Re: ordering of constructors

[Gabriel Dos Reis <gdr at integrable-solutions dot net>]

Neal Becker <ndbecker2@verizon.net> writes:

| Gabriel Dos Reis wrote:
| 
| > Neal Becker <ndbecker2@verizon.net> writes:
| > 
| > | Hi.  I'm trying to port CLN-1.1.6 to x86_64.  Currently it segfaults on
| > | all
| > | tests.  The problem appears to be some asm code whose purpose is to make
| > | sure global constructors are ordered.
| > | 
| > | I'm not that familiar yet with this code, but I think the way it is used
| > | is that if a file F.cc needs a global object A, and A requires B, then a
| > | macro is used to ensure the constructor for B was called before A.
| > 
| > Why not put a function call in the constructor for A that make sure B
| > initialized?
| > 
| 
| I'm not sure what you mean.  Consider this example:
| 
| A.H:
| struct A{ some constructor ...};
| extern A a;
| 
| A.cc:
| A a;
| 
| B.H:
| #include "A.H"
| struct B{...}
| 
| B.cc:
| B b;
| 
| Let's assume that B's constructor uses the global object 'a', so that the
| global cons for A must run before that for B.

[ In the scenario you just examplified, it is B who requires A,
  contrary to previous statement of the problem.  But, let's say that
  is not an issue. ]

| What do you suggest?

Insert a function call in B constructor that makes sure that a is
constructed. 

For example, it can be something like

   A.H:
   struct A { some constructor ... };
   extern A a;
   void make_sure_a_is_constructed();

   A.C
   A a;

   void make_sure_a_is_constructed() { /* empty */ }



   B.H:
   #include "A.H"
   struct B { ... }

   B::B()
   {
      make_sure_a_is_constructed();
      // use a...
   }

   B.cc;
   B b; 
   


The call to make_sure_a_is_constructed(), will provoke the
initialization of a, before that function is executed.  

-- Gaby