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From: Paul Eggert <eggert@cs.ucla.edu>
To: bug-gnulib@gnu.org
Cc: Paul Eggert <eggert@cs.ucla.edu>
Subject: [PATCH] stdnoreturn: deprecate
Date: Sat, 24 Dec 2022 01:35:07 -0800	[thread overview]
Message-ID: <20221224093507.207827-1-eggert@cs.ucla.edu> (raw)

C23 says <stdnoreturn.h> is obsolescent, so deprecate the
stdnoreturn module.  I don't think it was being used anyway
as it had too many problems.
* modules/stdnoreturn: Mark as obsolete.
 ChangeLog                          |  8 +++++++
 NEWS                               |  3 +++
 doc/noreturn.texi                  | 35 ++++++++++++++----------------
 doc/posix-headers/stdnoreturn.texi |  2 ++
 lib/stdnoreturn.in.h               |  4 +++-
 modules/stdnoreturn                |  6 +++++
 6 files changed, 38 insertions(+), 20 deletions(-)

diff --git a/ChangeLog b/ChangeLog
index 3b6c6cf98e..91370af964 100644
--- a/ChangeLog
+++ b/ChangeLog
@@ -1,3 +1,11 @@
+2022-12-24  Paul Eggert  <eggert@cs.ucla.edu>
+	stdnoreturn: deprecate
+	C23 says <stdnoreturn.h> is obsolescent, so deprecate the
+	stdnoreturn module.  I don't think it was being used anyway
+	as it had too many problems.
+	* modules/stdnoreturn: Mark as obsolete.
 2022-12-23  Paul Eggert  <eggert@cs.ucla.edu>
 	file-has-acl: improve recent NFSv4 support
diff --git a/NEWS b/NEWS
index bc620ce86a..dd2374c4fd 100644
--- a/NEWS
+++ b/NEWS
@@ -74,6 +74,9 @@ User visible incompatible changes
 Date        Modules         Changes
+2022-12-24  stdnoreturn     This module is deprecated.  Use _Noreturn
+                            or the noreturn module instead.
 2022-12-21  ctime           This module is deprecated.  Use localtime_r
                             and strftime (or even sprintf) instead.
diff --git a/doc/noreturn.texi b/doc/noreturn.texi
index a3a394409c..ad0a286f4a 100644
--- a/doc/noreturn.texi
+++ b/doc/noreturn.texi
@@ -15,22 +15,26 @@
 @cindex @code{noreturn}
 @cindex @code{stdnoreturn}
 A "non-returning" function is a function which cannot return normally.
-It can transfer control only through @code{longjmp()}, @code{throw}
-(in C++), or similar mechanisms.  The most prominent function of this
-class is the @code{abort} function.  Non-returning functions are
+Instead of returning, it can loop forever, or it can transfer control via
+@code{abort}, @code{execvp}, @code{exit}, @code{longjmp}, @code{throw}
+(in C++), or similar mechanisms.  Non-returning functions are
 declared with a @code{void} return type.
 It helps the compiler's ability to emit sensible warnings, following
 data-flow analysis, to declare which functions are non-returning.
+It can also help generate more-efficient code, as there is no need
+to save a return address when calling a non-returning function.
-To decorate function declarations and function definitions, you can
-use the @code{_Noreturn} keyword.  No modules are needed, as Gnulib
+Gnulib has multiple ways to support such a declaration''
+@itemize @bullet
+The @code{_Noreturn} keyword.  No modules are needed, as Gnulib
 arranges for @code{<config.h>} to define @code{_Noreturn} to an
 appropriate replacement on platforms lacking it.
+Unfortunately, although this approach works for all current C versions,
+the @code{_Noreturn} keyword is obsolescent in C23.
-Gnulib has two modules that support such a declaration:
-@itemize @bullet
 The @samp{noreturn} module.  It provides a way to put this declaration
 at function declarations, at function definitions, and in function
@@ -44,20 +48,13 @@ definitions.
 @end itemize
 The include file is @code{<noreturn.h>}.
-The @samp{stdnoreturn} module.  This can improve readability by
-letting you use @code{noreturn} instead of @code{_Noreturn};
-unfortunately, @code{noreturn} is a no-op on some platforms even
-though @code{_Noreturn} works on them.  The include file is
 @end itemize
-Which of the two modules to use?  If the non-returning functions you
+Which of the approaches to use?  If the non-returning functions you
 have to declare are unlikely to be accessed through function pointers,
-you should use module @code{stdnoreturn}; otherwise the module
+you should use @code{_Noreturn}; otherwise the module
 @code{noreturn} provides for better data-flow analysis and thus for
 better warnings.
-For a detailed description of the @code{stdnoreturn} module, see
+There is also an obsolete @code{stdnoreturn} module, but its use is no
+longer recommended.
diff --git a/doc/posix-headers/stdnoreturn.texi b/doc/posix-headers/stdnoreturn.texi
index 3e1c5882db..ebe31ffc9f 100644
--- a/doc/posix-headers/stdnoreturn.texi
+++ b/doc/posix-headers/stdnoreturn.texi
@@ -22,6 +22,8 @@ MSVC/clang.
 Portability problems not fixed by Gnulib:
+@code{<stdnoreturn.h>} and the @code{noreturn} macro are obsolescent in C23.
 @code{<stdnoreturn.h>} cannot be #included in C++ mode on some platforms:
 FreeBSD 13.1.
diff --git a/lib/stdnoreturn.in.h b/lib/stdnoreturn.in.h
index d9e746699d..446e11b0b2 100644
--- a/lib/stdnoreturn.in.h
+++ b/lib/stdnoreturn.in.h
@@ -24,7 +24,9 @@
    ISO C11 (latest free draft
-   section 7.23 */
+   section 7.23
+   <stdnoreturn.h> is obsolescent in C23, so new code should avoid it.  */
 /* The definition of _Noreturn is copied here.  */
diff --git a/modules/stdnoreturn b/modules/stdnoreturn
index 1ef894d51f..ce6b04a35e 100644
--- a/modules/stdnoreturn
+++ b/modules/stdnoreturn
@@ -1,6 +1,12 @@
 A <stdnoreturn.h> that nearly conforms to ISO C11.
+This module is obsolete.

             reply	other threads:[~2022-12-24  9:35 UTC|newest]

Thread overview: 3+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2022-12-24  9:35 Paul Eggert [this message]
2022-12-27 10:14 ` [PATCH] stdnoreturn: deprecate Bruno Haible
  -- strict thread matches above, loose matches on Subject: below --
2022-12-27 18:59 [PATCH 0/6] build-aux/bootstrap that doesn't need to replace itself Paul Eggert
2022-12-27 18:59 ` [PATCH] stdnoreturn: deprecate Paul Eggert

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