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c++: issue a compile-time warning when #define YYSTYPE is used

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Using #define YYSTYPE has always been strongly discouraged in C++.
Macros are dangerous and can result in subtle bugs.
https://lists.gnu.org/r/bug-bison/2020-12/msg00007.html

Maybe some people are currently using #define YYSTYPE.  Instead of
dropping support right now, first issue a warning.  Bison can "see" if
YYDEBUG is defined (it could even be on the command line), only the
compiler knows.  Unfortunately `#warning` is non-portable, and
actually GCC even dies on it when `-pedantic` is enabled.  So we need
to use `#pragma message`.  We must make it conditional as some
compilers might not support it, but it doesn't matter if only _some_
compilers emit the warning: it should be enough to catch the attention
of the developers.

* data/skeletons/c++.m4: Issue a warning when the user defined
YYSTYPE.
* tests/actions.at: Don't #define YYSTYPE.
* tests/headers.at (Several parsers): Ignore the YYSTYPE in the
warning.
This commit is contained in:
Akim Demaille
2021-01-31 16:05:13 +01:00
parent dc8fe0678a
commit 9acc9d2aee
3 changed files with 18 additions and 12 deletions
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9
data/skeletons/c++.m4
View File

@@ -227,10 +227,13 @@ m4_define([b4_value_type_declare],
# Define the public types: token, semantic value, location, and so forth. # Define the public types: token, semantic value, location, and so forth.
# Depending on %define token_lex, may be output in the header or source file. # Depending on %define token_lex, may be output in the header or source file.
m4_define([b4_public_types_declare], m4_define([b4_public_types_declare],
[[#ifndef ]b4_api_PREFIX[STYPE [[#ifdef ]b4_api_PREFIX[STYPE
]b4_value_type_declare[ # ifdef __GNUC__
#else # pragma GCC message "bison: do not #define ]b4_api_PREFIX[STYPE in C++, use %define api.value.type"
# endif
typedef ]b4_api_PREFIX[STYPE value_type; typedef ]b4_api_PREFIX[STYPE value_type;
#else
]b4_value_type_declare[
#endif #endif
/// Backward compatibility (Bison 3.8). /// Backward compatibility (Bison 3.8).
typedef value_type semantic_type;]b4_locations_if([ typedef value_type semantic_type;]b4_locations_if([

4
tests/actions.at
View File

@@ -1777,8 +1777,6 @@ AT_DATA_GRAMMAR([[input.y]],
float fval; float fval;
} sem_type; } sem_type;
# define YYSTYPE sem_type
]AT_CXX_IF([[ ]AT_CXX_IF([[
# include <cstdio> // EOF. # include <cstdio> // EOF.
# include <iostream> # include <iostream>
@@ -1800,6 +1798,8 @@ AT_DATA_GRAMMAR([[input.y]],
]])[ ]])[
} }
%define api.value.type {sem_type}
%code %code
{ {
]AT_YYERROR_DECLARE[ ]AT_YYERROR_DECLARE[

17
tests/headers.at
View File

@@ -328,15 +328,18 @@ AT_TEST([xb], [%locations %define api.location.file none %language "c++" %define
# C++ output relies on namespaces and still uses yy a lot. # C++ output relies on namespaces and still uses yy a lot.
# #
# - no 'YY' left. # - no 'YY' left.
# Ignore comments, YYChar (template parameter), YYPUSH_MORE(_DEFINED)? # Ignore YYPUSH_MORE(_DEFINED)? (constant definition),
# (constant definition), YY_\w+_INCLUDED (header guards).
# YYDEBUG (not renamed) can be read, but not changed. # YYDEBUG (not renamed) can be read, but not changed.
AT_PERL_CHECK([[-n -0777 -e ' AT_PERL_CHECK([[-n -0777 -e '
# Ignore comments.
s{/\*.*?\*/}{}gs; s{/\*.*?\*/}{}gs;
s{//.*}{}g; s{//.*}{}g;
# Ignore warnings.
s{# *pragma .* message ".*"}{}g;
s{\b((defined|if)\ YYDEBUG s{\b((defined|if)\ YYDEBUG
|YYChar |YYChar # Template parameter.
|YYNTOKENS # This is actual scoped in a C++ class. |YYNTOKENS # This is actually scoped in a C++ class.
|YYPUSH_MORE(?:_DEFINED)? |YYPUSH_MORE(?:_DEFINED)?
|S_(YY(ACCEPT|EMPTY|EOF|error|UNDEF)) # These guys are scoped. |S_(YY(ACCEPT|EMPTY|EOF|error|UNDEF)) # These guys are scoped.
|YY(?:_REINTERPRET)?_CAST |YY(?:_REINTERPRET)?_CAST
@@ -354,9 +357,9 @@ AT_PERL_CHECK([[-n -0777 -e '
|YY_NULLPTR |YY_NULLPTR
|YY_RVREF |YY_RVREF
|YY_USE |YY_USE
|YY_\w+_INCLUDED |YY_\w+_INCLUDED # Header guards.
|FILE\ \*yyo # Function argument. |FILE\ \*yyo # Function argument.
|const\ yylocp # Function argument. |const\ yylocp # Function argument.
)\b}{}gx; )\b}{}gx;
while (/^(.*YY.*)$/gm) while (/^(.*YY.*)$/gm)
{ {