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tables: avoid warnings and save bits

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The yydefgoto table uses -1 as an invalid for an impossible case (we
never use yydefgoto[0], since it corresponds to the reduction to
$accept, which never happens).  Since yydefgoto is a table of state
numbers, this -1 forces a signed type uselessly, which (1) might
trigger compiler warnings when storing a value from yydefgoto into a
state number (nonnegative), and (2) wastes bits which might result in
using a int16 where a uint8 suffices.

Reported by Jot Dot <jotdot@shaw.ca>.
https://lists.gnu.org/r/bug-bison/2020-11/msg00027.html

* src/tables.c (default_goto): Use 0 rather than -1 as invalid value.
* tests/regression.at: Adjust.
This commit is contained in:
Akim Demaille
2020-12-02 21:39:26 +01:00
parent 9840e5b621
commit 24233748ec
4 changed files with 15 additions and 8 deletions
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10
src/parse-gram.c
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@@ -1,4 +1,4 @@
/* A Bison parser, made by GNU Bison 3.7.3.118-d0ea7-dirty. */
/* A Bison parser, made by GNU Bison 3.7.4.133-f40c-dirty. */
/* Bison implementation for Yacc-like parsers in C
@@ -46,10 +46,10 @@
USER NAME SPACE" below. */
/* Identify Bison output, and Bison version. */
#define YYBISON 30703
#define YYBISON 30704
/* Bison version string. */
#define YYBISON_VERSION "3.7.3.118-d0ea7-dirty"
#define YYBISON_VERSION "3.7.4.133-f40c-dirty"
/* Skeleton name. */
#define YYSKELETON_NAME "yacc.c"
@@ -799,9 +799,9 @@ static const yytype_int16 yypgoto[] =
};
/* YYDEFGOTO[NTERM-NUM]. */
static const yytype_int16 yydefgoto[] =
static const yytype_uint8 yydefgoto[] =
{
-1, 1, 2, 43, 81, 115, 76, 45, 83, 46,
0, 1, 2, 43, 81, 115, 76, 45, 83, 46,
50, 49, 51, 47, 60, 158, 120, 121, 122, 96,
92, 93, 94, 128, 142, 86, 87, 88, 99, 70,
77, 78, 79, 136, 146, 147, 113, 55, 105, 71,

2
src/parse-gram.h
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@@ -1,4 +1,4 @@
/* A Bison parser, made by GNU Bison 3.7.3.118-d0ea7-dirty. */
/* A Bison parser, made by GNU Bison 3.7.4.133-f40c-dirty. */
/* Bison interface for Yacc-like parsers in C

9
src/tables.c
View File

@@ -512,7 +512,14 @@ default_goto (symbol_number sym, size_t state_count[])
{
const goto_number begin = goto_map[sym - ntokens];
const goto_number end = goto_map[sym - ntokens + 1];
state_number res = -1;
/* In the case this symbol is never reduced to ($accept), use state
0. We used to use -1, but as a result the yydefgoto table must
be signed, which (1) might trigger compiler warnings when storing
a value from yydefgoto into a state number (nonnegative), and (2)
wastes bits which might result in using a int16 where a uint8
suffices. */
state_number res = 0;
if (begin != end)
{