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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 89d2b69c1b
commit 1d3df34671
4 changed files with 29 additions and 10 deletions
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26
src/parse-gram.c
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@@ -1,4 +1,4 @@
/* A Bison parser, made by GNU Bison 3.7.3.7-d831b. */
/* A Bison parser, made by GNU Bison 3.7.4.6-89d2b-dirty. */
/* Bison implementation for Yacc-like parsers in C
@@ -45,11 +45,11 @@
define necessary library symbols; they are noted "INFRINGES ON
USER NAME SPACE" below. */
/* Identify Bison output. */
#define YYBISON 30703
/* Identify Bison output, and Bison version. */
#define YYBISON 30704
/* Bison version. */
#define YYBISON_VERSION "3.7.3.7-d831b"
/* Bison version string. */
#define YYBISON_VERSION "3.7.4.6-89d2b-dirty"
/* Skeleton name. */
#define YYSKELETON_NAME "yacc.c"
@@ -365,6 +365,18 @@ typedef int_least16_t yytype_int16;
typedef short yytype_int16;
#endif
/* Work around bug in HP-UX 11.23, which defines these macros
incorrectly for preprocessor constants. This workaround can likely
be removed in 2023, as HPE has promised support for HP-UX 11.23
(aka HP-UX 11i v2) only through the end of 2022; see Table 2 of
<https://h20195.www2.hpe.com/V2/getpdf.aspx/4AA4-7673ENW.pdf>. */
#ifdef __hpux
# undef UINT_LEAST8_MAX
# undef UINT_LEAST16_MAX
# define UINT_LEAST8_MAX 255
# define UINT_LEAST16_MAX 65535
#endif
#if defined __UINT_LEAST8_MAX__ && __UINT_LEAST8_MAX__ <= __INT_MAX__
typedef __UINT_LEAST8_TYPE__ yytype_uint8;
#elif (!defined __UINT_LEAST8_MAX__ && defined YY_STDINT_H \
@@ -791,9 +803,9 @@ static const yytype_int16 yypgoto[] =
};
/* YYDEFGOTO[NTERM-NUM]. */
static const yytype_int16 yydefgoto[] =
static const yytype_uint8 yydefgoto[] =
{
-1, 1, 2, 43, 82, 115, 77, 45, 84, 46,
0, 1, 2, 43, 82, 115, 77, 45, 84, 46,
50, 49, 47, 156, 120, 121, 122, 97, 93, 94,
95, 128, 141, 87, 88, 89, 55, 56, 78, 79,
80, 135, 144, 145, 113, 63, 106, 57, 81, 58,

2
src/parse-gram.h
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@@ -1,4 +1,4 @@
/* A Bison parser, made by GNU Bison 3.7.3.7-d831b. */
/* A Bison parser, made by GNU Bison 3.7.4.6-89d2b-dirty. */
/* Bison interface for Yacc-like parsers in C

9
src/tables.c
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@@ -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)
{