tree 638b7ee2d0ae8c93fbddb25503a661bf21c98d17
parent 50070e7744fbeb2cd128bd174b5d436a282977b6
author Daniel Sanders <daniel_l_sanders@apple.com> 1547836835 +0000
committer Daniel Sanders <daniel_l_sanders@apple.com> 1547836835 +0000

[adt] Twine(nullptr) derefs the nullptr. Add a deleted Twine(std::nullptr_t)

Summary:
nullptr can implicitly convert to Twine as Twine(nullptr) in which case it
resolves to Twine(const char *). This constructor derefs the pointer and
therefore doesn't work. Add a Twine(std::nullptr_t) = delete to make it a
compile time error.

It turns out that in-tree usage of Twine(nullptr) is confined to a single
private method in IRBuilder where foldConstant(... const Twine &Name = nullptr)
and this method is only ever called with an explicit Name argument as making it
a mandatory argument doesn't cause compile-time or run-time errors.

Reviewers: jyknight

Reviewed By: jyknight

Subscribers: dexonsmith, kristina, llvm-commits

Differential Revision: https://reviews.llvm.org/D56870

git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@351572 91177308-0d34-0410-b5e6-96231b3b80d8