C++Talk.NET

Isaac Rodriguez · Guest

Hi,

Is this a bug in VC7.0, a bad programming practice, or both? I have a
singleton
class that is defined something like this:

class DatabaseMgr
{
public:

static DatabaseMgr& instance () {

static DatabaseMgr inst;
return inst;
}

void initialize (const String& filename) {

pDb_ = new Database(filename);
// and some other stuff.
inited = true;
}

Database* db () {

if( !inited_ ) {

throw MyException; // Assum derived from std::exception
}
return pDb_;
}

private:

Database* pDb_;
bool inited_;

DatabaseMgr() : pDb_(NULL), inited_(false) {};
DatabaseMgr(const DatabaseMgr& src);
~DatabaseMgr() { delete pDb_; };

DatabaseMgr& operator= (const DatabaseMgr& src);
}

Then, in my code I have something like this:

int main ()
{
try {

DatabaseMgr::instance().initialize("mydatabase.db");

// Some other stuff where I make calls to the database and everything
// is fine. So the following call works like a charm.
//
DatabaseMgr::instance().db()->executeQuery("SELECT * FROM Table");

}
catch (std::exception& exc) {

// Handle and exit with error.
return 1;
}

return 0;
}

The problem I was having is that when I built the application in a Release
configuration with optimizations, the DatabaseMgr::instance() call was
working
for the most part, but however, in some situations it will create a new
instance
and of course the call to db() will throw an exception because the Database
object is not initialized.

I tried a couple of things, but I finally resolved the problem by moving the
implementation of the instance() method to a .cpp so that it doesn't inline.

My question is, can a compiler generate multiple instances of an static
method?
Keep in mind that the keyword inline was not used, just that the
implementation
was inside of the class declaration. What does the standard says on this
aspect?
Is it just a bug in VC7.0?

Thanks,

--

Isaac Rodriguez
SW Engineer - Autodesk
----------------------------------------
There are 10 types of people.
Those who understand binary,
and those who don't.

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bitleo · Guest

This is not a bug. This is what c++ is supposed to do.
A class static object is created the first time it is declared and
destroyed once at the termination of the program. There is exactly one
copy of a static class member. It belongs to the class, not the
object/instance. Same thing with the functions.
Good luck

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Kurt Krueckeberg · Guest

Allan W · Guest

If a function is implemented inside the class declaration, it IS
inline, even if that keyword is not present.

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Isaac Rodriguez · Guest

"Kurt Krueckeberg" <kurtk (AT) pobox (DOT) com> wrote

Isaac Rodriguez · Guest

If there is exactly one copy of a static class member, why it is creating
two copies of the static object there declared. If I understand you
correctly, it seems to me that it is a bug with the optimizations in VC7.0
that it is inlining the static instance() member function in some of the
calls; therefore creating more than one copy of the static variable inst_.

Thanks,

--

Isaac Rodriguez
SW Engineer - Autodesk
----------------------------------------
There are 10 types of people.
Those who understand binary,
and those who don't.

"bitleo" <bitleo (AT) gmail (DOT) com> wrote

Isaac Rodriguez · Guest

So you mean that it will be inlined even if it is an static function? That
doesn't make much sense to me. Are you sure that the standard says something
like that?

Thanks,

--

Isaac Rodriguez
SW Engineer - Autodesk
----------------------------------------
There are 10 types of people.
Those who understand binary,
and those who don't.

"Allan W" <allan_w (AT) my-dejanews (DOT) com> wrote

Daniel Krügler (ne Spange · Guest

Hello Isaac Rodriguez,

Isaac Rodriguez schrieb:

Vladimir Marko · Guest

Allan W wrote:

Isaac Rodriguez · Guest