Re: singleton initialization
Eric wrote:
I created a singleton class as in the example below. The application
sporadically crashes in the second line of the main function as shown.
However, when I change the singleton such that the static pointer is a
class member (defined in the cpp file) and the instance function
creates the object if the pointer is NULL, then it works fine. I would
appreciate any explanations as to why this happens.
class CTestClass
{
public:
static CTestClass& instance()
{
static CTestClass* m_instance = new CTestClass;
return *m_instance;
}
private:
CTestClass() { /* do some stuff */ }
};
I'm not sure if you're attempting to use a "Meyers Singleton," which is
very similar to what you are doing here, but that style singleton just
constructs the object locally, instead of allocating it on the heap:
....
static CTestClass & instance()
{
static CTestClass m_instance;
return m_instance;
}
....
int main()
{
CTestClass::instance(); // initialize singleton here to
avoid future race conditions
// sporadically crashes here when using CTestClass::instance()
}
It's a memory leak (there's no matching delete, not that it matters with
singletons most of the time, though it can), and constructing it locally
will solve that.
I can't claim to know why your program crashes, however. I tried
running your original program repeatedly on my platform, and no such
crash happened. It may be that your platform dislikes leaked memory.
--
John Moeller
fishcorn@gmail.com
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