From: Pascal Bourguignon <pjb@informatimago.com>
Reply-To: <pjb@informatimago.com>
To: yjchenx@hotmail.com
CC: help-gnustep@gnu.org
Subject: Re: Link to C++ library
Date: Wed, 11 Sep 2002 01:24:02 +0200 (CEST)
> From: "Yen-Ju Chen" <yjchenx@hotmail.com>
> Date: Tue, 10 Sep 2002 17:55:15 -0400
>
>
> Which version of GCC are you using ? I use 3.0.4.
I still have 2.95.3:
[pascal@thalassa]$ g++ --version
2.95.3
> How can you compile .c using g++ and .m using gcc
> in the same GNUmakefile ?
Actually, when specifying CC=g++ in GNUmakefile, the makefile system
of GNUstep will use g++ to compile everything, both .c and .m files.
> If I use CC=gcc++ at the beginning,
> it will complain that g++ unrecognize option '-MP'
> and cc1obj invalide option '-fconstant-string-class=NSConstantString'
> Here is what I have:
>
> g++ main.m -c \
> -MMD -MP -DGNUSTEP -DGNUSTEP_BASE_LIBRARY=1 ...
> -o shared_objc/ix86/freebsd/gnu-gnu-gnu/main.o
> ...
>
> So I use CC=gcc to get the .o file first.
> Then use CC=g++ again, I got the error in previous message...
>
> So weird... need to look into it....
The fact is, when you want to link C++ code with C (or Objective-C)
code, you have to take care of the name mangling done by the C++
compiler. One way to do it is to use only a C++ compiler, therefore
you only generate mangled names (for C and C++ objects) and there's no
linking problem. Another option is to use extern "C"{ ... } in C/C++
code. See attached files.
> Yen-Ju
>
> >From: Pascal Bourguignon <pjb@informatimago.com>
> >Reply-To: <pjb@informatimago.com>
> >To: yjchenx@hotmail.com
> >CC: help-gnustep@gnu.org
> >Subject: Re: Link to C++ library
> >Date: Tue, 10 Sep 2002 23:28:28 +0200 (CEST)
> >
> > > From: "Yen-Ju Chen" <yjchenx@hotmail.com>
> > > Date: Tue, 10 Sep 2002 16:55:52 -0400
> > >
> > >
> > > Thanx a lot. It helps.
> > > But can I directly link Objective-C to C++ throught
> > > the C interface which the C++ library offers ?
> > >
> > > After apply the CC=g++, the error message becomes
> > >
> > > .../libgnustep-base.so: undefined reference to
'__objc_msg_forward'
> > > .../libgnustep-base.so: undefined reference to
'__objc_msg_thread_add'
> > > .../libgnustep-base.so: undefined reference to
> >'__objc_msg_thread_remove'
> > >
> > > Or do I need to write a C library as the bridge between
Objective-C
> >and
> > > C++ ?
> >
> >You seem to be missing the Objective-C runtime. I still use a GNUstep
> >some months old, but it's makefiles automatically cite -lobjc on the
> >link line. I have something like:
> >
> > g++ -rdynamic \
> > -o MyApp.app/ix86/linux-gnu/gnu-gnu-gnu/MyApp \
> > shared_obj/ix86/linux-gnu/gnu-gnu-gnu/MyObjects.o ... \
> > -L/home/pascal/GNUstep/Libraries/ix86/linux-gnu/gnu-gnu-gnu \
> > -L/home/pascal/GNUstep/Libraries/ix86/linux-gnu \
> > -L/local/gnustep/Local/Libraries/ix86/linux-gnu/gnu-gnu-gnu \
> > -L/local/gnustep/Local/Libraries/ix86/linux-gnu \
> > -L/local/gnustep/Network/Libraries/ix86/linux-gnu/gnu-gnu-gnu \
> > -L/local/gnustep/Network/Libraries/ix86/linux-gnu \
> > -L/local/gnustep/System/Libraries/ix86/linux-gnu/gnu-gnu-gnu \
> > -L/local/gnustep/System/Libraries/ix86/linux-gnu \
> > -L/local/gnustep/System/Libraries/ix86/linux-gnu \
> > -lgnustep-gui -lgnustep-base -lobjc \
> > -lz -lcallback -lavcall -lxml2 -lz -lm -lgmp -lpthread -ldl -lm
\
> > $(MyApp_OTHER_LIBRARIES)
> >
> >
> > > Thanx again.
> > >
> > > Yen-Ju
> > >
> > > >From: Pascal Bourguignon <pjb@informatimago.com>
> > > >Date: Tue, 10 Sep 2002 22:38:13 +0200 (CEST)
> > > > > From: "Yen-Ju Chen" <yjchenx@hotmail.com>
> > > > > Date: Tue, 10 Sep 2002 15:52:52 -0400
> > > > >
> > > > > I try to use the id3lib (http://www.id3lib.org), which is a
> > > > > C++ library, but offer the C interface. But I met a problem
> > > > > about linking between id3lib and standard C++ library. Is it
> > > > > possible to use such C++ library with C interface in GNUstep ?
> > > >
> > > >I do link routinely C++ libraries into GNUstep /
Objective-C
> > > >applications without any problem, passing thru a C interface.
> > > >
> > > >Here is an example of GNUmakefile I used lately. The only
notable
> > > >thing is the use of the g++ compiler (CC=g++) to compile
the
> > > >MyCppLibCalls.c file, which contains only simple C functions
each
> > > >sending a message to a C++ object from libMyCppLib.a, which
is a
> > > >library of C++ objects.
--
__Pascal_Bourguignon__ http://www.informatimago.com/
----------------------------------------------------------------------
The name is Baud,...... James Baud.
<< stuff.h >>
<< stuff.h__ >>
<< stuff.c__ >>
<< main.m >>
<< Makefile >>
<< compile.log >>