Testing for a null managed pointer

[Robin Imrie]

Hi,

I have some code like this....

MyObject ^o = gcnew MyObject();

My2ndObject ^obj2 = o->GetObject();

if( obj2 != NULL )
{
//... do stuff
}

when i compile this I get an error(C2446) no conversion from 'int' to
'My2ndObject ^'
no user-defined-conversion operator available, or
no standard conversion exists from the boxed form of the arithetic type
to the target type

I could do this in VS2003 what do I now need to do now for VS2005?

Thanks

Robin

[Bruno van Dooren [MVP VC++]]

I have some code like this....

>
MyObject ^o = gcnew MyObject();

My2ndObject ^obj2 = o->GetObject();

if( obj2 != NULL )
{
//... do stuff
}

when i compile this I get an error(C2446) no conversion from 'int' to
'My2ndObject ^'
no user-defined-conversion operator available, or
no standard conversion exists from the boxed form of the arithetic type
to the target type

I could do this in VS2003 what do I now need to do now for VS2005?

Hi,
NULL is an pointer sized variable that happens to have a decimal value of 0.
For managed pointers you can use nullptr. Syntax highlighting will color it
blue.

--

Kind regards,
Bruno van Dooren
br**********************@hotmail.com
Remove only "_nos_pam"

[Robin Imrie]

Excelent thanks alot I thought that it must be something like that failed to
find that in the documentation when i looked.

Robin

>I have some code like this....

MyObject ^o = gcnew MyObject();

My2ndObject ^obj2 = o->GetObject();

if( obj2 != NULL )
{
//... do stuff
}

when i compile this I get an error(C2446) no conversion from 'int' to
'My2ndObject ^'
no user-defined-conversion operator available, or
no standard conversion exists from the boxed form of the arithetic
type to the target type

I could do this in VS2003 what do I now need to do now for VS2005?

Hi,
NULL is an pointer sized variable that happens to have a decimal value of
0.
For managed pointers you can use nullptr. Syntax highlighting will color
it blue.

--

Kind regards,
Bruno van Dooren
br**********************@hotmail.com
Remove only "_nos_pam"

[Carl Daniel [VC++ MVP]]

Robin Imrie wrote:

Excelent thanks alot I thought that it must be something like that
failed to find that in the documentation when i looked.

FYI, You can use nullptr for native pointers as well.

-cd

[=?Utf-8?B?UGF2ZWwgQS4=?=]

"Carl Daniel [VC++ MVP]" wrote:

FYI, You can use nullptr for native pointers as well.

So, is NULL redefined to nullptr somewhere in VC++ headers?

--PA

[Ben Voigt]

"Pavel A." <pa*****@NOwritemeNO.comwrote in message
news:76**********************************@microsof t.com...

"Carl Daniel [VC++ MVP]" wrote:

>FYI, You can use nullptr for native pointers as well.

So, is NULL redefined to nullptr somewhere in VC++ headers?

No, nullptr evaluates to 0 (same as NULL) when used as a native pointer.

>
--PA

[Tamas Demjen]

Ben Voigt wrote:

No, nullptr evaluates to 0 (same as NULL) when used as a native pointer.

nullptr has a very big advantage to NULL, though. The expression nullptr
implicates that the value is a pointer, while NULL doesn't. Here's an
exmaple:

void f(void*)
{
std::cout << "f(void*)\n";
}

void f(int)
{
std::cout << "f(int)\n";
}

int main()
{
f(NULL);
f(nullptr);
}

This prints
f(int)
f(void*)

NULL was recognized as an integer (its value is the integer 0
constant), while nullptr is treated as a real pointer (as if it was
(void*)0).

Currently the keyword doesn't work in native projects. It must be a /CLR
project in VC8. However, nullptr is very likely becoming a C++ standard
in 2009. Over time, more and more compilers will support it.

Tom

[Ben Voigt]

"Tamas Demjen" <td*****@yahoo.comwrote in message
news:eD****************@TK2MSFTNGP02.phx.gbl...

Ben Voigt wrote:

>No, nullptr evaluates to 0 (same as NULL) when used as a native pointer.

nullptr has a very big advantage to NULL, though. The expression nullptr
implicates that the value is a pointer, while NULL doesn't. Here's an
exmaple:

Agreed.

But I was responding to Pavel, who hearing that nullptr worked for native
pointers, wondered whether the SDK headers did

#define NULL nullptr