Getting error 87 (INVALID_PARAMETER) when executing RegGetValueA

Question

My code:

HKEY hKey;
char *path = "SYSTEM\\CurrentControlSet\\Control\\IDConfigDB\\Hardware Profiles\\0001";
LONG result1 = RegOpenKeyExA(HKEY_LOCAL_MACHINE, path, 0, KEY_ALL_ACCESS, &hKey);
QString q = QString::number(result1);

if (result1 == ERROR_SUCCESS) {
    LPDWORD b {};
    char *buffer[250];
    LONG result12 = RegGetValueA(hKey, path, "HwProfileGuid", RRF_RT_REG_SZ, NULL, &buffer, b);

    if (result12 == ERROR_SUCCESS) {

        QMessageBox messageBox1;
        messageBox1.critical(0,"Error", "Sucesso");
        messageBox1.setFixedSize(500,200);
    } else {
        QString q = QString::number(result12);
        QMessageBox messageBox2;
        messageBox2.critical(0,"Error", q);
        messageBox2.setFixedSize(500,200);
    }


} else {
    QMessageBox messageBox2;
    messageBox2.critical(0,"Error", q);
    messageBox2.setFixedSize(500,200);
}

I am a beginner and I am unsure of what parameter is the invalid one.

Answer 1

RegGetValueA function (winreg.h) - Win32 apps | Microsoft Docs says:

The pcbData parameter can be NULL only if pvData is NULL.

Your pvData is &buffer , which won't be NULL , but your pcbData is b , which is initialized to NULL . Therefore this condition is not satisfied.

Also there looks like more errors:

• The parameter should be a pointer where the length of buffer passed to pvData is stored.
• It looks weird to use an array of pointer as the buffer to receive the data.
• the key to read is already specified for RegOpenKeyExA , so you shouldn't specify that for RegGetValueA again. Otherwise, it will try to read the path under the path ( SYSTEM\...\0001\SYSTEM\...\0001 ).

The part

LPDWORD b {};
char *buffer[250];
LONG result12 = RegGetValueA(hKey, NULL, "HwProfileGuid", RRF_RT_REG_SZ, NULL, &buffer, b);

should be

char buffer[250];
DWORD b = sizeof(buffer);
LONG result12 = RegGetValueA(hKey, path, "HwProfileGuid", RRF_RT_REG_SZ, NULL, buffer, &b);