[ADT] Make Twine's copy constructor private.

There's a lot of misuse of Twine scattered around LLVM.  This
ranges in severity from benign (returning a Twine from a function
by value that is just a string literal) to pretty sketchy (storing
a Twine by value in a class).  While there are some uses for
copying Twines, most of the very compelling ones are confined
to the Twine class implementation itself, and other uses are
either dubious or easily worked around.

This patch makes Twine's copy constructor private, and fixes up
all callsites.

Differential Revision: https://reviews.llvm.org/D38767

llvm-svn: 315530

1 files changed, 2 insertions, 4 deletions

diff --git a/llvm/lib/Support/Twine.cpp b/llvm/lib/Support/Twine.cpp
index d17cd4e6643..bf434f34e43 100644
--- a/llvm/lib/Support/Twine.cpp
+++ b/llvm/lib/Support/Twine.cpp
@@ -120,12 +120,10 @@ void Twine::printOneChildRepr(raw_ostream &OS, Child Ptr,
        << Ptr.cString << "\"";
     break;
   case Twine::StdStringKind:
-    OS << "std::string:\""
-       << Ptr.stdString << "\"";
+    OS << "std::string:\"" << *Ptr.stdString << "\"";
     break;
   case Twine::StringRefKind:
-    OS << "stringref:\""
-       << Ptr.stringRef << "\"";
+    OS << "stringref:\"" << *Ptr.stringRef << "\"";
     break;
   case Twine::SmallStringKind:
     OS << "smallstring:\"" << *Ptr.smallString << "\"";