[boost] RE: errorcheck

From: Reece Dunn (msclrhd_at_[hidden])
Date: 2004-03-26 19:51:06

Eljay Love-Jensen wrote:
>Hi Reece,
>
>Cool!  I think I'll add that to my repertoire.

Glad you like it :).

>A slight tweak, and it can ignore the passed in value, and peep at errno.  
>I'd call that "errnocheck" (or errnoCheck ... my orthographical standard).

Sure. The class I posted is an adaption of com::result that deals with 
Windows/COM HRESULT error handling that simplifies COM object usage.

It may be possible to use a policy-based approach, something like:

struct DefaultCheck
{
   static bool IsError( int err )
   {
      return( err < 0 );
   }
};

struct ErrNoCheck
{
   static bool IsError( int err )
   {
      return( errno < 0 ); // ???
   }
};

struct HRESULTCheck
{
   static bool IsError( HRESULT hr )
   {
      return( FAILED( hr ));
   }
};

template< class ErrorPolicy = DefaultCheck, typename T = int >
class errorcheck
{
   public:
      inline errorcheck( T e ): error( e )
      {
         if( ErrorPolicy::IsError( e )) throw( *this );
      }
   // ...
};

// example usage:

errorcheck<> error;
error = open( ... );
// ...

errorcheck< ErrNoCheck > en;
en = std::sin( -1 );

errorcheck< HRESULTCheck, HRESULT > hr;
BSTR str;
hr = pStyle -> get_color( &str );

or maybe to have extended information, so you could use something like:

error( open( ... ), "open" );

en( ::sin( -1 ), errno );
en( ::cos( 0 )); // use errno by default

Regards,
Reece

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