Provided by: cmake-data_3.5.1-1ubuntu1_all bug

NAME

       cmake-buildsystem - CMake Buildsystem Reference

INTRODUCTION

       A  CMake-based  buildsystem  is  organized  as  a set of high-level logical targets.  Each
       target corresponds to an executable or library, or is a custom  target  containing  custom
       commands.   Dependencies between the targets are expressed in the buildsystem to determine
       the build order and the rules for regeneration in response to change.

BINARY TARGETS

       Executables and  libraries  are  defined  using  the  add_executable()  and  add_library()
       commands.   The  resulting binary files have appropriate prefixes, suffixes and extensions
       for the platform targeted.  Dependencies between binary targets are  expressed  using  the
       target_link_libraries() command:

          add_library(archive archive.cpp zip.cpp lzma.cpp)
          add_executable(zipapp zipapp.cpp)
          target_link_libraries(zipapp archive)

       archive  is  defined  as  a  static library -- an archive containing objects compiled from
       archive.cpp, zip.cpp, and  lzma.cpp.   zipapp  is  defined  as  an  executable  formed  by
       compiling  and linking zipapp.cpp.  When linking the zipapp executable, the archive static
       library is linked in.

   Binary Executables
       The add_executable() command defines an executable target:

          add_executable(mytool mytool.cpp)

       Commands such as add_custom_command(), which generates rules to be run at build  time  can
       transparently  use  an  EXECUTABLE  target as a COMMAND executable.  The buildsystem rules
       will ensure that the executable is built before attempting to run the command.

   Binary Library Types
   Normal Libraries
       By default, the  add_library()  command  defines  a  static  library,  unless  a  type  is
       specified.  A type may be specified when using the command:

          add_library(archive SHARED archive.cpp zip.cpp lzma.cpp)

          add_library(archive STATIC archive.cpp zip.cpp lzma.cpp)

       The  BUILD_SHARED_LIBS  variable may be enabled to change the behavior of add_library() to
       build shared libraries by default.

       In the context of the buildsystem definition as a whole, it is largely irrelevant  whether
       particular  libraries  are SHARED or STATIC -- the commands, dependency specifications and
       other APIs work similarly regardless of the library type.   The  MODULE  library  type  is
       dissimilar  in that it is generally not linked to -- it is not used in the right-hand-side
       of the target_link_libraries() command.  It is a type which is loaded as  a  plugin  using
       runtime  techniques.   If  the library does not export any unmanaged symbols (e.g. Windows
       resource DLL, C++/CLI DLL), it is required that  the  library  not  be  a  SHARED  library
       because CMake expects SHARED libraries to export at least one symbol.

          add_library(archive MODULE 7z.cpp)

   Apple Frameworks
       A SHARED library may be marked with the FRAMEWORK target property to create an OS X or iOS
       Framework Bundle.  The MACOSX_FRAMEWORK_IDENTIFIER  sets  CFBundleIdentifier  key  and  it
       uniquely identifies the bundle.

          add_library(MyFramework SHARED MyFramework.cpp)
          set_target_properties(MyFramework PROPERTIES
            FRAMEWORK TRUE
            FRAMEWORK_VERSION A
            MACOSX_FRAMEWORK_IDENTIFIER org.cmake.MyFramework
          )

   Object Libraries
       The  OBJECT  library  type  is also not linked to. It defines a non-archival collection of
       object files resulting from compiling the given source files.  The object files collection
       can be used as source inputs to other targets:

          add_library(archive OBJECT archive.cpp zip.cpp lzma.cpp)

          add_library(archiveExtras STATIC $<TARGET_OBJECTS:archive> extras.cpp)

          add_executable(test_exe $<TARGET_OBJECTS:archive> test.cpp)

       OBJECT  libraries  may only be used locally as sources in a buildsystem -- they may not be
       installed, exported, or used in the right hand side of target_link_libraries().  They also
       may  not  be  used  as  the  TARGET  in  a  use  of the add_custom_command(TARGET) command
       signature.

       Although   object   libraries   may   not   be   named   directly   in   calls   to    the
       target_link_libraries()  command,  they  can  be "linked" indirectly by using an Interface
       Library whose INTERFACE_SOURCES target property is set to name $<TARGET_OBJECTS:objlib>.

BUILD SPECIFICATION AND USAGE REQUIREMENTS

       The         target_include_directories(),         target_compile_definitions()         and
       target_compile_options()   commands   specify  the  build  specifications  and  the  usage
       requirements  of  binary  targets.   The  commands   populate   the   INCLUDE_DIRECTORIES,
       COMPILE_DEFINITIONS   and  COMPILE_OPTIONS  target  properties  respectively,  and/or  the
       INTERFACE_INCLUDE_DIRECTORIES, INTERFACE_COMPILE_DEFINITIONS and INTERFACE_COMPILE_OPTIONS
       target properties.

