How to install object files using CMake - cmake

Question

There is an object library in CMake:
add_library( librevolta_runtime_x86 OBJECT
crt0.S
crti.S
crtn.S
)
install( TARGETS librevolta_runtime_x86 EXPORT revolta
OBJECTS DESTINATION "${CMAKE_INSTALL_PREFIX}/lib"
)
which is linked to my static library:
add_library( revolta STATIC )
target_link_libraries( revolta
PUBLIC
librevolta-runtime-x86
)
# Install all the revolta headers into include directory and copy the built library
install( TARGETS revolta EXPORT revolta
FILE_SET HEADERS DESTINATION "${CMAKE_INSTALL_PREFIX}/include"
ARCHIVE DESTINATION "${CMAKE_INSTALL_PREFIX}/lib"
)
# Export librevolta targets
install( EXPORT revolta DESTINATION "${CMAKE_INSTALL_PREFIX}/lib/cmake/revolta" )
The problem is once the library revota is build and installed, the result is:
<CMAKE_INSTALL_PREFIX>/lib/objects-Debug/librevolta-runtime-x86/crt0.S.obj
<CMAKE_INSTALL_PREFIX>/lib/objects-Debug/librevolta-runtime-x86/crti.S.obj
<CMAKE_INSTALL_PREFIX>/lib/objects-Debug/librevolta-runtime-x86/crtn.S.obj
But I need to make up the installation like:
<CMAKE_INSTALL_PREFIX>/lib/crt0.o
<CMAKE_INSTALL_PREFIX>/lib/crti.o
<CMAKE_INSTALL_PREFIX>/lib/crtn.o
Note: <CMAKE_INSTALL_PREFIX> is just the placeholder for the path being specified in the CMake variable.
So I need to:
Rename the object files from *.S.obj to simple *.o
Adapt the path so that all the object files are installed into pure <CMAKE_INSTALL_PREFIX>/lib/ directory
Due to target_link_libraries(...) dependency, make up the
librevolta_runtime_x86 the member of revolta export set
Many thanks to anyone willing to help me. Martin

Answer 1

EDIT: The simple macro as promised
macro(install_objects OBJFILE_LIST)
foreach(OBJFILE ${${OBJFILE_LIST}})
# Available since CMake 3.20 you can use get_filename_component
# To get any specific information you can wish for about a file
# Before 3.20 you would have to use string(REGEX MATCH ...)
# get_filename_component(OBJ_DIR ${OBJFILE} DIRECTORY) <-- path
# get_filename_component(OBJ_EXT ${OBJFILE} EXT) <-- extension
get_filename_component(OBJ_NAME ${OBJFILE} NAME)
# You can uncomment the message to see what you can get
# MESSAGE(STATUS "OBJ_DIR: ${OBJ_DIR} OBJ_NAME: ${OBJ_NAME} OBJ_EXT: ${OBJ_EXT}")
# This is just an example, but you can also use ${OBJ_DIR} for example to specify a better path
install(FILES ${OBJFILE} DESTINATION [wherever_you_want_them] RENAME "${OBJ_NAME}.o")
endforeach(OBJFILE)
endmacro(install_objects)
#example usage
set(MY_OBJECTS
"test.s.obj"
"somepath/test2.S.obj"
"whatever/whatever/test3.s.OBJ"
)
install_objects(MY_OBJECTS)
The above MY_OBJECTS would give you the following variables:
-- OBJ_DIR: OBJ_NAME: test.s.obj OBJ_EXT: .s.obj
-- OBJ_DIR: somepath OBJ_NAME: test2.S.obj OBJ_EXT: .S.obj
-- OBJ_DIR: whatever/whatever OBJ_NAME: test3.s.OBJ OBJ_EXT: .s.OBJ
As you can see it is pretty robust and keeps your CMakeLists.txt clean. Just make sure to create your OBJECT_LIST using pre-defined variables such as ${CMAKE_BINARY_DIR}
This will simplify your object files installs. IMO it also answers both ad1) ad2)
Ad3) I'm not sure what is your issue here or what exactly is happening, as the question itself is focused on installing objects.
Is there any specific reason why you wish to install the intermediate object files? This is an important question because a static library when linked will be unpacked and optimized - take a look at this question/answer.
The OBJECT libraries are a useful thing in CMake when you know that some parts of your codebase would be compiled multiple times (due to the fact that it uses the same code). It makes sense to couple these parts into a reusable object library.
All of this aside: What you are looking for is
INSTALL(FILES file-name.abc DESTINATION dest-folder RENAME file-name.xyz)