[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, 2 deletions

diff --git a/llvm/tools/llvm-nm/llvm-nm.cpp b/llvm/tools/llvm-nm/llvm-nm.cpp
index 4ad0d95d67f..6b9ae463979 100644
--- a/llvm/tools/llvm-nm/llvm-nm.cpp
+++ b/llvm/tools/llvm-nm/llvm-nm.cpp
@@ -195,12 +195,12 @@ bool HadError = false;
 std::string ToolName;
 } // anonymous namespace
 
-static void error(Twine Message, Twine Path = Twine()) {
+static void error(const Twine &Message, const Twine &Path = Twine()) {
   HadError = true;
   errs() << ToolName << ": " << Path << ": " << Message << ".\n";
 }
 
-static bool error(std::error_code EC, Twine Path = Twine()) {
+static bool error(std::error_code EC, const Twine &Path = Twine()) {
   if (EC) {
     error(EC.message(), Path);
     return true;