From:	"Rafal Maj" <maj_rafal AT poczta DOT onet DOT pl>
Newsgroups:	comp.os.msdos.djgpp
Subject:	Templates in library - continue
Date:	Sat, 20 Jan 2001 20:00:40 +0100
Organization:	Academic Computer Center CYFRONET AGH
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To:	djgpp AT delorie DOT com
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Reply-To:	djgpp AT delorie DOT com

Sorry, maybe I don't understand way of writing C++ libraries...
but I think this is correct :

In file lib.h I write :
  class cBox { public : void move(); }
In lib.cc :
  void cBox::move() {    /* ..............very long algoritm............
/  }
In main.cc :
  #include "lib.h"   main() { cBox obj;  obj.move();  }
In project file :
  - add  "main.c"
  - add "lib.cc"

Now everything is correct, when I'm doing change in main.cc only main.cc is
re-compiling, same fore lib.cc

--------------------
But when I want "cBox" to ba template class :
    lib.h :  template <class typ> class cBox { public : void move(); }
    lib.cc :   template <class typ> void cBox<typ>::move() {    /*
    ..............very long algoritm............ */  }
    main.c :   #include "lib.h"   main() { cBox obj<int>;  obj.move();  }

I get error while building (not when compiling) :
  Compiling: main.cc
  no errors
  Creating: main.exe
  Error: main.o: In function `main':
  main.cc(2) Error: undefined reference to `box<int>::move()'
  There were some errors

When I copy-paste source of lib.cc / lib.h into main.cc everything is O.K.,
but any small change to main() function makes class cBox recompile and
vice-versa. In my program, when it is divided to several files it compile +
build after changing one library in about 5sec,  when this program was in
one file it took about 20s to re-compile after every change.

I read in Rhide help about CXX compile flags, that some flags (like -frepo,
falt-external-templates,
-fno-implicit-templates) are needed for such programs (or maybe I didn't
understand docs... my
english is bad). When I simply select compile option -frepo it didn't help.

So what compile/link flags I should use to make this library (.cc + .h) work
while using template classes in it ???

Please help...
Thanks in advice,
Rafał

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