       Each of the commands has a PRIVATE, PUBLIC and INTERFACE mode.  The PRIVATE mode populates
       only the non-INTERFACE_ variant of the target property and the  INTERFACE  mode  populates
       only  the  INTERFACE_  variants.  The PUBLIC mode populates both variants of the repective
       target property.  Each command may be invoked with multiple uses of each keyword:

          target_compile_definitions(archive
            PRIVATE BUILDING_WITH_LZMA
            INTERFACE USING_ARCHIVE_LIB
          )

       Note that usage requirements are not designed as a way to make downstreams use  particular
       COMPILE_OPTIONS  or  COMPILE_DEFINITIONS  etc  for  convenience only.  The contents of the
       properties must be requirements, not merely recommendations or convenience.

       See the  Creating  Relocatable  Packages  section  of  the  cmake-packages(7)  manual  for
       discussion  of additional care that must be taken when specifying usage requirements while
       creating packages for redistribution.

   Target Properties
       The contents of the INCLUDE_DIRECTORIES, COMPILE_DEFINITIONS  and  COMPILE_OPTIONS  target
       properties are used appropriately when compiling the source files of a binary target.

       Entries  in  the  INCLUDE_DIRECTORIES  are  added  to the compile line with -I or -isystem
       prefixes and in the order of appearance in the property value.

       Entries in the COMPILE_DEFINITIONS are prefixed with -D or /D and  added  to  the  compile
       line  in  an  unspecified  order.   The  DEFINE_SYMBOL  target property is also added as a
       compile definition as a special convenience case for SHARED and MODULE library targets.

       Entries in the COMPILE_OPTIONS are escaped for  the  shell  and  added  in  the  order  of
       appearance in the property value.  Several compile options have special separate handling,
       such as POSITION_INDEPENDENT_CODE.

       The  contents  of  the  INTERFACE_INCLUDE_DIRECTORIES,  INTERFACE_COMPILE_DEFINITIONS  and
       INTERFACE_COMPILE_OPTIONS target properties are Usage Requirements -- they specify content
       which consumers must use to correctly compile and link with the  target  they  appear  on.
       For  any  binary target, the contents of each INTERFACE_ property on each target specified
       in a target_link_libraries() command is consumed:

          set(srcs archive.cpp zip.cpp)
          if (LZMA_FOUND)
            list(APPEND srcs lzma.cpp)
          endif()
          add_library(archive SHARED ${srcs})
          if (LZMA_FOUND)
            # The archive library sources are compiled with -DBUILDING_WITH_LZMA
            target_compile_definitions(archive PRIVATE BUILDING_WITH_LZMA)
          endif()
          target_compile_definitions(archive INTERFACE USING_ARCHIVE_LIB)

          add_executable(consumer)
          # Link consumer to archive and consume its usage requirements. The consumer
          # executable sources are compiled with -DUSING_ARCHIVE_LIB.
          target_link_libraries(consumer archive)

       Because it is common  to  require  that  the  source  directory  and  corresponding  build
       directory are added to the INCLUDE_DIRECTORIES, the CMAKE_INCLUDE_CURRENT_DIR variable can
       be enabled to conveniently add the corresponding directories to the INCLUDE_DIRECTORIES of
       all  targets.   The  variable CMAKE_INCLUDE_CURRENT_DIR_IN_INTERFACE can be enabled to add
       the corresponding directories to the INTERFACE_INCLUDE_DIRECTORIES of all  targets.   This
       makes  use  of  targets  in  multiple  different directories convenient through use of the
       target_link_libraries() command.

   Transitive Usage Requirements
       The usage requirements  of  a  target  can  transitively  propagate  to  dependents.   The
       target_link_libraries()  command has PRIVATE, INTERFACE and PUBLIC keywords to control the
       propagation.

          add_library(archive archive.cpp)
          target_compile_definitions(archive INTERFACE USING_ARCHIVE_LIB)

          add_library(serialization serialization.cpp)
          target_compile_definitions(serialization INTERFACE USING_SERIALIZATION_LIB)

          add_library(archiveExtras extras.cpp)
          target_link_libraries(archiveExtras PUBLIC archive)
          target_link_libraries(archiveExtras PRIVATE serialization)
          # archiveExtras is compiled with -DUSING_ARCHIVE_LIB
          # and -DUSING_SERIALIZATION_LIB

          add_executable(consumer consumer.cpp)
          # consumer is compiled with -DUSING_ARCHIVE_LIB
          target_link_libraries(consumer archiveExtras)

       Because archive is a PUBLIC dependency of archiveExtras, the usage requirements of it  are
       propagated to consumer too.  Because serialization is a PRIVATE dependency of archive, the
       usage requirements of it are not propagated to consumer.

