Concatenating #define in C++

Question

I have something like:

#define BASE_FOLDER = "Resources" #define PREFERENCE_FILE_NAME = "AppPreferences.txt" #define SPLASH_FILE_NAME = "Splash.png" #define PREFERENCE_PATH = ".\\" + BASE_FOLDER + "\\" + PREFERENCE_FILE_NAME #define SPLASH_PATH = ".\\" + BASE_FOLDER + "\\" + SPLASH_FILE_NAME

and the compiler is throwing errors where PREFERENCE_PATH is used.

expecting primary expression before = token.

These all worked when I was doing

#define PREFERENCE_PATH = ".\\Resources\\AppPreferences.txt" #define SPLASH_PATH = ".\\Resources\\Splash.png"

What am I doing wrong?

#define PREFERENCE_PATH = ".\\Resources\\AppPreferences.txt" This really worked? — Falmarri
– Falmarri, Commented Jan 30, 2013 at 20:10
@Falmarri, const char * path PREFERENCE_PATH; lol. I'm guessing it wasn't used. — Qaz
– Qaz, Commented Jan 30, 2013 at 20:10
@Falmarri = Yes the orignal way worked. I just asked the old developer of this code as it is his — Jasmine
– Jasmine, Commented Jan 30, 2013 at 20:11

John Kugelman · Accepted Answer · 2013-01-30 20:08:48Z

Get rid of the equal signs. Preprocessor definitions don't use equal signs.

Then get rid of the pluses. String literals are concatenated when you put them side by side without a plus in between. Emphasis on literals because this is a compile-time feature that only works with double-quoted literals, as in "foo" "bar" → "foobar". It doesn't work with variables.

#define BASE_FOLDER "Resources" #define PREFERENCE_FILE_NAME "AppPreferences.txt" #define SPLASH_FILE_NAME "Splash.png" #define PREFERENCE_PATH ".\\" BASE_FOLDER "\\" PREFERENCE_FILE_NAME #define SPLASH_PATH ".\\" BASE_FOLDER "\\" SPLASH_FILE_NAME

Tomer Arazy · Accepted Answer · 2013-01-30 20:09:50Z

You can't concatenate strings (char* that is) in C++ like that...there is no + operator for them.

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