std::string 和 const char 情况下的连接优先级

Question

Is it ok to write the following code?

std::string first = "str";
"1" + first + "2" + std::to_string(1).c_str();

Will first be concatenated with "2" before "2 + std::to_string" concatenation, so there will be no "pointers concatenation" error?

Answer 1

Addition is left-associative, so that's

(("1" + first) + "2") + std::to_string(1).c_str(); 

In other words, first will not be concatenated with "2" , and neither will "2" (fail to) be concatenated with std::to_string(1).c_str() .