Re: [boost] Global variable initialization

From: David Abrahams (david.abrahams_at_[hidden])
Date: 2002-04-02 09:52:13

Hi Carlos,

This isn't an appropriate forum for general C++ questions not related to
boost or library development. Please try comp.lang.c++.moderated et al
(or give me a call and ask me for help)

Ciao,
Dave

----- Original Message -----
From: "Carlos Pinto Coelho" <cfspc_at_[hidden]>

>
> Greetings
>
> Is there a way to force the initialization of a global
> object that is defined in a library without having to
> access its members?
>
> I have a class registrar:
>
> // file registrar.hpp
> struct registrar_map;
> struct registrar
> {
>     struct enroll
>     {
>         enroll(std::string const& name)
>         {
>             registrar::add_entry(name);
>         }
>     };
>
>     static void add_entry(std::string const& name);
>     static std::size_t num_entries();
>
>  private:
>     static registrar_map& entries();
> };
>
> And I wish to "enroll" clients by instantiating
> the inner class enroll:
>
> // file: registrar_client.cpp
> #include "registrar.hpp"
>
> registrar::enroll enroll_foo("foo");
>
> I am then testing the number of enrolled elements
> by simply:
> ...
> int main()
> {
>     std::cout << registrar::num_entries() << std::endl;
> }
>
> If I compile registrar_client.cpp, registrar.cpp and main.cpp together
> the number of enrolled elements comes out ok. However, if
> I compile the register_client.cpp in a separate library
> and link it with the remaining code, the number of
> enrolled elements comes out wrong.
>
> I put a breakpoint in registar::add_entry and it is not
> being called which seems to mean that the global
> enroll_foo is not being initialized when it is in the
> library. I have seen this behaviour in gcc-3.0.1,
> metrowerks c++ codewarrior 7.0, and msvc 6.0 sp5.
>
> Is there a way to force the initialization
> of these global variables without having to
> access them explicitly from main? Note that
> the purpose of having the mechanism in the first
> place was to avoid having a central file knowing
> all the clients.
>
> I have also tried making enroll foo a static
> member of a static function in a class in
> registrar_client.cpp but it did not work either.
>
> Thanks in advance,
>
> Carlos Pinto Coelho
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