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V836. Expression's value is copied at t…
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V836. Expression's value is copied at the variable declaration. The variable is never modified. Consider declaring it as a reference.

Dec 01 2022

The analyzer detected a situation where a redundant copying may occur when a variable is declared.

Look at the example:

void foo(const std::vector<std::string> &cont)
{
  for (auto item : cont) // <=
  {
    std::cout << item;
  }
}

In the 'for' loop, a container containing elements of the 'std::string' type is traversed. According to the template argument deduction, the resulting type of the 'item' variable is 'std::string'. Because of that, the container element is copied at each iteration. You can also see that the 'item' variable is not modified in the loop's body. Thus, you can avoid redundant copying. Just replace the 'auto' type with 'const auto &'.

The correct code fragment:

void foo(const std::vector<std::string> &containter)
{
  for (const auto &item : containter) // <=
  {
    std::cout << item;
  }
}

Look at another example:

void use(const std::string &something);

void bar(const std::string &name)
{
  auto myName = name;
  use(myName);
}

In this case, it's better to replace 'auto' with 'const auto &' since 'myName" is not modified in the function's body. The correct code fragment:

void use(const std::string &something);

void bar(const std::string &name)
{
  const auto &myName = name;
  use(myName);
}

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