A slot cause program to finish unexpectedly

[SIFE]

I am copying my question from stackoverflow:
I wrote a simple application on Qt4 that modifier network adapter parameters, for that I have a slot called setInterfaceParams, implemented as so:

DWORD WinNetInterface::setInterfaceParams(QString index, QString ip, QString netmask, QString gateway)
{
    DWORD res = NULL;
    HINSTANCE lib = (HINSTANCE) LoadLibrary((WCHAR *)"iphlpapi.dll");
    _SetAdapterIpAddress SetAdapterIpAddress = (_SetAdapterIpAddress) GetProcAddress(lib, "SetAdapterIpAddress");
 
    PWSTR pszGUID = NULL;
    //char  *szGUID = (char *)index.toStdString().c_str();
    QByteArray a = index.toLocal8Bit();
    char  *szGUID = a.data();
    WideCharToMultiByte(CP_ACP, 0, pszGUID, -1, szGUID, sizeof(szGUID), NULL, NULL);
 
 
// Method 01
    res = SetAdapterIpAddress(szGUID,
                        0,
                        inet_addr(ip.toStdString().c_str()),
                        inet_addr(netmask.toStdString().c_str()),
                        inet_addr(gateway.toStdString().c_str()));
// End of method 01
 
// Method 02
    /*res = SetAdapterIpAddress("{422C5689-A17B-402D-A6A2-22CE13E857B5}",
                                0,
                                inet_addr("192.168.1.10"),
                                inet_addr("255.255.255.0"),
                                inet_addr("192.168.1.1"));*/
// End of method 02
    return res;
}

DWORD WinNetInterface::setInterfaceParams(QString index, QString ip, QString netmask, QString gateway)
{
    DWORD res = NULL;
    HINSTANCE lib = (HINSTANCE) LoadLibrary((WCHAR *)"iphlpapi.dll");
    _SetAdapterIpAddress SetAdapterIpAddress = (_SetAdapterIpAddress) GetProcAddress(lib, "SetAdapterIpAddress");

    PWSTR pszGUID = NULL;
    //char  *szGUID = (char *)index.toStdString().c_str();
    QByteArray a = index.toLocal8Bit();
    char  *szGUID = a.data();
    WideCharToMultiByte(CP_ACP, 0, pszGUID, -1, szGUID, sizeof(szGUID), NULL, NULL);


// Method 01
    res = SetAdapterIpAddress(szGUID,
                        0,
                        inet_addr(ip.toStdString().c_str()),
                        inet_addr(netmask.toStdString().c_str()),
                        inet_addr(gateway.toStdString().c_str()));
// End of method 01

// Method 02
    /*res = SetAdapterIpAddress("{422C5689-A17B-402D-A6A2-22CE13E857B5}",
                                0,
                                inet_addr("192.168.1.10"),
                                inet_addr("255.255.255.0"),
                                inet_addr("192.168.1.1"));*/
// End of method 02
    return res;
}

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When I click on button that connected to slot setInterfaceParams, I get segmentation fault. If I comment method01, nothing happen, the some thing happen when I use method02. I tried this function on a simple c++ application and it is work fine, test on Windows XP SP3.

#include <windows.h>
#include <winsock2.h>
#include <iphlpapi.h>
#include <stdio.h>
#include <iostream>
 
 
typedef DWORD (WINAPI *_SetAdapterIpAddress )(char *szAdapterGUID, 
                                              DWORD dwDHCP, 
                                              DWORD dwIP, 
                                              DWORD dwMask, 
                                              DWORD dwGateway); 
 
 
int main()
{
    HINSTANCE lib = (HINSTANCE) LoadLibrary("iphlpapi.dll"); 
    _SetAdapterIpAddress SetAdapterIpAddress = (_SetAdapterIpAddress) GetProcAddress(lib, "SetAdapterIpAddress");
 
    PWSTR pszGUID = NULL;
    char  szGUID[] = "{422C5689-A17B-402D-A6A2-22CE13E857B5}";
    DWORD dwSize = 0;
    WideCharToMultiByte(CP_ACP, 0, pszGUID, -1, szGUID, sizeof(szGUID), NULL, NULL);
 
    DWORD res = SetAdapterIpAddress(szGUID, 
                        0, 
                        inet_addr("192.168.1.10"),
                        inet_addr("255.255.255.0"),
                        inet_addr("192.168.1.1"));
 
    std::cout << res;                   
 
    return 0;
}

#include <windows.h>
#include <winsock2.h>
#include <iphlpapi.h>
#include <stdio.h>
#include <iostream>


typedef DWORD (WINAPI *_SetAdapterIpAddress )(char *szAdapterGUID, 
                                              DWORD dwDHCP, 
                                              DWORD dwIP, 
                                              DWORD dwMask, 
                                              DWORD dwGateway); 


int main()
{
    HINSTANCE lib = (HINSTANCE) LoadLibrary("iphlpapi.dll"); 
    _SetAdapterIpAddress SetAdapterIpAddress = (_SetAdapterIpAddress) GetProcAddress(lib, "SetAdapterIpAddress");

    PWSTR pszGUID = NULL;
    char  szGUID[] = "{422C5689-A17B-402D-A6A2-22CE13E857B5}";
    DWORD dwSize = 0;
    WideCharToMultiByte(CP_ACP, 0, pszGUID, -1, szGUID, sizeof(szGUID), NULL, NULL);

    DWORD res = SetAdapterIpAddress(szGUID, 
                        0, 
                        inet_addr("192.168.1.10"),
                        inet_addr("255.255.255.0"),
                        inet_addr("192.168.1.1"));

    std::cout << res;                   

    return 0;
}

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[mvuori]

I guess you should first test with the very same arguments for SetAdapterIpAddress as in yout test program -- just copy and paste the section with hard-coded values -- to see whether the problem is in the calling environment or in some subtle bug in the arguments.

[ChrisW67]

This looks like a Windows API question and nothing to do with Qt.

What is the value of lib after line 4?

Compare line 4 in your first listing and line 17 in your second listing. There's an obvious difference. What do you think casting a "const char *" to "WCHAR *" does?

[Lesiok]

Maybe this, line 11 should be :

WideCharToMultiByte(CP_ACP, 0, pszGUID, -1, szGUID, strlen(szGUID)+1, NULL, NULL);

WideCharToMultiByte(CP_ACP, 0, pszGUID, -1, szGUID, strlen(szGUID)+1, NULL, NULL);

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