Robert Ramey wrote:
My general conception is that parsing can be consider as various quasi - independent phases.
a) specification of grammar - source code preparation b) compiliation c) instantiontion/construction of grammar definition d) usage of c) to parse a text string e) destruction of instance.
From this I want to conclude that phase d) does not change the grammar definition so so that in a multi-threading environment, the invocation of the scoped_lock would be limited to phases c) and e).
That is, I want to believe that the following example adapted from the spirit documentation would work:
const my_grammar g; // note addition of const
if (parse(first, last, g, space_p).full) cout << "parsing succeeded\n"; else cout << "parsing failed\n";
The reason I ask is that the serialization library uses spirit to parse xml archives. Recently, I made changes to make the library thread-safe. I did this without using mutexes/locks by confine all non-const operations to construction and destruction and using static object constructed/destructed at pre-main and post main time time. Although the jury is still out on this, I believe it will make the serialization library thread safe without the need for using threading primitives and libraries.
Alas, it's not as simple as that. The grammar itself is thread-safe. It's the instantiation of the grammar::definition that is not, and requires BOOST_SPIRIT_THREADSAFE, and hence, reliance on Boost.Threads. (FWIW, Spirit-2 solves the thread-safety problems and does away with Threads. I won't expect you to switch to Spirit2 any time soon though.) A potential solution is to "prime" the grammar at pre-main. There's no direct way to do it ATM, but you can do a dummy parse to achieve the effect (e.g. have a static object that does that in its constructor). Another potential solution (one that Spirit2 does) is to instantiate the grammar::definition directly in the stack and call its "start" rule directly. Also, if you do it this way, don't use closures (I recall you are using ASTs, right?). Spirit-1 has problems with thread-safety in 2 areas: grammar-definitions and closures. Regards, -- Joel de Guzman http://www.boostpro.com http://spirit.sf.net