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Re: [Bison-Announce] Bison 3.4.91 released [beta]
From: |
Akim Demaille |
Subject: |
Re: [Bison-Announce] Bison 3.4.91 released [beta] |
Date: |
Sun, 1 Dec 2019 09:49:21 +0100 |
Hi Frank,
> Le 1 déc. 2019 à 09:15, Frank Heckenbach <address@hidden> a écrit :
>
> No sweat about the warnings, but if the empty_state comparison is
> actually wrong (if my test was correct), this might be more urgent.
Yes, I'll have a look at it. I thought I had started with something
simple, but there are plenty of ramifications all over the place...
> AFAICS, it would then access yystos_[0xff], out of bounds (usually).
>
>> --- a/data/skeletons/c++.m4
>> +++ b/data/skeletons/c++.m4
>> @@ -545,7 +545,7 @@ m4_define([b4_yytranslate_define],
>> const int user_token_number_max_ = ]b4_user_token_number_max[;
>> const token_number_type undef_token_ = ]b4_undef_token_number[;
>>
>> - if (static_cast<int> (t) <= yyeof_)
>> + if (t <= 0)
>> return yyeof_;
>> else if (static_cast<int> (t) <= user_token_number_max_)
>> return translate_table[t];
>
> You did notice there's another "static_cast<int> (t)" in the
> "else if" line?
>
> If you can't use "int { t }" as I suggested (doesn't work with older
> C++ standards, does it?), maybe you can use a temporary like
> "int tt = t;" to avoid both casts at once.
Yes, I did notice this cast/warning too. And it took me a while to
be sure how to address it. See below. Cheers!
commit 478cb5cf12fb6ac0f3b34077fed70a29c5eefca8
Author: Akim Demaille <address@hidden>
Date: Sat Nov 30 13:20:48 2019 +0100
c++: remove useless cast about user_token_number_max_
Reported by Frank Heckenbach.
https://lists.gnu.org/archive/html/bug-bison/2019-11/msg00016.html
The cast is needed when yytranslate_'s argument type is token_type,
i.e., when api.token.constructor is defined.
373. types.at:138: testing lalr1.cc api.value.type=variant
api.token.constructor ...
======== Testing with C++ standard flags: ''
../../tests/types.at:138: bison --color=no -fno-caret -o test.cc test.y
../../tests/types.at:138: $CXX $CXXFLAGS $CPPFLAGS $LDFLAGS -o test
test.cc $LIBS
stderr:
test.cc:966:16: error: result of comparison of constant 257 with
expression of type 'yy::parser::token_type'
(aka 'yy::parser::token::yytokentype') is always true
[-Werror,-Wtautological-constant-out-of-range-compare]
else if (t <= user_token_number_max_)
~ ^ ~~~~~~~~~~~~~~~~~~~~~~
1 error generated.
It is because it is expected that when api.token.constructor is
defined, only symbol constructors will be used, that yytranslate_ then
takes a token_type. But it is wrong: we still allow literal
characters in this case, as demonstrated by test 373 for instance.
%define api.value.type variant
%define api.token.constructor
%token <std::pair<int, int>> '1' '2';
[...]
static yy::parser::symbol_type yylex ()
{
static char const input[] = "12";
int res = input[toknum++];
typedef yy::parser::symbol_type symbol;
if (res)
return symbol (res, std::make_pair (res - '0', res - '0' + 1));
else
return symbol (res);
}
So let yytranslate_ always take an int, which makes the cast truly
useless.
* data/skeletons/c++.m4, data/skeletons/lalr1.cc (yytranslate_): here.
diff --git a/data/skeletons/c++.m4 b/data/skeletons/c++.m4
index c78ebed6..6e825ff3 100644
--- a/data/skeletons/c++.m4
+++ b/data/skeletons/c++.m4
@@ -529,8 +529,7 @@ m4_define([b4_token_constructor_define], [])
# sometimes in the cc file.
m4_define([b4_yytranslate_define],
[ b4_inline([$1])b4_parser_class[::token_number_type
- ]b4_parser_class[::yytranslate_ (]b4_token_ctor_if([token_type],
- [int])[ t)
+ ]b4_parser_class[::yytranslate_ (int t)
{
]b4_api_token_raw_if(
[[ return static_cast<yy::parser::token_number_type> (t);]],
@@ -546,7 +545,7 @@ m4_define([b4_yytranslate_define],
if (t <= 0)
return yyeof_;
- else if (static_cast<int> (t) <= user_token_number_max_)
+ else if (t <= user_token_number_max_)
return translate_table[t];
else
return yy_undef_token_;]])[
diff --git a/data/skeletons/lalr1.cc b/data/skeletons/lalr1.cc
index 5c8a67df..8a2bee04 100644
--- a/data/skeletons/lalr1.cc
+++ b/data/skeletons/lalr1.cc
@@ -268,7 +268,9 @@ m4_define([b4_shared_declarations],
static const ]b4_int_type(b4_table_ninf, b4_table_ninf)[ yytable_ninf_;
/// Convert a scanner token number \a t to a symbol number.
- static token_number_type yytranslate_ (]b4_token_ctor_if([token_type],
[int])[ t);
+ /// In theory \a t should be a token_type, but character literals
+ /// are valid, yet not member of the token_type enum.
+ static token_number_type yytranslate_ (int t);
// Tables.
]b4_parser_tables_declare[]b4_error_verbose_if([