Re: wierd problem about pointer usage when convertion data type

From:

"Alexander Nickolov" <agnickolov@mvps.org>

Newsgroups:

microsoft.public.vc.atl

Date:

Wed, 23 Aug 2006 09:40:02 -0700

Message-ID:

<OiTIJLtxGHA.3492@TK2MSFTNGP02.phx.gbl>

Never, never, NEVER do that!!! A VARIANT cannot hold
a class pointer - period. This crashes nicely via marshaling
of course, but it may not work even without marshaling if the
client and the server are built with different compilers, or even
with the same compiler using different compilation settings.

What you want is a VARIANT containing a safe array:

V_VT(&vt) = VT_ARRAY | VT_I4;
V_ARRAY(&vt) = SafeArrayCreate(...);
....

--
=====================================
Alexander Nickolov
Microsoft MVP [VC], MCSD
email: agnickolov@mvps.org
MVP VC FAQ: http://www.mvps.org/vcfaq
=====================================

"thinktwice" <memorialday@gmail.com> wrote in message
news:1156300641.339766.37750@74g2000cwt.googlegroups.com...

std::vector<int> vec;
std::vector<int>::iterator iterBegin,iterEnd;
vec.push_back(1);
vec.push_back(2);
vec.push_back(3);

CComVariant vt;
vt.lVal = (long)(long*)&vec;
vt.vt =VT_I4;
iterBegin = vec.begin(); //just for debug
iterEnd = vec.end(); //just for debug;
put_data(vt);

void put_data(VARIANT vt)
{
  std::vector<int> *pVec;
  pVec = (std::vector<int> *)vt.lVal;
  std::vector<int>::iterator iterBegin,iterEnd;
  iterBegin = pVec->begin(); //for debug here it's an invalid value
like 0xcccccc..
  iterEnd = pVec->end(); //for debug , it's the address of the first
item in the vec,why?????

}