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

[Yubin Ruan]

FYI, I compile GCC11.2 with

    > ../src/gcc-%{VERSION}/configure --enable-languages=c,c++
--disable-multilib --prefix=/usr/local/mygcc

on a CentOS7.2 with intel x64

On Thu, Apr 7, 2022 at 10:37 AM Yubin Ruan <ablacktshirt@gmail.com> 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;
> 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