[cmake] Provide extract_flags macro in share/cmake directory, simplify creation of docs_cpp2rst target

doc/CMakeLists.txt

@@ -4,23 +4,10 @@ configure_file(${CMAKE_CURRENT_SOURCE_DIR}/conf.py.in ${CMAKE_CURRENT_BINARY_DIR
 # -----------------------------------------------------------------------------
 # Create an optional target that allows us to regenerate the C++ doc with c++2rst
 # -----------------------------------------------------------------------------
-foreach(t app4triqs_c triqs)
-  get_property(INCLUDE_DIRS TARGET ${t} PROPERTY INTERFACE_INCLUDE_DIRECTORIES)
-  get_property(SYSTEM_INCLUDE_DIRS TARGET ${t} PROPERTY INTERFACE_SYSTEM_INCLUDE_DIRECTORIES)
-  if(SYTEM_INCLUDE_DIRS)
-    list(REMOVE_ITEM INCLUDE_DIRS ${SYSTEM_INCLUDE_DIRS})
-  endif()
-  foreach(DIR ${INCLUDE_DIRS})
-    set(CPP2RST_INCLUDE_FLAGS ${CPP2RST_INCLUDE_FLAGS} -I${DIR})
-  endforeach()
-  foreach(DIR ${SYSTEM_INCLUDE_DIRS})
-    set(CPP2RST_INCLUDE_FLAGS ${CPP2RST_INCLUDE_FLAGS} -isystem=${DIR})
-  endforeach()
-  get_property(COMPILE_OPTIONS TARGET ${t} PROPERTY INTERFACE_COMPILE_OPTIONS)
-  set(CPP2RST_CXXFLAGS ${CPP2RST_CXXFLAGS} ${COMPILE_OPTIONS})
-endforeach()
-
 add_custom_target(docs_cpp2rst)
+include(${PROJECT_SOURCE_DIR}/share/cmake/extract_flags.cmake)
+extract_flags(app4triqs_c)
+separate_arguments(app4triqs_c_CXXFLAGS)
 macro(generate_docs header_file)
   add_custom_command(
     TARGET docs_cpp2rst
@@ -30,8 +17,8 @@ macro(generate_docs header_file)
       ${header_file}
       -N app4triqs
       --output_directory ${CMAKE_CURRENT_SOURCE_DIR}/cpp2rst_generated
-      --cxxflags="${CPP2RST_CXXFLAGS}"
+      -I${PROJECT_SOURCE_DIR}/c++
-      ${CPP2RST_INCLUDE_FLAGS}
+      --cxxflags="${app4triqs_c_CXXFLAGS}"
   )
 endmacro(generate_docs)
 

share/cmake/extract_flags.cmake

@@ -0,0 +1,67 @@
+# Recursively fetch all targets that the interface of a target depends upon
+macro(get_all_interface_targets name target)
+  get_property(TARGET_LINK_LIBRARIES TARGET ${target} PROPERTY INTERFACE_LINK_LIBRARIES)
+  foreach(lib IN LISTS TARGET_LINK_LIBRARIES)
+    if(TARGET ${lib})
+      # Append to list
+      list(APPEND ${name}_INTERFACE_TARGETS ${lib})
+      # Recure into target dependencies
+      get_all_interface_targets(${name} ${lib})
+    endif()
+  endforeach()
+endmacro()
+
+# Extract the property from the target and recursively from all targets it depends upon
+macro(get_property_recursive)
+  cmake_parse_arguments(get_property_recursive "" "TARGET" "PROPERTY" ${ARGN})
+  set(target ${get_property_recursive_TARGET})
+  set(property ${get_property_recursive_PROPERTY})
+  get_all_interface_targets(${target} ${target})
+  foreach(t IN LISTS ${target}_INTERFACE_TARGETS ITEMS ${target})
+    get_property(p TARGET ${t} PROPERTY ${property})
+    list(APPEND ${ARGV0} ${p})
+  endforeach()
+  # Clean duplicates and any occurance of '/usr/include' dirs
+  if(${ARGV0})
+    list(REMOVE_DUPLICATES ${ARGV0})
+    list(REMOVE_ITEM ${ARGV0} /usr/include)
+  endif()
+endmacro()
+
+# Recursively fetch all compiler flags attached to the interface of a target
+macro(extract_flags target)
+
+  get_property_recursive(opts TARGET ${target} PROPERTY INTERFACE_COMPILE_OPTIONS)
+  foreach(opt ${opts})
+    set(${target}_LDFLAGS "${${target}_LDFLAGS} ${opt}")
+    set(${target}_CXXFLAGS "${${target}_CXXFLAGS} ${opt}")
+  endforeach()
+
+  get_property_recursive(defs TARGET ${target} PROPERTY INTERFACE_COMPILE_DEFINITIONS)
+  foreach(def ${defs})
+    set(${target}_CXXFLAGS "${${target}_CXXFLAGS} -D${def}")
+  endforeach()
+
+  get_property_recursive(inc_dirs TARGET ${target} PROPERTY INTERFACE_INCLUDE_DIRECTORIES)
+  get_property_recursive(sys_inc_dirs TARGET ${target} PROPERTY INTERFACE_SYSTEM_INCLUDE_DIRECTORIES)
+  list(REMOVE_ITEM inc_dirs ${sys_inc_dirs})
+  foreach(dir ${inc_dirs})
+    set(${target}_CXXFLAGS "${${target}_CXXFLAGS} -I${dir}")
+  endforeach()
+  foreach(dir ${sys_inc_dirs})
+    set(${target}_CXXFLAGS "${${target}_CXXFLAGS} -isystem${dir}")
+  endforeach()
+
+  get_property_recursive(libs TARGET ${target} PROPERTY INTERFACE_LINK_LIBRARIES)
+  foreach(lib ${libs})
+    if(NOT TARGET ${lib})
+      set(${target}_LDFLAGS "${${target}_LDFLAGS} ${lib}")
+    endif()
+  endforeach()
+
+  # We have to replace generator expressions explicitly
+  string(REGEX REPLACE "\\$<INSTALL_INTERFACE:([^ ]*)>" "\\1" ${target}_LDFLAGS "${${target}_LDFLAGS}")
+  string(REGEX REPLACE "\\$<INSTALL_INTERFACE:([^ ]*)>" "\\1" ${target}_CXXFLAGS "${${target}_CXXFLAGS}")
+  string(REGEX REPLACE " [^ ]*\\$<[^ ]*:[^ ]*>" "" ${target}_LDFLAGS "${${target}_LDFLAGS}")
+  string(REGEX REPLACE " [^ ]*\\$<[^ ]*:[^ ]*>" "" ${target}_CXXFLAGS "${${target}_CXXFLAGS}")
+endmacro()