On Friday 03 June 2005 11:29, Mws wrote:
> imho this is not how to use a singleton at all.
> think about what you do.
I don't see any problem, could you please be elaborate?
> On Friday 03 June 2005 12:25, Filipe Sousa wrote:
> > I have 3 files, the library (singleton.h/.cc) and the main program
> > (main.cc)
> >
> > -- singleton.h --
> > #pragma once
> >
> > #include <iostream>
> >
> > class singleton {
> > public:
> > singleton() { std::cout << __PRETTY_FUNCTION__ << std::endl; }
> > static singleton* instance() {
> > static singleton s;
> > return &s;
> > }
> > };
> >
> > -- singleton.cc --
> > #include "singleton.h"
> >
> > void foo()
> > {
> > singleton::instance();
> > }
> >
> > -- main.cc --
> > #include "singleton.h"
> >
> > int main() {
> > foo();
> > singleton::instance();
> > return 0;
> > }
> >
> > c++ -g -fPIC -Wall -c singleton.cc -o singleton.o
> > c++ -fPIC -shared -Wl,-soname,libsingleton.so -o libsingleton.so
> > singleton.o c++ -Wall -g -c main.cc -o main.o
> > c++ -g -fPIC main.o -o main -rdynamic -L${PWD} -lsingleton
> > -Wl,-rpath,${PWD}
> >
> > fsousa@neptuno ~/tmp/vis $ ./main
> > singleton::singleton()
> >
> > Here, the singleton is only instanciated once as expected, but if I add
> > visibility support to the code
> >
> > -- singleton.h --
> > #pragma once
> >
> > #include <iostream>
> >
> > class __attribute__ ((visibility("default"))) singleton {
> > public:
> > singleton() { std::cout << __PRETTY_FUNCTION__ << std::endl; }
> > static singleton* instance() {
> > static singleton s;
> > return &s;
> > }
> > };
> >
> > __attribute__ ((visibility("default"))) void foo();
> >
> > c++ -g -fPIC -Wall -fvisibility-inlines-hidden -fvisibility=hidden -c
> > singleton.cc -o singleton.o
> > c++ -fPIC -fvisibility-inlines-hidden -fvisibility=hidden -shared
> > -Wl,-soname,libsingleton.so -o libsingleton.so singleton.o
> > c++ -Wall -g -c main.cc -o main.o
> > c++ -g -fPIC main.o -o main -rdynamic -L${PWD} -lsingleton
> > -Wl,-rpath,${PWD}
> >
> > fsousa@neptuno ~/tmp/vis $ ./main
> > singleton::singleton()
> > singleton::singleton()
> >
> > I have more than one instance. Am I doing something wrong?
> >
> > gcc (GCC) 4.0.1-beta20050526 (Gentoo 4.0.1_beta20050526)
> >
> > -- Filipe Sousa
--
Filipe Sousa
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