From: Masahiro Yamada Date: Tue, 11 Dec 2018 11:00:49 +0000 (+0900) Subject: kconfig: fix ambiguous grammar in terms of new lines X-Git-Url: https://jxself.org/git/?a=commitdiff_plain;h=6f9083050fd2aa04490cdd5fb6e52120fb3e74f8;hp=6f9083050fd2aa04490cdd5fb6e52120fb3e74f8;p=carl9170fw.git kconfig: fix ambiguous grammar in terms of new lines This commit decreases 8 shift/reduce conflicts. A certain amount of grammatical ambiguity comes from how to reduce excessive T_EOL tokens. Let's take a look at the example code below: 1 config A 2 bool "a" 3 4 depends on B 5 6 config B 7 def_bool y The line 3 is melt into "config_option_list", but the line 5 can be either a part of "config_option_list" or "common_stmt" by itself. Currently, the lexer converts '\n' to T_EOL verbatim. In Kconfig, a new line works as a statement terminator, but new lines in empty lines are not critical since empty lines (or lines that contain only whitespaces/comments) are just no-op. If the lexer simply discards no-op lines, the parser will not be bothered by excessive T_EOL tokens. Of course, this means we are shifting the complexity from the parser to the lexer, but it is much easier than tackling on shift/reduce conflicts. I introduced the second stage lexer to tweak the behavior. Discard T_EOL if the previous token is T_EOL or T_HELPTEXT. Two T_EOL tokens in a row is meaningless. T_HELPTEXT is a special token that is reduced without T_EOL. Signed-off-by: Masahiro Yamada Signed-off-by: Christian Lamparter ---