[CMake] Multiple occurrences of a library on linux (ldd)

[Thiago Crepaldi]

Thanks, Thompson, I will look into BUILD_RPATH and possibly INSTALL_RPATH.

I just learned about `export LD_DEBUG=files` to debug linking issues
on linux. It provides more detail on the ldd output, as below:

18843: file=libc10.so [0];  needed by
/home/dev/miniconda3/datareaders_py37/build/stage/datareader/lib/libdatareader.so
[0]
               (no linking information)
18843: file=libdatareader.so [0];  needed by
subprojects/Build/datareaders_core_test/standalone_gtests [0]
18843: file=libdatareader.so [0];  generating link map
                (linking information)
(...)
18843: file=libc10.so [0];  needed by
/home/dev/miniconda3/datareaders_py37/build/subprojects/Source/pytorch_external/torch/lib/libcaffe2.so
[0]
18843: file=libc10.so [0];  generating link map
               (linking information)
18843: file=libcaffe2.so [0];  needed by
subprojects/Build/datareaders_core_test/standalone_gtests [0]
18843: file=libcaffe2.so [0];  generating link map
               (linking information)

Now I can see that the missing libc10.so is needed by
`libdatareader.so`, which was linked against `standalone_gtests`.

However, RUNPATH for both `libdatareader.so` and `standalone_gtests`
seems to be correct and point to the same torch/lib folder that has
libc10.so:
libdatareader.so:
RUNPATH=/home/dev/miniconda3/datareaders_py37/build/stage/boost/lib:/home/dev/miniconda3/datareaders_py37/build/subprojects/Source/pytorch_external/torch/lib:
standalone_gtests:
RUNPATH=/home/dev/miniconda3/datareaders_py37/build/stage/boost/lib:/home/dev/miniconda3/datareaders_py37/build/subprojects/Source/pytorch_external/torch/lib:/home/dev/miniconda3/datareaders_py37/build/stage/datareader/lib

So, libdatareader.so links to libcaffe2.so which links to libc10.so
successfully; standalone_gtests links to libcaffe2.so which links to
libc10.so successully too; however, when standalone_gtests links to
libdatareader.so, there is a transitive linking issue with
libdatareader.so dependency on libc10.so, like the diagram below:

libdatareader.so ---> libcaffe2.so ---> libc10.so (ok)

standalone_gtests 0 ---> libcaffe2.so ---> libc10.so (ok)
              |
              -------------------> libdatareader.so ---> libc10.so (not found)


Thanks again,
Thiago



On Thu, Feb 14, 2019 at 6:13 AM Thompson, KT <kgt at lanl.gov> wrote:
>
> Thiago,
>
>
>
> I haven’t see the double entry pattern that you mention below.  However, you might want to tell CMake to embed a BUILD_RPATH in your libraries.  This should get around the issue of manually setting LD_LIBRARY_PATH.
>
>
>
> https://cmake.org/cmake/help/latest/prop_tgt/BUILD_RPATH.html?highlight=rpath
>
>
>
> -kt
>
>
>
> From: CMake <cmake-bounces at cmake.org> On Behalf Of Thiago Crepaldi
> Sent: Thursday, February 14, 2019 12:43 AM
> To: cmake at cmake.org
> Subject: [CMake] Multiple occurrences of a library on linux (ldd)
>
>
>
> Hello all,
>
>
>
> After reading CMake Cookbook I have written my first "complex" CMake build script based on the superbuild pattern. I am excited to heave a better understanding on CMake, but I definitely will learn much more from experience and your kind help.
>
> In summary, the standalone google test application `standalone_gtests` publicly links to `libdatareader.so` and to pytorch libraries (`libc10.so`,`libcafee2.so`, `libtorch.so`).
>
> `libdatareader.so` also publicly links to pytorch libraries (I have a theoretical question on why `standalone_gtests` had to link to pytorch libraries if `libdatareader.so` already did, but that can wait).
>
>
>
> Compilation finishes successfully, but when I try to run `standalone_gtests`, it aborts because it cant find `libc10.so`.
>
> After executing `ldd standalone_gtests`, the weird result was that there were two entries for `libc10.so`.
>
> The first one maps to "not found" while the second had the correct path to the library. `libcaffe2.so`, which is also a pytorch library, has a single occurrence with full path.
>
> If I add the (...)/pytorch_external/(...) (see ldd output below) path to LD_LIBRARY_PATH, then everything works, but I would like to avoid this, if possible.
>
>
>
> `ldd ./subprojects/Build/datareaders_core_test/standalone_gtests
>
> libdatareader.so => /home/dev/miniconda3/datareaders_py37/build/stage/datareader/lib/libdatareader.so
>
> libcaffe2.so => /home/dev/miniconda3/datareaders_py37/build/subprojects/Source/pytorch_external/torch/lib/libcaffe2.so
>
> libc10.so => not found
>
> libc10.so => /home/dev/miniconda3/datareaders_py37/build/subprojects/Source/pytorch_external/torch/lib/libc10.so
>
> (...)`
>
>
>
> Have anyone seen multiple entries for the same library on ldd before? Why is that? Is it because `standalone_gtests` links to libc10.so and to `libdatareader.so`, which in turn also links to `libc10.so`?
>
> Both CMakeLists.txt (libdatareader and standalone_gtests) succeeds at find_package(Torch REQUIRED QUIET) commands (${TORCH_LIBRARY} returns the correct path).
>
>
>
>
>
> I run the same build on my Mac and everything works fine, so that is confined to linux environment. I have destroyed my conda environment and performed multiple clean builds in the process and no luck :(
>
> Hoping this was some sort of ldconfig issue, I tried `sudo ldconfig` and `sudo rm /etc/ld.so.cache`, but that doesn't fix it.
>
>
>
> Any ideas?
>
>
>
> best regards,
>
> Thiago



-- 
Thiago