Fix INSTANTIATE_TEST_CASE_P with zero variadic arguments

googletest/include/gtest/gtest-param-test.h

@@ -544,9 +544,9 @@ internal::CartesianProductHolder10<Generator1, Generator2, Generator3,
       GTEST_TEST_CLASS_NAME_(test_suite_name, test_name)::AddToRegistry();     \
   void GTEST_TEST_CLASS_NAME_(test_suite_name, test_name)::TestBody()
 
-// The optional last argument to INSTANTIATE_TEST_SUITE_P allows the user
+// The last argument to INSTANTIATE_TEST_SUITE_P allows the user to specify generator
-// to specify a function or functor that generates custom test name suffixes
+// and an optional function or functor that generates custom test name suffixes
-// based on the test parameters. The function should accept one argument of
+// based on the test parameters. Such a function or functor should accept one argument of
 // type testing::TestParamInfo<class ParamType>, and return std::string.
 //
 // testing::PrintToStringParamName is a builtin test suffix generator that
@@ -556,15 +556,15 @@ internal::CartesianProductHolder10<Generator1, Generator2, Generator3,
 // alphanumeric characters or underscore. Because PrintToString adds quotes
 // to std::string and C strings, it won't work for these types.
 
-#define INSTANTIATE_TEST_SUITE_P(prefix, test_suite_name, generator, ...)     \
+#define INSTANTIATE_TEST_SUITE_P(prefix, test_suite_name, ...)                \
   static ::testing::internal::ParamGenerator<test_suite_name::ParamType>      \
       gtest_##prefix##test_suite_name##_EvalGenerator_() {                    \
-    return generator;                                                         \
+    return VA_GETFIRST(__VA_ARGS__);                                          \
   }                                                                           \
   static ::std::string gtest_##prefix##test_suite_name##_EvalGenerateName_(   \
       const ::testing::TestParamInfo<test_suite_name::ParamType>& info) {     \
-    return ::testing::internal::GetParamNameGen<test_suite_name::ParamType>(  \
+    return ::testing::internal::CreateParamGenerator<                         \
-        __VA_ARGS__)(info);                                                   \
+        test_suite_name::ParamType>(VA_GETREST(__VA_ARGS__, 0))(info);        \
   }                                                                           \
   static int gtest_##prefix##test_suite_name##_dummy_                         \
       GTEST_ATTRIBUTE_UNUSED_ =                                               \

googletest/include/gtest/internal/gtest-param-util.h

@@ -41,6 +41,7 @@
 #include <memory>
 #include <set>
 #include <tuple>
+#include <type_traits>
 #include <utility>
 #include <vector>
 
@@ -396,6 +397,30 @@ typename ParamNameGenFunc<ParamType>::Type *GetParamNameGen() {
   return DefaultParamName;
 }
 
+// INTERNAL IMPLEMENTATION - DO NOT USE IN USER CODE.
+//
+// Macroses allow to address an issue with zero element variadic macro
+
+#define EXPAND(X) X
+#define VA__GETFIRST(X, ...) X
+#define VA_GETFIRST(...) EXPAND(VA__GETFIRST(__VA_ARGS__, 0))
+#define VA_GETREST(X, ...) __VA_ARGS__
+
+// INTERNAL IMPLEMENTATION - DO NOT USE IN USER CODE.
+//
+// Function is intended to swallow 0 as last argument and call GetParamNameGen
+
+template <class ParamType>
+auto CreateParamGenerator(int) -> decltype(GetParamNameGen<ParamType>()) {
+  return GetParamNameGen<ParamType>();
+}
+
+template <class ParamType, class Arg>
+auto CreateParamGenerator(Arg&& arg, int) -> decltype(
+    GetParamNameGen<ParamType>(std::forward<Arg>(arg))) {
+  return GetParamNameGen<ParamType>(std::forward<Arg>(arg));
+}
+
 // INTERNAL IMPLEMENTATION - DO NOT USE IN USER CODE.
 //
 // Stores a parameter value and later creates tests parameterized with that