Programming_Micro_Note_20161128.md

Programming Micro Note 20161128

Temporary objects

Source:
When do temporary parameter values go out of scope?

Q:
I have code

int LegacyFunction(const char *s) {
    // do something with s, like print it to standard output
    // this function does NOT retain any pointer to s after it returns.
    return strlen(s);
}

std::string ModernFunction() {
    // do something that returns a string
    return "Hello";
}

LegacyFunction(ModernFunction().c_str());

Is it safe?

A:
Yes, the destruction of copy will be after evaluation of full expression.
According to n3337 12.2/3

Temporary objects are destroyed as the last step in evaluating the full-expression (1.9) that (lexically) contains the point where they were created.