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runtime lib: a mechanism to set an "immutable" flag on an object for COW buffer runtime checking.

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In an assert built of the library, store an extra boolean flag (isImmutable) in the object side-buffer table.
This flag can be set and get by the Array implementation to sanity check the immutability status of the buffer object.
This commit is contained in:
Erik Eckstein
2020-06-08 15:00:12 +02:00
parent 1559fe333f
commit 3bfebf10f7
4 changed files with 69 additions and 0 deletions
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17
stdlib/public/runtime/HeapObject.cpp
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@@ -887,6 +887,23 @@ WeakReference *swift::swift_weakTakeAssign(WeakReference *dest,
#ifndef NDEBUG
/// Returns true if the "immutable" flag is set on \p object.
///
/// Used for runtime consistency checking of COW buffers.
SWIFT_RUNTIME_EXPORT
bool _swift_isImmutableCOWBuffer(HeapObject *object) {
return object->refCounts.isImmutableCOWBuffer();
}
/// Sets the "immutable" flag on \p object to \p immutable and returns the old
/// value of the flag.
///
/// Used for runtime consistency checking of COW buffers.
SWIFT_RUNTIME_EXPORT
bool _swift_setImmutableCOWBuffer(HeapObject *object, bool immutable) {
return object->refCounts.setIsImmutableCOWBuffer(immutable);
}
void HeapObject::dump() const {
auto *Self = const_cast<HeapObject *>(this);
printf("HeapObject: %p\n", Self);