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744171ddbf
Currently pstate_new does not set up its variables, this task is left to yypush_parse. This was probably to share more code with usual pull parsers, where these (local) variables are indeed initialized by yyparse. But as a consequence yyexpected_tokens crashes at the very beginning of the parse, since, for instance, the stacks are not even set up. See https://lists.gnu.org/r/bison-patches/2020-03/msg00001.html. The fix could have very simple, but the documentation actually makes it very clear that we can reuse a pstate for several parses: After yypush_parse returns a status other than YYPUSH_MORE, the parser instance yyps may be reused for a new parse. so we need to restore the parser to its pristine state so that (i) it is ready to run the next parse, (ii) it properly supports yyexpected_tokens for the next run. * data/skeletons/yacc.c (b4_initialize_parser_state_variables): New, extracted from the top of yyparse/yypush_parse. (yypstate_clear): New. (yypstate_new): Use it when push parsers are enabled. Define after the yyps macros so that we can use the same code as the regular pull parsers. (yyparse): Use it when push parsers are _not_ enabled. * examples/c/bistromathic/bistromathic.test: Check the completion on the beginning of the line.
bistromathic - all the bells and whistles
This example demonstrates best practices when using Bison.
- Its hand-written scanner tracks locations.
- Its interface is pure.
- Its interface is "incremental", well suited for interaction: it uses the push-parser API to feed the parser with the incoming tokens.
- It features an interactive command line with completion based on the
parser state, based on
yyexpected_tokens. - It uses a custom syntax error with location, lookahead correction and token internationalization.
- It supports debug traces with semantic values.
- It uses named references instead of the traditional $1, $2, etc.