       Generally, a dependency should be specified in a use of target_link_libraries()  with  the
       PRIVATE  keyword  if  it  is  used by only the implementation of a library, and not in the
       header files.  If a dependency is additionally used in the header files of a library (e.g.
       for  class inheritance), then it should be specified as a PUBLIC dependency.  A dependency
       which is not used by the implementation of a library, but only by its  headers  should  be
       specified  as an INTERFACE dependency.  The target_link_libraries() command may be invoked
       with multiple uses of each keyword:

          target_link_libraries(archiveExtras
            PUBLIC archive
            PRIVATE serialization
          )

       Usage requirements are propagated by reading the INTERFACE_ variants of target  properties
       from  dependencies and appending the values to the non-INTERFACE_ variants of the operand.
       For example, the INTERFACE_INCLUDE_DIRECTORIES of dependencies is read and appended to the
       INCLUDE_DIRECTORIES  of the operand.  In cases where order is relevant and maintained, and
       the order  resulting  from  the  target_link_libraries()  calls  does  not  allow  correct
       compilation,  use  of  an  appropriate command to set the property directly may update the
       order.

       For example, if the linked libraries for a target must be specified in the order lib1 lib2
       lib3 , but the include directories must be specified in the order lib3 lib1 lib2:

          target_link_libraries(myExe lib1 lib2 lib3)
          target_include_directories(myExe
            PRIVATE $<TARGET_PROPERTY:lib3,INTERFACE_INCLUDE_DIRECTORIES>)

       Note  that care must be taken when specifying usage requirements for targets which will be
       exported for installation using the install(EXPORT) command.  See  Creating  Packages  for
       more.

   Compatible Interface Properties
       Some target properties are required to be compatible between a target and the interface of
       each dependency.  For example, the POSITION_INDEPENDENT_CODE target property may specify a
       boolean  value  of whether a target should be compiled as position-independent-code, which
       has platform-specific consequences.  A target  may  also  specify  the  usage  requirement
       INTERFACE_POSITION_INDEPENDENT_CODE  to  communicate  that  consumers  must be compiled as
       position-independent-code.

          add_executable(exe1 exe1.cpp)
          set_property(TARGET exe1 PROPERTY POSITION_INDEPENDENT_CODE ON)

          add_library(lib1 SHARED lib1.cpp)
          set_property(TARGET lib1 PROPERTY INTERFACE_POSITION_INDEPENDENT_CODE ON)

          add_executable(exe2 exe2.cpp)
          target_link_libraries(exe2 lib1)

       Here, both exe1 and exe2 will be compiled as position-independent-code.  lib1 will also be
       compiled  as  position-independent-code  because  that  is  the default setting for SHARED
       libraries.  If dependencies have conflicting, non-compatible requirements cmake(1)  issues
       a diagnostic:

          add_library(lib1 SHARED lib1.cpp)
          set_property(TARGET lib1 PROPERTY INTERFACE_POSITION_INDEPENDENT_CODE ON)

          add_library(lib2 SHARED lib2.cpp)
          set_property(TARGET lib2 PROPERTY INTERFACE_POSITION_INDEPENDENT_CODE OFF)

          add_executable(exe1 exe1.cpp)
          target_link_libraries(exe1 lib1)
          set_property(TARGET exe1 PROPERTY POSITION_INDEPENDENT_CODE OFF)

          add_executable(exe2 exe2.cpp)
          target_link_libraries(exe2 lib1 lib2)

       The  lib1  requirement  INTERFACE_POSITION_INDEPENDENT_CODE  is  not "compatible" with the
       POSITION_INDEPENDENT_CODE  property  of  the  exe1  target.   The  library  requires  that
       consumers  are  built  as position-independent-code, while the executable specifies to not
       built as position-independent-code, so a diagnostic is issued.

       The lib1 and lib2 requirements are not "compatible".  One of them requires that  consumers
       are  built  as  position-independent-code, while the other requires that consumers are not
       built as position-independent-code.  Because exe2 links to both and they are in  conflict,
       a diagnostic is issued.

       To  be  "compatible",  the  POSITION_INDEPENDENT_CODE  property, if set must be either the
       same, in a boolean sense,  as  the  INTERFACE_POSITION_INDEPENDENT_CODE  property  of  all
       transitively specified dependencies on which that property is set.

