On 5/1/20 12:58 AM, Marc Nieper-Wißkirchen wrote: > this can even be reused by many existing Gnulib modules,
That suggests that we should define _GL_ATTRIBUTE* variants, which can be used in Gnulib header files safely. A fancier patch is attached, to do that. I also looked for other uses of __attribute__ in Gnulib and add macros for most of them. I haven't tested this, or seen how to use it to simplify other modules; it's merely a proof of concept. > To my knowledge, C2x will standardize attributes Ah, I hadn't been following that. Thanks for mentioning it. I incorporated that into the attached patch.
>From de35c4f63bb070063cbcac0b982670c9005ade99 Mon Sep 17 00:00:00 2001 From: Paul Eggert <egg...@cs.ucla.edu> Date: Fri, 1 May 2020 18:12:12 -0700 Subject: [PROOF-OF-CONCEPT] New module attribute * MODULES.html.sh: Add attribute. * doc/attribute.texi, lib/attribute-gl.h, lib/attribute.h: * modules/attribute: New files. * doc/gnulib.texi (Particular Modules): Add Attributes. --- ChangeLog | 8 +++ MODULES.html.sh | 1 + doc/attribute.texi | 43 ++++++++++++++ doc/gnulib.texi | 3 + lib/attribute-gl.h | 140 +++++++++++++++++++++++++++++++++++++++++++++ lib/attribute.h | 48 ++++++++++++++++ modules/attribute | 21 +++++++ 7 files changed, 264 insertions(+) create mode 100644 doc/attribute.texi create mode 100644 lib/attribute-gl.h create mode 100644 lib/attribute.h create mode 100644 modules/attribute diff --git a/ChangeLog b/ChangeLog index 033f3be48..9e9c0a827 100644 --- a/ChangeLog +++ b/ChangeLog @@ -1,3 +1,11 @@ +2020-05-01 Paul Eggert <egg...@cs.ucla.edu> + + New module attribute + * MODULES.html.sh: Add attribute. + * doc/attribute.texi, lib/attribute-gl.h, lib/attribute.h: + * modules/attribute: New files. + * doc/gnulib.texi (Particular Modules): Add Attributes. + 2020-05-01 Bruno Haible <br...@clisp.org> list: Add remove_first and remove_last operations. diff --git a/MODULES.html.sh b/MODULES.html.sh index 240a9ee20..318a15a1d 100755 --- a/MODULES.html.sh +++ b/MODULES.html.sh @@ -2364,6 +2364,7 @@ func_all_modules () func_echo "$element" func_begin_table + func_module attribute func_module builtin-expect func_module ieee754-h func_module limits-h diff --git a/doc/attribute.texi b/doc/attribute.texi new file mode 100644 index 000000000..86591f16c --- /dev/null +++ b/doc/attribute.texi @@ -0,0 +1,43 @@ +@c attribute module documentation + +@c Copyright 2020 Free Software Foundation, Inc. + +@c Permission is granted to copy, distribute and/or modify this document +@c under the terms of the GNU Free Documentation License, Version 1.3 or +@c any later version published by the Free Software Foundation; with no +@c Invariant Sections, no Front-Cover Texts, and no Back-Cover Texts. A +@c copy of the license is at <https://www.gnu.org/licenses/fdl-1.3.en.html>. + +@node Attributes +@section Attributes + +@cindex Attributes +@findex __attribute__ + +This module provides a header file @file{attribute.h} that defines +macros related to C and C++ attributes and the GCC +@code{__attribute__} keyword. + +Here is an example of its use: + +@example +#include <attribute.h> + +extern char *crypt (char const *, char const *) + ATTRIBUTE_NOTHROW ATTRIBUTE_LEAF ATTRIBUTE_NONNULL ((1, 2)); +@end example + +@noindent +@code{ATTRIBUTE_NOTHROW} expands to @code{__attribute__ +((__nothrow__))} if the compiler is a recent-enough GCC or GCC-like +compiler, and to nothing otherwise. Similarly for +@code{ATTRIBUTE_LEAF}. @code{ATTRIBUTE_NONNULL ((1, 2))} expands to +@code{__attribute__ ((__nonnull__ (1, 2)))} if the compiler is +recent-enough GCC, and to nothing otherwise. + +Most of these attribute names begin with @code{ATTRIBUTE_}. +A few do not, because they are part of C2X and their +names are not likely to clash with other macro names. +These macros are @code{DEPRECATED}, @code{FALLTHROUGH}, +@code{MAYBE_UNUSED}, and @code{NODISCARD}, which can +be defined to @code{[[deprecated]]} etc.