Convert a preprocessor token to a string

Question

I'm looking for a way to convert a preprocessor token to a string.

Specifically, I've somewhere got:

#define MAX_LEN 16 

and I want to use it to prevent buffer overrun:

char val[MAX_LEN+1]; // room for \0 sscanf(buf, "%"MAX_LEN"s", val); 

I'm open to other ways to accomplish the same thing, but standard library only.

Answer 1

see http://www.decompile.com/cpp/faq/file_and_line_error_string.htm specifically:

#define STRINGIFY(x) #x #define TOSTRING(x) STRINGIFY(x) #define AT __FILE__ ":" TOSTRING(__LINE__) 

so your problem can be solved by doing sscanf(buf, "%" TOSTRING(MAX_LEN) "s", val);

Answer 2

I found an answer online.

#define VERSION_MAJOR 4 #define VERSION_MINOR 47  #define VERSION_STRING "v" #VERSION_MAJOR "." #VERSION_MINOR 

The above does not work but hopefully illustrates what I would like to do, i.e. make VERSION_STRING end up as "v4.47".

To generate the proper numeric form use something like

#define VERSION_MAJOR 4 #define VERSION_MINOR 47  #define STRINGIZE2(s) #s #define STRINGIZE(s) STRINGIZE2(s) #define VERSION_STRING "v" STRINGIZE(VERSION_MAJOR) \ "." STRINGIZE(VERSION_MINOR)  #include <stdio.h> int main() {     printf ("%s\n", VERSION_STRING);     return 0; }