Add test case for nonnull attribute.
Fix indexing bug.


git-svn-id: https://llvm.org/svn/llvm-project/cfe/trunk@53882 91177308-0d34-0410-b5e6-96231b3b80d8
diff --git a/lib/Sema/SemaDeclAttr.cpp b/lib/Sema/SemaDeclAttr.cpp
index 3800fa3..edf9a66 100644
--- a/lib/Sema/SemaDeclAttr.cpp
+++ b/lib/Sema/SemaDeclAttr.cpp
@@ -14,6 +14,7 @@
 #include "Sema.h"
 #include "clang/AST/ASTContext.h"
 #include "clang/Basic/TargetInfo.h"
+#include <sstream>
 using namespace clang;
 
 //===----------------------------------------------------------------------===//
@@ -266,10 +267,14 @@
     unsigned x = (unsigned) ArgNum.getZExtValue();
         
     if (x < 1 || x > NumArgs) {
+      std::ostringstream os;
+      os << I.getArgNum();
       S.Diag(Attr.getLoc(), diag::err_attribute_argument_out_of_bounds,
-             "nonnull", Ex->getSourceRange());
+             "nonnull", os.str(), Ex->getSourceRange());
       return;
     }
+    
+    --x;
 
     // Is the function argument a pointer type?
     if (!proto->getArgType(x).getCanonicalType()->isPointerType()) {