2 files changed, 26 insertions, 0 deletions
diff --git a/lib/Basic/Builtins.cpp b/lib/Basic/Builtins.cpp
index 1a3293775e..040cdb5d55 100644
--- a/lib/Basic/Builtins.cpp
+++ b/lib/Basic/Builtins.cpp
@@ -93,3 +93,23 @@ Builtin::Context::isPrintfLike(unsigned ID, unsigned &FormatIdx,
   return true;
 }
 
+// FIXME: Refactor with isPrintfLike.
+bool
+Builtin::Context::isScanfLike(unsigned ID, unsigned &FormatIdx,
+                              bool &HasVAListArg) {
+  const char *Scanf = strpbrk(GetRecord(ID).Attributes, "sS");
+  if (!Scanf)
+    return false;
+
+  HasVAListArg = (*Scanf == 'S');
+
+  ++Scanf;
+  assert(*Scanf == ':' && "s or S specifier must have be followed by a ':'");
+  ++Scanf;
+
+  assert(strchr(Scanf, ':') && "printf specifier must end with a ':'");
+  FormatIdx = strtol(Scanf, 0, 10);
+  return true;
+}
+
+
diff --git a/lib/Sema/SemaDecl.cpp b/lib/Sema/SemaDecl.cpp
index c1c898fac5..76cb90565b 100644
--- a/lib/Sema/SemaDecl.cpp
+++ b/lib/Sema/SemaDecl.cpp
@@ -4905,6 +4905,12 @@ void Sema::AddKnownFunctionAttributes(FunctionDecl *FD) {
         FD->addAttr(::new (Context) FormatAttr(Context, "printf", FormatIdx+1,
                                                HasVAListArg ? 0 : FormatIdx+2));
     }
+    if (Context.BuiltinInfo.isScanfLike(BuiltinID, FormatIdx,
+                                             HasVAListArg)) {
+     if (!FD->getAttr<FormatAttr>())
+       FD->addAttr(::new (Context) FormatAttr(Context, "scanf", FormatIdx+1,
+                                              HasVAListArg ? 0 : FormatIdx+2));
+    }
 
     // Mark const if we don't care about errno and that is the only
     // thing preventing the function from being const. This allows