Using MSADO15.DLL and C++ with MinGW/GCC on Windows Vista

Question

INTRODUCTION

Hi,

I am very new to C++, is my 1st statement.

I have started initially with VC++ 2008 Express, I've notice that GCC becomes kind of standard so I am trying to make the right steps event from the beginning.

I have written a piece of code that connects to MSSQL Server via ADO, on VC++ it's working like a charm by importing MSADO15.dll:

#import "msado15.dll" no_namespace rename("EOF", "EndOfFile")

Because I am going to move from VC++ I was looking for an alternative (eventually multi-platform) IDE, so I stick (for this time) with Code::Block (I'm using last nightly buil, SVN 6181).

As compiler I choose to use GCC 3.4.5 (ported via MinGW 5.1.6), under Vista.

I was trying to compile a simple "hello world" application with GCC that use/import the same msado15.dll (#import "c:\Program Files\Common Files\System\ADO\msado15.dll" no_namespace rename("EOF", "EndOfFile")) and I was surprised to see a lot of compile-time errors.

I was expected that the #import compiler's directive will generate a library from "msado15.dll" so it can link to it later (link-edit time or whatever). Instead it was trying to read it as a normal file (like a header file,if you like) because it was trying to interprete each line in the DLL (which has a MZ signature):

Example:

Compiling: main.cpp
E:\MyPath\main.cpp:2:64: warning: extra tokens at end of #import directive
In file included from E:\MyPath\main.cpp:2:
c:\Program Files\Common Files\System\ADO\msado15.dll:1: error: stray '\144' in program
In file included from E:\MyPath\main.cpp:2: c:\Program Files\Common Files\System\ADO\msado15.dll:1:4: warning: null character(s) ignored
c:\Program Files\Common Files\System\ADO\msado15.dll:1: error: stray '\3' in program c:\Program Files\Common Files\System\ADO\msado15.dll:1:6: warning: null character(s) ignored
c:\Program Files\Common Files\System\ADO\msado15.dll:1: error: stray '\4' in program ...
and so on.

MY QUESTION

Well, it is obvious that under this version of GCC the #import directive does not do the expected job (perhaps #import is not supported anymore by GCC), so finally my question:

• how to use the ADO to access MSSQL database on a C++ program compiled with GCC (v3.4.5)?

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Answer 1

The #import directive is not part of the standard C++ programming language. I don't know what (if anything) it does in GCC. The normal way to use a DLL is to include its header file(s) in your code and then link with its import library (the .LIB file). I've never programmed in ADO, but in ODBC you would

#include <sql.h>

and when compiling/linking

g++ mystuff.cpp -lodbc32

to get the import library.

Also, the version of the MinGW compiler you are using is very old. You can get a much more up-to-date one at http://tdragon.net/recentgcc.

Answer 2

GCC and MSVC use #import for different things. In GCC, #import is an objective-c variant of #include that only includes the header file once. In MSVC, #import triggers a Microsoft extension that builds a smart pointer implementation and header files from a COM type library.

In GCC you are going to have to import the COM object the old fashioned way. Find the existing interface definitions or use a tool like OleSpy to generate the definitions from the tlb.

Answer 3

Whats happens you try to import in very non-standard and MSVC specific way COM object...

AFAIK the support of COM with MSYS is far from begin perfect, search for: "component object model" and gcc in google.

I would suggest using FreeTDS or library like SOCI for communication with MS-SQL. It is also cross platform ;-)