Add FMT_VARIADIC_VOID to emulate variadic functions on old compilers.

format.h

@@ -864,6 +864,35 @@ public:
   }
 };
 
+// Generates a comma-separated list by applying f to numbers 1..n.
+#define FMT_GEN(n, f) FMT_GEN##n(f)
+#define FMT_GEN1(f) f(1)
+#define FMT_GEN2(f) FMT_GEN1(f), f(2)
+#define FMT_GEN3(f) FMT_GEN2(f), f(3)
+#define FMT_GEN4(f) FMT_GEN3(f), f(4)
+#define FMT_GEN5(f) FMT_GEN4(f), f(5)
+#define FMT_GEN6(f) FMT_GEN5(f), f(6)
+#define FMT_GEN7(f) FMT_GEN6(f), f(7)
+#define FMT_GEN8(f) FMT_GEN7(f), f(8)
+#define FMT_GEN9(f) FMT_GEN8(f), f(9)
+
+#define FMT_MAKE_TEMPLATE_ARG(n) typename T##n
+#define FMT_MAKE_ARG(n) const T##n &v##n
+#define FMT_MAKE_REF(n) MakeArg(v##n)
+
+#define FMT_TEMPLATE(func_name, n) \
+  template <FMT_GEN(n, FMT_MAKE_TEMPLATE_ARG)> \
+  inline void func_name(BasicStringRef<Char> format, FMT_GEN(n, FMT_MAKE_ARG)) { \
+    const fmt::internal::ArgInfo args[] = {FMT_GEN(n, FMT_MAKE_REF)}; \
+    func_name(format, fmt::ArgList(args, sizeof(args) / sizeof(*args))); \
+  }
+
+// Defines a variadic function returning void.
+#define FMT_VARIADIC_VOID(func_name) \
+  FMT_TEMPLATE(format, 1) FMT_TEMPLATE(format, 2) FMT_TEMPLATE(format, 3) \
+  FMT_TEMPLATE(format, 4) FMT_TEMPLATE(format, 5) FMT_TEMPLATE(format, 6) \
+  FMT_TEMPLATE(format, 7) FMT_TEMPLATE(format, 8) FMT_TEMPLATE(format, 9)
+
 /**
   \rst
   This template provides operations for formatting and writing data into
@@ -1249,6 +1278,9 @@ class BasicWriter {
     BasicArg<> arg_array[internal::NonZero<sizeof...(Args)>::VALUE] = {args...};
     this->printf(format, ArgList(arg_array, sizeof...(Args)));
   }
+  
+#else
+  FMT_VARIADIC_VOID(format)
 #endif
 
   template <typename T>