🚀 go-pugleaf

In article <C1DtoB.FJ3@fiu.edu>, feathers@serss0 (Michael Feathers) writes:
> 
> Has the ANSI committee done any more work of the lifetime of temporaries?
> I'm very curious about this aspect of the emerging standard.

At the Boston meeting last November, some straw votes were taken to get
the sense of the committee of the whole.  IMO there was a clear leader
among the possibilities which seemed viable at the time.  Unfortunately
no prize was awarded. :-)  38 voted that the following was acceptable,
and none voted that it was unacceptable.

     Temporaries are normally destroyed at the end of the statement
     in which they are created.  The exception is that temporaries
     created within a branch of a conditional (?:) operator are destroyed
     when that branch is completed (and analogously for && and ||).

I would say that the committee was ready to compromise and decide on this
except for one thing.  Nearly all of the discussion has assumed that we
know what is a "temporary".  When asked directly regarding the formal
argument x in the function
     class C { ...  C (const C&);  ... };
     void f(class C x) {   ... use x ...   }
most people would say x is _not_ a temporary.  On the other hand, a very
popular implementation of C++ gives x the same extended lifetime as a
temporary.  Also, more than one example presented in favor of long-lived 
temporaries has actually needed long-lived formal arguments!  If I recall
correctly, an example was
     String x, y;
     char *z;
     extern char *f(String);
     z = f(x+y);
--
Prescott K. Turner, Jr.
Liant Software Corp. (developers of LPI languages)
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