Different behavior in visual c++ versus gcc/clang while stringifying parameter which contains comma -


i'm using stringizing operator convert parameter may contains comma passed macro string. know, characters cannot stringified – notably, comma(,) because used delimit parameters , right parenthesis()) because marks end of parameter. use variadic macro pass commas stringizing operator this:

#include <stdio.h>  #define test 10, 20  #define make_string(...)  #__va_args__ #define string(x)       make_string(x)  int main() {     printf("%s\n", string(test) );     return 0; }

it works fine. occurs me happen without variadic macro, modify macro: #define make_string(x) #x. compiles fine unexpectedly in visual c++ 2008/2010, , output 10, 20 while gcc/clang give compilation error expected:

macro "make_string" passed 2 arguments, takes 1

so question: visual c++ doing additional work or behavior undefined?

vs in general allows parameters in macros , drops them silently: string(10, 20, 30) - still works , prints 10. not case here, pretty means vs don't have error gcc threw @ you.

it's not additional work "merely" difference in substitution order.


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