       This property of "compatible interface requirement" may be extended to other properties by
       specifying the property in the content of the COMPATIBLE_INTERFACE_BOOL  target  property.
       Each  specified  property  must  be  compatible  between  the  consuming  target  and  the
       corresponding property with an INTERFACE_ prefix from each dependency:

          add_library(lib1Version2 SHARED lib1_v2.cpp)
          set_property(TARGET lib1Version2 PROPERTY INTERFACE_CUSTOM_PROP ON)
          set_property(TARGET lib1Version2 APPEND PROPERTY
            COMPATIBLE_INTERFACE_BOOL CUSTOM_PROP
          )

          add_library(lib1Version3 SHARED lib1_v3.cpp)
          set_property(TARGET lib1Version3 PROPERTY INTERFACE_CUSTOM_PROP OFF)

          add_executable(exe1 exe1.cpp)
          target_link_libraries(exe1 lib1Version2) # CUSTOM_PROP will be ON

          add_executable(exe2 exe2.cpp)
          target_link_libraries(exe2 lib1Version2 lib1Version3) # Diagnostic

       Non-boolean properties  may  also  participate  in  "compatible  interface"  computations.
       Properties   specified   in   the  COMPATIBLE_INTERFACE_STRING  property  must  be  either
       unspecified or compare to the same string among all transitively  specified  dependencies.
       This  can  be  useful  to  ensure that multiple incompatible versions of a library are not
       linked together through transitive requirements of a target:

          add_library(lib1Version2 SHARED lib1_v2.cpp)
          set_property(TARGET lib1Version2 PROPERTY INTERFACE_LIB_VERSION 2)
          set_property(TARGET lib1Version2 APPEND PROPERTY
            COMPATIBLE_INTERFACE_STRING LIB_VERSION
          )

          add_library(lib1Version3 SHARED lib1_v3.cpp)
          set_property(TARGET lib1Version3 PROPERTY INTERFACE_LIB_VERSION 3)

          add_executable(exe1 exe1.cpp)
          target_link_libraries(exe1 lib1Version2) # LIB_VERSION will be "2"

          add_executable(exe2 exe2.cpp)
          target_link_libraries(exe2 lib1Version2 lib1Version3) # Diagnostic

       The  COMPATIBLE_INTERFACE_NUMBER_MAX  target  property  specifies  that  content  will  be
       evaluated numerically and the maximum number among all specified will be calculated:

          add_library(lib1Version2 SHARED lib1_v2.cpp)
          set_property(TARGET lib1Version2 PROPERTY INTERFACE_CONTAINER_SIZE_REQUIRED 200)
          set_property(TARGET lib1Version2 APPEND PROPERTY
            COMPATIBLE_INTERFACE_NUMBER_MAX CONTAINER_SIZE_REQUIRED
          )

          add_library(lib1Version3 SHARED lib1_v3.cpp)
          set_property(TARGET lib1Version3 PROPERTY INTERFACE_CONTAINER_SIZE_REQUIRED 1000)

          add_executable(exe1 exe1.cpp)
          # CONTAINER_SIZE_REQUIRED will be "200"
          target_link_libraries(exe1 lib1Version2)

          add_executable(exe2 exe2.cpp)
          # CONTAINER_SIZE_REQUIRED will be "1000"
          target_link_libraries(exe2 lib1Version2 lib1Version3)

       Similarly,  the  COMPATIBLE_INTERFACE_NUMBER_MIN  may  be  used  to  calculate the numeric
       minimum value for a property from dependencies.

       Each calculated "compatible" property value may be read in the consumer  at  generate-time
       using generator expressions.

       Note  that for each dependee, the set of properties specified in each compatible interface
       property must not intersect with the set specified in any of the other properties.

   Property Origin Debugging
       Because build specifications can be determined by dependencies, the lack  of  locality  of
       code which creates a target and code which is responsible for setting build specifications
       may make the code more difficult to reason about.  cmake(1) provides a debugging  facility
       to print the origin of the contents of properties which may be determined by dependencies.
       The properties which can be  debugged  are  listed  in  the  CMAKE_DEBUG_TARGET_PROPERTIES
       variable documentation:

          set(CMAKE_DEBUG_TARGET_PROPERTIES
            INCLUDE_DIRECTORIES
            COMPILE_DEFINITIONS
            POSITION_INDEPENDENT_CODE
            CONTAINER_SIZE_REQUIRED
            LIB_VERSION
          )
          add_executable(exe1 exe1.cpp)

       In     the     case    of    properties    listed    in    COMPATIBLE_INTERFACE_BOOL    or
       COMPATIBLE_INTERFACE_STRING, the debug output  shows  which  target  was  responsible  for
       setting the property, and which other dependencies also defined the property.  In the case
       of COMPATIBLE_INTERFACE_NUMBER_MAX and COMPATIBLE_INTERFACE_NUMBER_MIN, the  debug  output
       shows the value of the property from each dependency, and whether the value determines the
       new extreme.

