[CMake] DLL handling under CMake

[Louis-Paul CORDIER]

Hi,

I'm using CMake for a while now for cross-platform project.

In opposition to Linux, Windows does not have a library system 
management through a repository system. I would say that 99% of 
applications that have common libraries between them does not share the 
runtimes. Each time, the .dll files are duplicated for each application. 
We have to live with that, and to create proper CMakeLists.txt that can 
handle DLL integration.

I think many of CMake users have the following pipeline on Windows:

1. Run CMake (this will execute some find_library to get the correct 
.lib files)
2. Compile the application
3. Run the INSTALL target
4. Copy the .dll files into the output binary folder.
5. Package the application with the DLL inside (e.g innosetup)

Currently find_library does not search for runtime, but only for .lib. 
So even if a developer is using find_library, he/she has to implement 
some additional CMake code to retrieve the path to .dll files and copy 
them using the install or the file CMake commands. I added my current 
code for handling Qt library in my project at the end of this email. (I 
put a huge part of it if someone want to reuse it). You will notice that 
this code is handling the case where you are debugging using Visual 
Studio, to avoid the missing .DLL issue.

This steps are tedious and I'm wondering if there is a mechanism that 
exists or that have to be imagined to make the DLL nightmare end.

All the best

Louis-Paul Cordier


...

#Folder where compiled files for release/debug install will be placed
set(G3_RELEASE_DIR  "release")
set(G3_DEBUG_DIR "debug")

find_package(Qt5 ${QT5VC2015_VERSION} EXACT COMPONENTS Core OpenGL 
Concurrent REQUIRED)

QT5_WRAP_UI(...)
QT5_WRAP_CPP(...)
target_include_directories(...)
target_compile_definitions(...)

#Add Qt libraries to the linker
target_link_libraries(${PROJECT_NAME}
   ${Qt5Widgets_LIBRARIES}
   ${Qt5OpenGL_LIBRARIES}
   ${Qt5Concurrent_LIBRARIES}
   )

if( WIN32 )
   SET(QT_DLL
       Qt5Core
       Qt5Gui
       Qt5Widgets
       Qt5OpenGL
       Qt5Concurrent
       )

     foreach( _file ${QT_DLL} )
       list( APPEND DLL_LIBRARIES  "${QT5_DIR}/bin/${_file}.dll" )
       list( APPEND DLL_LIBRARIES_D  "${QT5_DIR}/bin/${_file}d.dll" )
     endforeach( _file ${QT_DLL} )

     #TODO: add the platform libraries.

endif( WIN32 )

# I add other DLLs of other project's library by appending to 
DLL_LIBRARIES and DLL_LIBRARIES_D

#Handle DLLs under Windows.
if(WIN32)

   set(DLL_LIBRARIES_PATH "")
   set(DLL_LIBRARIES_D_PATH "")

   #Process Release libraries.
   foreach( _file ${DLL_LIBRARIES} )

     # Convert path to CMake path to avoid escaping issues.
     file(TO_CMAKE_PATH ${_file} _file_cmake_path)

     #check file existance
     if(NOT EXISTS ${_file_cmake_path})
       message(FATAL_ERROR "Missing dll file: ${_file_cmake_path}")
     endif(NOT EXISTS ${_file_cmake_path})

     # Add the DLL to the installation process.
     install(FILES ${_file_cmake_path}
       DESTINATION ${G3_RELEASE_DIR}
       CONFIGURATIONS Release RelWithDebInfo MinSizeRel Release_CMT 
Release_Net)

     # Extract the folder path of the DLL. It allows to add the folder 
where the
     # DLLs are stored to the PATH environment of Visual Studio, in 
order to avoid
     # copying DLL after each builds.
     if(MSVC)
       get_filename_component(_dll_folder ${_file} DIRECTORY)
       list(APPEND DLL_LIBRARIES_PATH ${_dll_folder})
     endif(MSVC)

   endforeach( _file ${DLL_LIBRARIES} )

   #Process Debug libraries.
   foreach( _file ${DLL_LIBRARIES_D} )

