map initialization: object code is 50 times larger than source code

Question

I am working in C++ with BCC32. I initialized a map with about 1000 entries like this:

extern map<string, string> city ;
void region_init_0 (void) { 
city["abc01"] = "Brussels" ;
city["xyz03"] = "Liege" ;
...
}

The length of the .cpp file is 40 KB. After compilation, I get a .obj file of 2.2 MB. After linking with other modules, the .exe file is also 2 MB longer than before I added the map. I don't understand why I get this ratio of 50 between the length of the object code and the total length of the ASCII strings.

How can I reduce that? I guess that there must be more clever ways to initialize a map that will remain constant during the execution of the program.

Thanks.

Answer 1

Have you enabled optimizations in your compiler?

You could perhaps have some code like

typedef std::pair<const char*,const char*> paircstr_t;
const paircstr_t initarr[] = {
  { "abc01", "Brussels" },
  { "xyz02", "Paris" },
  /// etc...
  { (const char*)0, (const char*)0 } // terminating null placeholder
};

extern map<string, string> city ;
void region_init_0 (void) { 
   for (int i = 0;; i++) {
      const char* curname = initarr[i].first;
      const char* curcity = initarr[i].second;
      if (!curname || !curcity) break;
      map[curname] = curcity;
   }
}

The object code size might be smaller, but the runtime heap size won't change.

Answer 2

Just a guess: Is operator[] inline? Hopefully you can change this by (un)defining some preprocessor constant. Is the release build larger or smaller than debug?