diff --git a/flang/include/flang/Runtime/cpp-type.h b/flang/include/flang/Runtime/cpp-type.h
--- a/flang/include/flang/Runtime/cpp-type.h
+++ b/flang/include/flang/Runtime/cpp-type.h
@@ -23,14 +23,14 @@
 
 using common::TypeCategory;
 
-template <TypeCategory CAT, int KIND> struct CppTypeForHelper {};
+template <TypeCategory CAT, int KIND> struct CppTypeForHelper {
+  using type = void;
+};
 template <TypeCategory CAT, int KIND>
 using CppTypeFor = typename CppTypeForHelper<CAT, KIND>::type;
 
-template <TypeCategory CAT, int KIND, bool SFINAE = false>
-constexpr bool HasCppTypeFor{false};
 template <TypeCategory CAT, int KIND>
-constexpr bool HasCppTypeFor<CAT, KIND, true>{
+constexpr bool HasCppTypeFor{
     !std::is_void_v<typename CppTypeForHelper<CAT, KIND>::type>};
 
 template <int KIND> struct CppTypeForHelper<TypeCategory::Integer, KIND> {
diff --git a/flang/runtime/dot-product.cpp b/flang/runtime/dot-product.cpp
--- a/flang/runtime/dot-product.cpp
+++ b/flang/runtime/dot-product.cpp
@@ -147,24 +147,24 @@
 };
 
 extern "C" {
-std::int8_t RTNAME(DotProductInteger1)(
+CppTypeFor<TypeCategory::Integer, 1> RTNAME(DotProductInteger1)(
     const Descriptor &x, const Descriptor &y, const char *source, int line) {
   return DotProduct<TypeCategory::Integer, 1>{}(x, y, source, line);
 }
-std::int16_t RTNAME(DotProductInteger2)(
+CppTypeFor<TypeCategory::Integer, 2> RTNAME(DotProductInteger2)(
     const Descriptor &x, const Descriptor &y, const char *source, int line) {
   return DotProduct<TypeCategory::Integer, 2>{}(x, y, source, line);
 }
-std::int32_t RTNAME(DotProductInteger4)(
+CppTypeFor<TypeCategory::Integer, 4> RTNAME(DotProductInteger4)(
     const Descriptor &x, const Descriptor &y, const char *source, int line) {
   return DotProduct<TypeCategory::Integer, 4>{}(x, y, source, line);
 }
-std::int64_t RTNAME(DotProductInteger8)(
+CppTypeFor<TypeCategory::Integer, 8> RTNAME(DotProductInteger8)(
     const Descriptor &x, const Descriptor &y, const char *source, int line) {
   return DotProduct<TypeCategory::Integer, 8>{}(x, y, source, line);
 }
 #ifdef __SIZEOF_INT128__
-common::int128_t RTNAME(DotProductInteger16)(
+CppTypeFor<TypeCategory::Integer, 16> RTNAME(DotProductInteger16)(
     const Descriptor &x, const Descriptor &y, const char *source, int line) {
   return DotProduct<TypeCategory::Integer, 16>{}(x, y, source, line);
 }
@@ -172,16 +172,16 @@
 
 // TODO: REAL/COMPLEX(2 & 3)
 // Intermediate results and operations are at least 64 bits
-float RTNAME(DotProductReal4)(
+CppTypeFor<TypeCategory::Real, 4> RTNAME(DotProductReal4)(
     const Descriptor &x, const Descriptor &y, const char *source, int line) {
   return DotProduct<TypeCategory::Real, 4>{}(x, y, source, line);
 }
-double RTNAME(DotProductReal8)(
+CppTypeFor<TypeCategory::Real, 8> RTNAME(DotProductReal8)(
     const Descriptor &x, const Descriptor &y, const char *source, int line) {
   return DotProduct<TypeCategory::Real, 8>{}(x, y, source, line);
 }
 #if LDBL_MANT_DIG == 64
-long double RTNAME(DotProductReal10)(
+CppTypeFor<TypeCategory::Real, 10> RTNAME(DotProductReal10)(
     const Descriptor &x, const Descriptor &y, const char *source, int line) {
   return DotProduct<TypeCategory::Real, 10>{}(x, y, source, line);
 }
@@ -193,24 +193,25 @@
 }
 #endif
 
-void RTNAME(CppDotProductComplex4)(std::complex<float> &result,
+void RTNAME(CppDotProductComplex4)(CppTypeFor<TypeCategory::Complex, 4> &result,
     const Descriptor &x, const Descriptor &y, const char *source, int line) {
-  auto z{DotProduct<TypeCategory::Complex, 4>{}(x, y, source, line)};
-  result = std::complex<float>{
-      static_cast<float>(z.real()), static_cast<float>(z.imag())};
+  result = DotProduct<TypeCategory::Complex, 4>{}(x, y, source, line);
 }
-void RTNAME(CppDotProductComplex8)(std::complex<double> &result,
+void RTNAME(CppDotProductComplex8)(CppTypeFor<TypeCategory::Complex, 8> &result,
     const Descriptor &x, const Descriptor &y, const char *source, int line) {
   result = DotProduct<TypeCategory::Complex, 8>{}(x, y, source, line);
 }
 #if LDBL_MANT_DIG == 64
-void RTNAME(CppDotProductComplex10)(std::complex<long double> &result,
-    const Descriptor &x, const Descriptor &y, const char *source, int line) {
+void RTNAME(CppDotProductComplex10)(
+    CppTypeFor<TypeCategory::Complex, 10> &result, const Descriptor &x,
+    const Descriptor &y, const char *source, int line) {
   result = DotProduct<TypeCategory::Complex, 10>{}(x, y, source, line);
 }
-#elif LDBL_MANT_DIG == 113
-void RTNAME(CppDotProductComplex16)(std::complex<CppFloat128Type> &result,
-    const Descriptor &x, const Descriptor &y, const char *source, int line) {
+#endif
+#if LDBL_MANT_DIG == 113 || HAS_FLOAT128
+void RTNAME(CppDotProductComplex16)(
+    CppTypeFor<TypeCategory::Complex, 16> &result, const Descriptor &x,
+    const Descriptor &y, const char *source, int line) {
   result = DotProduct<TypeCategory::Complex, 16>{}(x, y, source, line);
 }
 #endif