   Build Specification with Generator Expressions
       Build specifications may  use  generator  expressions  containing  content  which  may  be
       conditional  or  known  only  at  generate-time.  For example, the calculated "compatible"
       value of a property may be read with the TARGET_PROPERTY expression:

          add_library(lib1Version2 SHARED lib1_v2.cpp)
          set_property(TARGET lib1Version2 PROPERTY
            INTERFACE_CONTAINER_SIZE_REQUIRED 200)
          set_property(TARGET lib1Version2 APPEND PROPERTY
            COMPATIBLE_INTERFACE_NUMBER_MAX CONTAINER_SIZE_REQUIRED
          )

          add_executable(exe1 exe1.cpp)
          target_link_libraries(exe1 lib1Version2)
          target_compile_definitions(exe1 PRIVATE
              CONTAINER_SIZE=$<TARGET_PROPERTY:CONTAINER_SIZE_REQUIRED>
          )

       In this case, the exe1 source files will be compiled with -DCONTAINER_SIZE=200.

       Configuration determined build specifications may be conveniently  set  using  the  CONFIG
       generator expression.

          target_compile_definitions(exe1 PRIVATE
              $<$<CONFIG:Debug>:DEBUG_BUILD>
          )

       The  CONFIG  parameter  is compared case-insensitively with the configuration being built.
       In the presence of IMPORTED targets, the  content  of  MAP_IMPORTED_CONFIG_DEBUG  is  also
       accounted for by this expression.

       Some  buildsystems  generated  by cmake(1) have a predetermined build-configuration set in
       the CMAKE_BUILD_TYPE variable.  The buildsystem for the IDEs such  as  Visual  Studio  and
       Xcode  are  generated  independent  of  the  build-configuration,  and  the  actual  build
       configuration is not known until build-time.  Therefore, code such as

          string(TOLOWER ${CMAKE_BUILD_TYPE} _type)
          if (_type STREQUAL debug)
            target_compile_definitions(exe1 PRIVATE DEBUG_BUILD)
          endif()

       may appear to work for Makefile based and Ninja generators, but is  not  portable  to  IDE
       generators.   Additionally, the IMPORTED configuration-mappings are not accounted for with
       code like this, so it should be avoided.

       The unary TARGET_PROPERTY generator expression and the TARGET_POLICY generator  expression
       are  evaluated  with  the  consuming  target context.  This means that a usage requirement
       specification may be evaluated differently based on the consumer:

          add_library(lib1 lib1.cpp)
          target_compile_definitions(lib1 INTERFACE
            $<$<STREQUAL:$<TARGET_PROPERTY:TYPE>,EXECUTABLE>:LIB1_WITH_EXE>
            $<$<STREQUAL:$<TARGET_PROPERTY:TYPE>,SHARED_LIBRARY>:LIB1_WITH_SHARED_LIB>
            $<$<TARGET_POLICY:CMP0041>:CONSUMER_CMP0041_NEW>
          )

          add_executable(exe1 exe1.cpp)
          target_link_libraries(exe1 lib1)

          cmake_policy(SET CMP0041 NEW)

          add_library(shared_lib shared_lib.cpp)
          target_link_libraries(shared_lib lib1)

       The exe1 executable will be compiled with -DLIB1_WITH_EXE,  while  the  shared_lib  shared
       library  will  be compiled with -DLIB1_WITH_SHARED_LIB and -DCONSUMER_CMP0041_NEW, because
       policy CMP0041 is NEW at the point where the shared_lib target is created.

       The BUILD_INTERFACE expression wraps requirements which are only used when consumed from a
       target  in  the  same  buildsystem,  or  when consumed from a target exported to the build
       directory using the export() command.  The INSTALL_INTERFACE expression wraps requirements
       which are only used when consumed from a target which has been installed and exported with
       the install(EXPORT) command:

          add_library(ClimbingStats climbingstats.cpp)
          target_compile_definitions(ClimbingStats INTERFACE
            $<BUILD_INTERFACE:ClimbingStats_FROM_BUILD_LOCATION>
            $<INSTALL_INTERFACE:ClimbingStats_FROM_INSTALLED_LOCATION>
          )
          install(TARGETS ClimbingStats EXPORT libExport ${InstallArgs})
          install(EXPORT libExport NAMESPACE Upstream::
                  DESTINATION lib/cmake/ClimbingStats)
          export(EXPORT libExport NAMESPACE Upstream::)

          add_executable(exe1 exe1.cpp)
          target_link_libraries(exe1 ClimbingStats)

       In    this     case,     the     exe1     executable     will     be     compiled     with
       -DClimbingStats_FROM_BUILD_LOCATION.   The  exporting  commands  generate IMPORTED targets
       with either the INSTALL_INTERFACE or the  BUILD_INTERFACE  omitted,  and  the  *_INTERFACE
       marker  stripped  away.   A  separate  project  consuming  the ClimbingStats package would
       contain:

          find_package(ClimbingStats REQUIRED)

          add_executable(Downstream main.cpp)
          target_link_libraries(Downstream Upstream::ClimbingStats)

       Depending on whether the ClimbingStats package was used from the  build  location  or  the
       install    location,    the    Downstream   target   would   be   compiled   with   either
       -DClimbingStats_FROM_BUILD_LOCATION or  -DClimbingStats_FROM_INSTALL_LOCATION.   For  more
       about packages and exporting see the cmake-packages(7) manual.

