Re: x3 static initialisation problems

 I guess I need to clarify my previous mail.

Let's look at the expression parser from the 1.65.1 calc9 example.

expression.hpp declares 'parser::expression_type const& expression()'.
This function allows other rules to access the expression rule. It may
be called before the static initializers of expression.o have been
called.

The definion of expression() is in expression_def.hpp. When it's called
before static initialization, two things happen:
- add_keywords() tries to modify uninitialized static x3::symbols<>
  objects.
- a reference to an unintialized object is returned.

So I think that this initialization pattern is broken.

In my code I use several separately compiled rules calling each other.
So the Executable is quite prone to SIOF. And yes, the assertion added
to x3::traits::get_info<>() fired immediately, showing that some rules
were uninitialized and this problem is real.

As a conlusion, I think that the examples need to be fixed.

The solution I came up with:
Let's assume a rule named coordinates. The parser::coordinates()
acessor function returns a reference to a function static
coordinates_type object. This rnsures that all calls return a valid
object.

The static x3::symbols<> parsers used by the coordinates rule are
initialized with symbols_gen functions. (Just as the pattern was in
1.60) symbols<> parsers will be properly initialzed before being
called from within main().

This solution works for me. It has one little wart, though. One still
needs to keep a namespace object called coordinates. The
BOOST_SPIRIT_DEFINE_ macro uses it to figure out the type of the rule
object. 



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