export from dll

[andrey_zh]

1) I do this to understand Windows better, get experience in work with different kind of tools and so on. Also export from dll helps me to understand assembler. I'm not going to write code in assembler, as the process in not effective.

2) At the moment I have the following:

#include <windows.h>
//#include <wtypes.h>
#include <oleauto.h>

#include <stdlib.h>
#include <wctype.h>
#include <stdint.h>
#include <assert.h>





//----------------------------------------------------------------------------

char *allocate_bstr( const wchar_t *string )
{
    int32_t length = wcslen( string );

    char *result = (char *)malloc( 4 + length * 2 + 2 );

    memcpy( result                      , &length           , 4 );
    memcpy( result + 4                  , string            , length * 2 );
    memcpy( result + 4 + length * 2     , 0x0000            , 2 );

    return result;
}





//----------------------------------------------------------------------------

int WINAPI WinMain( HINSTANCE   hThisInstance,
                    HINSTANCE   hPrevInstance,
                    LPSTR       lpszCmdLine,
                    int         nCmdShow )
{
    typedef void (* procedure_type) ( BSTR arg_1 );

    BSTR string =   //(BSTR)allocate_bstr( L"I am a happy BSTR" );
                    SysAllocString( (const OLECHAR *)L"I am a happy BSTR" );
                    //NULL;

    HMODULE module_handle = LoadLibrary( "msvbvm60.dll" );

    assert( SUCCEEDED(module_handle) );

    procedure_type procedure = (procedure_type)GetProcAddress( module_handle, "rtcMsgBox" );

    assert( procedure != NULL );

    procedure( string );

    FreeLibrary( module_handle );

    //free( string );
    

    return 0;
}

This code compiles with (BSTR)allocate_bstr( L"I am a happy BSTR" ) and program fails with no msg box,

and the following compile time error occurs on MinGW 4.4.0,

C:\DOCUME~1\andrey\LOCALS~1\Temp\ccI7IhPE.o:loadlib.cpp:(.text+0x95): undefined reference to `SysAllocString@4'
collect2: ld returned 1 exit status

I've also tried procedure type with 2 argument with and without return value of type BSTR.