   Include Directories and Usage Requirements
       Include   directories   require   some  special  consideration  when  specified  as  usage
       requirements and when used with generator expressions.   The  target_include_directories()
       command accepts both relative and absolute include directories:

          add_library(lib1 lib1.cpp)
          target_include_directories(lib1 PRIVATE
            /absolute/path
            relative/path
          )

       Relative paths are interpreted relative to the source directory where the command appears.
       Relative paths are not allowed in the INTERFACE_INCLUDE_DIRECTORIES of IMPORTED targets.

       In cases where a non-trivial generator expression is used, the  INSTALL_PREFIX  expression
       may  be  used within the argument of an INSTALL_INTERFACE expression.  It is a replacement
       marker which expands to the installation prefix when imported by a consuming project.

       Include directories usage requirements commonly differ  between  the  build-tree  and  the
       install-tree.  The BUILD_INTERFACE and INSTALL_INTERFACE generator expressions can be used
       to describe separate usage requirements based on the usage location.  Relative  paths  are
       allowed  within  the  INSTALL_INTERFACE  expression  and  are  interpreted relative to the
       installation prefix.  For example:

          add_library(ClimbingStats climbingstats.cpp)
          target_include_directories(ClimbingStats INTERFACE
            $<BUILD_INTERFACE:${CMAKE_CURRENT_BINARY_DIR}/generated>
            $<INSTALL_INTERFACE:/absolute/path>
            $<INSTALL_INTERFACE:relative/path>
            $<INSTALL_INTERFACE:$<INSTALL_PREFIX>/$<CONFIG>/generated>
          )

       Two convenience APIs are provided relating to include directories usage requirements.  The
       CMAKE_INCLUDE_CURRENT_DIR_IN_INTERFACE  variable may be enabled, with an equivalent effect
       to:

          set_property(TARGET tgt APPEND PROPERTY INTERFACE_INCLUDE_DIRECTORIES
            $<BUILD_INTERFACE:${CMAKE_CURRENT_SOURCE_DIR};${CMAKE_CURRENT_BINARY_DIR}>
          )

       for  each  target  affected.   The  convenience  for  installed  targets  is  an  INCLUDES
       DESTINATION component with the install(TARGETS) command:

          install(TARGETS foo bar bat EXPORT tgts ${dest_args}
            INCLUDES DESTINATION include
          )
          install(EXPORT tgts ${other_args})
          install(FILES ${headers} DESTINATION include)

       This    is    equivalent    to    appending    ${CMAKE_INSTALL_PREFIX}/include    to   the
       INTERFACE_INCLUDE_DIRECTORIES of each of the installed IMPORTED targets when generated  by
       install(EXPORT).

       When  the  INTERFACE_INCLUDE_DIRECTORIES of an imported target is consumed, the entries in
       the property are treated as SYSTEM include directories, as if  they  were  listed  in  the
       INTERFACE_SYSTEM_INCLUDE_DIRECTORIES  of  the  dependency.  This can result in omission of
       compiler warnings for headers found in those  directories.   This  behavior  for  Imported
       Targets may be controlled with the NO_SYSTEM_FROM_IMPORTED target property.

       If  a binary target is linked transitively to a Mac OX framework, the Headers directory of
       the framework is also treated as a usage requirement.  This has the same effect as passing
       the framework directory as an include directory.

   Link Libraries and Generator Expressions
       Like  build  specifications,  link  libraries  may  be specified with generator expression
       conditions.  However, as consumption of usage requirements is  based  on  collection  from
       linked  dependencies,  there  is  an additional limitation that the link dependencies must
       form a "directed acyclic graph".  That is, if linking to a  target  is  dependent  on  the
       value  of  a  target  property,  that  target  property may not be dependent on the linked
       dependencies:

          add_library(lib1 lib1.cpp)
          add_library(lib2 lib2.cpp)
          target_link_libraries(lib1 PUBLIC
            $<$<TARGET_PROPERTY:POSITION_INDEPENDENT_CODE>:lib2>
          )
          add_library(lib3 lib3.cpp)
          set_property(TARGET lib3 PROPERTY INTERFACE_POSITION_INDEPENDENT_CODE ON)

          add_executable(exe1 exe1.cpp)
          target_link_libraries(exe1 lib1 lib3)

       As the value of the POSITION_INDEPENDENT_CODE property of the exe1 target is dependent  on
       the  linked  libraries  (lib3),  and  the  edge  of linking exe1 is determined by the same
       POSITION_INDEPENDENT_CODE property, the dependency graph above contains a cycle.  cmake(1)
       issues a diagnostic in this case.

