CMake linking libraries into one single library - c++

Question

I used CMake to compile a framework into three different .lib files, and one .sln file. The project is structured as such
UeiDaqFramework
|-CMakeLists.txt
|-build
| |-Framework_static.sln
| | - other cmake files and stuff
|-UeiDaqCore
| |-CMakeLists.txt
| |-source code for this subproject
|-UeiSimuDriver
| |-CMakeLists.txt
| |-source code for this subproject
|-UeiPDNADriver
| |-CMakeLists.txt
| |-source code for this subproject
|
|-Output
|-UeiDaqCore.lib
|-UeiSimuDriver.lib
|-UeiPDNADriver.lib
My test code require a Framework_static.lib in its include file instead of a .sln file, and I do not know how to combine the three existing .lib files using cmake. I did attempt to follow what this CMake - combine multiple libraries into one answer suggested, by just building all the source files into a single library, but I'm new to CMake, and it did not work. Here is the CmakeLists.txt file at the top directory of my project.
cmake_minimum_required(VERSION 3.13.0 FATAL_ERROR)
set(CMAKE_SYSTEM_VERSION CACHE TYPE INTERNAL FORCE)
project(Framework_static_vc15)
################################################################################
# Set target arch type if empty. Visual studio solution generator provides it.
################################################################################
if(NOT CMAKE_VS_PLATFORM_NAME)
set(CMAKE_VS_PLATFORM_NAME "x64")
endif()
message("${CMAKE_VS_PLATFORM_NAME} architecture in use")
if(NOT ("${CMAKE_VS_PLATFORM_NAME}" STREQUAL "Win32"))
message(FATAL_ERROR "${CMAKE_VS_PLATFORM_NAME} arch is not supported!")
endif()
################################################################################
# Global configuration types
################################################################################
set(CMAKE_CONFIGURATION_TYPES
"Debug"
"Release"
CACHE STRING "" FORCE
)
################################################################################
# Global compiler options
################################################################################
if(MSVC)
# remove default flags provided with CMake for MSVC
set(CMAKE_CXX_FLAGS "")
set(CMAKE_CXX_FLAGS_DEBUG "")
set(CMAKE_CXX_FLAGS_RELEASE "")
endif()
################################################################################
# Global linker options
################################################################################
if(MSVC)
# remove default flags provided with CMake for MSVC
set(CMAKE_EXE_LINKER_FLAGS "")
set(CMAKE_MODULE_LINKER_FLAGS "")
set(CMAKE_SHARED_LINKER_FLAGS "")
set(CMAKE_STATIC_LINKER_FLAGS "")
set(CMAKE_EXE_LINKER_FLAGS_DEBUG "${CMAKE_EXE_LINKER_FLAGS}")
set(CMAKE_MODULE_LINKER_FLAGS_DEBUG "${CMAKE_MODULE_LINKER_FLAGS}")
set(CMAKE_SHARED_LINKER_FLAGS_DEBUG "${CMAKE_SHARED_LINKER_FLAGS}")
set(CMAKE_STATIC_LINKER_FLAGS_DEBUG "${CMAKE_STATIC_LINKER_FLAGS}")
set(CMAKE_EXE_LINKER_FLAGS_RELEASE "${CMAKE_EXE_LINKER_FLAGS}")
set(CMAKE_MODULE_LINKER_FLAGS_RELEASE "${CMAKE_MODULE_LINKER_FLAGS}")
set(CMAKE_SHARED_LINKER_FLAGS_RELEASE "${CMAKE_SHARED_LINKER_FLAGS}")
set(CMAKE_STATIC_LINKER_FLAGS_RELEASE "${CMAKE_STATIC_LINKER_FLAGS}")
endif()
################################################################################
# Nuget packages function stub.
################################################################################
function(use_package TARGET PACKAGE VERSION)
message(WARNING "No implementation of use_package. Create yours.")
endfunction()
################################################################################
# Common utils
################################################################################
include(CMake/Utils.cmake)
################################################################################
# Additional Global Settings(add specific info there)
################################################################################
include(CMake/GlobalSettingsInclude.cmake OPTIONAL)
################################################################################
# Use solution folders feature
################################################################################
set_property(GLOBAL PROPERTY USE_FOLDERS ON)
################################################################################
# Sub-projects
################################################################################
add_subdirectory(Source/UeiDaqCore)
add_subdirectory(Source/UeiPDNADriver)
add_subdirectory(Source/UeiSimuDriver)
These CMakeLists.txt files were generated automatically by a generator that takes a visual studio .sln file and converts it to a .txt tree. Heres the link to the converter if anyone is interested. https://cmakeconverter.readthedocs.io/en/develop/intro.html
Im not sure if I need to rewrite Just the top level .txt file, or if I need to rewrite all the CMakeLists.txt files. Any help would be appreciated.

Answer 1

I assume the build of the shared libs is within the subdirectories, because your CMakeLists.txt does not contain any add_library command.
To get a static library containing all sources you have to
Collect all sources
Add command to build the static library
For 1. add the following to every subdir/CMakeLists.txt
set(SOURCES # This creates a list of sources called SOURCES
myFileA.cpp # This adds an item to the list
myFileB.cpp
${SOURCES} # This adds all items of existing list SOURCES to the current list
PARENT_SCOPE # This makes SOURCES visible in the parent CMakeLists.txt
)
For 2. add the static library
add_library(myTestLib_static.c STATIC ${SOURCES})