cppcoreguidelines-misleading-capture-default-by-value¶
Warns when lambda specify a by-value capture default and capture this.
By-value capture defaults in member functions can be misleading about whether
data members are captured by value or reference. This occurs because specifying
the capture default [=] actually captures the this pointer by value,
not the data members themselves. As a result, data members are still indirectly
accessed via the captured this pointer, which essentially means they are
being accessed by reference. Therefore, even when using [=], data members
are effectively captured by reference, which might not align with the user’s
expectations.
Examples:
struct AClass {
  int member;
  void misleadingLogic() {
    int local = 0;
    member = 0;
    auto f = [=]() mutable {
      local += 1;
      member += 1;
    };
    f();
    // Here, local is 0 but member is 1
  }
  void clearLogic() {
    int local = 0;
    member = 0;
    auto f = [this, local]() mutable {
      local += 1;
      member += 1;
    };
    f();
    // Here, local is 0 but member is 1
  }
};
This check implements F.54 from the C++ Core Guidelines.