cmake cross-compile for raspberry pi - cmake

Question

I am cross-compiling a library (ORBSLAM3) on pc using /usr and /lib
from rpi4 (After using rsync). And I put them in a folder named "rootf".The prerequisite libraries have been installed before so they are now in ~/rootf/usr and ~/rootf/lib. I need to compile ORBSLAM3 using ~/rootf/ as the root.
The thing is I am not familiar with cmake so I have been struggling for a while.
The process of compiling is this:
using Toolchain-rpi.cmake for the CMakeLists.txt on the top level of ORBSLAM3.
In CMakeLists.txt, it finds pangolin by find_package(Pangolin REQUIRED)
find_package() is actually doing the right.
It successfully finds
/home/ethan/raspberrypi/rootfs/usr/local/lib/cmake/Pangolin/PangolinTargets.cmake
The CMAKE_PREFIX_PATH in this CMakeLists.txt is right, which is
/home/ethan/raspberrypi/rootfs/usr/local/lib;/home/ethan/raspberrypi/rootfs/usr/lib/arm-linux-gnueabihf
After I uninstall pangolin on ubuntu, I get this:
CMake Error at /home/ethan/raspberrypi/rootfs/usr/local/lib/cmake/Pangolin/PangolinTargets.cmake:80 (message):
The imported target "pangolin" references the file
"/usr/local/lib/libpangolin.so"
but this file does not exist. Possible reasons include:
* The file was deleted, renamed, or moved to another location.
Since Pangolin was originally installed on board, so on board libpangolin.so is at /usr/local/lib/libpangolin.so.
I guess when I use PangolinTargets.cmake, it is doing the same thing.
I output CMAKE_SYSROOT,CMAKE_PREFIX_PATH,_IMPORT_PREFIX in PangolinTargets.cmake. It's what I expect.
CMAKE_SYSROOT = /home/ethan/raspberrypi/rootfs
CMAKE_PREFIX_PATH = ;/home/ethan/raspberrypi/rootfs/usr/local/lib;/home/ethan/raspberrypi/rootfs/usr/lib/arm-linux-gnueabihf
_IMPORT_PREFIX = /home/ethan/raspberrypi/rootfs/usr/local
Even if I add /home/ethan/raspberrypi/rootfs as prefix to the below paths, nothing changed.
set_target_properties(pangolin PROPERTIES
INTERFACE_INCLUDE_DIRECTORIES "/usr/include;/usr/include;/usr/include;/usr/local/include/eigen3;${_IMPORT_PREFIX}/include"
INTERFACE_LINK_LIBRARIES "rt;pthread;/usr/lib/arm-linux-gnueabihf/libGL.so;/usr/lib/arm-linux-gnueabihf/libGLU.so;
INTERFACE_SYSTEM_INCLUDE_DIRECTORIES "/usr/include;/usr/include;/usr/include;/usr/local/include/eigen3"
)
Here is the content of PangolinTargets.cmake. I am not sure which parts leads to searching only /usr. Thanks all.
# Generated by CMake
if("${CMAKE_MAJOR_VERSION}.${CMAKE_MINOR_VERSION}" LESS 2.5)
message(FATAL_ERROR "CMake >= 2.6.0 required")
endif()
cmake_policy(PUSH)
cmake_policy(VERSION 2.6)
#----------------------------------------------------------------
# Generated CMake target import file.
#----------------------------------------------------------------
# Commands may need to know the format version.
set(CMAKE_IMPORT_FILE_VERSION 1)
# Protect against multiple inclusion, which would fail when already imported targets are added once more.
set(_targetsDefined)
set(_targetsNotDefined)
set(_expectedTargets)
foreach(_expectedTarget pangolin)
list(APPEND _expectedTargets ${_expectedTarget})
if(NOT TARGET ${_expectedTarget})
list(APPEND _targetsNotDefined ${_expectedTarget})
endif()
if(TARGET ${_expectedTarget})
list(APPEND _targetsDefined ${_expectedTarget})
endif()
endforeach()
if("${_targetsDefined}" STREQUAL "${_expectedTargets}")
unset(_targetsDefined)
unset(_targetsNotDefined)
unset(_expectedTargets)
set(CMAKE_IMPORT_FILE_VERSION)
