TITLE: New ruling on lifetime of temporaries (part II)


PROBLEM: Viktor Yurkovsky <n4mation@panix.com>

According to the ARM, the lifetime of temporary objects is
implementation-dependent.  Therefore, you should not rely on the
existance of temporary objects beyond their normal function of
assignment.


RESPONSE: maxtal@physics.su.OZ.AU (John Max Skaller)

Out of date. A temporary lasts to "end of full expression",
which is usually the end of the statement.


RESPONSE: ehsjony@ehs.ericsson.se

!!!!

Usually ? :-)

Does somebody know if there is a formal definition for the life-time which can 
be reasonably easily understood. When this new rule for temporaries was
introduced
I read some explanations on the net but never quite managed to grasp this
rule.


RESPONSE: maxtal@physics.su.OZ.AU (John Max Skaller), 12 Jan 95

	There are two exceptions.

	1) A non-parameter non-class const reference bound to
	a temporary has the duration of the reference (static or
	automatic). For example:

	void f() {
		const int & i = 1;
		int j= i; // fine, "i" still exists
	}

	2) A temporary used in a || or && or as the first argument
	in a ?: expression or conditional dies after it has been evaluated:

		int* f(int const &a) { return &a; }
		int* pi;	
		if(pi=f(1)) { cout << *pi; } // error!

See the WP12.2/2.