Steps to reproduce:
using GLib;

namespace GCalculator {

    public const string PACKAGE_GLADE_DIR = "";
    public const string MAIN_GLADE_FILE = GCalculator.PACKAGE_GLADE_DIR + "/main_frame.glade";
}


Stack trace:
The code generate:

#define GCALCULATOR_PACKAGE_GLADE_DIR ""
#define GCALCULATOR_MAIN_GLADE_FILE GCALCULATOR_PACKAGE_GLADE_DIR + "/main_frame.glade"

Other information:
The plus sign cannot be applied in C since it is a string literal