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Date: Thu, 14 Aug 2008 12:21:00 -0000
Subject: Re: External variables in shared library constructor code
From: Eljay Love-Jensen <eljay@adobe.com>
To: smokyboy <smokyboy0@lycos.com>, GCC-help <gcc-help@gcc.gnu.org>
Message-ID: <C4C985B3.7D24%eljay@adobe.com>
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Hi smokyboy,

There are no guarantees as to the order of initialization in the C/C++
standards.

Some compilers provide initialization ordering extensions, but those are
usually within a package (such as a DLL), and not across packages (DLLs).

One solution is to hide the external variable within a global function call:

// C++
extern int& GlobalIntValue();

// C
extern int* GlobalIntValue();

That way, the function call can guarantee the variable is initialized on
demand, and that the global variable is only initialized once.

The routine will look like this, in C++:

int& GlobalIntValue()
{
  static int foo = 77;
  return foo;
}

And in C:

int* GlobalIntValue()
{
  static int foo = 77;
  return &foo;
}

HTH,
--Eljay