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Tom
Guest
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 Posted: Tue Sep 12, 2006 9:10 am Post subject: how safe is this mapping |
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I create a object in function foo and then I pass the reference of the
object to function bar like this
void foo()
{
class_foo myFoo();
bar(myFoo);
}
void bar(class_foo& object)
{
}
and bar places the object in to a global map by passing the address of
the object parameter.
Now if I then leave function foo, is the object in the global map still
safe?
TIA,
Tom. |
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Markus Moll
Guest
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| Posted: Tue Sep 12, 2006 9:10 am Post subject: Re: how safe is this mapping |
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Hi
Tom wrote:
| Quote: | void foo()
{
class_foo myFoo();
bar(myFoo);
}
void bar(class_foo& object)
{
}
and bar places the object in to a global map by passing the address of
the object parameter.
Now if I then leave function foo, is the object in the global map still
safe?
|
You have a compiler error before that.
"class_foo myFoo();" declares a function myFoo.
If you correct that to "class_foo myFoo;", then you have a dangling pointer
as soon as foo's scope is left. Anything that you might then do with that
pointer results in undefined behavior.
You might want to look at boost::shared_ptr.
Markus |
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David Harmon
Guest
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| Posted: Tue Sep 12, 2006 9:10 am Post subject: Re: how safe is this mapping |
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On 12 Sep 2006 01:14:45 -0700 in comp.lang.c++, "Tom"
<anbother_freemail (AT) gawab (DOT) com> wrote,
| Quote: | I create a object in function foo and then I pass the reference of the
object to function bar like this
void foo()
{
class_foo myFoo();
bar(myFoo);
}
void bar(class_foo& object)
{
}
and bar places the object in to a global map by passing the address of
the object parameter.
Now if I then leave function foo, is the object in the global map still
safe?
|
No!
The object will cease to exist (and its destructor run, if any) when
function foo exits. To further confuse you, if you call foo again
there's a good chance in many implementations that the new object it
requires will be constructed at exactly the same address. |
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Carlos Martinez
Guest
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| Posted: Tue Sep 12, 2006 9:10 am Post subject: Re: how safe is this mapping |
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Tom wrote:
| Quote: | I create a object in function foo and then I pass the reference of the
object to function bar like this
void foo()
{
class_foo myFoo();
bar(myFoo);
}
void bar(class_foo& object)
{
}
and bar places the object in to a global map by passing the address of
the object parameter.
Now if I then leave function foo, is the object in the global map still
safe?
|
myFoo's lifetime ends with end of foo function. As a consequence object
pointed from map doesn't exists.
In general you must not keep references or pointers to local variables.
Instead you can keep a copy of that object or create it in heap.
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