Make ManagedStatic constexpr constructible

Apparently it needs member initializers so that it can be constructed in
a constexpr context. I explained my investigation of this in PR41367.

llvm-svn: 357655

1 files changed, 8 insertions, 3 deletions

diff --git a/llvm/include/llvm/Support/ManagedStatic.h b/llvm/include/llvm/Support/ManagedStatic.h
index 441f24e0..ebf9bba 100644
--- a/llvm/include/llvm/Support/ManagedStatic.h
+++ b/llvm/include/llvm/Support/ManagedStatic.h
@@ -37,13 +37,18 @@ class ManagedStaticBase {
 protected:
   // This should only be used as a static variable, which guarantees that this
   // will be zero initialized.
-  mutable std::atomic<void *> Ptr;
-  mutable void (*DeleterFn)(void*);
-  mutable const ManagedStaticBase *Next;
+  mutable std::atomic<void *> Ptr{nullptr};
+  mutable void (*DeleterFn)(void *) = nullptr;
+  mutable const ManagedStaticBase *Next = nullptr;
 
   void RegisterManagedStatic(void *(*creator)(), void (*deleter)(void*)) const;
 
 public:
+  /// ManagedStaticBase must be constexpr constructed so that they can be
+  /// accessed and constructed lazily during dynamic initilization of other
+  /// global variables, such as cl::opt command line flags.
+  constexpr ManagedStaticBase() = default;
+
   /// isConstructed - Return true if this object has not been created yet.
   bool isConstructed() const { return Ptr != nullptr; }