return more useful error messages by using strerror to format errno
instead of returning an ambiguous reason.


git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@90275 91177308-0d34-0410-b5e6-96231b3b80d8
diff --git a/lib/Support/MemoryBuffer.cpp b/lib/Support/MemoryBuffer.cpp
index b04864a..df1aa6a 100644
--- a/lib/Support/MemoryBuffer.cpp
+++ b/lib/Support/MemoryBuffer.cpp
@@ -176,7 +176,7 @@
 #endif
   int FD = ::open(Filename.str().c_str(), O_RDONLY|OpenFlags);
   if (FD == -1) {
-    if (ErrStr) *ErrStr = "could not open file";
+    if (ErrStr) *ErrStr = strerror(errno);
     return 0;
   }
   
@@ -186,7 +186,7 @@
     struct stat FileInfo;
     // TODO: This should use fstat64 when available.
     if (fstat(FD, &FileInfo) == -1) {
-      if (ErrStr) *ErrStr = "could not get file length";
+      if (ErrStr) *ErrStr = strerror(errno);
       ::close(FD);
       return 0;
     }
@@ -230,8 +230,8 @@
       // try again
     } else {
       // error reading.
+      if (ErrStr) *ErrStr = strerror(errno);
       close(FD);
-      if (ErrStr) *ErrStr = "error reading file data";
       return 0;
     }
   }