Joe Buck wrote:
On Sat, Nov 12, 2005 at 04:01:07PM -0500, Andrew Pinski wrote:
Was there an example of:
int f(int &);
int g(void)
{
int *a = 0;
return f(*a);
}
Yes this would be undefined code but so what.
In a case like this, gcc could emit an error (since we can already
detect that a reference is always initialized to a null pointer).
If it did so, I can almost guarantee that some free software package
will be flagged (I recall writing such code myself 10+ years ago, before I
knew better), but it still might be a good thing.
Of course, it's not hard to hide the fact that a reference is null from
the compiler, and the compiler might then do optimizations based on the
assumption that the argument to f is a non-null reference. That would
be valid according to the standard.
Excuse me. IANALL nor am I a compiler expert but ...
what kind of optimization might be done with the information
that a reference *should* never be null? Especially within
the server code (the implementation of "int f(int& a)" in this case.)
Perhaps incorrectly, but I tend to use a (C++) reference when I
require the caller/client to supply a non-null "pointer" to a
single object (as opposed to an array of objects.) Client code
is free to dereference a pointer to an object (perhaps allocated
in the heap) and invoke the operation.
And what is the meaning of code that does this:
int foo(int& a)
{
int* b = &a;
if(b ==0)
{
a();
}
else
{
b();
}
}
Not that this example makes any sense, nor would
I intentionally code this way ... but...
Is function a() invoked?
Is function b() invoked?
Or (most likely) am I just one of those people
that hasn't groked the subtleties of the C++ standard
despite having used it for more years than I care to
remember ;-)
--
Michael N. Moran (h) 770 516 7918
5009 Old Field Ct. (c) 678 521 5460
Kennesaw, GA, USA 30144 http://mnmoran.org
"So often times it happens, that we live our lives in chains
and we never even know we have the key."
The Eagles, "Already Gone"
The Beatles were wrong: 1 & 1 & 1 is 1
