cannot convert parameter 1 from 'char *' to 'long'

[MrLucky]

Ok, I switched to Visual C++ 2005 Express edition.

I have this code:

request.h

// Create prototype from Request class
class Request
{
      public:
             Request();
             ~Request();
             
             // Main function
             bool handle_requests();
             
             // MySQL Functions
             bool connect_to_db();
             
      protected:             
             // Winamp vars
             WINAMPCOMLib::IApplicationPtr winamp;
             
             // MySQL vars
             MYSQL * mysql_conn;
             MYSQL_RES * result;
             MYSQL_ROW row;
             
};

and main.cpp

#include <windows.h>
#include <mysql.h>
#include <iostream>
#include <stdio.h>

#import "c:\program files\winamp\plugins\gen_com.dll"
#include "request.h"

using namespace std;

Request::Request()
{
	// Create winamp instance
	Request::winamp.CreateInstance(__uuidof(WINAMPCOMLib::Application));			
}
Request::~Request()
{
	mysql_close(Request::mysql_conn);
}

bool Request::connect_to_db()
{
	mysql_init(Request::mysql_conn);
	if(!mysql_real_connect(Request::mysql_conn, "localhost", "lucas", "***", "luckyradio", 0, NULL, 0))
	{
		cout << "Could not connect to database:\n" << mysql_error(Request::mysql_conn) << endl;
		return false;
	}
	return true;
}

bool Request::handle_requests()
{
	cout << "Started Winamp Request Handler" << endl;
	while(true)
	{
		if(!Request::winamp->CurrentPos)
		{
			if(!mysql_query(Request::mysql_conn, "SELECT * FROM e107_wa_request ORDER BY request_id ASC LIMIT 1"))
			{
				cout << "Error in selecting requests:\n" << mysql_error(Request::mysql_conn) << endl;
				return false;
			}
			
			result = mysql_use_result(Request::mysql_conn);
			row = mysql_fetch_row(result);
			
			Request::winamp->put_PlayListPos(row[1]);
			Request::winamp->Play();
			
			cout << "Requesting: " << Request::winamp->GetSongTitle(row[1]) << "..." << endl;  						
		}
	}
	
	return false;
}

int main()
{
	Request request;
	if(request.connect_to_db())
	{
		while(request.handle_requests())
		{
			// do nothing
		}
	
		cin.get();
	}
	
	return 1;
}

But I Get this error:

------ Rebuild All started: Project: Requester, Configuration: Debug Win32 ------
Deleting intermediate and output files for project 'Requester', configuration 'Debug|Win32'
Compiling...
main.cpp
.\main.cpp(48) : error C2664: 'WINAMPCOMLib::IApplication:ut_PlayListPos' : cannot convert parameter 1 from 'char *' to 'long'
There is no context in which this conversion is possible
.\main.cpp(51) : error C2664: 'WINAMPCOMLib::IApplication::GetSongTitle' : cannot convert parameter 1 from 'char *' to 'long'
There is no context in which this conversion is possible
Build log was saved at "file://c:\Documents and Settings\Lucas\My Documents\Visual Studio 2005\Projects\Requester\Requester\Debug\BuildLog.h tm"
Requester - 2 error(s), 0 warning(s)
========== Rebuild All: 0 succeeded, 1 failed, 0 skipped ==========

Does anyone know how I can fix this?

[Darryl]

It appears that your functions are looking for long and not char*. If this a "work-around" for passing a pointer to the function then you will have to use reinterpret_cast<long>. I can only gues the function internal will cast it back to the pointer in order to use it.

[MrLucky]

something like this?

Request::winamp->put_PlayListPos(<long>row[1]);

?

[Darryl]

something like this?

Request::winamp->put_PlayListPos(<long>row[1]);

?

You forgot the reinterpret_cast part. Like this.

Request::winamp->put_PlayListPos(reinterpret_cast<long>row[1]);

This will work as far as solving the "type" conflict, whether or not it works logical I do not know without knowing the underlying code.

[MrLucky]

I've got this now:

bool Request::handle_requests()
{
	cout << "Started Winamp Request Handler" << endl;
	while(true)
	{
		if(!Request::winamp->CurrentPos)
		{
			if(!mysql_query(Request::mysql_conn, "SELECT * FROM e107_wa_request ORDER BY request_id ASC LIMIT 1"))
			{
				cout << "Error in selecting requests:\n" << mysql_error(Request::mysql_conn) << endl;
				return false;
			}
			
			result = mysql_use_result(Request::mysql_conn);
			row = mysql_fetch_row(result);
			
			long playlist_pos = reinterpret_cast<long>(row[1]);
			
			Request::winamp->put_PlayListPos(playlist_pos);
			Request::winamp->Play();
			
			cout << "Requesting: " << Request::winamp->GetSongTitle(playlist_pos) << "..." << endl;  						
		}
	}
	
	return false;
}

and this works

But now, I get some other errors..

------ Build started: Project: Requester, Configuration: Debug Win32 ------
Compiling...
main.cpp
Linking...
main.obj : error LNK2019: unresolved external symbol _mysql_close@4 referenced in function "public: __thiscall Request::~Request(void)" (??1Request@@QAE@XZ)
main.obj : error LNK2019: unresolved external symbol _mysql_error@4 referenced in function "public: bool __thiscall Request::connect_to_db(void)" (?connect_to_db@Request@@QAE_NXZ)
main.obj : error LNK2019: unresolved external symbol _mysql_real_connect@32 referenced in function "public: bool __thiscall Request::connect_to_db(void)" (?connect_to_db@Request@@QAE_NXZ)
main.obj : error LNK2019: unresolved external symbol _mysql_init@4 referenced in function "public: bool __thiscall Request::connect_to_db(void)" (?connect_to_db@Request@@QAE_NXZ)
main.obj : error LNK2019: unresolved external symbol _mysql_fetch_row@4 referenced in function "public: bool __thiscall Request::handle_requests(void)" (?handle_requests@Request@@QAE_NXZ)
main.obj : error LNK2019: unresolved external symbol _mysql_use_result@4 referenced in function "public: bool __thiscall Request::handle_requests(void)" (?handle_requests@Request@@QAE_NXZ)
main.obj : error LNK2019: unresolved external symbol _mysql_query@8 referenced in function "public: bool __thiscall Request::handle_requests(void)" (?handle_requests@Request@@QAE_NXZ)
C:\Documents and Settings\Lucas\My Documents\Visual Studio 2005\Projects\Requester\Debug\Requester.exe : fatal error LNK1120: 7 unresolved externals
Build log was saved at "file://c:\Documents and Settings\Lucas\My Documents\Visual Studio 2005\Projects\Requester\Requester\Debug\BuildLog.h tm"
Requester - 8 error(s), 0 warning(s)
========== Build: 0 succeeded, 1 failed, 0 up-to-date, 0 skipped ==========

I think I know how to fix this problem, just add the libmysql linker to my project. But does anyone know where I can add linkers to my project in Visual C++ 2005?

[Darryl]

These are linker errors, have you inluded the mysql libraries in your project? With MSVC there are 2 ways you could do this. Easiest but non-portable is put this in your file: pragma comment (lib, "name_of_your_library"). The second way is to put it in the project linker properties in the "include additional libraries" option ( do it for both debug and release)

[MrLucky]

something like this?

#pragma "c:\mysql\lib\libmysqlclient.lib"

?

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