How do you force compiler to pass some variable by reference in C++?

问题

Here is a simple example;

template <typename T>
void foo(T t) {}

std::string str("some huge text");
foo(str);

My question is how can I force the compiler to pass str by reference without modifying function foo?

回答1:

Pass the reference type explicitly:

template <typename T>
void foo(T t) {}

int main() {
   std::string str("some huge text");
   foo<std::string&>(str);
}

This does modify the function instantiation that you get (by generating a void foo<std::string&>(std::string& t)), but it doesn't modify the function template.

Live demo.

回答2:

You can bypass template argument deduction and explicitly pass std::string&.

回答3:

Apart from the other answers, you can also think to overload foo():

template <typename T>
void foo(T t) {}

void foo(std::string &t) {}

std::string str("some huge text");
foo(str);

This way you don't change the actual foo() behavior and get your work done with the overloaded version.

回答4:

boost::reference_wrapper should also solve your problem.

来源：https://stackoverflow.com/questions/6800824/how-do-you-force-compiler-to-pass-some-variable-by-reference-in-c