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Basic: correct use-after-move on Windows #19099

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Merged
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Sep 1, 2018
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Basic: correct use-after-move on Windows #19099

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12 changes: 10 additions & 2 deletions include/swift/Basic/OwnedString.h
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Original file line number Diff line number Diff line change
Expand Up @@ -87,8 +87,16 @@ class OwnedString {
return makeUnowned(Str);
} else {
llvm::IntrusiveRefCntPtr<TextOwner> OwnedPtr(TextOwner::make(Str));
return OwnedString(StringRef(OwnedPtr->getText(), Str.size()),
std::move(OwnedPtr));
// Allocate the StringRef on the stack first. This is to ensure that the
// order of evaluation of the arguments is specified. The specification
// does not specify the order of evaluation for the arguments. Itanium
// chose to evaluate left to right, while Windows evaluates right to left.
// As such, it is possible that the OwnedPtr has already been `std::move`d
// by the time that the StringRef is attempted to be created. In such a
// case, the offset of the field (+4) is used instead of the pointer to
// the text, resulting in invalid memory references.
StringRef S(OwnedPtr->getText(), Str.size());
return OwnedString(S, std::move(OwnedPtr));
}
}

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