Fix crash comparing empty file against nonempty file.

git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@19782 91177308-0d34-0410-b5e6-96231b3b80d8

diff --git a/lib/Support/FileUtilities.cpp b/lib/Support/FileUtilities.cpp
index 7ae476b5975d104cb6e15a7d35687d493e2d221a..99db439d327a2717b4ca0566e26beb86510f0390 100644 (file)
--- a/lib/Support/FileUtilities.cpp
+++ b/lib/Support/FileUtilities.cpp
@@ -93,7 +93,8 @@ static bool CompareNumbers(char *&F1P, char *&F2P, char *F1End, char *F2End,
 // with a number.  Because of this, if needed, we pad the file so that it starts
 // and ends with a null character.
 static void PadFileIfNeeded(char *&FileStart, char *&FileEnd, char *&FP) {
-  if (isNumberChar(FileStart[0]) || isNumberChar(FileEnd[-1])) {
+  if (FileStart-FileEnd < 2 ||
+      isNumberChar(FileStart[0]) || isNumberChar(FileEnd[-1])) {
     unsigned FileLen = FileEnd-FileStart;
     char *NewFile = new char[FileLen+2];
     NewFile[0] = 0;              // Add null padding