In the following code a member function set() is called on a model, which is a null pointer. This would be undefined behavior. However, the parameter of the member function is a result of another function call that checks whether the model is a null pointer and throws in that case. Is it guaranteed that estimate() will always be called before the model is accessed or is it still Undefined Behaviour (UB)?
#include <iostream>
#include <memory>
#include <vector>
struct Model
{
void set(int x)
{
v.resize(x);
}
std::vector<double> v;
};
int estimate(std::shared_ptr<Model> m)
{
return m ? 3 : throw std::runtime_error("Model is not set");
}
int main()
{
try
{
std::shared_ptr<Model> model; // null pointer here
model->set(estimate(model));
}
catch (const std::runtime_error& e)
{
std::cout << e.what();
}
return 0;
}
