On 1/8/21 8:31 PM, Joe Nelson wrote:
Hi, my project uses lib/_Noreturn.h, but gets a warning when compiled with "-std=c99 -pedantic":warning: _Noreturn functions are a C11-specific feature
-pedantic can be such a pain sometimes, as can Clang. Thanks for reporting the problem, I guess. I installed the attached patch; please give it a try.
>From 077ffc1e416a6be980dd45979547201e572962f6 Mon Sep 17 00:00:00 2001 From: Paul Eggert <egg...@cs.ucla.edu> Date: Sat, 9 Jan 2021 14:17:32 -0800 Subject: [PATCH] snippet/_Noreturn: port to pedantic clang Problem reported by Joe Nelson in: https://lists.gnu.org/r/bug-gnulib/2021-01/msg00152.html * doc/noreturn.texi: Improve. * lib/_Noreturn.h (_Noreturn): * m4/gnulib-common.m4 (gl_COMMON_BODY): Do not assume _Noreturn works as-is when __STRICT_ANSI__ is defined, unless __STDC_VERSION__ indicates C11 or later. * lib/_Noreturn.h (_Noreturn): Fall back on __attribute__ ((__noreturn__)) if Clang; this merges the 2020-08-10T23:53:13zbr...@clisp.org patch to m4/gnulib-common.m4. --- ChangeLog | 14 ++++++++++++++ doc/noreturn.texi | 20 ++++++++++++-------- lib/_Noreturn.h | 16 +++++++++------- m4/gnulib-common.m4 | 11 ++++++----- 4 files changed, 41 insertions(+), 20 deletions(-) diff --git a/ChangeLog b/ChangeLog index b713bedb4..4329b81d9 100644 --- a/ChangeLog +++ b/ChangeLog @@ -1,3 +1,17 @@ +2021-01-09 Paul Eggert <egg...@cs.ucla.edu> + + snippet/_Noreturn: port to pedantic clang + Problem reported by Joe Nelson in: + https://lists.gnu.org/r/bug-gnulib/2021-01/msg00152.html + * doc/noreturn.texi: Improve. + * lib/_Noreturn.h (_Noreturn): + * m4/gnulib-common.m4 (gl_COMMON_BODY): + Do not assume _Noreturn works as-is when __STRICT_ANSI__ is + defined, unless __STDC_VERSION__ indicates C11 or later. + * lib/_Noreturn.h (_Noreturn): Fall back on __attribute__ + ((__noreturn__)) if Clang; this merges the + 2020-08-10T23:53:13zbr...@clisp.org patch to m4/gnulib-common.m4. + 2021-01-09 Darshit Shah <dar...@gnu.org> Allow setting CVS username for gnu-web-doc-update. diff --git a/doc/noreturn.texi b/doc/noreturn.texi index e119ff88a..86bcc351e 100644 --- a/doc/noreturn.texi +++ b/doc/noreturn.texi @@ -23,17 +23,14 @@ 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. +To decorate function declarations and function definitions, you can +use 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. + Gnulib has two modules that support such a declaration: @itemize @bullet -@item -The @samp{stdnoreturn} module. It provides a way to put this -declaration at function declarations and function definitions, but not -in function pointer types. The identifier to use is @code{_Noreturn} -or @code{noreturn}; @code{_Noreturn} is to be preferred because -@code{noreturn} is a no-op on some platforms. The include file is -@code{<stdnoreturn.h>}. - @item The @samp{noreturn} module. It provides a way to put this declaration at function declarations, at function definitions, and in function @@ -47,6 +44,13 @@ definitions. @end itemize @noindent The include file is @code{<noreturn.h>}. + +@item +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 +@code{<stdnoreturn.h>}. @end itemize Which of the two modules to use? If the non-returning functions you diff --git a/lib/_Noreturn.h b/lib/_Noreturn.h index f5003b9be..cb72f2620 100644 --- a/lib/_Noreturn.h +++ b/lib/_Noreturn.h @@ -26,14 +26,16 @@ 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) \ - || 4 < __GNUC__ + (7 <= __GNUC_MINOR__) \ - || (defined __apple_build_version__ \ - ? 6000000 <= __apple_build_version__ \ - : 3 < __clang_major__ + (5 <= __clang_minor__)))) +# elif ((!defined __cplusplus || defined __clang__) \ + && (201112 <= (defined __STDC_VERSION__ ? __STDC_VERSION__ : 0) \ + || (!defined __STRICT_ANSI__ \ + && (__4 < __GNUC__ + (7 <= __GNUC_MINOR__) \ + || (defined __apple_build_version__ \ + ? 6000000 <= __apple_build_version__ \ + : 3 < __clang_major__ + (5 <= __clang_minor__)))))) /* _Noreturn works as-is. */ -# elif 2 < __GNUC__ + (8 <= __GNUC_MINOR__) || 0x5110 <= __SUNPRO_C +# elif (2 < __GNUC__ + (8 <= __GNUC_MINOR__) || defined __clang__ \ + || 0x5110 <= __SUNPRO_C) # define _Noreturn __attribute__ ((__noreturn__)) # elif 1200 <= (defined _MSC_VER ? _MSC_VER : 0) # define _Noreturn __declspec (noreturn) diff --git a/m4/gnulib-common.m4 b/m4/gnulib-common.m4 index 535359b2c..3d87fd840 100644 --- a/m4/gnulib-common.m4 +++ b/m4/gnulib-common.m4 @@ -39,11 +39,12 @@ AC_DEFUN([gl_COMMON_BODY], [ this syntax with 'extern'. */ # define _Noreturn [[noreturn]] # elif ((!defined __cplusplus || defined __clang__) \ - && (201112 <= (defined __STDC_VERSION__ ? __STDC_VERSION__ : 0) \ - || _GL_GNUC_PREREQ (4, 7) \ - || (defined __apple_build_version__ \ - ? 6000000 <= __apple_build_version__ \ - : 3 < __clang_major__ + (5 <= __clang_minor__)))) + && (201112 <= (defined __STDC_VERSION__ ? __STDC_VERSION__ : 0) \ + || (!defined __STRICT_ANSI__ \ + && (_GL_GNUC_PREREQ (4, 7) \ + || (defined __apple_build_version__ \ + ? 6000000 <= __apple_build_version__ \ + : 3 < __clang_major__ + (5 <= __clang_minor__)))))) /* _Noreturn works as-is. */ # elif _GL_GNUC_PREREQ (2, 8) || defined __clang__ || 0x5110 <= __SUNPRO_C # define _Noreturn __attribute__ ((__noreturn__)) -- 2.27.0
