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

[Thiago Crepaldi]

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
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