Index: clang-tidy/cert/CERTTidyModule.cpp
===================================================================
--- clang-tidy/cert/CERTTidyModule.cpp
+++ clang-tidy/cert/CERTTidyModule.cpp
@@ -15,6 +15,7 @@
 #include "../misc/NewDeleteOverloadsCheck.h"
 #include "../misc/NonCopyableObjects.h"
 #include "../misc/StaticAssertCheck.h"
+#include "VariadicFunctionDefCheck.h"
 
 namespace clang {
 namespace tidy {
@@ -25,6 +26,8 @@
   void addCheckFactories(ClangTidyCheckFactories &CheckFactories) override {
     // C++ checkers
     // DCL
+    CheckFactories.registerCheck<VariadicFunctionDefCheck>(
+        "cert-dcl50-cpp");
     CheckFactories.registerCheck<misc::NewDeleteOverloadsCheck>(
         "cert-dcl54-cpp");
     CheckFactories.registerCheck<google::build::UnnamedNamespaceInHeaderCheck>(
Index: clang-tidy/cert/CMakeLists.txt
===================================================================
--- clang-tidy/cert/CMakeLists.txt
+++ clang-tidy/cert/CMakeLists.txt
@@ -2,6 +2,7 @@
 
 add_clang_library(clangTidyCERTModule
   CERTTidyModule.cpp
+  VariadicFunctionDefCheck.cpp
 
   LINK_LIBS
   clangAST
Index: clang-tidy/cert/VariadicFunctionDefCheck.h
===================================================================
--- clang-tidy/cert/VariadicFunctionDefCheck.h
+++ clang-tidy/cert/VariadicFunctionDefCheck.h
@@ -0,0 +1,34 @@
+//===--- VariadicFunctionDefCheck.h - clang-tidy-----------------*- C++ -*-===//
+//
+//                     The LLVM Compiler Infrastructure
+//
+// This file is distributed under the University of Illinois Open Source
+// License. See LICENSE.TXT for details.
+//
+//===----------------------------------------------------------------------===//
+
+#ifndef LLVM_CLANG_TOOLS_EXTRA_CLANG_TIDY_CERT_VARIADICFUNCTIONDEF_H
+#define LLVM_CLANG_TOOLS_EXTRA_CLANG_TIDY_CERT_VARIADICFUNCTIONDEF_H
+
+#include "../ClangTidy.h"
+
+namespace clang {
+namespace tidy {
+
+/// Guards against any C-style variadic function definitions (not declarations).
+///
+/// For the user-facing documentation see:
+/// http://clang.llvm.org/extra/clang-tidy/checks/cert-variadic-function-def.html
+class VariadicFunctionDefCheck : public ClangTidyCheck {
+public:
+  VariadicFunctionDefCheck(StringRef Name, ClangTidyContext *Context)
+      : ClangTidyCheck(Name, Context) {}
+  void registerMatchers(ast_matchers::MatchFinder *Finder) override;
+  void check(const ast_matchers::MatchFinder::MatchResult &Result) override;
+};
+
+} // namespace tidy
+} // namespace clang
+
+#endif // LLVM_CLANG_TOOLS_EXTRA_CLANG_TIDY_CERT_VARIADICFUNCTIONDEF_H
+
Index: clang-tidy/cert/VariadicFunctionDefCheck.cpp
===================================================================
--- clang-tidy/cert/VariadicFunctionDefCheck.cpp
+++ clang-tidy/cert/VariadicFunctionDefCheck.cpp
@@ -0,0 +1,38 @@
+//===--- VariadicfunctiondefCheck.cpp - clang-tidy-------------------------===//
+//
+//                     The LLVM Compiler Infrastructure
+//
+// This file is distributed under the University of Illinois Open Source
+// License. See LICENSE.TXT for details.
+//
+//===----------------------------------------------------------------------===//
+
+#include "VariadicFunctionDefCheck.h"
+#include "clang/AST/ASTContext.h"
+#include "clang/ASTMatchers/ASTMatchFinder.h"
+
+using namespace clang::ast_matchers;
+
+namespace clang {
+namespace tidy {
+
+void VariadicFunctionDefCheck::registerMatchers(MatchFinder *Finder) {
+  if (!getLangOpts().CPlusPlus)
+    return;
+
+  // We only care about function *definitions* that are variadic.
+  Finder->addMatcher(functionDecl(isDefinition(), isVariadic()).bind("func"),
+                     this);
+}
+
+void VariadicFunctionDefCheck::check(const MatchFinder::MatchResult &Result) {
+  const auto *FD = Result.Nodes.getNodeAs<FunctionDecl>("func");
+
+  diag(FD->getLocation(),
+       "do not define a C-style variadic function; consider using a function "
+       "parameter pack or currying instead");
+}
+
+} // namespace tidy
+} // namespace clang
+
Index: docs/clang-tidy/checks/cert-variadic-function-def.rst
===================================================================
--- docs/clang-tidy/checks/cert-variadic-function-def.rst
+++ docs/clang-tidy/checks/cert-variadic-function-def.rst
@@ -0,0 +1,13 @@
+cert-dcl50-cpp
+========================
+
+A variadic function using an ellipsis has no mechanisms to check the type safety
+of arguments being passed to the function or to check that the number of
+arguments being passed matches the semantics of the function definition.
+Consequently, a runtime call to a C-style variadic function that passes
+inappropriate arguments yields undefined behavior. Such undefined behavior could
+be exploited to run arbitrary code.
+
+This check corresponds to the CERT C++ Coding Standard rule
+`DCL50-CPP. Do not define a C-style variadic function
+<https://www.securecoding.cert.org/confluence/display/cplusplus/DCL50-CPP.+Do+not+define+a+C-style+variadic+function>`_.
Index: docs/clang-tidy/checks/list.rst
===================================================================
--- docs/clang-tidy/checks/list.rst
+++ docs/clang-tidy/checks/list.rst
@@ -2,6 +2,7 @@
 =========================
 
 .. toctree::
+   cert-variadic-function-def
    google-build-explicit-make-pair
    google-build-namespaces
    google-build-using-namespace
Index: test/clang-tidy/cert-variadic-function-def.cpp
===================================================================
--- test/clang-tidy/cert-variadic-function-def.cpp
+++ test/clang-tidy/cert-variadic-function-def.cpp
@@ -0,0 +1,18 @@
+// RUN: %python %S/check_clang_tidy.py %s cert-dcl50-cpp %t
+
+// Variadic function definitions are diagnosed.
+// CHECK-MESSAGES: :[[@LINE+1]]:6: warning: do not define a C-style variadic function; consider using a function parameter pack or currying instead [cert-dcl50-cpp]
+void f1(int, ...) {}
+
+// Variadic function *declarations* are not diagnosed.
+void f2(int, ...); // ok
+
+// Function parameter packs are good, however.
+template <typename Arg, typename... Ts>
+void f3(Arg F, Ts... Rest) {}
+
+struct S {
+  void f(int, ...); // ok
+  // CHECK-MESSAGES: :[[@LINE+1]]:8: warning: do not define a C-style variadic function; consider using a function parameter pack or currying instead [cert-dcl50-cpp]
+  void f1(int, ...) {}
+};