cmake_policy(POP)
return()
endif()
if(NOT "${_targetsDefined}" STREQUAL "")
message(FATAL_ERROR "Some (but not all) targets in this export set were already defined.\nTargets Defined: ${_targetsDefined}\nTargets not yet defined: ${_targetsNotDefined}\n")
endif()
unset(_targetsDefined)
unset(_targetsNotDefined)
unset(_expectedTargets)
# Compute the installation prefix relative to this file.
get_filename_component(_IMPORT_PREFIX "${CMAKE_CURRENT_LIST_FILE}" PATH)
get_filename_component(_IMPORT_PREFIX "${_IMPORT_PREFIX}" PATH)
get_filename_component(_IMPORT_PREFIX "${_IMPORT_PREFIX}" PATH)
get_filename_component(_IMPORT_PREFIX "${_IMPORT_PREFIX}" PATH)
if(_IMPORT_PREFIX STREQUAL "/")
set(_IMPORT_PREFIX "")
endif()
# Create imported target pangolin
add_library(pangolin SHARED IMPORTED)
set_target_properties(pangolin PROPERTIES
INTERFACE_INCLUDE_DIRECTORIES "/usr/include;/usr/include;/usr/include;/usr/local/include/eigen3;${_IMPORT_PREFIX}/include"
INTERFACE_LINK_LIBRARIES "rt;pthread;/usr/lib/arm-linux-gnueabihf/libGL.so;/usr/lib/arm-linux-gnueabihf/libGLU.so;/usr/lib/arm-linux-gnueabihf/libGLEW.so;/usr/lib/arm-linux-gnueabihf/libEGL.so;/usr/lib/arm-linux-gnueabihf/libSM.so;/usr/lib/arm-linux-gnueabihf/libICE.so;/usr/lib/arm-linux-gnueabihf/libX11.so;/usr/lib/arm-linux-gnueabihf/libXext.so;rt;pthread;/usr/lib/arm-linux-gnueabihf/libdc1394.so;/usr/lib/arm-linux-gnueabihf/libpng.so;/usr/lib/arm-linux-gnueabihf/libz.so;/usr/lib/arm-linux-gnueabihf/libjpeg.so;/usr/lib/arm-linux-gnueabihf/libtiff.so;/usr/lib/arm-linux-gnueabihf/libIlmImf.so"
INTERFACE_SYSTEM_INCLUDE_DIRECTORIES "/usr/include;/usr/include;/usr/include;/usr/local/include/eigen3"
)
if(CMAKE_VERSION VERSION_LESS 2.8.12)
message(FATAL_ERROR "This file relies on consumers using CMake 2.8.12 or greater.")
endif()
# Load information for each installed configuration.
get_filename_component(_DIR "${CMAKE_CURRENT_LIST_FILE}" PATH)
file(GLOB CONFIG_FILES "${_DIR}/PangolinTargets-*.cmake")
foreach(f ${CONFIG_FILES})
include(${f})
endforeach()
# Cleanup temporary variables.
set(_IMPORT_PREFIX)
# Loop over all imported files and verify that they actually exist
foreach(target ${_IMPORT_CHECK_TARGETS} )
foreach(file ${_IMPORT_CHECK_FILES_FOR_${target}} )
if(NOT EXISTS "${file}" )
message(FATAL_ERROR "The imported target \"${target}\" references the file
\"${file}\"
but this file does not exist. Possible reasons include:
* The file was deleted, renamed, or moved to another location.
* An install or uninstall procedure did not complete successfully.
* The installation package was faulty and contained
\"${CMAKE_CURRENT_LIST_FILE}\"
but not all the files it references.
")
endif()
endforeach()
unset(_IMPORT_CHECK_FILES_FOR_${target})
endforeach()
unset(_IMPORT_CHECK_TARGETS)
# This file does not depend on other imported targets which have
# been exported from the same project but in a separate export set.
# Commands beyond this point should not need to know the version.
set(CMAKE_IMPORT_FILE_VERSION)
cmake_policy(POP)

Answer 1

how to show the path of the file for the one that we search using find_package( )?
CMAKE_PREFIX_PATH
Semicolon-separated list of directories specifying installation prefixes to be searched by the find_package()...
set(CMAKE_PREFIX_PATH /home/users/rootf/usr/local/lib)
# additionalllly I also do a precaution
set(CMAKE_IGNORE_PATH / /bin /include /usr/lib /usr/local/lib)
You might also to manipulate with CMAKE_FIND_USE_*_PATH variables.