x3 static initialisation problems

Hello,

I did create a x3 project using boost 1.60 at the time. This project
contains several separately compile rules.

When I got back to it recently I updated to 1.65.1. And I got hit
immediately with the "uninitialized rule" assert in
traits::get_info<>().

Looking at the myrule_def.hpp file, I realized that the static myrule
object gets returned by reference in the parser::myrule() function.
Of course that's subject to the static initialization order fiasco.

So I checked the calc9 expression_def example file to see how the
examples handled the problem. I saw that the static object still
gets returned by reference. But now a static symbol parser is also
inititialized by the parser::myrule() function. So now the function may
try to modify an object that hasn't even started it's lifetime yet.  

My solution: Return reference to rule from a Meyers singlenton. Keep
symbol initialization within the static section like in 1.60. 

Caveat: I still need to keep a namespace myrule object as the
BOOST_SPIRIT_DEFINE_ macro expects it. The macro only uses the name
in decltype(name), so maybe the macro could be changed to use
PP_CAT(rule_name, _type) to generate the type of the rule.

Cheers, Dirk


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