Add the ability to specify the necessary CXX features.

This increases the minimum necessary version of CMake to 3.1.

There are three levels:
1. TDE_CXX_FEATURES common for all TDE modules
2. PROJECT_CXX_FEATURES common at invidual module level
3. CXX_FEATURES and CXX_FEATURES_PRIVATE for individual libraries and binaries

Public CXX_FEATURES for libraries become part of the exported CMake target.

Signed-off-by: Slávek Banko <slavek.banko@axis.cz>

modules/TDEMacros.cmake

@@ -23,6 +23,10 @@ include( CheckCXXCompilerFlag )
 ##### initialization...
 
 if( NOT TDE_CMAKE_ROOT )
+  if( "${CMAKE_VERSION}" VERSION_LESS "3.1" )
+    message( FATAL_ERROR "CMake >= 3.1.0 required" )
+  endif()
+
   if( ${CMAKE_CURRENT_LIST_DIR} STREQUAL ${CMAKE_ROOT}/Modules )
 
     # TDE CMake is installed in the system directory
@@ -792,6 +796,8 @@ macro( tde_add_library _arg_target )
   unset( _version )
   unset( _release )
   unset( _sources )
+  unset( _cxx_features )
+  unset( _cxx_features_private )
   unset( _destination )
   unset( _embed )
   unset( _link )
@@ -878,6 +884,18 @@ macro( tde_add_library _arg_target )
       set( _storage "_sources" )
     endif( "+${_arg}" STREQUAL "+SOURCES" )
 
+    # found directive "CXX_FEATURES"
+    if( "+${_arg}" STREQUAL "+CXX_FEATURES" )
+      set( _skip_store 1 )
+      set( _storage "_cxx_features" )
+    endif( "+${_arg}" STREQUAL "+CXX_FEATURES" )
+
+    # found directive "CXX_FEATURES_PRIVATE"
+    if( "+${_arg}" STREQUAL "+CXX_FEATURES_PRIVATE" )
+      set( _skip_store 1 )
+      set( _storage "_cxx_features_private" )
+    endif( "+${_arg}" STREQUAL "+CXX_FEATURES_PRIVATE" )
+
     # found directive "EMBED"
     if( "+${_arg}" STREQUAL "+EMBED" )
       set( _skip_store 1 )
@@ -997,6 +1015,15 @@ macro( tde_add_library _arg_target )
   # add target
   add_library( ${_target} ${_type} ${_exclude_from_all} ${_sources} )
 
+  # set cxx features
+  if( _cxx_features )
+    target_compile_features( ${_target} PUBLIC ${_cxx_features} )
+  endif( )
+  if( TDE_CXX_FEATURES OR PROJECT_CXX_FEATURES OR _cxx_features_private )
+    target_compile_features( ${_target} PRIVATE
+      ${TDE_CXX_FEATURES} ${PROJECT_CXX_FEATURES} ${_cxx_features_private} )
+  endif( )
+
   # we assume that modules have no prefix and no version
   # also, should not link
   if( ${_type} STREQUAL "MODULE" )
@@ -1235,6 +1262,7 @@ macro( tde_add_executable _arg_target )
   unset( _meta_includes )
   unset( _setuid )
   unset( _sources )
+  unset( _cxx_features )
   unset( _destination )
   unset( _link )
   unset( _dependencies )
@@ -1289,6 +1317,12 @@ macro( tde_add_executable _arg_target )
       set( _storage "_sources" )
     endif( "+${_arg}" STREQUAL "+SOURCES" )
 
+    # found directive "CXX_FEATURES"
+    if( "+${_arg}" STREQUAL "+CXX_FEATURES" )
+      set( _skip_store 1 )
+      set( _storage "_cxx_features" )
+    endif( "+${_arg}" STREQUAL "+CXX_FEATURES" )
+
     # found directive "LINK"
     if( "+${_arg}" STREQUAL "+LINK" )
       set( _skip_store 1 )
@@ -1372,6 +1406,12 @@ macro( tde_add_executable _arg_target )
   # add target
   add_executable( ${_target} ${_sources} )
 
+  # set cxx features
+  if( TDE_CXX_FEATURES OR PROJECT_CXX_FEATURES OR _cxx_features )
+    target_compile_features( ${_target} PRIVATE
+      ${TDE_CXX_FEATURES} ${PROJECT_CXX_FEATURES} ${_cxx_features} )
+  endif( )
+
   # set link libraries
   if( _link )
     target_link_libraries( ${_target} ${_link} )

templates/tde_export_library.cmake

@@ -1,6 +1,7 @@
 add_library( @_target@ @_type@ IMPORTED )
 
 set_target_properties( @_target@ PROPERTIES
+  INTERFACE_COMPILE_FEATURES "@_cxx_features@"
   IMPORTED_LINK_INTERFACE_LIBRARIES "@_shared_libs@"
   IMPORTED_LOCATION "@_location@"
   IMPORTED_SONAME "@_soname@" )