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runtime: Fix overflow of swift_unownedRetain reference counts

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On 32bit platforms there are 7 bits reserved for the unowned retain count. This
makes overflow a likely scenario. Implement overflow into the side table.

rdar://33495003
This commit is contained in:
Arnold Schwaighofer
2017-08-01 08:08:56 -07:00
parent 17ddc5802f
commit d8abd2fed9
6 changed files with 100 additions and 7 deletions
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16
stdlib/public/runtime/RefCount.cpp
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@@ -143,6 +143,22 @@ HeapObjectSideTableEntry* RefCounts<InlineRefCountBits>::formWeakReference()
return nullptr;
}
template <typename RefCountBits>
void RefCounts<RefCountBits>::incrementUnownedSlow(uint32_t n) {
auto side = allocateSideTable();
if (side)
return side->incrementUnowned(n);
// Overflow but side table allocation failed.
swift_abortUnownedRetainOverflow();
}
template void RefCounts<InlineRefCountBits>::incrementUnownedSlow(uint32_t n);
template <>
void RefCounts<SideTableRefCountBits>::incrementUnownedSlow(uint32_t n) {
// Overflow from side table to a new side table?!
swift_abortUnownedRetainOverflow();
}
// namespace swift
} // namespace swift