[boost] [transact] transaction language macros (was: Re: [transact] code in sandbox)

Subject: [boost] [transact] transaction language macros (was: Re: [transact] code in sandbox)
From: strasser_at_[hidden]
Date: 2010-02-19 10:07:12

here's my implementation of the macros for discussion:

https://svn.boost.org/trac/boost/changeset/59760

below are some example use cases. the (unachievable) ideal syntax would be

transaction{
   //...
}

for each case.
actual syntax:

begin_transaction{
   //...
}end_transaction;

in user loops with support for control statements:

for(...){
   begin_transaction{
     if(something) break;
   }end_transaction_in_loop;
}

the non-loop variant can be used in user loops if there are no control  
statements used.

user code on retry, for example, limiting the number of retries to 5:

int retries=0;
begin_transaction{
   //...
}retry{
   if(retries++ == 5) break;
}end_retry;

the same in a user loop:

for(...){
   begin_transaction{
     if(something) break;
   }retry{
     ...
   }end_retry_in_loop;
}

the same can be used for the (RM-specific) case we've discussed before  
to increase transaction priority on retry:

int priority=0;
begin_transaction{
   stm::set_priority(priority);
   //...
}retry{
   ++priority;
}end_retry;

stm::set_priority() can use transaction_manager::active_transaction()  
to obtain the transaction.

rolling back a transaction on exception:

try{
   begin_transaction{
     //...
     throw my_exc();
     //...
   }end_transaction;
}catch(my_exc &){
   //transaction is rolled back
}

committing the transaction in case of a specific exception:

begin_transaction{
   try{
     //...
     throw my_exc();
     //...
   }catch(my_exc &){
     //tx will commit if my_exc is not rethrown
   }
}end_transaction;

invalid use cases:

using in_loop outside of user loops:

begin_transaction{

}end_transaction_in_loop; //compiler error: illegal "break"

using control statements without in_loop:

for(...){
   begin_transaction{
     if(something) break;
   }end_transaction; //error
}

this raises a runtime assertion if something==true.
ideal would be a compiler error, but I don't think that is possible.

are there any additional use cases to consider?
comments on syntax?

regards,

Stefan