C++ Coding Standards: 101 Rules, Guidelines, and Best Practices

48. Prefer initialization to assignment in constructors

Summary

Set once, use everywhere: In constructors, using initialization instead of assignment to set member variables prevents needless run-time work and takes the same amount of typing.

Discussion

Constructors generate initialization code under the covers. Consider:

In reality, constructor’s code is generated as if you wrote:

A() : s1_(), s2_() { s1_ = "Hello, "; s2_ = "world"; }

That is, the objects not explicitly initialized by you are automatically initialized using their default constructors, and then assigned to using their assignment operators. Most often, the assignment operator ...