Variadic macros with 0 arguments in C99
c99, macros, variadic
Solution
I see two solutions to this problem. (Three if you count 'stick with gcc').
Extra special case macro
Add a new macro for when you want to print a fixed string.
#define my_errorf(str) my_error(str, NULL)
Pro: Minimum amount of extra code. Con: It's easy to use the wrong macro (but at least you notice this at compile time).
Put `fmt` inside the '...'
Vararg macro's can have only __VA_ARGS__ as parameter (unlike vararg functions). So you can put the `fmt` argument inside the __VA_ARGS__ and change your function.
void __my_error(const char *loc, ...);
#define my_error(...) __my_error(AT, __VA_ARGS__)
Pro: One syntax/macro for all error messages. Con: Requires rewriting of your `__my_error` function, which might not be possible.
Problem
I have some debugging code that looks like the following: ``` #define STRINGIFY(x) #x #define TOSTRING(x) STRINGIFY(x) #define AT __FILE__ ":" TOSTRING(__LINE__) void __my_error(const char*loc, const char *fmt, ...); #define my_error(fmt, ...) __my_error(AT, fmt, ##__VA_ARGS__) ``` The last macro is used so I can insert the location into the debug output as to where the error occurred. However, when I call the function like this: ``` my_error("Uh oh!"); ``` I would like my code to be C99, so I find when this compiles, I get the following error: ``` error: ISO C99 requires rest arguments to be used ``` I know I can solve this by changing the call to ``` my_error("Uh oh!", NULL); ``` But is there any way to make this look less ugly? Thanks!