Do I have to delete/release a BSTR

[Abubakar]

Hi,

Lets say I write this line:
BSTR b = m_pdoc->Getxml ();
where m_pdoc is MSXML2::IXMLDOMDocumentPtr.

Now "b" contains the xml text. When I exit the function in which this line
is written, do I have to take care about deleting "b"? And how do I do it ?

Regards,

-Ab.

[Bruno van Dooren [MVP VC++]]

Lets say I write this line:

BSTR b = m_pdoc->Getxml ();
where m_pdoc is MSXML2::IXMLDOMDocumentPtr.

Now "b" contains the xml text. When I exit the function in which this line
is written, do I have to take care about deleting "b"? And how do I do it
?

Hi,
You can use use SysFreeString for that.
Or you could use _bstr_t instead of BSTR.
It is a wrapper around BSTR, and it will do those things for you

--

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

[Abubakar]

wow , cool.

-Ab.

"Bruno van Dooren [MVP VC++]" <br**********************@hotmail.comwrote
in message news:OT*************@TK2MSFTNGP02.phx.gbl...

Lets say I write this line:
BSTR b = m_pdoc->Getxml ();
where m_pdoc is MSXML2::IXMLDOMDocumentPtr.

Now "b" contains the xml text. When I exit the function in which this

line

is written, do I have to take care about deleting "b"? And how do I do

it

?

Hi,
You can use use SysFreeString for that.
Or you could use _bstr_t instead of BSTR.
It is a wrapper around BSTR, and it will do those things for you

--

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

[Kim Gräsman]

Hi Abubakar,

Lets say I write this line:
BSTR b = m_pdoc->Getxml ();
where m_pdoc is MSXML2::IXMLDOMDocumentPtr.
Now "b" contains the xml text. When I exit the function in which this
line is written, do I have to take care about deleting "b"? And how do
I do it ?

Actually, I believe your code is incorrect. IXMLDOMDocumentPtr is a compiler-generated
wrapper for the raw COM interface, and does not return a BSTR, but a _bstr_t.

By assigning the return value to a BSTR, you are invoking a conversion operator
on the returned _bstr_t, which is subsequently destroyed. Your b variable
is essentially pointing to random memory.

If you are going to use the wrappers generated by #import, prefer the wrapper
types to the raw automation types, and do something like this:

_bstr_t b = m_pdoc->Getxml();
// b can now be used safely until it goes out of scope

_bstr_t deallocates the contained string in its destructor, so you generally
don't need to worry about any deallocation.

--
Best Regards,
Kim Gräsman

[Abubakar]

Actually, I believe your code is incorrect. IXMLDOMDocumentPtr is a
compiler-generated

you are right but in my case it was working just fine.

If you are going to use the wrappers generated by #import, prefer the

wrapper

types to the raw automation types, and do something like this:

_bstr_t b = m_pdoc->Getxml();
// b can now be used safely until it goes out of scope

_bstr_t deallocates the contained string in its destructor, so you

generally

don't need to worry about any deallocation.

Understood.

Thanks.

-ab.

"Kim Gräsman" <ki*@mvps.orgwrote in message
news:45**************************@news.microsoft.c om...

Hi Abubakar,

Lets say I write this line:
BSTR b = m_pdoc->Getxml ();
where m_pdoc is MSXML2::IXMLDOMDocumentPtr.
Now "b" contains the xml text. When I exit the function in which this
line is written, do I have to take care about deleting "b"? And how do
I do it ?

Actually, I believe your code is incorrect. IXMLDOMDocumentPtr is a

compiler-generated

wrapper for the raw COM interface, and does not return a BSTR, but a

_bstr_t.

>
By assigning the return value to a BSTR, you are invoking a conversion

operator

on the returned _bstr_t, which is subsequently destroyed. Your b variable
is essentially pointing to random memory.

If you are going to use the wrappers generated by #import, prefer the

wrapper

types to the raw automation types, and do something like this:

_bstr_t b = m_pdoc->Getxml();
// b can now be used safely until it goes out of scope

_bstr_t deallocates the contained string in its destructor, so you

generally

don't need to worry about any deallocation.

--
Best Regards,
Kim Gräsman