[bt-devel] namespace problems

[Joachim Ansorg]

Thank you for your help!

It worked pretty well!

Joachim

> Joachim,
>
> If you have a constant in C++ that is shared across multiple translation
> units (i.e. source files), you must declare it in the header file, but
> define it in the source file.
>
> i.e. in the header file, you will have:
>
> extern const QString tooltip;
>
> while in the source file you will have:
>
> const QString tooltip = makeToolTip( i18n("Clear the printing queue") );
>
> This is because you want the symbol to be shared among many source
> files, so you have to put a declaration in the header file, but the C++
> "One Definition Rule" states that a symbol can only be defined once,
> across all translation units, and so you may not put the definition in a
> header file - only a source file.
>
> You will obviously need the namespace structure reflected in both the
> source file and the header file.
>
> Yes, it is a little annoying having to do this, and it does make one
> wish that C++ had a real module system, but it doesn't, so we have to
> live with what we've got.
>
> Let me know if you need anymore help.
>
> -David.
>
> On Sun, 2002-10-20 at 06:34, Joachim Ansorg wrote:
> > David White, I think this eMail is especially for you because you know
> > the namespaces well.
> >
> > You pointed me into the direction to use namespaces for the treelike
> > structure I wanted.
> >
> > Now I have something like
> >
> > namespace CResMgr {
> >   inline const QString makeToolTip( const QString& text ) {
> >     return text;
> >   };
> >   inline const QString makeWhatsThis( const QString& title, const
> > QString& description )  {
> >     return
> > QString::fromLatin1("<center><B>%1</B></center><HR>%2").arg(title).arg(de
> >scription); };
> >
> >   namespace mainMenu { //Main menu
> >     namespace file { //Main menu->File
> >       namespace clearQueue {
> >         const QString tooltip     = makeToolTip( i18n("Clear the printing
> > queue") );
> >         const QString whatsthis   = makeWhatsThis( tooltip, i18n("Clear
> > the print queue of BibleTime. All items will be removed from the list and
> > the print button will be disabled.") );
> >         const QString icon        = QString::fromLatin1("queue");
> >         const KShortcut accel     = KShortcut();
> >         const char* actionName    = "fileClearQueue_action";
> >       }
> >       namespace print { //a standard action
> >         const QString tooltip     = makeToolTip( i18n("Open the
> > printerdialog") );
> >         const QString whatsthis   = makeWhatsThis( tooltip, i18n("Open
> > the printer dialog of BibleTime.  Here you can edit the print queue and
> > assign styles to the items.") );
> >       }
> >       namespace quit { //a standard action
> >         const QString tooltip     = makeToolTip( i18n("Close BibleTime")
> > ); const QString whatsthis   = makeWhatsThis( tooltip, i18n("Close
> > BibleTime and save the settings.") );
> >       }
> >     }
> > }
> > etc.
> >
> > But compiling BibleTime with this header included in two or more places I
> > get the following compiler warnings about multiple symbol definitions:
> >
> > ./frontend/searchdialog/libsearchdialog.a(csearchdialog.o)(.data+0x0):
> > multiple definition of `CResMgr::mainMenu::file::clearQueue::actionName'
> > bibletime_init.o(.data+0x0): first defined here
> > ./frontend/searchdialog/libsearchdialog.a(csearchdialog.o)(.data+0x4):
> > multiple definition of
> > `CResMgr::mainMenu::view::showMainIndex::actionName'
> > bibletime_init.o(.data+0x4): first defined here
> > ./frontend/searchdialog/libsearchdialog.a(csearchdialog.o)(.data+0x8):
> > multiple definition of `CResMgr::mainMenu::mainIndex::search::actionName'
> > bibletime_init.o(.data+0x8): first defined here
> > ./frontend/searchdialog/libsearchdialog.a(csearchdialog.o)(.data+0xc):
> > multiple definition of
> > `CResMgr::mainMenu::window::loadProfile::actionName'
> > bibletime_init.o(.data+0xc): first defined here
> >
> > How can I avoid these problems? I have no idea.
> > Thank you very much for any help!
> > --
> > Joachim Ansorg
> > www.bibletime.de
> > www.ansorgs.de

-- 
Joachim Ansorg
www.bibletime.de
www.ansorgs.de