Re: Feedback from GSL folks on libflame 4.0

["Field G. Van Zee" <field at cs dot utexas dot edu>]

Brian,

Thanks for the suggestion. I'm preparing to leave for SIAM 2010, but once I get
back I will look into implementing some changes to the error-checking in
libflame. We may have to go Gerard's route and have dual interfaces, or we might
do it as you propose. Error checking right now in libflame is a bit of an
organized hack, and so I'll need to sit down and look at just how much code will
need to be updated to implement any changes.

As always, we appreciate your input!

Field

Brian Gough wrote:
>> It seemed like a better idea to just get our attention so we could
>> fix the problem. We agree that using return values would be a more
>> standard way of handling errors, but we're also somewhat cynical in
>> that we don't trust our users to check return values.
> 
> The approach in GSL is to have an abort() by default, for the same
> reason.  But the user can turn off the abort() and use the error
> return values instead by providing an alternative error handler as a
> function pointer.  Here's how it would look with your functions:
> 
> === FLA_macro_defs.h ===
> 
> // Error code translation and output macro definition.
> #define FLA_Check_error_code( code ) \
>   do { \
>        if (code != FLA_SUCCESS) {  \
>          FLA_Check_error_code_helper( code, __FILE__, __LINE__ ); \
>          return code; \    /* see comment below about void functions */
>        } \
>   } while (0)
> 
> 
> === FLA_main_prototypes.h ===
> 
> typedef void FLA_error_handler_t (int code, const char * file, int line);
> 
> 
> === FLA_Check.c ===
> 
> static FLA_error_handler_t * FLA_error_handler = NULL;
> 
> void FLA_Check_error_code_helper( int code, char* file, int line )
> {
>   if ( code == FLA_SUCCESS )
>     return;
> 
>   if (FLA_error_handler) 
>     {
>       (*FLA_error_handler) (code, file, line);
>       return ;
>     }
> 
>   if ( FLA_ERROR_CODE_MAX <= code && code <= FLA_ERROR_CODE_MIN )
>   {
>     FLA_Print_message( FLA_Error_string_for_code( code ),
>                        file, line );
>     FLA_Abort();
>   }
>   else
>   {
>     FLA_Print_message( FLA_Error_string_for_code( FLA_UNDEFINED_ERROR_CODE ),
>                        file, line );
>     FLA_Abort();
>   }
> }
> 
> 
> (We actually have three macro GSL_ERROR, GSL_ERROR_VOID and
> GSL_ERROR_VAL to handle different types of return value - error code,
> void, and "other".  This is to avoid warnings about "returning a value
> from a void function" etc).