[m-dev.] for review: handle exceptions in the ODBC interface

[Simon Taylor]

> On 21-Mar-2000, Simon Taylor <stayl at cs.mu.OZ.AU> wrote:
> > 
> > Handle exceptions thrown by the closure passed to odbc__transaction.
> > 
> > extras/odbc/odbc.m:
> > 	Abort the transaction if the closure passed to odbc__transaction
> > 	throws an exception, and rethrow the exception to the caller.
> ...
> > +		/*
> > +		** There was a Mercury exception -- abort the transaction.
> > +		*/
> > +		DEBUG(printf(
> > +			""Mercury exception in transaction: aborting\\n""));
> > +		SQLTransact(odbc_env_handle, odbc_connection, SQL_ROLLBACK);
> 
> Here you are ignoring the return value of SQLTransact().
> That is probably a reasonable thing to do under the circumstances,
> but you should document this, at least by adding a cast to (void)
> in front of that call, and perhaps also with a comment in the source.
 

--- odbc.m	2000/03/21 05:19:16	1.2
+++ odbc.m	2000/03/21 05:19:35
@@ -543,10 +543,14 @@
 
 		/*
 		** There was a Mercury exception -- abort the transaction.
+		** The return value of the call to SQLTransact() is
+		** ignored because the caller won't look at the result --
+		** it will just rethrow the exception.
 		*/
 		DEBUG(printf(
 			""Mercury exception in transaction: aborting\\n""));
-		SQLTransact(odbc_env_handle, odbc_connection, SQL_ROLLBACK);
+		(void) SQLTransact(odbc_env_handle,
+				odbc_connection, SQL_ROLLBACK);
 	}
 		
 	*Status = SQL_SUCCESS;

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