Support/MemoryBuffer: Replace all uses of std::string *ErrMsg with error_code &ec. And fix clients.

git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@121379 91177308-0d34-0410-b5e6-96231b3b80d8

tools/llvm-nm/llvm-nm.cpp

@@ -26,6 +26,7 @@
 #include "llvm/Support/PrettyStackTrace.h"
 #include "llvm/Support/raw_ostream.h"
 #include "llvm/Support/Signals.h"
+#include "llvm/Support/system_error.h"
 #include <algorithm>
 #include <cctype>
 #include <cerrno>
@@ -143,8 +144,11 @@ static void DumpSymbolNamesFromFile(std::string &Filename) {
   sys::Path aPath(Filename);
   // Note: Currently we do not support reading an archive from stdin.
   if (Filename == "-" || aPath.isBitcodeFile()) {
+    error_code ec;
     std::auto_ptr<MemoryBuffer> Buffer(
-                   MemoryBuffer::getFileOrSTDIN(Filename, &ErrorMessage));
+                   MemoryBuffer::getFileOrSTDIN(Filename, ec));
+    if (Buffer.get() == 0)
+      ErrorMessage = ec.message();
     Module *Result = 0;
     if (Buffer.get())
       Result = ParseBitcodeFile(Buffer.get(), Context, &ErrorMessage);