Re: returning a (const) reference to a temporary

SG <>
Tue, 22 Feb 2011 01:34:07 -0800 (PST)
On 22 Feb., 10:21, AdlerSam wrote:

On 22 Feb., 10:07, Paul Brettschneider wrote:

AdlerSam wrote:

As far as I understand, a const reference _extends_ the lifetime of a
temporary until the very last reference instance that refers to the
temporary goes out of scope. Thus, where is the problem that justyfie=


the warning?

This assumption is - of course - nonsense.

Hm - Then where do I have mistaken Herb Sutters GotW #88:?


To quote the important part:

Normally, a temporary object lasts only until the end of the full
expression in which it appears. However, C++ deliberately specifies tha=


binding a temporary object to a reference to const on the stack lengthe=


the lifetime of the temporary to the lifetime of the reference itself,
and thus avoids what would otherwise be a common dangling reference
error. In the example above, the temporary returned by f() lives until
the closing curly brace. (Note this only applies to stack-based
references. It doesn't work for references that are members of object=


This is just a simplification of the C++ rules. It only applies to
cases like

  string source();

  void test() {
    string const& x = source();
    // x still refers to a valid string object
    cout << x << endl;

However, returning references to function-local objects is never ok,


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