Add nullary macro versions.

Author: renatoGarcia

README.md

@@ -476,6 +476,10 @@ one, just define `ICECREAM_LONG_NAME` before the inclusion of `icecream.hpp` hea
 #include "icecream.hpp"
 ```
 
+While most compilers will work just fine, until the C++20 the standard requires at least
+one argument when calling a variadic macro. To handle this the nullary macros `IC0()` and
+`ICECREAM0()` are defined alongside `IC(...)` and `ICECREAM(...)`.
+
 ## Similar projects
 
 The [CleanType](https://github.com/pthom/cleantype) library has a focus on printing

icecream.hpp

@@ -55,8 +55,10 @@
 
 #if defined(ICECREAM_LONG_NAME)
     #define ICECREAM(...) (::icecream::detail::Dispatcher{__FILE__, __LINE__, ICECREAM_FUNCTION, #__VA_ARGS__}).ret(__VA_ARGS__)
+    #define ICECREAM0() (::icecream::detail::Dispatcher{__FILE__, __LINE__, ICECREAM_FUNCTION, ""}).ret()
 #else
     #define IC(...) (::icecream::detail::Dispatcher{__FILE__, __LINE__, ICECREAM_FUNCTION, #__VA_ARGS__}).ret(__VA_ARGS__)
+    #define IC0() (::icecream::detail::Dispatcher{__FILE__, __LINE__, ICECREAM_FUNCTION, ""}).ret()
 #endif