Get MAC address on Windows [closed]

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I am trying to get MAC address on my Windows PC but I have been facing an error when trying to convert it to string.

This is my code:

string UniqueKeyGenerator::getMacAddress () {
 try {
 IP_ADAPTER_INFO adapterInfo[16];
 DWORD bufLen = sizeof(adapterInfo);
 string adapter;
 string mac_address;
 // Get the adapter info
 DWORD dwStatus = GetAdaptersInfo(adapterInfo, &bufLen);
 if (dwStatus != ERROR_SUCCESS) {
 std::cerr << "GetAdaptersInfo failed with error " << dwStatus << std::endl;
 return "";
 }
 // Iterate over the adapters and display the MAC addresses
 PIP_ADAPTER_INFO pAdapterInfo = adapterInfo;
 while (pAdapterInfo) {
 adapter = pAdapterInfo->AdapterName;
 std::cout << "Adapter: " << adapter << std::endl;
 // Skip empty MAC addresses
 if (pAdapterInfo->Address[0] == 0) {
 std::cerr << "Empty MAC address for adapter: " << adapter << std::endl;
 } else {
 mac_address = macAddressToString(pAdapterInfo->Address);
 std::cout << "MAC Address: " << mac_address << std::endl;
 return mac_address; // Return the first MAC address found
 }
 pAdapterInfo = pAdapterInfo->Next;
 }
 return "Mac address not found";
 
 } catch (const exception& e) {
 cerr<<"Exception in: "<< e.what() <<endl;
 return e.what();
 }
 
 }
 std::string macAddressToString(const BYTE* macAddr) {
 char macStr[18];
 snprintf(macStr, sizeof(macStr), "%02X:%02X:%02X:%02X:%02X:%02X", 
 macAddr[0], macAddr[1], macAddr[2], macAddr[3], macAddr[4], macAddr[5]);
 return std::string(macStr); 
 }

The error occurs at line:

mac_address = macAddressToString(pAdapterInfo->Address);

that function returns only "".

This is the error:

FAILED: lv.exe 
C:\WINDOWS\system32\cmd.exe /C "cd . && C:\PROGRA~1\LLVM\bin\CLANG_~1.EXE -nostartfiles -nostdlib -O0 -g -Xclang -gcodeview -D_DEBUG -D_DLL -D_MT -Xclang --dependent-lib=msvcrtd -Xlinker /subsystem:cons
ole -fuse-ld=lld-link CMakeFiles/lv.dir/main.cpp.obj -o lv.exe -Xlinker /MANIFEST:EMBED -Xlinker /implib:lv.lib -Xlinker /pdb:lv.pdb -Xlinker /version:0.0 LicenseVerifier.lib -lkernel32 -luser32 -lg
di32 -lwinspool -lshell32 -lole32 -loleaut32 -luuid -lcomdlg32 -ladvapi32 -loldnames && cd ."
lld-link: error: undefined symbol: private: class std::basic_string<char, struct std::char_traits<char>, class std::allocator<char>> __cdecl LicenseVerifier::UniqueKeyGenerator::macAddressToString(unsig
ned char const *)
>>> referenced by C:\Users\Do Duy Manh\Desktop\manh\tasks\license_verifier_c_cpp\license_verifier_c_cpp\src\UniqueKeyGenerator.cpp:103
>>> CMakeFiles/lv.dir/main.cpp.obj:(private: class std::basic_string<char, struct std::char_traits<char>, class std::allocator<char>> __cdecl LicenseVerifier::UniqueKeyGenerator::getMacAdd
ress(void))
clang++: error: linker command failed with exit code 1 (use -v to see invocation)
ninja: build stopped: subcommand failed.

• Pepijn Kramer: Side node : If all you need is some unique number, you might want to have a look at : stackoverflow.com/questions/1327157/…. That mechanism stopped using MAC addresses because it left traces in the generated key.
• Mạnh Đỗ Duy: Thank you for the link. However, I just want to return the MAC address as a string, and I don't understand why the error occurs at the line where the function is invoked: mac_address = macAddressToString(pAdapterInfo->Address)
• Pepijn Kramer: Have you tried debugging yet? And checked that all your pointer and return values are what you would expect? pAdapterInfo = pAdapterInfo->Next; this looks suspicious, since you only have room in your buffer for one entry DWORD bufLen = sizeof(adapterInfo); not 16
• Tangentially Perpendicular: If you're seeing an error message, post the complete text of the message in your question. Many things could be wrong here, but you're making us guess.
• user207421: You are ;facing an error' when compiling your code.

Answer 1

You are getting a linker error. Your linker cant find the implementation code for the function you are trying to call.

The error says it can't find UniqueKeyGenerator::macAddressToString() but the implementation of macAddressToString() you have shown is not a member of UniqueKeyGenerator.

It seems that you likely declared macAddressToString() as a member of UniqueKeyGenerator, but you did not define it as a member, like you did with getMacAddress(). Try adding that qualification to your function's definition:

 std::string UniqueKeyGenerator::macAddressToString(const BYTE* macAddr) {
 //^^^^^^^^^^^^^^^^^^^^
 char macStr[18];
 snprintf(macStr, sizeof(macStr), "%02X:%02X:%02X:%02X:%02X:%02X", 
 macAddr[0], macAddr[1], macAddr[2], macAddr[3], macAddr[4], macAddr[5]);
 return std::string(macStr); 
 }

• Mạnh Đỗ Duy: Thank you for your help. I just switched from Python to C++ for a few day and try to get familiar with it
• user4581301: @DDManh afraid it'll take more than a few days. C++ covers a lot of ground and is very picky.