Xref: utzoo gnu.g++.help:177 comp.lang.c++:10500
Path: utzoo!utgpu!news-server.csri.toronto.edu!cs.utexas.edu!usc!apple!snorkelwacker.mit.edu!bloom-beacon!eru!hagbard!sunic!mcsun!unido!danetis!engeln
From: engeln@danetis.UUCP (Werner Engeln)
Newsgroups: gnu.g++.help,comp.lang.c++
Subject: initialization of objects within a library
Keywords: c++,library,initialization
Message-ID: <3306@danetis.UUCP>
Date: 22 Nov 90 12:34:32 GMT
Sender: news@danetis.UUCP
Reply-To: engeln@danetis.UUCP ()
Organization: Danet-IS GmbH, Stuttgart, West Germany
Lines: 99

To ensure that global objects of a library is initialized befor its first
use, I implemented a counter to maintain the number of translation units
using it (see "the annotated C++ reference manual section 3.4, Ellis &
Stroustrup).[example below]
To my confusion, my library objects are constructed (and destructed) twice !
How can I reduce constructor calls to only ONE for each global object ??

mail, and I will post a summary

engeln@danetis.uucp
------------------------------- cut here -- nifty_library.h -----------
// nifty_library.h
#ifndef nifty_h
#define nifty_h

class foo {
public :
	foo (const char *);
	~foo ();
	void print ();
private :
	const char * name;
};

class nifty_counter {
public :
	nifty_counter ();
	~nifty_counter ();
private :
	static count;
};

#ifndef nifty_cc
// global objects
extern foo aFoo;

// counter of translation units
static nifty_counter nifty;

#endif nifty_cc
#endif nifty_h
------------------------------- cut here -- nifty_library.cc ----------
#define nifty_cc
extern "C" void printf (const char *, ...);

// declare global objects to resolve external references
foo aFoo ("aFoo by library startup");

// memberfunctions
foo::foo (const char * c)
: name (c)
{
	printf ("constructing %s\n", name);
}

foo::~foo ()
{
	printf ("destructing %s\n", name);
}

void foo::print ()
{
	printf ("foo named %s\n", name);
}

// counter implementation
nifty_counter::nifty_counter ()
{
	if (count++ == 0) {
		// initialize global objects
		aFoo.foo ("aFoo by nifty_counter");
	}
}

nifty_counter::~nifty_counter ()
{
	if (--count == 0) {
		// clean up global objects
		aFoo.foo::~foo ();
	}
}
------------------------------- cut here -- nifty_user.cc -------------
#include "nifty.h"

void main ()
{
	aFoo.print ();
}
------------------------------- cut here -- output --------------------
constructing aFoo by nifty_counter
constructing aFoo by library startup
foo named aFoo by library startup
destructing aFoo by library startup
destructing aFoo by library startup
--
Werner Engeln                Phone: +49-711/736051  FAX: +49-711/736054
Danet-IS GmbH                UUCP:   engeln@danetis.uucp
Waldburgstrasse 17 - 19      BITNET: engeln%danetis.uucp@unido.bitnet
D-7000 Stuttgart 80          X.400:  C=DE;A=DBP;P=DANET;O=IS;S=Engeln