Concatenating strings using macros

[girishkeshavan]

Can someone tell me what is wrong here ?

#define LOG_MACRO(format,args...) printf(format,args)
 
#define TEST_MACRO(__arg1, __arg2, __format, args...) LOG_MACRO("ARG1: %s, ARG2 : %s" ## __format, ##args)
 
char* arg1 = "test";
char* arg2 = "test";
TEST_MACRO(arg1,arg2,"Testing Macro %s","foo");

error: pasting ""ARG1: %s, ARG2 : %s"" and ""Testing Macro %s"" does not give a valid preprocessing token

[weaknessforcats]

I m not a macro expoert but the args... looks incorrect. Remove the ...

Ellipsis arguments work in printf because they are coded in the function. There is nothing in your macro support va_arg.

[girishkeshavan]

I only need to paste two strings to make it look like one string so that it goes as one argument to one function. args... is not the issue here. Even If remove it I get the same error.

[donbock]

What compiler are you using?
Standard support for variable arguments in macros was not available until C99, but it was available as a nonstandard extension in some compilers before that. The first thing to determine is whether your compiler follows the new Standard or if it has its own idiosyncratic way.

[Banfa]

The error is in this bit

"ARG1: %s, ARG2 : %s" ## __format

The first part is a string and __format is also a string, they do not need to be concatenated with ## the compiler automatically concatenates consecutive strings.

Also you are note using __arg1 and __arg2

These appear to be strings which probably means you want your macro to be

#define TEST_MACRO(__arg1, __arg2, __format, args...) LOG_MACRO("ARG1: "%s, ARG2 : %s" __format, __arg1, __arg2, ##args)
 

If you are using the gcc extension that removes the final , if args is empty.