[PATCH] Support: ensure proper state in ErrorOr copy ctors before calling 'get'

[Meador Inge]

Some paths through the copy constructors for 'ErrorOr' were calling
'get' when 'HasError' and 'IsValid' were not properly initialized.
Depending on what happened to be in memory for those member variables
the asserts in 'get' might incorrectly fire.  Fixed by ensuring that
the member variables in question are always initialized before calling
'get'.

I found this when running the LLD test suite on GNU/Linux.  OK?

---
 include/llvm/Support/ErrorOr.h | 11 ++++-------
 1 file changed, 4 insertions(+), 7 deletions(-)

diff --git a/include/llvm/Support/ErrorOr.h b/include/llvm/Support/ErrorOr.h
index 452d85c..828d77b 100644
--- a/include/llvm/Support/ErrorOr.h
+++ b/include/llvm/Support/ErrorOr.h
@@ -202,18 +202,17 @@ public:
     // Construct an invalid ErrorOr if other is invalid.
     if (!Other.IsValid)
       return;
+    IsValid = true;
     if (!Other.HasError) {
       // Get the other value.
-      new (get()) storage_type(*Other.get());
       HasError = false;
+      new (get()) storage_type(*Other.get());
     } else {
       // Get other's error.
       Error = Other.Error;
       HasError = true;
       Error->aquire();
     }
-
-    IsValid = true;
   }
 
   ErrorOr &operator =(const ErrorOr &Other) {
@@ -231,11 +230,11 @@ public:
     // Construct an invalid ErrorOr if other is invalid.
     if (!Other.IsValid)
       return;
+    IsValid = true;
     if (!Other.HasError) {
       // Get the other value.
-      IsValid = true;
-      new (get()) storage_type(std::move(*Other.get()));
       HasError = false;
+      new (get()) storage_type(std::move(*Other.get()));
       // Tell other not to do any destruction.
       Other.IsValid = false;
     } else {
@@ -245,8 +244,6 @@ public:
       // Tell other not to do any destruction.
       Other.IsValid = false;
     }
-
-    IsValid = true;
   }
 
   ErrorOr &operator =(ErrorOr &&Other) {
-- 
1.8.1