Fix bug with determening whether project is top level

Author: Anton Pantyukhin

CMakeLists.txt

@@ -3,9 +3,7 @@ project(mylib
     VERSION 1.0.0
     DESCRIPTION "Template for C++ library built with CMake"
     LANGUAGES CXX)
-
 include(cmake/utils.cmake)
-set_project_is_top_level()
 
 add_library(mylib) # initialized below
 add_library(mylib::mylib ALIAS mylib)
@@ -16,6 +14,11 @@ add_library(mylib::mylib ALIAS mylib)
 
 include(GNUInstallDirs)
 
+if(NOT DEFINED PROJECT_IS_TOP_LEVEL AND "${CMAKE_SOURCE_DIR}" STREQUAL "${CMAKE_CURRENT_SOURCE_DIR}")
+    # support older CMake versions (prior 3.21) which do not define this variable
+    set(PROJECT_IS_TOP_LEVEL YES)
+endif()
+
 # MYLIB_SHARED_LIBS option (undefined by default) can be used to force shared/static build
 option(MYLIB_BUILD_TESTS "Build mylib tests" OFF)
 option(MYLIB_BUILD_EXAMPLES "Build mylib examples" OFF)

cmake/utils.cmake

@@ -7,30 +7,14 @@ macro(set_if_undefined variable)
     endif()
 endmacro()
 
-# set_project_is_top_level()
-#
-# Sets variable PROJECT_IS_TOP_LEVEL for older CMake versions.
-macro(set_project_is_top_level)
-    if(NOT DEFINED PROJECT_IS_TOP_LEVEL)
-        if("${CMAKE_SOURCE_DIR}" STREQUAL "${CMAKE_CURRENT_SOURCE_DIR}")
-            set(PROJECT_IS_TOP_LEVEL YES)
-        else()
-            set(PROJECT_IS_TOP_LEVEL NO)
-        endif()
-    endif()
-endmacro()
-
 # win_copy_deps_to_target_dir(<target> [<target-dep>]...)
 #
 # Creates custom command to copy runtime dependencies to target's directory after building the target.
-# Function does nothing if platform is not Windows or current project is built as stand-alone (top-level)
-# project. Additionally, it ignores all dependencies except shared libraries.
+# Function does nothing if platform is not Windows and ignores all dependencies except shared libraries.
 # On CMake 3.21 or newer, function uses TARGET_RUNTIME_DLLS generator expression to obtain list of runtime
 # dependencies. Specified dependencies (if any) are still used to find and copy PDB files for debug builds.
 function(win_copy_deps_to_target_dir target)
-    set_project_is_top_level()
-
-    if(NOT WIN32 OR PROJECT_IS_TOP_LEVEL)
+    if(NOT WIN32)
         return()
     endif()
 

examples/add/CMakeLists.txt

@@ -1,8 +1,11 @@
 cmake_minimum_required(VERSION 3.14)
 project(mylib-add LANGUAGES CXX)
-
 include("../../cmake/utils.cmake")
-set_project_is_top_level()
+
+if(NOT DEFINED PROJECT_IS_TOP_LEVEL AND "${CMAKE_SOURCE_DIR}" STREQUAL "${CMAKE_CURRENT_SOURCE_DIR}")
+    # support older CMake versions (prior 3.21) which do not define this variable
+    set(PROJECT_IS_TOP_LEVEL YES)
+endif()
 
 if(PROJECT_IS_TOP_LEVEL)
     find_package(mylib REQUIRED)
@@ -14,4 +17,7 @@ source_group(TREE "${CMAKE_CURRENT_SOURCE_DIR}" FILES ${sources})
 add_executable(mylib-add)
 target_sources(mylib-add PRIVATE ${sources})
 target_link_libraries(mylib-add PRIVATE mylib::mylib)
-win_copy_deps_to_target_dir(mylib-add mylib::mylib)
+
+if(NOT PROJECT_IS_TOP_LEVEL)
+    win_copy_deps_to_target_dir(mylib-add mylib::mylib)
+endif()

tests/CMakeLists.txt

@@ -1,13 +1,16 @@
 cmake_minimum_required(VERSION 3.14)
 project(mylib-tests)
-
 include("../cmake/utils.cmake")
-set_project_is_top_level()
 
 #----------------------------------------------------------------------------------------------------------------------
 # general settings and options
 #----------------------------------------------------------------------------------------------------------------------
 
+if(NOT DEFINED PROJECT_IS_TOP_LEVEL AND "${CMAKE_SOURCE_DIR}" STREQUAL "${CMAKE_CURRENT_SOURCE_DIR}")
+    # support older CMake versions (prior 3.21) which do not define this variable
+    set(PROJECT_IS_TOP_LEVEL YES)
+endif()
+
 if(PROJECT_IS_TOP_LEVEL)
     enable_testing()
 endif()
@@ -56,7 +59,9 @@ target_link_libraries(mylib-tests
         mylib::mylib
         gtest_main)
 
-win_copy_deps_to_target_dir(mylib-tests mylib::mylib)
+if(NOT PROJECT_IS_TOP_LEVEL)
+    win_copy_deps_to_target_dir(mylib-tests mylib::mylib)
+endif()
 
 include(GoogleTest)
 gtest_discover_tests(mylib-tests)