diff --git a/llvm/include/llvm/Debugger/SourceFile.h b/llvm/include/llvm/Debugger/SourceFile.h
index 6d49fbe5d221..e54660cb7a92 100644
--- a/llvm/include/llvm/Debugger/SourceFile.h
+++ b/llvm/include/llvm/Debugger/SourceFile.h
@@ -50,7 +50,10 @@ namespace llvm {
     /// reading it, or if the user cancels the operation.  Instead, it will just
     /// be an empty source file.
     SourceFile(const std::string &fn, const GlobalVariable *Desc)
-      : Filename(fn), Descriptor(Desc), File(Filename) {
+      : Filename(fn), Descriptor(Desc), File() {
+        std::string ErrMsg;
+      if (File.open(Filename, sys::MappedFile::READ_ACCESS, &ErrMsg))
+        throw ErrMsg;
       readFile();
     }
     ~SourceFile() {
diff --git a/llvm/lib/Debugger/SourceFile.cpp b/llvm/lib/Debugger/SourceFile.cpp
index 222cdfa26aaa..799231fc8ddb 100644
--- a/llvm/lib/Debugger/SourceFile.cpp
+++ b/llvm/lib/Debugger/SourceFile.cpp
@@ -19,7 +19,9 @@ using namespace llvm;
 /// readFile - Load Filename
 ///
 void SourceFile::readFile() {
-  File.map();
+  std::string ErrMsg;
+  if (File.map(&ErrMsg))
+    throw ErrMsg;
 }
 
 /// calculateLineOffsets - Compute the LineOffset vector for the current file.
diff --git a/llvm/lib/Support/FileUtilities.cpp b/llvm/lib/Support/FileUtilities.cpp
index d4608ccb65b3..313598942a74 100644
--- a/llvm/lib/Support/FileUtilities.cpp
+++ b/llvm/lib/Support/FileUtilities.cpp
@@ -147,9 +147,11 @@ int llvm::DiffFilesWithTolerance(const sys::Path &FileA,
                                  double AbsTol, double RelTol,
                                  std::string *Error) {
   sys::FileStatus FileAStat, FileBStat;
-  if (FileA.getFileStatus(FileAStat, Error) ||
-      FileB.getFileStatus(FileBStat, Error))
+  if (FileA.getFileStatus(FileAStat, Error))
     return 2;
+  if (FileB.getFileStatus(FileBStat, Error))
+    return 2;
+
   // Check for zero length files because some systems croak when you try to
   // mmap an empty file.
   size_t A_size = FileAStat.getSize();
@@ -165,10 +167,16 @@ int llvm::DiffFilesWithTolerance(const sys::Path &FileA,
   try {
     // Now its safe to mmap the files into memory becasue both files
     // have a non-zero size.
-    sys::MappedFile F1(FileA);
-    sys::MappedFile F2(FileB);
-    F1.map();
-    F2.map();
+    sys::MappedFile F1;
+    if (F1.open(FileA, sys::MappedFile::READ_ACCESS, Error))
+      return 2;
+    sys::MappedFile F2;
+    if (F2.open(FileB, sys::MappedFile::READ_ACCESS, Error))
+      return 2;
+    if (!F1.map(Error))
+      return 2;
+    if (!F2.map(Error))
+      return 2;
 
     // Okay, now that we opened the files, scan them for the first difference.
     char *File1Start = F1.charBase();