CMake refuses to link shared library - c++

Question

Probably the error is trivial for CMake experts but I seem to be blind to it. I've tried two approaches.
I have a library written in C and compiled using gcc 9.4.0 as both, static and dynamic library. I've compiled the library apart and it successfully builds and links against its main.c to produce an executable using a Makefile. When I do nm -D mylib.so I get all the symbols and functions I need.
Now, I am trying to use this library with ROS (meaning build and link with CMake) but the program fails to link. I've tried both approaches: use the library as is, and re-build the library using CMake. Both fail. For the sake of keeping the example short I've removed the lines used by catkin that basically tell CMake to link against all ROS infrastructure. Suffices to say that the main.cpp of the target (my_node) consumes a void* CreateEnvironment(); function from the library which is not found (same with any other function). Say:
#include <mylib/mylib.h>
int main(int argc, char** argv){
foo();
return 0;
}
void foo(){
void ptr = CreateEnvironment();
}
Approach #1: Use pre-built library (preferred)
With CMake it refuses to link. CMakeLists.txt as follows:
cmake_minimum_required(VERSION 3.0.2)
find_library(
MY_LIB
NAME mylib
PATHS "${PROJECT_SOURCE_DIR}/lib"
NO_DEFAULT_PATH # Can add or remove this, no difference
)
add_library(mylib SHARED IMPORTED)
set_target_properties(mylib PROPERTIES IMPORTED_LOCATION "${MY_LIB}")
add_executable(my_node src/main.cpp)
target_link_libraries(my_node mylib ${catkin_LIBRARIES})
It runs:
/usr/bin/c++ -rdynamic CMakeFiles/…/main.cpp.o -o /home/…/clips_node -Wl,-rpath,/home/…/lib:/opt/ros/noetic/lib /home/…/lib/libmylib.so […]
/usr/bin/ld: CMakeFiles/…/main.cpp.o: in function `foo()':
main.cpp:(.text+0x11): undefined reference to `CreateEnvironment()'
Approach #2: Build library with CMake
Tried this approach thinking maybe the library I have was built with different standard, or not all symbols were exported, or exports were incompatible or whatever. A build made by the same system and forcing C++ rather than C should make it linkable... but did not.
Once again, the SO is created and all symbols are visible with nm -D. It is the linking with the executable target what fails.
cmake_minimum_required(VERSION 3.0.2)
## Build library
SET(MYLIB_INCLUDE_DIR "${PROJECT_SOURCE_DIR}/include/mylib")
AUX_SOURCE_DIRECTORY(${PROJECT_SOURCE_DIR}/src/mylib MYLIB_SOURCES)
add_library(mylib ${MYLIB_SOURCES})
target_include_directories(mylib PRIVATE ${MYLIB_INCLUDE_DIR})
set_target_properties(mylib PROPERTIES
LINKER_LANGUAGE "CXX"
ENABLE_EXPORTS 1
)
## Build node
add_executable(my_node src/main.cpp)
target_include_directories(my_node PUBLIC ${MYLIB_INCLUDE_DIR})
target_link_libraries(my_node mylib ${catkin_LIBRARIES})
Output is almost identical to that of the Approach #1, only the path of the library changes.
What else have I tried
Changing the order of the elements in target_link_libraries
Changing PRIVATE for PUBLIC
Add -lmylib to target_link_libraries
Add the full path to libmylib.so to target_link_libraries
Replace the shared object with a static library
So far it seems that the shared object is passed to the linker but, for some reason, it refuses to link the file. With a Makefile I know I can change the order since some libraries must be prepended and some appended, but CMake seems to be all automagic and I failed to find the error so far.