Re: [boost] Exceptions vs Assertion for library API?

Subject: Re: [boost] Exceptions vs Assertion for library API?
From: Christof Donat (cd_at_[hidden])
Date: 2017-11-13 15:41:50

Hi,

Am 11.11.2017 02:53, schrieb Jonathan Biggar via Boost:
> I'm building a small "transactional" library I'd like to contribute to
> boost  where certain API calls are constrained to only be valid if the
> transaction is still "in-progress".

I think there is some room of improvement on the API, whenever an issue 
like that arises. For a transactional library I'd try and create an 
interface, where the lifetime of the transaction object is in line with 
the transaction being "in progress". The destructor would simply roll 
back, if the transaction has not been moved from, while a commit() 
function that takes an rvalue reference to a transaction commits it. The 
compiler would warn, if the transaction object is used after it has been 
moved from.

Something like this:

----
// begin transaction
auto t = transaction{transactional_memory};
// do something
auto bar = t.find_foo("bar");
// might throw
bar.extend("blabla");
// will commit if extend() did not throw, rollback otherwise.
// Note, that t is moved into the parameter of commit here.
commit(t);
// undefined behaviour, compiler will warn.
auto lala = t.find_foo("lala");
// will do move assignment. t is usable again,
// but now refers to the other transaction.
t = get_another_transaction_somehow();
// now this is safe, but will of course use the new transaction.
auto lala = t.find_foo("lala");
----
But maybe I just misunderstood, what you are trying to do.
Christof