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stdlib: remove a wrong internal check for COW array mutation #34639

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Merged
eeckstein merged 2 commits into from
Nov 9, 2020
Merged

stdlib: remove a wrong internal check for COW array mutation #34639

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51c2bd0
stdlib: remove a wrong internal check for COW array mutation
eeckstein Nov 9, 2020
6d0bbba
stdlib: update comments for the array buffer endCowMutation functions.
eeckstein Nov 9, 2020
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2 changes: 1 addition & 1 deletion stdlib/public/core/ArrayBuffer.swift
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Original file line number Diff line number Diff line change
Expand Up @@ -138,7 +138,7 @@ extension _ArrayBuffer {

/// Puts the buffer in an immutable state.
///
/// - Precondition: The buffer must be mutable.
/// - Precondition: The buffer must be mutable or the empty array singleton.
///
/// - Warning: After a call to `endCOWMutation` the buffer must not be mutated
/// until the next call of `beginCOWMutation`.
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19 changes: 9 additions & 10 deletions stdlib/public/core/ContiguousArrayBuffer.swift
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Expand Up @@ -470,18 +470,17 @@ internal struct _ContiguousArrayBuffer<Element>: _ArrayBufferProtocol {
nonmutating set {
if #available(macOS 9999, iOS 9999, watchOS 9999, tvOS 9999, *) {
if (_COWChecksEnabled()) {
if newValue {
if capacity > 0 {
let wasImmutable = _swift_setImmutableCOWBuffer(_storage, true)
// Make sure to not modify the empty array singleton (which has a
// capacity of 0).
if capacity > 0 {
let wasImmutable = _swift_setImmutableCOWBuffer(_storage, newValue)
if newValue {
_internalInvariant(!wasImmutable,
"re-setting immutable array buffer to immutable")
} else {
_internalInvariant(wasImmutable,
"re-setting mutable array buffer to mutable")
}
} else {
_internalInvariant(capacity > 0,
"setting empty array buffer to mutable")
let wasImmutable = _swift_setImmutableCOWBuffer(_storage, false)
_internalInvariant(wasImmutable,
"re-setting mutable array buffer to mutable")
}
}
}
Expand Down Expand Up @@ -698,7 +697,7 @@ internal struct _ContiguousArrayBuffer<Element>: _ArrayBufferProtocol {

/// Puts the buffer in an immutable state.
///
/// - Precondition: The buffer must be mutable.
/// - Precondition: The buffer must be mutable or the empty array singleton.
///
/// - Warning: After a call to `endCOWMutation` the buffer must not be mutated
/// until the next call of `beginCOWMutation`.
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2 changes: 1 addition & 1 deletion stdlib/public/core/SliceBuffer.swift
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Expand Up @@ -329,7 +329,7 @@ internal struct _SliceBuffer<Element>

/// Puts the buffer in an immutable state.
///
/// - Precondition: The buffer must be mutable.
/// - Precondition: The buffer must be mutable or the empty array singleton.
///
/// - Warning: After a call to `endCOWMutation` the buffer must not be mutated
/// until the next call of `beginCOWMutation`.
Expand Down