From f8cadc731b0df0df9e93d009d5e96b0f752a9b3c Mon Sep 17 00:00:00 2001
From: Akim Demaille <akim.demaille@gmail.com>
Date: Wed, 31 Oct 2018 09:25:04 +0100
Subject: [PATCH] c: provide a definition of _Noreturn that works for C++

On Solaris, GCC 7.3 defines:

                      -std=c++14  -std=c++17
    __cplusplus       201402L       201703L
    __STDC_VERSION__  199901L       201112L

So the current #definition of _Noreturn sees that 201112 <=
__STDC_VERSION__, i.e., that C11 is supported, so it expects _Noreturn
to be supported.  Apparently it is not.

This is only for C++, the test suite works for C.  However, the test
suite does not try several C standards, maybe we should...

http://lists.gnu.org/archive/html/bug-bison/2018-10/msg00064.html

* data/c.m4 (b4_attribute_define): Define _Noreturn as [[noreturn]] in
modern C++.
---
 data/c.m4 | 21 ++++++++++++---------
 1 file changed, 12 insertions(+), 9 deletions(-)

diff --git a/data/c.m4 b/data/c.m4
index 04df3ffc..bb19b348 100644
--- a/data/c.m4
+++ b/data/c.m4
@@ -228,15 +228,18 @@ m4_define([b4_attribute_define],
 #endif
 
 ]m4_bmatch([$1], [\bnoreturn\b], [[/* The _Noreturn keyword of C11.  */
-#if ! (defined _Noreturn \
-       || (defined __STDC_VERSION__ && 201112 <= __STDC_VERSION__))
-# if (3 <= __GNUC__ || (__GNUC__ == 2 && 8 <= __GNUC_MINOR__) \
-      || 0x5110 <= __SUNPRO_C)
-#  define _Noreturn __attribute__ ((__noreturn__))
-# elif defined _MSC_VER && 1200 <= _MSC_VER
-#  define _Noreturn __declspec (noreturn)
-# else
-#  define _Noreturn
+#if ! defined _Noreturn
+# if defined __cplusplus && 201103L <= __cplusplus
+#  define _Noreturn [[noreturn]]
+# elif !(defined __STDC_VERSION__ && 201112 <= __STDC_VERSION__)
+#  if (3 <= __GNUC__ || (__GNUC__ == 2 && 8 <= __GNUC_MINOR__) \
+       || 0x5110 <= __SUNPRO_C)
+#   define _Noreturn __attribute__ ((__noreturn__))
+#  elif defined _MSC_VER && 1200 <= _MSC_VER
+#   define _Noreturn __declspec (noreturn)
+#  else
+#   define _Noreturn
+#  endif
 # endif
 #endif