Write docs.

doc/index.rst

@@ -31,6 +31,8 @@ namespace is usually omitted in examples.
 
 .. doxygenfunction:: fmt::print(std::FILE *, StringRef, const ArgList &)
 
+.. doxygenfunction:: fmt::print(std::ostream &, StringRef, const ArgList &)
+
 .. doxygendefine:: FMT_VARIADIC
 
 .. doxygenclass:: fmt::BasicWriter

format.h

@@ -2004,6 +2004,18 @@ inline void format_decimal(char *&buffer, T value) {
       fmt::print(format, args);
     }
     FMT_VARIADIC(void, print_error, const char *, int, const char *)
+
+  ``FMT_VARIADIC`` is used for compatibility with legacy C++ compilers that
+  don't implement variadic templates. You don't have to use this macro if
+  you don't need legacy compiler support and can use variadic templates
+  directly::
+
+    template<typename... Args>
+    void print_error(const char *file, int line, const char *format,
+                     const Args & ... args) {
+      fmt::print("{}: {}: ", file, line);
+      fmt::print(format, args...);
+    }
   \endrst
  */
 #define FMT_VARIADIC(ReturnType, func, ...) \

test/format-test.cc

@@ -1545,3 +1545,12 @@ TEST(FormatTest, ArgConverter) {
   ArgConverter<fmt::LongLong>(arg, 'd').visit(arg);
   EXPECT_EQ(Arg::LONG_LONG, arg.type);
 }
+
+#if FMT_USE_VARIADIC_TEMPLATES
+template<typename... Args>
+void print_error(const char *file, int line, const char *format,
+                 const Args & ... args) {
+  fmt::print("{}: {}: ", file, line);
+  fmt::print(format, args...);
+}
+#endif