> Le 20 nov. 2018 à 23:18, Akim Demaille <a...@lrde.epita.fr> a écrit :
>
> I don’t have any problems with having two pairs of parens, after all we’ve
> done that forever in the case of assignments in if’s etc. That’s a clear way
> to tell the others, including the compiler, that something fishy is
> intentional (until ‘sic’ becomes a keyword).
>
> The problem here is that it does not work, although it should.
This appears to be the proper fix.
commit cc050fd3218c4ee467dfe6c234867d84bd3e7119
Author: Akim Demaille <akim.demai...@gmail.com>
Date: Thu Nov 22 18:03:12 2018 +0100
warning: avoid warnings about unreachable code
Reported by Uxio Prego.
https://lists.gnu.org/archive/html/help-bison/2018-11/msg00031.html
We also need to move the unreachable 'goto' to a reachable place,
otherwise clang complains about the code being unreachable anyway.
See also https://bugs.llvm.org/show_bug.cgi?id=39736.
Interestingly, we don't have to apply that trick to
`#define YYCDEBUG if (false) std::cerr`, clang does not warn when the
code comes from macro expansion.
* configure.ac: Use -Wunreachable-code when supported.
* data/lalr1.cc, data/yacc.c: Pacify clang's warning about `if (0)`
by using a macro.
Another possibility was to move this statement to a reachable place.
* tests/actions.at, tests/c++.at: Avoid generating unreachable code.
diff --git a/configure.ac b/configure.ac
index 3d55f08c..959fc968 100644
--- a/configure.ac
+++ b/configure.ac
@@ -113,6 +113,7 @@ if test "$enable_gcc_warnings" = yes; then
-fno-color-diagnostics
-Wno-keyword-macro'
+
AC_LANG_PUSH([C])
# Clang supports many of GCC's -W options, but only issues warnings
# on the ones it does not recognize. In that case, gl_WARN_ADD
@@ -126,6 +127,11 @@ if test "$enable_gcc_warnings" = yes; then
# CFLAGS, and restore CFLAGS after the tests.
save_CFLAGS=$CFLAGS
gl_WARN_ADD([-Werror=unknown-warning-option], [CFLAGS])
+ # Accept this warning only if it is not too touchy (e.g., clang 3.3
+ # and 3.4).
+ gl_WARN_ADD([-Wunreachable-code], [WARN_CFLAGS],
+ [AC_LANG_PROGRAM([],
+ [[if (sizeof (long) < sizeof (int)) return 1;]])])
for i in $warn_common $warn_c;
do
gl_WARN_ADD([$i], [WARN_CFLAGS])
@@ -147,6 +153,7 @@ if test "$enable_gcc_warnings" = yes; then
CFLAGS=$save_CFLAGS
AC_LANG_POP([C])
+
AC_LANG_PUSH([C++])
save_CXXFLAGS=$CXXFLAGS
gl_WARN_ADD([-Werror=unknown-warning-option], [CXXFLAGS])
@@ -154,6 +161,11 @@ if test "$enable_gcc_warnings" = yes; then
do
gl_WARN_ADD([$i], [WARN_CXXFLAGS])
done
+ # Accept this warning only if it is not too touchy (e.g., clang 3.3
+ # and 3.4).
+ gl_WARN_ADD([-Wunreachable-code], [WARN_CXXFLAGS],
+ [AC_LANG_PROGRAM([],
+ [[if (sizeof (long) < sizeof (int)) return 1;]])])
gl_WARN_ADD([-Wzero-as-null-pointer-constant], [WARN_CXXFLAGS],
[AC_LANG_PROGRAM([], [nullptr])])
gl_WARN_ADD([-Werror], [WERROR_CXXFLAGS])
diff --git a/data/lalr1.cc b/data/lalr1.cc
index 8486f9e8..78f3d1e0 100644
--- a/data/lalr1.cc
+++ b/data/lalr1.cc
@@ -971,11 +971,11 @@ b4_dollar_popdef])[]dnl
| yyerrorlab -- error raised explicitly by YYERROR. |
`---------------------------------------------------*/
yyerrorlab:
- /* Pacify compilers like GCC when the user code never invokes
- YYERROR and the label yyerrorlab therefore never appears in user
- code. */
+ /* Pacify compilers when the user code never invokes YYERROR and
+ the label yyerrorlab therefore never appears in user code. */
if (false)
- goto yyerrorlab;
+ YYERROR;
+
/* Do not reclaim the symbols of the rule whose action triggered
this YYERROR. */
yypop_ (yylen);
diff --git a/data/yacc.c b/data/yacc.c
index 3f2883c6..ee0acd5b 100644
--- a/data/yacc.c
+++ b/data/yacc.c
@@ -1777,11 +1777,10 @@ yyerrlab:
| yyerrorlab -- error raised explicitly by YYERROR. |
`---------------------------------------------------*/
yyerrorlab:
- /* Pacify compilers like GCC when the user code never invokes
- YYERROR and the label yyerrorlab therefore never appears in user
- code. */
+ /* Pacify compilers when the user code never invokes YYERROR and the
+ label yyerrorlab therefore never appears in user code. */
if (0)
- goto yyerrorlab;
+ YYERROR;
/* Do not reclaim the symbols of the rule whose action triggered
this YYERROR. */
diff --git a/examples/calc++/local.mk b/examples/calc++/local.mk
index 059f2b05..8de5bf4d 100644
--- a/examples/calc++/local.mk
+++ b/examples/calc++/local.mk
@@ -20,7 +20,7 @@
# Don't depend on $(BISON) otherwise we would rebuild these files
# in srcdir, including during distcheck, which is forbidden.
-%D%/parser.stamp: $(BISON_IN)
+%D%/parser.stamp: $(BISON_IN) $(dist_pkgdata_DATA)
SUFFIXES += .yy .stamp
.yy.stamp:
$(AM_V_YACC)rm -f $@
diff --git a/tests/actions.at b/tests/actions.at
index deeed15d..7d692cd5 100644
--- a/tests/actions.at
+++ b/tests/actions.at
@@ -519,6 +519,8 @@ AT_DATA_GRAMMAR([[input.y]],
#define RANGE(Location) ]AT_LALR1_CC_IF([(Location).begin.line,
(Location).end.line],
[(Location).first_line, (Location).last_line])[
+#define USE(SYM)
+
/* Display the symbol type Symbol. */
#define V(Symbol, Value, Location, Sep) \
fprintf (stderr, #Symbol " (%d@%d-%d)%s", Value, RANGE(Location), Sep)
@@ -610,8 +612,8 @@ input:
;
check-spontaneous-errors:
- raise { abort(); $$ = $1; }
-| '(' raise ')' { abort(); $$ = $2; }
+ raise { abort(); USE(($$, $1)); }
+| '(' raise ')' { abort(); USE(($$, $2)); }
| error
{
$$ = 5;
diff --git a/tests/c++.at b/tests/c++.at
index 81c61863..2d5a4ac2 100644
--- a/tests/c++.at
+++ b/tests/c++.at
@@ -435,8 +435,6 @@ namespace yy
return parser::token::TEXT;]])[
}
}
-
- abort ();
}
}
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