-Wempty-rule: diagnose empty rules without %empty

[bison.git] / m4 / flex.m4

diff --git a/m4/flex.m4 b/m4/flex.m4
index 3327bf9be54b0141399209246008b0bb3e9ef69e..6f8530aecbbb2e059aaba95aa160dedca5cd6f28 100644 (file)
--- a/m4/flex.m4
+++ b/m4/flex.m4
@@ -1,5 +1,5 @@
-# flex.m4 serial 1
-# Copyright (C) 2012 Free Software Foundation, Inc.
+# flex.m4 serial 2
+# Copyright (C) 2012-2013 Free Software Foundation, Inc.
 # This file is free software; the Free Software Foundation
 # gives unlimited permission to copy and/or distribute it,
 # with or without modifications, as long as this notice is preserved.
@@ -12,7 +12,7 @@ AN_MAKEVAR([LEX],  [AC_PROG_LEX])
 AN_PROGRAM([lex],  [AC_PROG_LEX])
 AN_PROGRAM([flex], [AC_PROG_LEX])
 AC_DEFUN_ONCE([AC_PROG_LEX],
-[AC_CHECK_PROGS(LEX, flex lex, :)
+[AC_CHECK_PROGS([LEX], [flex lex], [:])
 if test "x$LEX" != "x:"; then
   _AC_PROG_LEX_YYTEXT_DECL
 fi])
@@ -20,10 +20,27 @@ fi])
 
 # _AC_PROG_LEX_YYTEXT_DECL
 # ------------------------
-# Check for the Lex output root, the Lex library, and whether Lex
-# declares yytext as a char * by default.
+# Check whether this is Flex, for the Lex output root, the Lex library,
+# and whether Lex declares yytext as a char * by default.
 m4_define([_AC_PROG_LEX_YYTEXT_DECL],
+[AC_CACHE_CHECK([whether lex is flex],
+                [ac_cv_prog_lex_is_flex],
 [cat >conftest.l <<_ACEOF[
+%option debug nodefault noinput nounput noyywrap never-interactive
+%x SC_CONF_TEST
+%%
+a { BEGIN SC_CONF_TEST; }
+]_ACEOF
+if _AC_DO_VAR([LEX conftest.l]); then
+  ac_cv_prog_lex_is_flex=yes
+else
+  ac_cv_prog_lex_is_flex=no
+fi
+])
+AC_SUBST([LEX_IS_FLEX],
+         [`test "$ac_cv_prog_lex_is_flex" = yes && echo true || echo false`])dnl
+
+cat >conftest.l <<_ACEOF[
 %%
 a { ECHO; }
 b { REJECT; }
@@ -43,7 +60,7 @@ main (void)
   return ! yylex () + ! yywrap ();
 }
 ]_ACEOF
-_AC_DO_VAR(LEX conftest.l)
+_AC_DO_VAR([LEX conftest.l])
 AC_CACHE_CHECK([lex output file root], [ac_cv_prog_lex_root], [
 if test -f lex.yy.c; then
   ac_cv_prog_lex_root=lex.yy
@@ -61,16 +78,17 @@ if test -z "${LEXLIB+set}"; then
     for ac_lib in '' -lfl -ll; do
       LIBS="$ac_lib $ac_save_LIBS"
       AC_LINK_IFELSE([AC_LANG_DEFINES_PROVIDED[`cat $LEX_OUTPUT_ROOT.c`]],
-       [ac_cv_lib_lex=$ac_lib])
+        [ac_cv_lib_lex=$ac_lib])
       test "$ac_cv_lib_lex" != 'none needed' && break
     done
     LIBS=$ac_save_LIBS
   ])
   test "$ac_cv_lib_lex" != 'none needed' && LEXLIB=$ac_cv_lib_lex
 fi
-AC_SUBST(LEXLIB)
+AC_SUBST([LEXLIB])
 
-AC_CACHE_CHECK(whether yytext is a pointer, ac_cv_prog_lex_yytext_pointer,
+AC_CACHE_CHECK([whether yytext is a pointer],
+               [ac_cv_prog_lex_yytext_pointer],
 [# POSIX says lex can declare yytext either as a pointer or an array; the
 # default is implementation-dependent.  Figure out which it is, since
 # not all implementations provide the %pointer and %array declarations.
@@ -85,9 +103,9 @@ LIBS=$ac_save_LIBS
 ])
 dnl
 if test $ac_cv_prog_lex_yytext_pointer = yes; then
-  AC_DEFINE(YYTEXT_POINTER, 1,
-           [Define to 1 if `lex' declares `yytext' as a `char *' by default,
-            not a `char[]'.])
+  AC_DEFINE([YYTEXT_POINTER], [1],
+            [Define to 1 if `lex' declares `yytext' as a `char *' by default,
+             not a `char[]'.])
 fi
 rm -f conftest.l $LEX_OUTPUT_ROOT.c
 ])# _AC_PROG_LEX_YYTEXT_DECL