   Output Artifacts
       The  buildsystem targets created by the add_library() and add_executable() commands create
       rules to create binary outputs.  The exact output location of the  binaries  can  only  be
       determined  at  generate-time  because  it  can  depend on the build-configuration and the
       link-language of linked dependencies etc.   TARGET_FILE,  TARGET_LINKER_FILE  and  related
       expressions  can  be  used  to  access the name and location of generated binaries.  These
       expressions do not work for OBJECT libraries however, as there is no single file generated
       by such libraries which is relevant to the expressions.

       There  are three kinds of output artifacts that may be build by targets as detailed in the
       following sections.  Their  classification  differs  between  DLL  platforms  and  non-DLL
       platforms.  All Windows-based systems including Cygwin are DLL platforms.

   Runtime Output Artifacts
       A runtime output artifact of a buildsystem target may be:

       · The  executable file (e.g. .exe) of an executable target created by the add_executable()
         command.

       · On DLL platforms: the executable file (e.g. .dll) of a shared library target created  by
         the add_library() command with the SHARED option.

       The  RUNTIME_OUTPUT_DIRECTORY  and  RUNTIME_OUTPUT_NAME  target  properties may be used to
       control runtime output artifact locations and names in the build tree.

   Library Output Artifacts
       A library output artifact of a buildsystem target may be:

       · The loadable module file (e.g. .dll or .so) of a module library target  created  by  the
         add_library() command with the MODULE option.

       · On  non-DLL  platforms:  the shared library file (e.g. .so or .dylib) of a shared shared
         library target created by the add_library() command with the SHARED option.

       The LIBRARY_OUTPUT_DIRECTORY and LIBRARY_OUTPUT_NAME target  properties  may  be  used  to
       control library output artifact locations and names in the build tree.

   Archive Output Artifacts
       An archive output artifact of a buildsystem target may be:

       · The  static  library  file  (e.g.  .lib or .a) of a static library target created by the
         add_library() command with the STATIC option.

       · On DLL platforms: the import library file (e.g. .lib) of a shared library target created
         by  the  add_library()  command with the SHARED option.  This file is only guaranteed to
         exist if the library exports at least one unmanaged symbol.

       · On DLL platforms: the import library file (e.g. .lib) of an executable target created by
         the add_executable() command when its ENABLE_EXPORTS target property is set.

       The  ARCHIVE_OUTPUT_DIRECTORY  and  ARCHIVE_OUTPUT_NAME  target  properties may be used to
       control archive output artifact locations and names in the build tree.

   Directory-Scoped Commands
       The         target_include_directories(),         target_compile_definitions()         and
       target_compile_options()  commands  have  an  effect  on  only  one target at a time.  The
       commands add_definitions(), add_compile_options() and include_directories() have a similar
       function, but operate at directory scope instead of target scope for convenience.

PSEUDO TARGETS

       Some  target  types  do  not represent outputs of the buildsystem, but only inputs such as
       external dependencies, aliases or other  non-build  artifacts.   Pseudo  targets  are  not
       represented in the generated buildsystem.

   Imported Targets
       An IMPORTED target represents a pre-existing dependency.  Usually such targets are defined
       by an upstream package and should be treated as immutable.  It is not possible to  use  an
       IMPORTED    target    in   the   left-hand-side   of   the   target_compile_definitions(),
       target_include_directories(),    target_compile_options()    or    target_link_libraries()
       commands,  as  that would be an attempt to modify it.  IMPORTED targets are designed to be
       used only in the right-hand-side of those commands.

       IMPORTED targets may have the  same  usage  requirement  properties  populated  as  binary
       targets,    such    as    INTERFACE_INCLUDE_DIRECTORIES,    INTERFACE_COMPILE_DEFINITIONS,
       INTERFACE_COMPILE_OPTIONS,                  INTERFACE_LINK_LIBRARIES,                  and
       INTERFACE_POSITION_INDEPENDENT_CODE.

       The LOCATION may also be read from an IMPORTED target, though there is rarely reason to do
       so.  Commands such as add_custom_command() can transparently use  an  IMPORTED  EXECUTABLE
       target as a COMMAND executable.

       The  scope  of the definition of an IMPORTED target is the directory where it was defined.
       It may be accessed and used from  subdirectories,  but  not  from  parent  directories  or
       sibling directories.  The scope is similar to the scope of a cmake variable.

       It is also possible to define a GLOBAL IMPORTED target which is accessible globally in the
       buildsystem.

