----- Original Message ----- From: <strasser@uni-bremen.de> To: "vicente.botet" <vicente.botet@wanadoo.fr> Cc: "Bob Walters" <bob.s.walters@gmail.com>; <boost@lists.boost.org> Sent: Thursday, February 11, 2010 6:01 AM Subject: Re: [transact] code in sandbox
Zitat von "vicente.botet" <vicente.botet@wanadoo.fr>:
*** new syntax for transaction scopes: syntax changed from: atomic{ ... }retry;
to
do atomic{
}commit();
I prefer that syntax because it resembles the do{}while(...) syntax. downside is that it conflicts with transaction::commit() if the user chooses to define BOOST_TRANSACT_COMMIT to "commit" (as is done above).
Maybe we can preserv both and see how the user react.
the user can easily create the old syntax using the existing macros:
#define atomic do BOOST_TRANSACT_ATOMIC #define retry BOOST_TRANSACT_COMMIT()
Hi, with your macro definitions #define BOOST_TRANSACT_BASIC_ATOMIC(TXMGR) \ { \ try{ \ boost::transact::basic_transaction<TXMGR> ___tx; #define BOOST_TRANSACT_BASIC_COMMIT(TXMGR) \ } \ ___tx.commit_(); \ }catch(boost::transact::isolation_exception &i){ \ i.unwind<TXMGR>(); \ continue; \ } \ }while(false); the catch has no access to the transaction variable as it out of scope (already destructed). Some times it is interesting to increase the priority of a transaction to avoid starvation. In this case we need to be able to access the transaction. On Boost.STM we have developed some macros (see stm/branches/vbe/boost/stm/language_like.hpp) . Next follows the Transact adaptation of some of them. #define BOOST_TRANSACT_BASIC_ATOMIC(TXMGR, TX)\ for (boost::transact::basic_transaction<TXMGR> TX; \ ! TX.committed() && TX.restart_if_not_inflight(); \ TX.no_throw_commit()) try #define BOOST_TRANSACT_BASIC_RETRY(TXMGR, TX) \ catch (boost::transact::isolation_exception &i) {} #define BOOST_TRANSACT_BASIC_BEFORE_RETRY(TXMGR, TX) catch (boost::transact::isolation_exception &i) #define BOOST_TRANSACT_BASIC_RETHROW(TXMGR, TX, E) \ catch (E&) {(TX).commit(); throw;} #define BOOST_TRANSACT_BASIC_ABORT_ON_EXCEPTION(TXMGR, TX, E) \ catch (E&) {(TX).force_to_abort();} BTW, what unwind does? Could you explain the problem it intend to solve. With these macros the user will be able to // retry when an a isolation exception occurs BOOST_TRANSACT_ATOMIC(_) { } BOOST_TRANSACT_RETRY(_) // increase the priority of the transaction before restart the transaction when an a isolation exception occurs BOOST_TRANSACT_ATOMIC(_) { } BOOST_TRANSACT_BEFORE_RETRY(_) {_.increase_priority(); }. // or retry when an a isolation exception occurs and retrow the exception Ex BOOST_TRANSACT_ATOMIC(_) { ... } BOOST_TRANSACT_RETRY BOOST_TRANSACT_RETHROW(_, Ex) // or retry when an a isolation exception occurs and abort when the exception Ex occurs BOOST_TRANSACT_ATOMIC(_) { ... } BOOST_TRANSACT_RETRY BOOST_TRANSACT_ABORTON_EXCEPTION(_, Ex) There are a lot of other macros. I'll present all these and more as for example how to exit succesfully from a transaction block (return, break, continue or goto) at BoostCon. Let me know if you want I add them to Boost.Transact; this could be my little contrinution to Boost.Transact for the moment. Best, Vicente