How gnu linker choose which dynamic library to link - c++

Question

I was using gpgpu-sim, a GPU simulator, to conduct researches. There are several .so files in my own folder:
And there are some alternatives .so in Nvidia's cudart lib folder:
And there are some .o files and need to be linked with libcudart.so, when I type in the command:
g++ -L "Path/to/MyFolder" -l cudart *.o
I hope the generated a.out would link to libcudart.so, but it just linked to a strange so file:
libcudart_gpgpu-sim_git-commit-6443f21d433f1b642003867e56fe1f54efae55e3_modified_0.so => not found
And when I typed this code:
g++ -L "Path/to/NvidiaFolder" -l cudart *.o
The program can sussessfully find libcudart.so.9 in my LD_LIBRARY_PATH folder,but it shows that the version can't match!:
./a.out: /path/to/myFolder/libcudart.so.9.0: version `libcudart.so.9.0'not found (required by ./a.out)
Can anybody tell me how ld works and how to solve those problems?

Answer 1

I finally find out the reason.
if you use this code to link objects to generate a shared library:
g++ -shared -Wl,-soname,libNAME_A.so -o libNAME_B.so
then, if some on is trying to link NAME_B.so using:
g++ <INPUT> -lNAME_B -o <OUTPUT>
the output will finally look for libNAME_A.so.
refer to g++ man page:
-Wl,option
Pass option as an option to the linker. If option contains commas,
it is split into multiple options at the commas. You can use this
syntax to pass an argument to the option. For example,
-Wl,-Map,output.map passes -Map output.map to the linker. When
using the GNU linker, you can also get the same effect with
-Wl,-Map=output.map.
and for ld man page:
-soname=name
When creating an ELF shared object, set the internal DT_SONAME
field to the specified name. When an executable is linked with a
shared object which has a DT_SONAME field, then when the executable
is run the dynamic linker will attempt to load the shared object
specified by the DT_SONAME field rather than the using the file
name given to the linker.

Answer 2

There is nothing to do with CUDA here, it's just a linking and runtime environment setup problem.
The ld linker searches for objects and library archives following the order specified by -L option parameters, and only after into default system directories. The linker will link the object code that first match this search.
At runtime, if you linked against dynamic libraries (.so files) you will need to properly define the LD_LIBRARY_PATH environment variable with a list of paths to look for dynamic libraries, separated by colon (:).
So if you link to your objects using libraries from your local path (assuming you are looking for libcudart.so):
g++ -o myprogram *.o -L "/Path/to/myFolder" -lcudart
you need to set LD_LIBRARY_PATH as follows before running your program:
export LD_LIBRARY_PATH="/Path/to/myFolder:$LD_LIBRARY_PATH"
./myprogram
I hope this help and clarify your understanding. Frankly I don't understand the origin of your libcudart_gpgpu-sim_git-commit match