What am I doing wrong with this variadic macro in C? - c

Question

I'm working on a university project and I made a macro wrapper of printf which can color the text, print the file, function and line of the instruction with a string error based on errno.
#define PRINT_WITH_COLOR(color, title, message, errno_code) printf(color "[" title "] " message " %s::%s:%d [%s]\n" RESET_COLOR_CONSOLE, __VA_ARGS__, __FILE__, __func__, __LINE__, strerror(errno_code));
This initially was divided in multiple printf but due to multithreading, the problem I'm facing is that when I have no argument to pass the comma remains there and the program doesn't compile.
For that reason I used the ## to remove commas around my variadic parameter:
#define PRINT_WITH_COLOR(color, title, message, errno_code) printf(color "[" title "] " message " %s::%s:%d [%s]\n" RESET_COLOR_CONSOLE, ## __VA_ARGS__, __FILE__, __func__, __LINE__, strerror(errno_code));
I thought it was working because I didn't receive any error on my VS Code but the gcc compiler gives me this error pointing on the right comma next to the __VA_ARGS__ , <----:
expected expression before ‘,’ token
Edit
Here is an example usage:
I use it indirectly by calling this macro
#define PRINT_WARNING(err_code, message, ...) PRINT_WITH_COLOR(YELLOW_COLOR, "Warning", message, __VA_ARGS__)
And in my code I use it like that
PRINT_WARNING(EINVAL, "File %s cannot be written!", pathname);
The output is a yellow message in console [Warning] File foo cannot be written! filepath::func:line [errno msg]

Answer 1

It is actually the macro expansion of PRINT_WARNING that eventually results in the problem, and you should use ## there too. I think you also wanted to pass the err_code as well:
#define PRINT_WARNING(err_code, message, ...) \
PRINT_WITH_COLOR(YELLOW_COLOR, "Warning", message, err_code, ##__VA_ARGS__)
And the PRINT_WITH_COLOR macro should also end in , ...)
#define PRINT_WITH_COLOR(color, title, message, errno_code, ...) \
printf(color "[" title "] " message " %s::%s:%d [%s]\n" RESET_COLOR_CONSOLE, \
##__VA_ARGS__, __FILE__, __func__, __LINE__, strerror(errno_code));