CMake: How to reuse source file definitions between targets without duplication? - cmake

Question

In my CMake project, I have 2 targets (a static library and a shared library) that share the same source code files, like this:
add_library("${PROJECT_NAME}" STATIC
"${PROJECT_SOURCE_DIR}/src/calculator/core/ShuntingYard.h"
"${PROJECT_SOURCE_DIR}/src/calculator/core/ShuntingYard.cpp"
"${PROJECT_SOURCE_DIR}/include/calculator/core/Calculator.h"
"${PROJECT_SOURCE_DIR}/src/calculator/core/Calculator.cpp"
)
add_library("${PROJECT_NAME}-shared" SHARED
"${PROJECT_SOURCE_DIR}/src/calculator/core/ShuntingYard.h"
"${PROJECT_SOURCE_DIR}/src/calculator/core/ShuntingYard.cpp"
"${PROJECT_SOURCE_DIR}/include/calculator/core/Calculator.h"
"${PROJECT_SOURCE_DIR}/src/calculator/core/Calculator.cpp"
)
Obviously, there is a problem here: the sources definition is duplicated. It's hard to maintain and it's also error prone.
In order to avoid that, I'd like to create a CMake list variable so that the sources definition could be reused in both targets.
I've tried this but it doesn't work:
set(CALCULATOR_CORE_SOURCES_LIST
"${PROJECT_SOURCE_DIR}/src/calculator/core/ShuntingYard.h"
"${PROJECT_SOURCE_DIR}/src/calculator/core/ShuntingYard.cpp"
"${PROJECT_SOURCE_DIR}/include/calculator/core/Calculator.h"
"${PROJECT_SOURCE_DIR}/src/calculator/core/Calculator.cpp"
)
string(REPLACE ";" " " CALCULATOR_CORE_SOURCES "${CALCULATOR_CORE_SOURCES_LIST}")
add_library("${PROJECT_NAME}" STATIC ${CALCULATOR_CORE_SOURCES})
add_library("${PROJECT_NAME}-shared" SHARED ${CALCULATOR_CORE_SOURCES})
It fails with the error: Cannot find source file.
So... how could I reuse source file definitions between targets without this duplication? Is it possible to do this using lists or is there a better approach to solve this issue?
PS: I'm using CMake 3.15

Answer 1

Your code is close; you can simply use the CALCULATOR_CORE_SOURCES_LIST variable to add the group of sources/headers to both add_library() calls:
set(CALCULATOR_CORE_SOURCES_LIST
${PROJECT_SOURCE_DIR}/src/calculator/core/ShuntingYard.h
${PROJECT_SOURCE_DIR}/src/calculator/core/ShuntingYard.cpp
${PROJECT_SOURCE_DIR}/include/calculator/core/Calculator.h
${PROJECT_SOURCE_DIR}/src/calculator/core/Calculator.cpp
)
add_library(${PROJECT_NAME} STATIC ${CALCULATOR_CORE_SOURCES_LIST})
add_library(${PROJECT_NAME}-shared SHARED ${CALCULATOR_CORE_SOURCES_LIST})
If the group of sources is the same for both libraries, you should only need to define the list once. From the documentation, the set command will do the following:
Multiple arguments will be joined as a semicolon-separated list to form the actual variable value to be set.
Thus, this list can be passed to the add_library() calls. You also shouldn't need the quotes (") around each file.