CODEWITHSUNDEEP
c++stl
will griffiths
will griffiths

Reputation: 85

Passing empty or uninitialised STL containers by reference

Is it always safe to pass an empty or uninitialised STL container to a function by reference? e.g.

void some_function(deque<string> &passed_by_ref) {

passed_by_ref.push_back("a string");

}

int main() {

deque<string> some_data;

some_function(some_data);

return 0;

}

I haven't had any problems with this approach, but not sure if there could possibly be any NULL reference issues.

Upvotes: 0

Views: 346

Answers (3)

ForEveR
ForEveR

Reputation: 55887

Yes, it's always safe. deque<T> is not a pointer type - it's an object type. The standard containers have a default constructor, so, after this statement

deque<string> some_data;

some_data is a correctly constructed empty deque.

Upvotes: 3

Ed Heal
Ed Heal

Reputation: 59987

The line

   deque<string> some_data;

ensures that the variable some_data is at least initialised, as the constructor is called.

Therefore you are just passing a reference to an empty STL container - which is safe.

Upvotes: 1

Andrew
Andrew

Reputation: 24846

STL containers have default constructors, which are called in that case:

deque<string> some_data;

So the container is initialized and it's totally ok to pass a reference to it

Upvotes: 2

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