Question

If I have the following two functions

std::string foo1()
{
    std::string temp;
    ...
    return temp;
}

and

const char* foo2()
{
    std::string temp;
    ...
    return temp.c_str();
}

and a function that takes a const char* as input;

void bar(const char* input) { ... }

Which one is safer to do:

bar(foo1().c_str());

or

bar(foo2());

If all I want to do is pass a string as an input to bar and then not care about the return value of either foo function will it actually matter?

Answer 1

const char* foo2()
{
    std::string temp;
    ...
    return temp.c_str();
}

foo2() is unsafe, you are returning a const char* to a local variable which will point to garbage when the function returns.

Just use foo1 which is a safe and idiomatic way in C++ to return an object. NRVO may kick-in
which will elide the copy of temp when foo1 returns.

std::string foo1()
{
    std::string temp;
    ...
    return temp;
}