[llvm] r195019 - Checking for a return value with FormatMessage; if the call fails, there's no guarantee that the buffer will be non-null.

[Aaron Ballman]

Author: aaronballman
Date: Mon Nov 18 11:43:22 2013
New Revision: 195019

URL: http://llvm.org/viewvc/llvm-project?rev=195019&view=rev
Log:
Checking for a return value with FormatMessage; if the call fails, there's no guarantee that the buffer will be non-null.

Modified:
    llvm/trunk/lib/Support/Windows/Windows.h

Modified: llvm/trunk/lib/Support/Windows/Windows.h
URL: http://llvm.org/viewvc/llvm-project/llvm/trunk/lib/Support/Windows/Windows.h?rev=195019&r1=195018&r2=195019&view=diff
==============================================================================
--- llvm/trunk/lib/Support/Windows/Windows.h (original)
+++ llvm/trunk/lib/Support/Windows/Windows.h Mon Nov 18 11:43:22 2013
@@ -39,11 +39,16 @@ inline bool MakeErrMsg(std::string* ErrM
   if (!ErrMsg)
     return true;
   char *buffer = NULL;
-  FormatMessage(FORMAT_MESSAGE_ALLOCATE_BUFFER|FORMAT_MESSAGE_FROM_SYSTEM,
-      NULL, GetLastError(), 0, (LPSTR)&buffer, 1, NULL);
-  *ErrMsg = prefix + buffer;
+  DWORD R = FormatMessage(FORMAT_MESSAGE_ALLOCATE_BUFFER |
+                          FORMAT_MESSAGE_FROM_SYSTEM,
+                          NULL, GetLastError(), 0, (LPSTR)&buffer, 1, NULL);
+  if (R)
+    *ErrMsg = prefix + buffer;
+  else
+    *ErrMsg = prefix + "Unknown error";
+
   LocalFree(buffer);
-  return true;
+  return R != 0;
 }
 
 template <typename HandleTraits>