Concatenate int to string using C Preprocessor

问题

I\'m trying to figure out how I can concatenate a #define\'d int to a #define\'d string using the C Preprocessor. My compiler is GCC 4.1 on CentOS 5. The solution should also work for MinGW.

I\'d like to append a version number onto a string, but the only way I can get it to work is to make a copy of the version number defines as strings.

The closest thing I could find was a method of quoting macro arguments, but it doesn\'t work for #defines

This is does not work.

#define MAJOR_VER 2
#define MINOR_VER 6
#define MY_FILE \"/home/user/.myapp\" #MAJOR_VER #MINOR_VER

It doesn\'t work without the #s either because the values are numbers and it would expand to \"/home/user/.myapp\" 2 6, which isn\'t valid C.

This does work, but I don\'t like having copies of the version defines because I do need them as numbers as well.

#define MAJOR_VER 2
#define MINOR_VER 6
#define MAJOR_VER_STR \"2\"
#define MINOR_VER_STR \"6\"
#define MY_FILE \"/home/user/.myapp\" MAJOR_VER_STRING MINOR_VER_STRING

回答1:

Classical C preprocessor question....

#define STR_HELPER(x) #x
#define STR(x) STR_HELPER(x)

#define MAJOR_VER 2
#define MINOR_VER 6
#define MY_FILE "/home/user/.myapp" STR(MAJOR_VER) STR(MINOR_VER)

The extra level of indirection will allow the preprocessor to expand the macros before they are converted to strings.

回答2:

A working way is to write MY_FILE as a parametric macro:

#define MY_FILE(x,y) "/home..." #x #y

EDIT: As noted by "Lindydancer", this solution doesn't expand macros in arguments. A more general solution is:

#define MY_FILE_(x,y) "/home..." #x #y
#define MY_FILE(x,y) MY_FILE_(x,y)

回答3:

You can do that with BOOST_PP_STRINGIZE:

#define MAJOR_VER 2
#define MINOR_VER 6
#define MY_FILE "/home/user/.myapp" BOOST_PP_STRINGIZE(MAJOR_VER) BOOST_PP_STRINGIZE(MINOR_VER)

来源：https://stackoverflow.com/questions/5459868/concatenate-int-to-string-using-c-preprocessor

标签

c-preprocessor

stringification