[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, 1 insertions, 1 deletions

diff --git a/llvm/tools/llvm-objcopy/llvm-objcopy.cpp b/llvm/tools/llvm-objcopy/llvm-objcopy.cpp
index 7f55a434b33..9fc2897959c 100644
--- a/llvm/tools/llvm-objcopy/llvm-objcopy.cpp
+++ b/llvm/tools/llvm-objcopy/llvm-objcopy.cpp
@@ -27,7 +27,7 @@ static StringRef ToolName;
 
 namespace llvm {
 
-LLVM_ATTRIBUTE_NORETURN void error(Twine Message) {
+LLVM_ATTRIBUTE_NORETURN void error(const Twine &Message) {
   errs() << ToolName << ": " << Message << ".\n";
   errs().flush();
   exit(1);