1 # 2 # Copyright 2021 Google, Inc. 3 # 4 # Licensed under the Apache License, Version 2.0 (the "License"); 5 # you may not use this file except in compliance with the License. 6 # You may obtain a copy of the License at: 7 # 8 # http://www.apache.org/licenses/LICENSE-2.0 9 # 10 # Unless required by applicable law or agreed to in writing, software 11 # distributed under the License is distributed on an "AS IS" BASIS, 12 # WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied. 13 # See the License for the specific language governing permissions and 14 # limitations under the License. 15 16 # Flex (fast lexical analyzer generator) is used for parsing languages. It is 17 # commonly used with a parser generator (like Bison). 18 19 # Generate source files using Flex. 20 # 21 # Note: We generate .cc files for Flex. However, you must set %option c++ if you 22 # want to generate a C++ scanner class. We don't use --c++ in case you have 23 # %option reentrant set, which is mutually exclusive with %option c++. 24 # 25 # Parameters: 26 # sources: Files used to generate the lexers. 27 template("flex_source") { 28 action_name = "${target_name}_gen" 29 action_foreach(action_name) { 30 forward_variables_from(invoker, [ "sources" ]) 31 assert(defined(sources), "sources must be set") 32 foreach(s, sources) { 33 assert(get_path_info(s, "extension") == "ll", 34 "Expecting Flex extension ll: ${s}") 35 } 36 37 script = "//common-mk/file_generator_wrapper.py" 38 outformat = "${target_gen_dir}/{{source_name_part}}.cc" 39 args = [ 40 "flex", 41 "-o", 42 outformat, 43 "{{source}}", 44 ] 45 outputs = [ outformat ] 46 } 47 48 all_dependent_config_name = "_${target_name}_all_dependent_config" 49 config(all_dependent_config_name) { 50 include_dirs = [ "${target_gen_dir}" ] 51 } 52 53 source_set(target_name) { 54 sources = get_target_outputs(":${action_name}") 55 all_dependent_configs = [ ":${all_dependent_config_name}" ] 56 deps = [ ":${action_name}" ] 57 58 if (defined(invoker.configs)) { 59 configs += invoker.configs 60 } 61 62 # Silence some warnings. The autogenerated code includes parts that have 63 # fallthroughs and unreachable code. This may silence legitimate issues in 64 # user written code in the lexer as well. User beware! 65 cflags_cc = [ 66 "-Wno-implicit-fallthrough", 67 "-Wno-unreachable-code", 68 ] 69 } 70 } 71