Don't call export_symbols.py with duplicate libs

[daltenty]

Summary

export_symbols.py discards duplicate symbols, assuming they have public definitions, so if we end
up calling it with duplicate libraries we will end up with an inaccurate export list.

[john.brawn]

llvm/cmake/modules/AddLLVM.cmake

854

Given that it's the static_libs list that's passed to extract_symbols.py it would make more sense to remove the duplicates from that list (i.e. after the below loop, in case the loop adds duplicates).

[daltenty]

• Move the deduplication after the loop, so we also cover the transitive dependencies

[john.brawn]

LGTM.

llvm/cmake/modules/AddLLVM.cmake

elseif (LLVM_EXPORT_SYMBOLS_FOR_PLUGINS)
     # executable links against.
     set_target_properties(${target} PROPERTIES ENABLE_EXPORTS 1)
     set(exported_symbol_file ${CMAKE_CURRENT_BINARY_DIR}/${CMAKE_CFG_INTDIR}/${target}.symbols)
     # We need to consider not just the direct link dependencies, but also the
     # transitive link dependencies. Do this by starting with the set of direct
     # dependencies, then the dependencies of those dependencies, and so on.
     get_target_property(new_libs ${target} LINK_LIBRARIES)
     set(link_libs ${new_libs})
     while(NOT "${new_libs}" STREQUAL "")
       foreach(lib ${new_libs})
         if(TARGET ${lib})
           get_target_property(lib_type ${lib} TYPE)
           if("${lib_type}" STREQUAL "STATIC_LIBRARY")
             list(APPEND static_libs ${lib})
           else()
             list(APPEND other_libs ${lib})
           endif()
           get_target_property(transitive_libs ${lib} INTERFACE_LINK_LIBRARIES)
           foreach(transitive_lib ${transitive_libs})
             list(FIND link_libs ${transitive_lib} idx)
             if(TARGET ${transitive_lib} AND idx EQUAL -1)
               list(APPEND newer_libs ${transitive_lib})
               list(APPEND link_libs ${transitive_lib})
             endif()
           endforeach(transitive_lib)
         endif()
       endforeach(lib)
       set(new_libs ${newer_libs})
       set(newer_libs "")
     endwhile()
+    list(REMOVE_DUPLICATES static_libs)
     if (MSVC)
       set(mangling microsoft)
     else()
       set(mangling itanium)
     endif()
     add_custom_command(OUTPUT ${exported_symbol_file}
                        COMMAND ${PYTHON_EXECUTABLE} ${LLVM_MAIN_SRC_DIR}/utils/extract_symbols.py --mangling=${mangling} ${static_libs} -o ${exported_symbol_file}
                        WORKING_DIRECTORY ${LLVM_LIBRARY_OUTPUT_INTDIR}