c++ - “dll_file”可能是 '0' : This does not adhere to the specification for the function 'GetProcAddress'

Question

所以我想使用我创建的 DLL，但我收到了一个非常奇怪的警告，我没有看到任何人有这个警告。我检查了 LoadLibray 是否返回“NULL”，事实并非如此。

typedef DATA_BLOB(*encryption_decryption)(DATA_BLOB, bool*);
HINSTANCE dll_file = LoadLibrary(L"dllForEncryptionNDecryptionn.dll");
if (dll_file != NULL) {
    cout << "Library loaded!" << endl;
}
else {
    failed();
}
encryption_decryption encryption = (encryption_decryption)GetProcAddress(dll_file,"encryption");
if(encryption != NULL)
{
    cout << "Workded!" << endl;
}
else
{
    failed();
}
void failed() {
    cout << GetLastError() << endl;
    cout << "Faild!" << endl;
}

Warning at the 8th line: "'dll_file' could be '0': this does not adhere to the specification for the function 'GetProcAddress'."

一切正常，当我运行它时，它不会写任何错误。

Answer 1

如果 LoadLibrary 中出现任何问题，您可以调用 failed() 来打印错误代码并返回。

HINSTANCE dll_file = LoadLibrary(L"dllForEncryptionNDecryptionn.dll");
if (dll_file != NULL) {
    cout << "Library loaded!" << endl;
}
else {
    failed(); // returns even when dll_file is NULL
}

// so, here you don't know if it's NULL or a valid handle which is why you get the warning
encryption_decryption encryption = (encryption_decryption)GetProcAddress(dll_file,"encryption");

如果LoadLibrary失败，您不应该使用该dll_file来调用GetProcAddress。

encryption_decryption encryption = nullptr;
HINSTANCE dll_file = LoadLibrary(L"dllForEncryptionNDecryptionn.dll");

if(dll_file) {
    encryption_decryption encryption = 
        (encryption_decryption)GetProcAddress(dll_file,"encryption");
} else {
    // do NOT call GetProcAddress
}

if(encryption) {
    // function successfully loaded
}