C++ constructing global variable

Question

i have a c++ code:

// includes, variables etc...
GraphStructure graphStructure;

void getInput() {
    graphStructure = GraphStructure(nodesCount, edgesCount);
    // HERE, the destructor is called!
    graphStructure.init(nodesCount, edgesCount);
    // Same code as constructor, but now its okay.
}

int main(int argc, char* argv[]) {
    getInput();
}

I would like to know, why the destructor of the object is called directly after its construction. Destructors are called after end of scope of a variable, which should be after the main function end.

Answer 1

GraphStructure(nodesCount, edgesCount) is a temporary instance of GraphStructure . As such, its destructor is called when the full expression in which it is contained is evaluated (the end being at the semicolon ; ).

If it were a local instance it would be bound by the scope of getInput() , not main() . Its destructor would get called when the compiler has reached the end of getInput() (just before the ending brace } ). And the destructors of any local variables in main would get called when main finishes execution.