Thanks for this fix. Minor: I don’t usually see the “goto x; x:” idiom as a way to “fall through” a case statement. I would probably keep the /*Fallthrough*/ comment (or add some equivalent comment) with an eye toward making this clear what’s going on.
In any case, thanks! Derek > On Jan 14, 2019, at 10:46 PM, Akim Demaille <a...@lrde.epita.fr> wrote: > > > >> Le 13 janv. 2019 à 22:20, Derek Clegg <de...@me.com> 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 <akim.demai...@gmail.com> > 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; > } >
