Re: the initialization of the main program and its loading DLL
On Nov 12, 5:06 am, blackbiscuit <infozyzh...@gmail.com> wrote:
Now in my current developing project, I have defined a global object
in the main program . In dlls, there are also some static object whose
constructor will use the global object in the main program. But the
problem is always the initialization of the dll is prior to the main
program. How can I do if I wanna the main program be initialized
first?
A standard portable solution for this problem is to have an explicit
initialisation (and often deinitialisation) function for your .dll
or .so. This function initialises the global state of the shared
library. Following this approach you don't depend on any platform
specific initialisation routines like DllMain or gcc constructor
functions.
Example:
// library.h
#include <memory>
#include <iosfwd>
struct Library
{
virtual ~Library() = 0;
virtual void foo() = 0;
virtual void bar() = 0;
// initialisation arguments
struct Args {
// arguments as needed, for example:
std::ostream* log;
};
// the initialisation routine / factory function
// only this functions needs to be exported
// (for .dll it should be __declspec(dllexport/import)
static std::auto_ptr<Library> open(Args const&);
};
// main application / library client
#include "library.h"
#include <iostream>
int main()
{
// open / initialise library
Library::Args lib_args = { &std::cout };
std::auto_ptr<Library> lib(Library::open(lib_args));
// use the library
lib->foo();
lib->bar();
// done with the library
// std::auto_ptr destructor calls Library::~Library
// which deinitialises the library
}
// library.cpp
#include <ostream>
#include "library.h"
namespace {
struct LibraryImpl : Library
{
Args args; // library global state
LibraryImpl(Args a) : args(a)
{
// do required initialisation here
*args.log << "Library has been initialised\n";
}
~LibraryImpl()
{
// do required deinitialisation here
*args.log << "Library has been deinitialised\n";
}
void foo() { *args.log << "Library::foo()\n"; }
void bar() { *args.log << "Library::bar()\n"; }
};
}
Library::~Library() {}
std::auto_ptr<Library> Library::open(Args const& args)
{
return std::auto_ptr<Library>(new LibraryImpl(args));
}
--
Max