[PATCH 2/5] c++: don't use YY_ASSERT at all if parse.assert is disabled

[Akim Demaille]

In some extreme situations (about 800 tokens), we generate a
single-line assertion long enough for Visual C++ to discard the end of
the line, thus falling into parse ends for the missing `);`.  On a
shorter example:

    YY_ASSERT (tok == token::TOK_YYEOF || tok == token::TOK_YYerror || tok == 
token::TOK_YYUNDEF || tok == token::TOK_ASSIGN || tok == token::TOK_MINUS || 
tok == token::TOK_PLUS || tok == token::TOK_STAR || tok == token::TOK_SLASH || 
tok == token::TOK_LPAREN || tok == token::TOK_RPAREN);

Whether NDEBUG is used or not is irrelevant, the parser dies anyway.

Reported by Jot Dot <jotdot@shaw.ca>.
https://lists.gnu.org/r/bug-bison/2020-11/msg00002.html

We should avoid emitting lines so long.

We probably should also use a range-based assertion (with extraneous
parens to pacify fascist compilers):

    YY_ASSERT ((token::TOK_YYEOF <= tok && tok <= token::TOK_YYUNDEF)
               || (token::TOK_ASSIGN <= tok && ...)

But anyway, we should simply not emit this assertion at all when not
asked for.

* data/skeletons/variant.hh: Do not define, nor use, YY_ASSERT when it
is not enabled.
---
 NEWS                      |  8 ++++++++
 data/skeletons/variant.hh | 17 +++++++----------
 2 files changed, 15 insertions(+), 10 deletions(-)

diff --git a/NEWS b/NEWS
index ebb3354a..c5775a69 100644
--- a/NEWS
+++ b/NEWS
@@ -4,9 +4,17 @@ GNU Bison NEWS
 
 ** Bug fixes
 
+*** Bug fixes in yacc.c
+
   In Yacc mode, all the tokens are defined twice: once as an enum, and then
   as a macro.  YYEMPTY was missing its macro.
 
+*** Bug fixes in lalr1.cc
+
+  The lalr1.cc skeleton used to emit internal assertions (using YY_ASSERT)
+  even when the `parse.assert` %define variable is not enabled.  It no
+  longer does.
+
 ** Changes
 
   The YYBISON macro in generated "regular C parsers" (from the "yacc.c"
diff --git a/data/skeletons/variant.hh b/data/skeletons/variant.hh
index 736a2677..1fe40145 100644
--- a/data/skeletons/variant.hh
+++ b/data/skeletons/variant.hh
@@ -71,12 +71,12 @@ m4_map([      b4_symbol_tag_comment], [$@])dnl
 # -------------------
 # The needed includes for variants support.
 m4_define([b4_variant_includes],
-[b4_parse_assert_if([[#include <typeinfo>]])[
+[b4_parse_assert_if([[#include <typeinfo>
 #ifndef YY_ASSERT
 # include <cassert>
 # define YY_ASSERT assert
 #endif
-]])
+]])])
 
 
 
@@ -110,8 +110,8 @@ m4_define([b4_value_type_declare],
     template <typename T>
     semantic_type (YY_RVREF (T) t)]b4_parse_assert_if([
       : yytypeid_ (&typeid (T))])[
-    {
-      YY_ASSERT (sizeof (T) <= size);
+    {]b4_parse_assert_if([[
+      YY_ASSERT (sizeof (T) <= size);]])[
       new (yyas_<T> ()) T (YY_MOVE (t));
     }
 
@@ -410,9 +410,6 @@ m4_define([_b4_token_constructor_define],
         : super_type(]b4_join([token_type (tok)],
                               b4_symbol_if([$1], [has_type], [std::move (v)]),
                               b4_locations_if([std::move (l)]))[)
-      {
-        YY_ASSERT (]m4_join([ || ], m4_map_sep([_b4_type_clause], [, ], 
[$@]))[);
-      }
 #else
       symbol_type (]b4_join(
           [int tok],
@@ -422,10 +419,10 @@ m4_define([_b4_token_constructor_define],
         : super_type(]b4_join([token_type (tok)],
                               b4_symbol_if([$1], [has_type], [v]),
                               b4_locations_if([l]))[)
-      {
-        YY_ASSERT (]m4_join([ || ], m4_map_sep([_b4_type_clause], [, ], 
[$@]))[);
-      }
 #endif
+      {]b4_parse_assert_if([[
+        YY_ASSERT (]m4_join([ || ], m4_map_sep([_b4_type_clause], [, ], 
[$@]))[);
+      ]])[}
 ]])])
 
 
-- 
2.29.2