🚀 go-pugleaf

I am writing a DLL that tries to expose methods to access an Access
database: here is much of the code:

void _export OpenADBDB();
void _export CloseADBDB();
void OpenADBDB()
{
    if (isOpen) return;
    ADBConn = new TADOConnection(NULL);
    ADBConn->ConnectionString = "Provider=Microsoft.Jet.OLEDB.4.0;Data
Source=F:\apps\adbmdb\adb.mdb";
    ADBConn->LoginPrompt = false;
    ADBConn->Open("","");
    isOpen = true;
}
void CloseADBDB()
{
    if (!isOpen) return;
    ADBConn->Close();
    isOpen = false;
    delete ADBConn;
}

If I eliminate the prototypes
void _export OpenADBDB();
void _export CloseADBDB();
everything links, but I don't export any functions. If I have those lines in
the code, I get the following errors:

[Linker Error] Unresolved external 'Adodb::TADOConnection::' referenced from
F:\APPS\ADBMDB\DLL\ASSETADB.OBJ
[Linker Error] Unresolved external '__fastcall
Adodb::TADOConnection::TADOConnection(Classes::TComponent *)' referenced
from F:\APPS\ADBMDB\DLL\ASSETADB.OBJ
[Linker Error] Unresolved external '__fastcall
Adodb::TADOConnection::SetConnectionString(const System::WideString)'
referenced from F:\APPS\ADBMDB\DLL\ASSETADB.OBJ
[Linker Error] Unresolved external '__fastcall
Adodb::TADOConnection::Open(const System::WideString, const
System::WideString)' referenced from F:\APPS\ADBMDB\DLL\ASSETADB.OBJ

Why does just trying to export functions create these linking errors, and is
there a documented workaround for this?

Mike