Finally I found the problem is
that the id3lib is compiled by gcc 2.9.x,
and GNUstep is by gcc 3.0.4.
After recompiling id3lib with gcc 3.0.4
and use CC=g++ for both .c and .m,
it works so far.
Thanx for all your help
Yen-Ju
>From: Pascal Bourguignon <[EMAIL PROTECTED]>
>Reply-To: <[EMAIL PROTECTED]>
>To: [EMAIL PROTECTED]
>CC: [EMAIL PROTECTED]
>Subject: Re: Link to C++ library
>Date: Wed, 11 Sep 2002 01:24:02 +0200 (CEST)
>
> > From: "Yen-Ju Chen" <[EMAIL PROTECTED]>
> > 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 <[EMAIL PROTECTED]>
> > >Reply-To: <[EMAIL PROTECTED]>
> > >To: [EMAIL PROTECTED]
> > >CC: [EMAIL PROTECTED]
> > >Subject: Re: Link to C++ library
> > >Date: Tue, 10 Sep 2002 23:28:28 +0200 (CEST)
> > >
> > > > From: "Yen-Ju Chen" <[EMAIL PROTECTED]>
> > > > 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 <[EMAIL PROTECTED]>
> > > > >Date: Tue, 10 Sep 2002 22:38:13 +0200 (CEST)
> > > > > > From: "Yen-Ju Chen" <[EMAIL PROTECTED]>
> > > > > > 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 >>
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