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POC++ conversion question
primarykey
Id
7113099
data
AcceptedAnswerId
7125492
AnswerCount
2
ClosedDate
CommentCount
6
CommunityOwnedDate
CreationDate
2011-08-18T19:36:35.830
FavoriteCount
0
LastActivityDate
2011-08-19T21:08:02.750
LastEditDate
2011-08-19T21:08:02.750
LastEditorUserId
264325
OwnerUserId
413766
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0
PostTypeId
1
Score
6
ViewCount
385
LastEditorDisplayName
text
Body
I know that I can use correctly the WinApi function <code>DsGetDcName</code> like this: <pre><code>DOMAIN_CONTROLLER_INFO* dcInfo = nullptr; unsigned long res = ::DsGetDcName(nullptr, nullptr, nullptr, nullptr, 0, &dcInfo); </code></pre> It is unnatural, I know, but I want to understand why one cannot write it also like this: <pre><code> void* dcInfo = nullptr; unsigned long res = ::DsGetDcName(nullptr, nullptr, nullptr, nullptr, 0, (DOMAIN_CONTROLLER_INFO**) dcInfo); if (res) { wchar_t* name; name = static_cast<DOMAIN_CONTROLLER_INFO*> (dcInfo)->DomainControllerName; } </code></pre> The second version uses <code>void*</code> as a pointer type, and this is why I get an acces violation when running it (at call to the <code>::DsGetDcName</code>). But I don't understand why is this? Does it have to do with the way the memory is aligned when specifying <code>void*</code> for <code>dcInfo</code> as opposed to type <code>DOMAIN_CONTROLLER_INFO* dcInfo</code> ? SOLUTION I find out the problem, I can use actually the convoluted unsafe void* version, I just didn't passed the right pointer address to that function. Here it is: <pre><code>void* dcInfo = nullptr; unsigned long res = ::DsGetDcName(nullptr, nullptr, nullptr, nullptr, 0, (DOMAIN_CONTROLLER_INFO**) &dcInfo); </code></pre> Notice that I pass <code>(DOMAIN_CONTROLLER_INFO**) &dcInfo</code> instead of <code>(DOMAIN_CONTROLLER_INFO**) dcInfo</code>. I was just shutting myself in the foot before because I told the compiler I know what I'm doing but passed to the function a pointer value instead of the address of the pointer needed (and yes, that pointer value was <code>nullptr</code> ) :-)) This is one more reason to use the right version (version 1). In this second case also the disadvantage is that you have to cast again the result like this: <pre><code>wchar_t* name; name = static_cast<DOMAIN_CONTROLLER_INFO*>(dcInfo)->DomainControllerName; // Get DC </code></pre>
Tags
<c++><pointers>
Title
C++ conversion question
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1. PO
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1. USGhita
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