libstdc++.so.0.29 contains undefined reference to libiconv

[Jonathan Wakely]

On Thu, 7 Apr 2022, 14:21 Yubin Ruan, <ablacktshirt@gmail.com> wrote:

> On Thu, Apr 7, 2022 at 5:02 PM Jonathan Wakely <jwakely.gcc@gmail.com>
> wrote:
> >
> >
> >
> > On Thu, 7 Apr 2022, 03:38 Yubin Ruan via Libstdc++, <
> libstdc++@gcc.gnu.org> wrote:
> >>
> >> Hi,
> >>
> >> I compile GCC 11.2 and get a libstdc++.so.6.0.29 (installed in
> >> "/usr/local/mygcc/lib64/") but this shared lib contains undefined
> >> reference to libiconv_*.
> >>
> >> When I compile a hello world program using gcc11.2, I get the following
> error:
> >>
> >> > /usr/local/mygcc/bin/g++ -Wall -std=c++17 hw.cc -o hw
> >>
> /usr/local/mygcc/bin/../lib/gcc/x86_64-pc-linux-gnu/11.2.0/../../../../lib64/libstdc++.so:
> >> undefined reference to `libiconv'
> >>
> /usr/local/mygcc/bin/../lib/gcc/x86_64-pc-linux-gnu/11.2.0/../../../../lib64/libstdc++.so:
> >> undefined reference to `libiconv_close'
> >>
> /usr/local/mygcc/bin/../lib/gcc/x86_64-pc-linux-gnu/11.2.0/../../../../lib64/libstdc++.so:
> >> undefined reference to `libiconv_open'
> >> collect2: error: ld returned 1 exit status
> >>
> >> Adding a "-liconv" flag will help this program compile.
> >>
> >> From ldd's output, the libstdc++.so does not has any dynamic reference
> >> to libiconv;
> >>
> >>   > ldd /usr/local/mygcc/lib64/libstdc++.so.6.0.29
> >>           linux-vdso.so.1 =>  (0x00007ffce1fea000)
> >>           libm.so.6 => /lib64/libm.so.6 (0x00007fefc74b8000)
> >>           libc.so.6 => /lib64/libc.so.6 (0x00007fefc70e9000)
> >>           /lib64/ld-linux-x86-64.so.2 (0x00007fefc7bd1000)
> >>           libgcc_s.so.1 =>
> >> /usr/local/$INSTALL_PREFX/lib64/libgcc_s.so.1 (0x00007fefc6ed1000)
> >>
> >> But from nm 's output, there are indeed undefined reference to libiconv*
> >>
> >>   > nm -D /usr/local/mygcc/lib64/libstdc++.so.6.0.29 |grep -i iconv
> >>                    U libiconv
> >>                    U libiconv_close
> >>                    U libiconv_open
> >>
> >> I already have libiconv installed under /usr/local when compiling
> >> GCC11.2, but this does not seems to help;
> >
> >
> > It doesn't help because that is the cause of the problem.
> >
> > Glibc defines the iconv routines that libstdc++ needs, and so you should
> not use libiconv on Linux systems using Glibc.
>
>
> So remove all libiconv libs and headers, and recompile GCC will be
> fine?


Yes.

Does it require any more configuration?
>

No.



> How do I make sure that the configuration is correct?
>

Check the config.log in the $TARGET/libstdc++-v3 build directory, it think
it should say where iconv is found.




>
> >> And by the way, libiconv seems to only provide dynamic lib; there is
> >> no libiconv.a;
> >>
> >>
> >> Previously I have GCC10.2 compiled & installed. The libstdc++.so.0.28
> >> also contains undefined ref to libiconv*
> >>
> >>   > nm -D /usr/local/mygcc/lib64/libstdc++.so.6.0.28 |grep -i iconv
> >>                    U libiconv
> >>                    U libiconv_close
> >>                    U libiconv_open
> >>
> >> but compiling with libstdc++.so.6.0.28 does NOT require "-liconv".
> >>
> >> So, is there anything that I missed when compiling GCC11.2 which can
> >> remove unnecessary dependency of libiconv ?
> >>
> >> Thanks,
> >> Yubin
>