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

[Yubin Ruan]

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