       See the cmake-packages(7) manual for more on creating packages with IMPORTED targets.

   Alias Targets
       An ALIAS target is a name which may be used interchangably with a binary  target  name  in
       read-only  contexts.   A  primary  use-case  for ALIAS targets is for example or unit test
       executables accompanying a library, which may be part of the  same  buildsystem  or  built
       separately based on user configuration.

          add_library(lib1 lib1.cpp)
          install(TARGETS lib1 EXPORT lib1Export ${dest_args})
          install(EXPORT lib1Export NAMESPACE Upstream:: ${other_args})

          add_library(Upstream::lib1 ALIAS lib1)

       In  another directory, we can link unconditionally to the Upstream::lib1 target, which may
       be an IMPORTED target from a package, or an ALIAS target if built  as  part  of  the  same
       buildsystem.

          if (NOT TARGET Upstream::lib1)
            find_package(lib1 REQUIRED)
          endif()
          add_executable(exe1 exe1.cpp)
          target_link_libraries(exe1 Upstream::lib1)

       ALIAS  targets are not mutable, installable or exportable.  They are entirely local to the
       buildsystem description.  A name can be tested for whether it is an ALIAS name by  reading
       the ALIASED_TARGET property from it:

          get_target_property(_aliased Upstream::lib1 ALIASED_TARGET)
          if(_aliased)
            message(STATUS "The name Upstream::lib1 is an ALIAS for ${_aliased}.")
          endif()

   Interface Libraries
       An  INTERFACE  target  has  no  LOCATION  and  is  mutable, but is otherwise similar to an
       IMPORTED target.

       It   may   specify   usage    requirements    such    as    INTERFACE_INCLUDE_DIRECTORIES,
       INTERFACE_COMPILE_DEFINITIONS,     INTERFACE_COMPILE_OPTIONS,    INTERFACE_LINK_LIBRARIES,
       INTERFACE_SOURCES, and INTERFACE_POSITION_INDEPENDENT_CODE.  Only the INTERFACE  modes  of
       the  target_include_directories(), target_compile_definitions(), target_compile_options(),
       target_sources(),  and  target_link_libraries()  commands  may  be  used  with   INTERFACE
       libraries.

       A primary use-case for INTERFACE libraries is header-only libraries.

          add_library(Eigen INTERFACE)
          target_include_directories(Eigen INTERFACE
            $<BUILD_INTERFACE:${CMAKE_CURRENT_SOURCE_DIR}/src>
            $<INSTALL_INTERFACE:include/Eigen>
          )

          add_executable(exe1 exe1.cpp)
          target_link_libraries(exe1 Eigen)

       Here,  the  usage requirements from the Eigen target are consumed and used when compiling,
       but it has no effect on linking.

       Another use-case is to employ an entirely target-focussed design for usage requirements:

          add_library(pic_on INTERFACE)
          set_property(TARGET pic_on PROPERTY INTERFACE_POSITION_INDEPENDENT_CODE ON)
          add_library(pic_off INTERFACE)
          set_property(TARGET pic_off PROPERTY INTERFACE_POSITION_INDEPENDENT_CODE OFF)

          add_library(enable_rtti INTERFACE)
          target_compile_options(enable_rtti INTERFACE
            $<$<OR:$<COMPILER_ID:GNU>,$<COMPILER_ID:Clang>>:-rtti>
          )

          add_executable(exe1 exe1.cpp)
          target_link_libraries(exe1 pic_on enable_rtti)

       This way, the build specification of exe1 is expressed entirely as linked targets, and the
       complexity of compiler-specific flags is encapsulated in an INTERFACE library target.

       The properties permitted to be set on or read from an INTERFACE library are:

       · Properties matching INTERFACE_*

       · Built-in properties matching COMPATIBLE_INTERFACE_*

       · EXPORT_NAME

       · IMPORTED

       · NAME

       · Properties matching MAP_IMPORTED_CONFIG_*

       INTERFACE  libraries  may  be  installed  and exported.  Any content they refer to must be
       installed separately:

          add_library(Eigen INTERFACE)
          target_include_directories(Eigen INTERFACE
            $<BUILD_INTERFACE:${CMAKE_CURRENT_SOURCE_DIR}/src>
            $<INSTALL_INTERFACE:include/Eigen>
          )

          install(TARGETS Eigen EXPORT eigenExport)
          install(EXPORT eigenExport NAMESPACE Upstream::
            DESTINATION lib/cmake/Eigen
          )
          install(FILES
              ${CMAKE_CURRENT_SOURCE_DIR}/src/eigen.h
              ${CMAKE_CURRENT_SOURCE_DIR}/src/vector.h
              ${CMAKE_CURRENT_SOURCE_DIR}/src/matrix.h
            DESTINATION include/Eigen
          )

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