Re: How to set the QT_DLL macro?

On Thursday 21 April 2005 23:51, Angus Leeming wrote:
> Ralf Habacker wrote:
> >>frontends/.libs/libfrontends.a(QBibitemDialogBase.o)(.text+0x583): In
> >>function `_ZNK6QGList5countEv':
> >>/home/angus/lyx/13x/build-mingw-xcompile/src/frontends/qt2/ui/QBibitemDia
> >>logBase.C: variable 'vtable for QSpacerItem' can't be auto-imported.
> >> Please read the documentation for ld's --enable-auto-import for details.
> >
> > This problem is fixed by adding the following line to
> > mkspecs\win32-g++\qmake.conf
> > QMAKE_LFLAGS            = -Wl,--enable-runtime-pseudo-reloc
>
> Hmmmm, not entirely true. I need to pass this flag to the linker, but I
> also need to pass QT_DLL to the compiler. Looking at the explicit echo of
> the compiler call when building the Qt libs, I see that you pass QT_DLL
> directly to the compiler too:
>
> i386-mingw32-g++ -c -Wall -O2 -fno-exceptions -fno-rtti
> -DUNICODE -DQT_DLL -DQT_NO_DEBUG
> -I"../interfaces" -I"../../../include" -I".moc/release-shared/"
> -I"/home/angus/mingw-xcompile/qt3/mkspecs/win32-g++-cross"
> -o .obj/release-shared/editor.o editor.cpp
>
> So, I guess that I'm doing the right thing here. I just need to work out
> how to tell automake to set this flag only when building on (or
> x-compiling for) Windows.

... which is added to the Makefile by qmake 

> > On cygwin I'm using the following switch, which may help to prevet seg
> > faults. It requires a relink of the qt-3.dll
> > QMAKE_LFLAGS            =
> > -Wl,--script,$(QTDIR)/mkspecs/cygwin-g++/i386pe.x-no-rdata
>
> Now that is very, very interesting. I'll try it out. (Am I correct to say
> that only the dll needs to be re-linked?

any executable, which is based on the dll too, because it changes the internal 
address layout of an application. 

> > add a -shared option to configure or add the term 'shared' to
> > .qmake.cache's CONFIG line  (qmake/generators/win32/mingw-make.cpp line
> > 406)
>
> I'm using an automake generated Makefile to build LyX, so I'm going to need
> to understand more about what Qt's "configure -shared" does.
>
I see, QT_DLL is added to a Makefile by qmake based on the current 
configuration. 

> I see that when linking designer.exe you pass a bunch of flags to the
> linker:
>
> i386-mingw32-g++ -Wl,-enable-stdcall-fixup -Wl,-enable-auto-import
> -Wl,-enable-runtime-pseudo-reloc -Wl,-s -Wl,-subsystem,windows -e
> __Z19QtWinMainCRTStartupv
> -o ../../../bin/designer.exe .obj/release-shared/main.o
>
> I'm currently building LyX as a console app, so guess that I don't need the
>     -Wl,-subsystem,windows -e __Z19QtWinMainCRTStartupv
> right?
>
> We've already discussed "-Wl,-enable-auto-import" and
> "-Wl,-enable-runtime-pseudo-reloc".
>
> What do "-Wl,-enable-stdcall-fixup" and "-Wl,-s" do?
>
> >>ps, linking against the qt3.dll is still excrutiatingly slow. Compilation
> >>is far quicker, but the final link still takes ~20 minutes :(
> >
> > This depends on the time of used machine. On a suse linux server system
> > with Xeon 2.6GHz and sata harddisc linking requires about 30-40 seconds.
>
> Linking takes something similar here when I'm linking qt3.dll or am linking
> against the Qt examples programs etc, but expands to 20 minutes when
> linking LyX (a *much* bigger app). This is linking against the qt3.dll.
> I'm using a 2.7GHz machine running Fedora Core 3. Memory usage when
> linking is 70%, so it's not a swap issue.

This is a linker issue. 

 However, Michael Schmitt reports
> that linking reduces to less than a minute when linking statically.

Yes

> >>pps, I may have compiled lyx, but trying to start it up on Windows
> >>results in an error dialog "The application failed to initialise itself
> >>correctly" :(
> >
> > I've heard of similar seg faults with mingw. Do you have tried to link
> > it static ?
>
> Not yet. Actually, what flags do I need to pass to i386-mingw32-g++ to
> ensure it links against libqt3.a not qt3.dll? I tried to just hide qt3.dll
> before linking on mingw/msys yesterday and the bloody thing still linked
> against it :)

this require reconfiguring using the -static option.  

> I'll also try out your magic script above.
> And passing the linker the same set of flags as you use.
the i386pe.x-no-rdata stuff may help to fix segfaults because it is a 
workaround documented at 
http://www.cygwin.com/ml/cygwin/2004-10/msg01052.html

> Lots and lots to try still.
>
> First, I'll wait for the qt lib to finish building in its entirety and will
> try out the examples. Currently we're at examples/dirview...
>
Ralf