Re: Bison 3.2.90 released [beta]

[Akim Demaille]

> Le 13 janv. 2019 à 22:20, Derek Clegg <address@hidden> a écrit :
> 
> Here’s another one:
> 
> aux/parser.cc:228:13: error: unannotated fall-through between switch labels
>      [-Werror,-Wimplicit-fallthrough]
>            default:
>            ^
> aux/parser.cc:228:13: note: insert '[[fallthrough]];' to silence this warning
>            default:
>            ^
>            [[fallthrough]]; 
> aux/parser.cc:228:13: note: insert 'break;' to avoid fall-through
>            default:
>            ^
>            break; 
> 1 error generated.
> 
> I fixed this like so:
> 
> diff -ur bison-3.2.90/data/skeletons/lalr1.cc bison/data/skeletons/lalr1.cc
> --- bison-3.2.90/data/skeletons/lalr1.cc        2019-01-10 21:59:08.000000000 
> -\
> 0800
> +++ bison/data/skeletons/lalr1.cc       2019-01-13 13:15:26.000000000 -0800
> @@ -533,6 +533,11 @@
>               if (*++yyp != '\\')
>                 goto do_not_strip_quotes;
>               // Fall through.
> +#ifdef __has_feature
> +#if __has_feature(cxx_attributes)
> +              [[fallthrough]];
> +#endif
> +#endif
>             default:
>               yyr += *yyp;
>               break;
> 
> There may be a more canonical way to do this; I don’ know.

Thanks for the report!  I'll install the following patch, once peer-reviewed by 
the CI.

commit 547fe5a0fb50ab5f5a4e576b588fe5064b8002a9
Author: Akim Demaille <address@hidden>
Date:   Tue Jan 15 07:43:16 2019 +0100

    c, c++: avoid implicit fall-throw
    
    Reported by Derek Clegg.
    http://lists.gnu.org/archive/html/bug-bison/2019-01/msg00004.html
    
    * configure.ac (warn_common): Add -Wimplicit-fallthrough.
    This does trigger failures in the test suite.
    * data/skeletons/glr.c, data/skeletons/lalr1.cc, tests/c++.at:
    Make fall-throws explicit.

diff --git a/configure.ac b/configure.ac
index b7ba45dc..23aeb86d 100644
--- a/configure.ac
+++ b/configure.ac
@@ -96,7 +96,8 @@ AM_CONDITIONAL([ENABLE_GCC_WARNINGS], [test 
"$enable_gcc_warnings" = yes])
 if test "$enable_gcc_warnings" = yes; then
   warn_common='-Wall -Wextra -Wno-sign-compare -Wcast-align
     -fparse-all-comments -Wdocumentation
-    -Wformat -Wnull-dereference -Wpointer-arith -Wshadow
+    -Wformat -Wimplicit-fallthrough -Wnull-dereference
+    -Wpointer-arith -Wshadow
     -Wundefined-func-template -Wwrite-strings'
   warn_c='-Wbad-function-cast -Wstrict-prototypes'
   warn_cxx='-Wextra-semi -Wnoexcept'
diff --git a/data/skeletons/glr.c b/data/skeletons/glr.c
index bc491d51..87f2830b 100644
--- a/data/skeletons/glr.c
+++ b/data/skeletons/glr.c
@@ -590,7 +590,10 @@ yytnamerr (char *yyres, const char *yystr)
           case '\\':
             if (*++yyp != '\\')
               goto do_not_strip_quotes;
-            /* Fall through.  */
+            else
+              goto append;
+
+          append:
           default:
             if (yyres)
               yyres[yyn] = *yyp;
diff --git a/data/skeletons/lalr1.cc b/data/skeletons/lalr1.cc
index f3ad181c..053ba3be 100644
--- a/data/skeletons/lalr1.cc
+++ b/data/skeletons/lalr1.cc
@@ -532,7 +532,10 @@ m4_if(b4_prefix, [yy], [],
             case '\\':
               if (*++yyp != '\\')
                 goto do_not_strip_quotes;
-              // Fall through.
+              else
+                goto append;
+
+            append:
             default:
               yyr += *yyp;
               break;
diff --git a/tests/c++.at b/tests/c++.at
index 215c032c..bb1d0dab 100644
--- a/tests/c++.at
+++ b/tests/c++.at
@@ -1242,7 +1242,8 @@ yylex (yy::parser::semantic_type *lvalp)
   default:
     lvalp->]AT_VARIANT_IF([build<Object> (res)],
                           [obj = new Object (res)])[;
-    // Fall through.
+    goto zero;
+  zero:
   case 0:
     return res;
   }