {false, nullptr} if the cast fails before unwrapping.
/// \returns {false, payloadType} if the cast should be attempted using an
/// equivalent payloadType.
static OptionalCastResult
checkDynamicCastFromOptional(OpaqueValue *dest,
OpaqueValue *src,
const Metadata *srcType,
const Metadata *targetType,
DynamicCastFlags flags) {
if (srcType->getKind() != MetadataKind::Optional)
return {false, srcType};
// Check if the target is an existential that Optional always conforms to.
if (targetType->getKind() == MetadataKind::Existential) {
// Attempt a conditional cast without destroying on failure.
DynamicCastFlags checkCastFlags
= flags - (DynamicCastFlags::Unconditional
| DynamicCastFlags::DestroyOnFailure);
assert((checkCastFlags - DynamicCastFlags::TakeOnSuccess)
== DynamicCastFlags::Default && "Unhandled DynamicCastFlag");
if (_dynamicCastToExistential(dest, src, srcType,
cast<ExistentialTypeMetadata>(targetType),
checkCastFlags)) {
return {true, nullptr};
}
}
const Metadata *payloadType =
cast<EnumMetadata>(srcType)->getGenericArgs()[0];
int enumCase =
swift_getEnumCaseSinglePayload(src, payloadType, 1 /*emptyCases=*/);
if (enumCase != -1) {
// Allow Optional<T>.None -> Optional<U>.None
if (targetType->getKind() != MetadataKind::Optional) {
_fail(src, srcType, targetType, flags);
return {false, nullptr};
}
// Inject the .None tag
swift_storeEnumTagSinglePayload(dest, payloadType, enumCase,
1 /*emptyCases=*/);
_succeed(dest, src, srcType, flags);
return {true, nullptr};
}
// .Some
// Single payload enums are guaranteed layout compatible with their
// payload. Only the source's payload needs to be taken or destroyed.
return {false, payloadType};
}
/// Perform a dynamic cast to an arbitrary type.
@@ -2004,28 +2048,11 @@ bool swift::swift_dynamicCast(OpaqueValue *dest,
const Metadata *srcType,
const Metadata *targetType,
DynamicCastFlags flags) {
// Check if the cast source is Optional and the target is not an existential
// that Optional conforms to. Unwrap one level of Optional and continue.
if (srcType->getKind() == MetadataKind::Optional
&& !canCastToExistential(dest, src, srcType, targetType)) {
const Metadata *payloadType =
cast<EnumMetadata>(srcType)->getGenericArgs()[0];
int enumCase =
swift_getEnumCaseSinglePayload(src, payloadType, 1 /*emptyCases=*/);
if (enumCase != -1) {
// Allow Optional<T>.None -> Optional<U>.None
if (targetType->getKind() != MetadataKind::Optional)
return _fail(src, srcType, targetType, flags);
// Inject the .None tag
swift_storeEnumTagSinglePayload(dest, payloadType, enumCase,
1 /*emptyCases=*/);
return _succeed(dest, src, srcType, flags);
}
// .Some
// Single payload enums are guaranteed layout compatible with their
// payload. Only the source's payload needs to be taken or destroyed.
srcType = payloadType;
}
auto unwrapResult = checkDynamicCastFromOptional(dest, src, srcType,
targetType, flags);
srcType = unwrapResult.payloadType;
if (!srcType)
return unwrapResult.success;
switch (targetType->getKind()) {
// Handle wrapping an Optional target.