Singleton leak. Let us finish this (aka Partial Solution)
Hello everyone,
Well, I kinda solved the leak I was having with a singleton for those of you who remember this issue. I did because I had to build another one to maintain my application configuration settings. It was leaking too. But it also had a non-related bug that, when solved, made the leak go away.
Anyways, I'll try and make this as simple as possible...
Here's a simple example of a singleton with a heap based data member...
Code:
class MySingleton {
public:
static MySingleton& GetInstance() {
if (instance_ == NULL) instance_ = new MySingleton();
return *instance_;
}
~MySingleton() {}
private:
static MySingleton* instance_;
MySingleton() {
heap_.push_back("hello");
}
std::vector<std::string> heap_;
};
/* implementation file */
MySingleton* MySingleton::instance_ = NULL;
As it is, this singleton is reported to leak by Microsoft Visual C++ 2005 Express. Go ahead and try it.
- It leaks inside the vector allocator and in the allocation inside GetInstance().
- It leaks only if you do more than one call to GetInstance().
- But it leaks only once no matter how many calls to GetInstance().
The call code can look something like this, for simplicity :
Code:
int main() {
MySingleton& a = MySingleton::GetInstance();
MySingleton& b = MySingleton::GetInstance();
MySingleton& c = MySingleton::GetInstance();
}
If it is really leaking or this is an erroneous report ,I'm yet to know. But I strongly suspect the latter.
However, if I make heap_ a static data member, the leak goes away. All I'm left with is a leak report of 1 byte pointing to instance_ allocation inside GetInstance(). It's the pointer. This one definitely has to be an erroneous report.
Help me figure this out.
