Thanks Peter and Darin.

In summary, looking at code like this

 B& b = c->foo();
 ...
 b.m();

If c->foo() returns a temporary ("return B();"), then it is safe.
If c->foo() returns a reference to a member variable ("return m_b;"), then it is up to the lifetime of of "c->m_b".

The cases that Adam changed were instances of the former.

dave


On Mon, Oct 4, 2010 at 12:36 PM, Peter Kasting <pkasting@chromium.org> wrote:
On Sun, Oct 3, 2010 at 10:31 AM, Darin Adler <darin@apple.com> wrote:
What you say here about object lifetime is not correct. I thought the same thing a year or so back. But the C++ language keeps these objects alive until the end of the block.

Correct.  One helpful section from the standard (12.2/5 "Temporary objects"):

"The temporary to which the reference is bound or the temporary that is the complete object to a subobject of which the temporary is bound persists for the lifetime of the reference except as specified below. A temporary bound to a reference member in a constructor’s ctor-initializer (12.6.2) persists until the constructor exits. A temporary bound to a reference parameter in a function call (5.2.2) persists until the completion of the full expression containing the call."

Adam's changes will not make any functional difference.

PK

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