From b5515215c188a48c0a9956a5cb03ddb951870477 Mon Sep 17 00:00:00 2001
From: Akim Demaille <akim.demaille@gmail.com>
Date: Tue, 23 Oct 2018 07:12:09 +0200
Subject: [PATCH] yacc.c: don't define _Noreturn uselessly

Clang warns:

     aux/x.h:97:11: error: macro name is a reserved identifier
           [-Werror,-Wreserved-id-macro]
     #  define _Noreturn YY_ATTRIBUTE ((__noreturn__))

Reported by Derek Clegg.
http://lists.gnu.org/archive/html/bug-bison/2018-10/msg00024.html

* data/c.m4 (b4_attribute_define): Don't define _Noreturn unconditionally.
* data/glr.c: Ask for _Noreturn.
---
 data/c.m4  | 15 ++++++++-------
 data/glr.c |  2 +-
 2 files changed, 9 insertions(+), 8 deletions(-)

diff --git a/data/c.m4 b/data/c.m4
index 2ec6ceea..2df76e77 100644
--- a/data/c.m4
+++ b/data/c.m4
@@ -204,11 +204,12 @@ m4_define([b4_table_value_equals],
 ## Compiler issues.  ##
 ## ----------------- ##
 
-# b4_attribute_define
-# -------------------
-# Provide portable compiler "attributes".
+# b4_attribute_define([noreturn])
+# -------------------------------
+# Provide portable compiler "attributes".  If "noreturn" is passed, define
+# _Noreturn.
 m4_define([b4_attribute_define],
-[#ifndef YY_ATTRIBUTE
+[[#ifndef YY_ATTRIBUTE
 # if (defined __GNUC__                                               \
       && (2 < __GNUC__ || (__GNUC__ == 2 && 96 <= __GNUC_MINOR__)))  \
      || defined __SUNPRO_C && 0x5110 <= __SUNPRO_C
@@ -226,7 +227,7 @@ m4_define([b4_attribute_define],
 # define YY_ATTRIBUTE_UNUSED YY_ATTRIBUTE ((__unused__))
 #endif
 
-#if !defined _Noreturn \
+]m4_bmatch([$1], [\bnoreturn\b], [[#if !defined _Noreturn \
      && (!defined __STDC_VERSION__ || __STDC_VERSION__ < 201112)
 # if defined _MSC_VER && 1200 <= _MSC_VER
 #  define _Noreturn __declspec (noreturn)
@@ -235,7 +236,7 @@ m4_define([b4_attribute_define],
 # endif
 #endif
 
-/* Suppress unused-variable warnings by "using" E.  */
+]])[/* Suppress unused-variable warnings by "using" E.  */
 #if ! defined lint || defined __GNUC__
 # define YYUSE(E) ((void) (E))
 #else
@@ -260,7 +261,7 @@ m4_define([b4_attribute_define],
 #ifndef YY_INITIAL_VALUE
 # define YY_INITIAL_VALUE(Value) /* Nothing. */
 #endif
-])
+]])
 
 
 # b4_null_define
diff --git a/data/glr.c b/data/glr.c
index 56788b80..f77da621 100644
--- a/data/glr.c
+++ b/data/glr.c
@@ -311,7 +311,7 @@ static YYLTYPE yyloc_default][]b4_yyloc_default;])[
  } while (yyfalse)
 #endif
 
-]b4_attribute_define[
+]b4_attribute_define([noreturn])[
 
 #ifndef YYASSERT
 # define YYASSERT(Condition) ((void) ((Condition) || (abort (), 0)))