From: Bruno Haible <bruno@clisp.org>
Date: Tue, 3 Dec 2019 08:19:17 +0000 (+0100)
Subject: Avoid hassles caused by [[noreturn]] in C++.
X-Git-Tag: v1.0~4557
X-Git-Url: https://gitweb.git.savannah.gnu.org/gitweb/?a=commitdiff_plain;h=56a2150cb8f33d7868f42098702173a0ccb38760;p=gnulib.git

Avoid hassles caused by [[noreturn]] in C++.

Reported by Christian Biesinger <cbiesinger@google.com> in
<https://lists.gnu.org/archive/html/bug-gnulib/2019-12/msg00010.html>.

* m4/gnulib-common.m4 (gl_COMMON_BODY): Disable the use of [[noreturn]].
* lib/_Noreturn.h: Likewise.
---

diff --git a/ChangeLog b/ChangeLog
index b441ffd1c4..2d26706b92 100644
--- a/ChangeLog
+++ b/ChangeLog
@@ -1,3 +1,11 @@
+2019-12-03  Bruno Haible  <bruno@clisp.org>
+
+	Avoid hassles caused by [[noreturn]] in C++.
+	Reported by Christian Biesinger <cbiesinger@google.com> in
+	<https://lists.gnu.org/archive/html/bug-gnulib/2019-12/msg00010.html>.
+	* m4/gnulib-common.m4 (gl_COMMON_BODY): Disable the use of [[noreturn]].
+	* lib/_Noreturn.h: Likewise.
+
 2019-12-02  Bruno Haible  <bruno@clisp.org>
 
 	Fix mistakes in --enable-threads=isoc fixes from 2019-12-01.
diff --git a/lib/_Noreturn.h b/lib/_Noreturn.h
index 06320b8cf2..d99e377a02 100644
--- a/lib/_Noreturn.h
+++ b/lib/_Noreturn.h
@@ -17,7 +17,14 @@
 #ifndef _Noreturn
 # if (defined __cplusplus \
       && ((201103 <= __cplusplus && !(__GNUC__ == 4 && __GNUC_MINOR__ == 7)) \
-          || (defined _MSC_VER && 1900 <= _MSC_VER)))
+          || (defined _MSC_VER && 1900 <= _MSC_VER)) \
+      && 0)
+    /* [[noreturn]] is not practically usable, because with it the syntax
+         extern _Noreturn void func (...);
+       would not be valid; such a declaration would only be valid with 'extern'
+       and '_Noreturn' swapped, or without the 'extern' keyword.  However, some
+       AIX system header files and several gnulib header files use precisely
+       this syntax with 'extern'.  */
 #  define _Noreturn [[noreturn]]
 # elif ((!defined __cplusplus || defined __clang__)                     \
         && (201112 <= (defined __STDC_VERSION__ ? __STDC_VERSION__ : 0)  \
diff --git a/m4/gnulib-common.m4 b/m4/gnulib-common.m4
index 479c9de9ea..d8f0d3fb56 100644
--- a/m4/gnulib-common.m4
+++ b/m4/gnulib-common.m4
@@ -1,4 +1,4 @@
-# gnulib-common.m4 serial 45
+# gnulib-common.m4 serial 46
 dnl Copyright (C) 2007-2019 Free Software Foundation, Inc.
 dnl This file is free software; the Free Software Foundation
 dnl gives unlimited permission to copy and/or distribute it,
@@ -19,7 +19,14 @@ AC_DEFUN([gl_COMMON_BODY], [
 #ifndef _Noreturn
 # if (defined __cplusplus \
       && ((201103 <= __cplusplus && !(__GNUC__ == 4 && __GNUC_MINOR__ == 7)) \
-          || (defined _MSC_VER && 1900 <= _MSC_VER)))
+          || (defined _MSC_VER && 1900 <= _MSC_VER)) \
+      && 0)
+    /* [[noreturn]] is not practically usable, because with it the syntax
+         extern _Noreturn void func (...);
+       would not be valid; such a declaration would only be valid with 'extern'
+       and '_Noreturn' swapped, or without the 'extern' keyword.  However, some
+       AIX system header files and several gnulib header files use precisely
+       this syntax with 'extern'.  */
 #  define _Noreturn [[noreturn]]
 # elif ((!defined __cplusplus || defined __clang__) \
         && (201112 <= (defined __STDC_VERSION__ ? __STDC_VERSION__ : 0)  \