Re: g++ libstdc++ linker question.

[Jonathan Wakely <jwakely.gcc@gmail.com>]

On 30 April 2012 13:39, F. Heitkamp wrote:
> People will tell me to ask on matplotlib list but I believe this a more
> generic GNU C++ question.
> I have been trying to run matplotlib that I built from source on my linux
> from scratch like box.
>
> When I try to run an example I get:
>
> bash-4.2$ python2.6 matplotlib-ex1.py
> Traceback (most recent call last):
>  File "matplotlib-ex1.py", line 13, in <module>
>    import matplotlib.pyplot as plt
>  File "/usr/lib/python2.6/site-packages/matplotlib/pyplot.py", line 23, in
> <module>
>    from matplotlib.figure import Figure, figaspect
>  File "/usr/lib/python2.6/site-packages/matplotlib/figure.py", line 16, in
> <module>
>    import artist
>  File "/usr/lib/python2.6/site-packages/matplotlib/artist.py", line 6, in
> <module>
>    from transforms import Bbox, IdentityTransform, TransformedBbox,
> TransformedPath
>  File "/usr/lib/python2.6/site-packages/matplotlib/transforms.py", line 34,
> in <module>
>    from matplotlib._path import affine_transform
> ImportError: /usr/lib/python2.6/site-packages/matplotlib/_path.so: undefined
> symbol:
> _ZSt16__ostream_insertIcSt11char_traitsIcEERSt13basic_ostreamIT_T0_ES6_PKS3_i
>
> I see this symbol is in 32 bits libstdc++ library, but does not seem to
> appear in 64 bits versions.

Right, the equivalent symbol in the 64-bit lib ends in _l instead of _i

> bash-4.2$ ldd /usr/lib/python2.6/site-packages/matplotlib/_path.so
>    linux-gate.so.1 =>  (0xffffe000)
>    libpython2.6.so.1.0 => /usr/lib/libpython2.6.so.1.0 (0xf74f7000)
>    libgcc_s.so.1 => /lib/libgcc_s.so.1 (0xf74de000)
>    libpthread.so.0 => /lib/libpthread.so.0 (0xf74c4000)
>    libc.so.6 => /lib/libc.so.6 (0xf7367000)
>    libdl.so.2 => /lib/libdl.so.2 (0xf7362000)
>    libutil.so.1 => /lib/libutil.so.1 (0xf735e000)
>    libm.so.6 => /lib/libm.so.6 (0xf7338000)
>    /lib/ld-linux.so.2 (0xf77d1000)
>
> libstdc++ is not shown as being linked with _path.so
>
> Any thoughts?

Is _path.so a 32-bit or 64-bit library?  From the missing symbol I'm
asuming 32-bit.

It would appear it wasn't correctly linked, so its dependency on
libstdc++.so isn't recorded in the library by a DT_NEEDED entry.

Does it help if you tell the dynamic linker to preload libstdc++.so?

LD_PRELOAD=/usr/lib/libstdc++.so python2.6 matplotlib-ex1.py