build ODE from source if the package is not found, even if flag is not set

Author: Michel Schmid

.github/workflows/build.yaml

@@ -35,7 +35,7 @@ jobs:
       - name: "Build"
         # for some reason qt5 is not correctly in the path and this will break whenever the location of it changes
         # 5.15.11 is for macos-12 and 5.15.12 is for macos-13
-        run: PATH=/usr/local/Cellar/qt@5/5.15.11/lib/cmake/Qt5:/usr/local/Cellar/qt@5/5.15.12/lib/cmake/Qt5:$PATH && make BUILD_ODE=ON
+        run: PATH=/usr/local/Cellar/qt@5/5.15.11/lib/cmake/Qt5:/usr/local/Cellar/qt@5/5.15.12/lib/cmake/Qt5:$PATH && make
 
   build-windows:
     runs-on: windows-latest

CMakeLists.txt

@@ -83,48 +83,24 @@ list(APPEND libs Qt5::Core Qt5::Widgets Qt5::OpenGL Qt5::Network)
 
 # ODE
 if(BUILD_ODE)
-  # build ODE, because some versions of it cause grSim to segfault somewhere
-  # could be because in some packages the double precision is turned off
-  include(ExternalProject)
-
-  ExternalProject_Add(ode_external
-      GIT_REPOSITORY    https://bitbucket.org/odedevs/ode.git
-      GIT_TAG           0.16.4
-      CMAKE_ARGS
-                        -DCMAKE_INSTALL_PREFIX:PATH=<INSTALL_DIR>
-                        -DCMAKE_TOOLCHAIN_FILE:PATH=${CMAKE_TOOLCHAIN_FILE}
-                        -DCMAKE_C_COMPILER:PATH=${CMAKE_C_COMPILER}
-                        -DCMAKE_CXX_COMPILER:PATH=${CMAKE_CXX_COMPILER}
-                        -DCMAKE_MAKE_PROGRAM:PATH=${CMAKE_MAKE_PROGRAM}
-                        # necessary, because it does not build the static libs if this is ON
-                        -DBUILD_SHARED_LIBS=OFF
-                        # if this is OFF grSim just dies instantly and INSTALL.md says it should be ON
-                        -DODE_DOUBLE_PRECISION=ON
-                        -DCMAKE_INSTALL_PREFIX=<INSTALL_DIR>
-    STEP_TARGETS install
-  )
-
-  set(ODE_LIB_SUBPATH "${CMAKE_INSTALL_LIBDIR}/${CMAKE_STATIC_LIBRARY_PREFIX}ode${CMAKE_STATIC_LIBRARY_SUFFIX}")
-
-  # the byproducts are available after the install step
-  ExternalProject_Add_Step(ode_external out
-    DEPENDEES install
-    BYPRODUCTS
-        "<INSTALL_DIR>/${ODE_LIB_SUBPATH}"
-  )
-
-  ExternalProject_Get_Property(ode_external install_dir)
-  set(ODE_LIBRARY "${install_dir}/${ODE_LIB_SUBPATH}")
-  list(APPEND libs ${ODE_LIBRARY})
-  target_include_directories(${app} PRIVATE "${install_dir}/include")
-
+  include(BuildODE)
   add_dependencies(${app} ode_external)
-elseif(WIN32)
-  find_package(ODE CONFIG REQUIRED)
-  list(APPEND libs ODE::ODE)
 else()
-  find_package(ODE REQUIRED)
-  list(APPEND libs ode::ode)
+  if(WIN32)
+    find_package(ODE CONFIG)
+    set(ODE_LIB_NAME ODE::ODE)
+  else()
+    find_package(ODE)
+    set(ODE_LIB_NAME ode::ode)
+  endif()
+
+  if(ODE_FOUND)
+    list(APPEND libs ${ODE_LIB_NAME})
+  else()
+    # if ODE could not be found just build it
+    include(BuildODE)
+    add_dependencies(${app} ode_external)
+  endif()
 endif()
 
 # VarTypes

cmake/modules/BuildODE.cmake

@@ -0,0 +1,34 @@
+# build ODE, because some versions of it cause grSim to segfault somewhere
+# could be because in some packages the double precision is turned off
+include(ExternalProject)
+
+ExternalProject_Add(ode_external
+    GIT_REPOSITORY    https://bitbucket.org/odedevs/ode.git
+    GIT_TAG           0.16.4
+    CMAKE_ARGS
+                      -DCMAKE_INSTALL_PREFIX:PATH=<INSTALL_DIR>
+                      -DCMAKE_TOOLCHAIN_FILE:PATH=${CMAKE_TOOLCHAIN_FILE}
+                      -DCMAKE_C_COMPILER:PATH=${CMAKE_C_COMPILER}
+                      -DCMAKE_CXX_COMPILER:PATH=${CMAKE_CXX_COMPILER}
+                      -DCMAKE_MAKE_PROGRAM:PATH=${CMAKE_MAKE_PROGRAM}
+                      # necessary, because it does not build the static libs if this is ON
+                      -DBUILD_SHARED_LIBS=OFF
+                      # if this is OFF grSim just dies instantly and INSTALL.md says it should be ON
+                      -DODE_DOUBLE_PRECISION=ON
+                      -DCMAKE_INSTALL_PREFIX=<INSTALL_DIR>
+  STEP_TARGETS install
+)
+
+set(ODE_LIB_SUBPATH "${CMAKE_INSTALL_LIBDIR}/${CMAKE_STATIC_LIBRARY_PREFIX}ode${CMAKE_STATIC_LIBRARY_SUFFIX}")
+
+# the byproducts are available after the install step
+ExternalProject_Add_Step(ode_external out
+  DEPENDEES install
+  BYPRODUCTS
+      "<INSTALL_DIR>/${ODE_LIB_SUBPATH}"
+)
+
+ExternalProject_Get_Property(ode_external install_dir)
+set(ODE_LIBRARY "${install_dir}/${ODE_LIB_SUBPATH}")
+list(APPEND libs ${ODE_LIBRARY})
+target_include_directories(${app} PRIVATE "${install_dir}/include")