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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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66
tests/reduce.at
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@@ -445,23 +445,69 @@ AT_CLEANUP
## ---------------- ##
## Empty Language. ##
## ---------------- ##
## ------------------- ##
## Bad start symbols. ##
## ------------------- ##
AT_SETUP([Empty Language])
AT_SETUP([Bad start symbols])
m4_pushdef([AT_TEST],
[
AT_DATA([[input.y]],
[[%output "input.c"
%%
exp: exp;
]])
[%%
$1
])
AT_BISON_CHECK([[input.y]], 1, [],
[$2
])
])
AT_TEST(
[[exp: exp;]],
[[input.y: warning: 2 nonterminals useless in grammar [-Wother]
input.y: warning: 2 rules useless in grammar [-Wother]
input.y:3.1-3: fatal error: start symbol exp does not derive any sentence
]])
input.y:2.1-3: error: start symbol exp does not derive any sentence]])
AT_TEST(
[[%start exp;
exp: exp;]],
[[input.y: warning: 2 nonterminals useless in grammar [-Wother]
input.y: warning: 2 rules useless in grammar [-Wother]
input.y:2.8-10: error: start symbol exp does not derive any sentence]])
AT_TEST(
[[%start exp stmt;
exp: exp;
stmt: "stmt"]],
[[input.y: warning: 1 nonterminal useless in grammar [-Wother]
input.y: warning: 2 rules useless in grammar [-Wother]
input.y:2.8-10: error: start symbol exp does not derive any sentence]])
AT_TEST(
[[%start exp stmt;
exp: exp;
stmt: stmt]],
[[input.y: warning: 3 nonterminals useless in grammar [-Wother]
input.y: warning: 4 rules useless in grammar [-Wother]
input.y:2.8-10: error: start symbol exp does not derive any sentence
input.y:2.12-15: error: start symbol stmt does not derive any sentence]])
AT_TEST(
[[%start exp;
stmt: stmt]],
[[input.y:2.8-10: warning: symbol 'exp' is used, but is not defined as a token and has no rules [-Wother]
input.y: warning: 3 nonterminals useless in grammar [-Wother]
input.y: warning: 2 rules useless in grammar [-Wother]
input.y:2.8-10: error: start symbol exp does not derive any sentence]])
AT_TEST(
[[%token FOO;
%start FOO;
stmt: FOO]],
[[input.y:2.8-10: error: the start symbol FOO is a token]])
m4_popdef([AT_TEST])
AT_CLEANUP