ambiguity between strings and keywords

[ggs67]

Analyzing the csync2 parser for extending the auto command I stumbled over a problem with an ambiguity between unquoted strings and keywords. For example if a host is called "auto", the statement 'host auto' will fail requiring quotes because auto is a keyword.

If you want to give it a try I have modified the flex and bison files in the parser-path branch of my fork. I can also file a pull request.

https://github.com/ggs67/csync2/tree/parser-patch

Commit comment of modifications:

1. Disambiguation of strings

  Modified lexer with non-exclusive start state STRTOKEN for strings without quotes.
  This resolves the conflict where strings matching keywords will fail if not quoted
  (ex. 'host auto;' required 'host "auto";')

2. Tokenized auto-methods

  Modified auto-methods from separate C-parsing code to include those by separate tokens in the
  lexer.

  This change was done to cleanup parsing, becoming more readable and in prepartation to extend the
  auto command.

[ggs67]

FYI: I identified some problems with my modifications. First I did add an unnecessary AUTO start state which I have already removed, but this is secondary (more cosmetic). I introduced this state because I thought it would be necessary for the eauto-feature, but I changed the syntax this it is no required anymore.

But another problem is the string handling which would not allow any unquoted string after a quoted string was found. This is due to the fact that "quote removal" is performed by the lexer and the related state changes. I will solve this by introducing as state stack. But this will probably only make it into the auto-feature branch