Embed code through macro - c++

Question

I try to embed a code block through the use of macro like this:
#define RUN_CODE_SNIPPET(c) do {\
c\
} while(0);
where 'c' is a code block enclosed inside '{ }'
Here is how to use it
#include <stdio.h>
#define RUN_CODE_SNIPPET(c) do {\
c\
} while(0);
int main(int argc, char *argv[]) {
RUN_CODE_SNIPPET({
//const char *message = "World";
const char message[] = {'w', 'o', 'r', 'l', 'd', '\0'};
printf("%s\r\n", message);
});
return 0;
}
You can run it here here
But I get compiler error when I use the initializer list format
test.c: In function ‘main’:
test.c:13:4: error: macro "RUN_CODE_SNIPPET" passed 6 arguments, but takes just 1
});
^
test.c:9:3: error: ‘RUN_CODE_SNIPPET’ undeclared (first use in this function)
RUN_CODE_SNIPPET({
^~~~~~~~~~~~~~~~
test.c:9:3: note: each undeclared identifier is reported only once for each
function it appears in
Seems the compiler is taking each element in the initializer list as the argument to the macro itself. The string initializer works fine.
What is wrong here?

Answer 1

The commas in what you pass inside the parentheses are interpreted as macro argument separators and the macro is expecting just one argument.
There are two ways around the problem:
parenthesize the commas-containing argument, i.e., pass (a,b,c) instead of a,b,c (not applicable in your case because your argument is not an expression)
use variadic macro arguments (... -> __VA_ARGS__)
In other words:
#define RUN_CODE_SNIPPET(...) do { __VA_ARGS__; }while(0)
will work (including the semicolon at the end of the macro is not advisable -- for a function-like macro, you should generally be able to do if(X) MACRO(something); else {} and the semicolon would mess that up).