     # Convert path to CMake path to avoid escaping issues.
     file(TO_CMAKE_PATH ${_file} _file_cmake_path)

     #check file existance
     if(NOT EXISTS ${_file_cmake_path})
       message(FATAL_ERROR "Missing dll file: ${_file_cmake_path}")
     endif(NOT EXISTS ${_file_cmake_path})

     # Add the DLL to the installation process.
     install(FILES ${_file_cmake_path}
       DESTINATION ${G3_DEBUG_DIR}
       CONFIGURATIONS Debug)

     # Extract the folder path of the DLL. It allows to add the folder 
where the
     # DLLs are stored to the PATH environment of Visual Studio, in 
order to avoid
     # copying DLL after each builds.
     if(MSVC)
       get_filename_component(_dll_folder ${_file} DIRECTORY)
       list(APPEND DLL_LIBRARIES_PATH_D ${_dll_folder})
     endif(MSVC)

   endforeach( _file ${DLL_LIBRARIES_D} )

   if(MSVC)
     #Remove duplicate entries
     list(REMOVE_DUPLICATES DLL_LIBRARIES_PATH)
     list(REMOVE_DUPLICATES DLL_LIBRARIES_PATH_D)

     #Set architecture
     if(ARCH_X64)
       set(DLL_LIBRARIES_ARCH "x64")
     else(ARCH_X64)
       set(DLL_LIBRARIES_ARCH "Win32")
     endif(ARCH_X64)

     # The output file goes in the build dir.
     # @ONLY means only variables of the form @VAR@ will be substituted.
     # This method need DLL_LIBRARIES_ARCH, DLL_LIBRARIES_PATH and 
DLL_LIBRARIES_PATH_D
     # variables to be set. DONT FORGET TO RESTART VISUAL STUDIO if DLL 
paths changes, as
     # vcxproj.user files are loaded only once at Visual Studio startup.

     configure_file(project.vcxproj.user.in 
${CMAKE_CURRENT_BINARY_DIR}/${PROJECT_NAME}.vcxproj.user @ONLY)
   endif(MSVC)

endif(WIN32)

-------------------

NOTE:

For those who are wondering the content of project.vcxproj.user.in:

<?xml version="1.0" encoding="utf-8"?>
<Project ToolsVersion="4.0" 
xmlns="http://schemas.microsoft.com/developer/msbuild/2003">
  <PropertyGroup 
Condition="'$(Configuration)|$(Platform)'=='Release|@DLL_LIBRARIES_ARCH@'">
  <LocalDebuggerEnvironment>PATH=@DLL_LIBRARIES_PATH@;%PATH%</LocalDebuggerEnvironment>
  <DebuggerFlavor>WindowsLocalDebugger</DebuggerFlavor>
  </PropertyGroup>

  <PropertyGroup 
Condition="'$(Configuration)|$(Platform)'=='RelWithDebInfo|@DLL_LIBRARIES_ARCH@'"> 

  <LocalDebuggerEnvironment>PATH=@DLL_LIBRARIES_PATH@;%PATH%</LocalDebuggerEnvironment>
  <DebuggerFlavor>WindowsLocalDebugger</DebuggerFlavor>
  </PropertyGroup>

  <PropertyGroup 
Condition="'$(Configuration)|$(Platform)'=='MinSizeRel|@DLL_LIBRARIES_ARCH@'"> 

  <LocalDebuggerEnvironment>PATH=@DLL_LIBRARIES_PATH@;%PATH%</LocalDebuggerEnvironment>
  <DebuggerFlavor>WindowsLocalDebugger</DebuggerFlavor>
  </PropertyGroup>

  <PropertyGroup 
Condition="'$(Configuration)|$(Platform)'=='Debug|@DLL_LIBRARIES_ARCH@'">
  <LocalDebuggerEnvironment>PATH=@DLL_LIBRARIES_PATH_D@;%PATH%</LocalDebuggerEnvironment>
  <DebuggerFlavor>WindowsLocalDebugger</DebuggerFlavor>
  </PropertyGroup>


</Project>


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