@: on C2X platforms. diff --git a/doc/gnulib.texi b/doc/gnulib.texi index c9501ca23..b27f91f58 100644 --- a/doc/gnulib.texi +++ b/doc/gnulib.texi @@ -6654,6 +6654,7 @@ to POSIX that it can be treated like any other Unix-like platform. * alloca:: * alloca-opt:: * Safe Allocation Macros:: +* GCC Attributes:: * Compile-time Assertions:: * Non-returning Functions:: * Integer Properties:: @@ -6685,6 +6686,8 @@ to POSIX that it can be treated like any other Unix-like platform. @include safe-alloc.texi +@include attribute.texi + @include verify.texi @include noreturn.texi diff --git a/lib/attribute-gl.h b/lib/attribute-gl.h new file mode 100644 index 000000000..ddb9aa5bd --- /dev/null +++ b/lib/attribute-gl.h @@ -0,0 +1,140 @@ +/* _GL_ATTRIBUTE_* macros for using attributes in GCC and similar compilers + + Copyright 2020 Free Software Foundation, Inc. + + This program is free software: you can redistribute it and/or modify it + under the terms of the GNU Lesser General Public License as published + by the Free Software Foundation; either version 3 of the License, or + (at your option) any later version. + + This program is distributed in the hope that it will be useful, + but WITHOUT ANY WARRANTY; without even the implied warranty of + MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU + Lesser General Public License for more details. + + You should have received a copy of the GNU Lesser General Public License + along with this program. If not, see <https://www.gnu.org/licenses/>. */ + +/* Written by Paul Eggert. */ + +/* Each _GL_ATTRIBUTE_* macro expands to the like-named GCC attribute if + possible. Parameters may need parenthsization. For example, + _GL_ATTRIBUTE_NONNULL ((1, 2)) is __attribute__ ((__nonnull__ (1, 2))) + if the compiler is recent-enough GCC, and empty otherwise. */ + +#ifndef _GL_ATTRIBUTE_GCC_GL_H +#define _GL_ATTRIBUTE_GCC_GL_H + +#ifndef __GNUC_PREREQ +# if defined __GNUC__ && defined __GNUC_MINOR__ +# define __GNUC_PREREQ(maj, min) ((maj) < __GNUC__ + ((min) <= __GNUC_MINOR__)) +# else +# define __GNUC_PREREQ(maj, min) 0 +# endif +#endif + +/* There is no _GL_ATTRIBUTE_ALIGNED; use stdalign's _Alignas instead. */ + +#if __GNUC_PREREQ (4, 3) +# define _GL_ATTRIBUTE_ALLOC_SIZE(args) __attribute__ ((__alloc_size__ args)) +#else +# define _GL_ATTRIBUTE_ALLOC_SIZE(args) +#endif + +#if __GNUC_PREREQ (3, 2) +# define _GL_ATTRIBUTE_ALWAYS_INLINE __attribute__ ((__always_inline__)) +#else +# define _GL_ATTRIBUTE_ALWAYS_INLINE +#endif +# define __attribute_artificial__ __attribute__ ((__artificial__)) + +#if __GNUC_PREREQ (4, 3) +# define _GL_ATTRIBUTE_ARTIFICIAL __attribute__ ((__artificial__)) +# define _GL_ATTRIBUTE_ERROR(msg) __attribute__((__error__ (msg))) +# define _GL_ATTRIBUTE_WARNING(msg) __attribute__((__warning__ (msg))) +#elsem +# define _GL_ATTRIBUTE_ARTIFICIAL +# define _GL_ATTRIBUTE_ERROR(msg) +# define _GL_ATTRIBUTE_WARNING(msg) +#endif + +#if 201710L < __STDC_VERSION__ +# define _GL_ATTRIBUTE_DEPRECATED [[__deprecated__]] +#elif __GNUC_PREREQ (3, 1) +# define _GL_ATTRIBUTE_DEPRECATED __attribute__ ((__deprecated__)) +#else +# define _GL_ATTRIBUTE_DEPRECATED +#endif + +/* FALLTHROUGH is special, because it always expands to something. */ +#if 201710L < __STDC_VERSION__ +# define _GL_ATTRIBUTE_FALLTHROUGH [[__fallthrough__]] +#elif __GNUC_PREREQ (7, 0) +# define _GL_ATTRIBUTE_FALLTHROUGH __attribute__ ((__fallthrough__)) +#else +# define _GL_ATTRIBUTE_FALLTHROUGH ((void) 0) +#endif + +#if __GNUC_PREREQ (2, 7) +# define _GL_ATTRIBUTE_FORMAT(spec) __attribute__ ((__format__ spec)) +#else +# define _GL_ATTRIBUTE_FORMAT(spec) +#endif + +#if __GNUC_PREREQ (4, 6) +# define _GL_ATTRIBUTE_LEAF __attribute__ ((__leaf__)) +#else +# define _GL_ATTRIBUTE_LEAF +#endif + +#if 201710L < __STDC_VERSION__ +# define _GL_ATTRIBUTE_MAYBE_UNUSED [[__maybe_unused__]] +#elif __GNUC_PREREQ (3, 1) +# define _GL_ATTRIBUTE_MAYBE_UNUSED __attribute__ ((__unused__)) +#else +# define _GL_ATTRIBUTE_MAYBE_UNUSED +#endif + +#if 201710L < __STDC_VERSION__ +# define _GL_ATTRIBUTE_NODISCARD [[__nodiscard__]] +#elif __GNUC_PREREQ (3, 4) +# define _GL_ATTRIBUTE_NODISCARD __attribute__ ((__warn_unused_result__)) +#else +# define _GL_ATTRIBUTE_NODISCARD +#endif + +#if __GNUC_PREREQ (3, 3) +# define _GL_ATTRIBUTE_NONNULL(args) __attribute__ ((__nonnull__ args)) +#else +# define _GL_ATTRIBUTE_NONNULL(args) +#endif + +#if __GNUC_PREREQ (8, 0) +# define _GL_ATTRIBUTE_NONSTRING __attribute__ ((__nonstring__)) +#else +# define _GL_ATTRIBUTE_NONSTRING +#endif + +/* There is no _GL_ATTRIBUTE_NORETURN; use _Noreturn instead. */ + +#if !defined __cplusplus && __GNUC_PREREQ (3, 3) +# define _GL_ATTRIBUTE_NOTHROW __attribute__ ((__nothrow__)) +#else +# define _GL_ATTRIBUTE_NOTHROW +#endif + +#if __GNUC_PREREQ (2, 7) +# define _GL_ATTRIBUTE_PACKED __attribute__ ((__packed__)) +#else +# define _GL_ATTRIBUTE_PACKED +#endif + +#if __GNUC_PREREQ (4, 0) +# define _GL_ATTRIBUTE_SENTINEL(pos) __attribute__ ((__sentinel__ pos)) +#else +# define _GL_ATTRIBUTE_SENTINEL(pos) +#endif + +/* There is no _GL_ATTRIBUTE_VISIBILITY; see m4/visibility.m4 instead. */ + +#endif /* _GL_ATTRIBUTE_GCC_GL_H */ diff --git a/lib/attribute.h b/lib/attribute.h new file mode 100644 index 000000000..a067ced92 --- /dev/null +++ b/lib/attribute.h @@ -0,0 +1,48 @@ +/* ATTRIBUTE_* macros for using attributes in GCC and similar compilers + + Copyright 2020 Free Software Foundation, Inc. + + This program is free software: you can redistribute it and/or modify it + under the terms of the GNU Lesser General Public License as published + by the Free Software Foundation; either version 3 of the License, or + (at your option) any later version. + + This program is distributed in the hope that it will be useful, + but WITHOUT ANY WARRANTY; without even the implied warranty of + MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU + Lesser General Public License for more details. + + You should have received a copy of the GNU Lesser General Public License + along with this program. If not, see <https://www.gnu.org/licenses/>. */ + +/* Written by Paul Eggert. */ + +/* Provide public ATTRIBUTE_* names for the private _GL_ATTRIBUTE_* + macros used within Gnulib. */ + +#ifndef _GL_ATTRIBUTE_GCC_H +#define _GL_ATTRIBUTE_GCC_H + +/* C2X standard attributes have macro names that do not begin with + 'ATTRIBUTE_'. */ +#define DEPRECATED _GL_ATTRIBUTE_DEPRECATED +#define FALLTHROUGH _GL_ATTRIBUTE_FALLTHROUGH +#define MAYBE_UNUSED _GL_ATTRIBUTE_MAYBE_UNUSED +#define NODISCARD _GL_ATTRIBUTE_NODISCARD + +/* Attributes from GCC have macro names beginning with 'ATTRIBUTE_' to + avoid name clashes. */ +#define ATTRIBUTE_ALLOC_SIZE(args) _GL_ATTRIBUTE_ALLOC_SIZE(args) +#define ATTRIBUTE_ALWAYS_INLINE _GL_ATTRIBUTE_ALWAYS_INLINE +#define ATTRIBUTE_ARTIFICIAL _GL_ATTRIBUTE_ARTIFICIAL +#define ATTRIBUTE_ERROR(msg) _GL_ATTRIBUTE_ERROR(msg) +#define ATTRIBUTE_FORMAT(spec) _GL_ATTRIBUTE_FORMAT(spec) +#define ATTRIBUTE_LEAF _GL_ATTRIBUTE_LEAF +#define ATTRIBUTE_NONNULL(args) _GL_ATTRIBUTE_NONNULL(args) +#define ATTRIBUTE_NONSTRING _GL_ATTRIBUTE_NONSTRING +#define ATTRIBUTE_NOTHROW _GL_ATTRIBUTE_NOTHROW +#define ATTRIBUTE_PACKED _GL_ATTRIBUTE_PACKED +#define ATTRIBUTE_SENTINEL(pos) _GL_ATTRIBUTE_SENTINEL(pos) +#define ATTRIBUTE_WARNING(msg) _GL_ATTRIBUTE_WARNING(msg) + +#endif diff --git a/modules/attribute b/modules/attribute new file mode 100644 index 000000000..9ece14fe0 --- /dev/null +++ b/modules/attribute @@ -0,0 +1,21 @@ +Description: +C/C++ attributes + +Files: +lib/attribute.h +lib/attribute-gl.h +m4/attribute.m4 + +Depends-on: + +configure.ac: + +Makefile.am: + +Include: + +License: +LGPLv2+ + +Maintainer: +all -- 2.17.1
