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multistart: turn start symbols into rules on $accept

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Now that the parser can read several start symbols, let's process
them, and create the corresponding rules.

* src/parse-gram.y (grammar_declaration): Accept a list of start symbols.
* src/reader.h, src/reader.c (grammar_start_symbol_set): Rename as...
(grammar_start_symbols_set): this.

* src/reader.h, src/reader.c (start_flag): Replace with...
(start_symbols): this.
* src/reader.c (grammar_start_symbols_set): Build a list of start
symbols.
(switching_token, create_start_rules): New.
(check_and_convert_grammar): Use them to turn the list of start
symbols into a set of rules.
* src/reduce.c (nonterminals_reduce): Don't complain about $accept,
it's an internal detail.
(reduce_grammar): Complain about all the start symbols that don't
derive sentences.

* src/symtab.c (startsymbol, startsymbol_loc): Remove, replaced by
start_symbols.
symbols_pack): Move the check about the start symbols
to...
* src/symlist.c (check_start_symbols): here.
Adjust to multiple start symbols.
* tests/reduce.at (Empty Language): Generalize into...
(Bad start symbols): this.
This commit is contained in:
Akim Demaille
2020-02-20 18:11:29 +01:00
parent db68f61595
commit 8eaddf326b
8 changed files with 194 additions and 54 deletions
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11
src/symtab.c
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@@ -60,8 +60,6 @@ symbol *errtoken = NULL;
symbol *undeftoken = NULL;
symbol *eoftoken = NULL;
symbol *acceptsymbol = NULL;
symbol *startsymbol = NULL;
location startsymbol_loc;
/* Precedence relation graph. */
static symgraph **prec_nodes;
@@ -1146,15 +1144,6 @@ symbols_pack (void)
symbols_token_translations_init ();
if (startsymbol->content->class == unknown_sym)
complain (&startsymbol_loc, fatal,
_("the start symbol %s is undefined"),
startsymbol->tag);
else if (startsymbol->content->class == token_sym)
complain (&startsymbol_loc, fatal,
_("the start symbol %s is a token"),
startsymbol->tag);
// If some user tokens are internationalized, the internal ones
// should be too.
if (has_translations ())