CODEWITHSUNDEEP
visual-studio-2010winapistackcalling-convention
okaerin
okaerin

Reputation: 799

behavior different when run outside of visual studio

I was surprised about the behavior of the following code:

if(RegQueryValueEx(....)!=ERROR_SUCCESS){
...
}

when it was run from visual studio it didn't enter this if block, because the key did exist. when ran outside of the visual studio environment it evaluated true and hence entered the block, even though the queried key existed. After some testing i found out that when i first save it to a variable it runs always fine. With the following code:

HKEY hSoftwareKey,hAppKey;
DWORD dwLength;
int iStatus=1;
char szBuffer[MAX_PATH];
if(iStatus&&RegOpenKeyA(HKEY_CURRENT_USER,"Software",&hSoftwareKey)!=ERROR_SUCCESS)
    iStatus = 0;
if(iStatus&&RegCreateKeyA(hSoftwareKey,"Amine",&hAppKey)!=ERROR_SUCCESS){
    iStatus = 0;
}

ZeroMemory(szBuffer,MAX_PATH);
LONG lRet;
lRet = RegQueryValueExA(hAppKey,"One",0,0,reinterpret_cast<LPBYTE>(szBuffer),&dwLength);

Does this bevavior have anything to do with the __stdcall/WINAPI calling convention? If so could somebody please explain why

Upvotes: 0

Views: 81

Answers (1)

Edward Clements
Edward Clements

Reputation: 5142

You need to initialize dwLength to MAX_PATH before calling RegQueryValueEx(), otherwise it's value is undefined.

from MSDN RegQueryValueEx:

lpcbData is a pointer to a variable that specifies the size of the buffer pointed to by the lpData parameter, in bytes. When the function returns, this variable contains the size of the data copied to lpData

Upvotes: 3

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