I just went to use some function attributes in findutils and noticed that information about which versions of GCC support various attributes is spread throughout gnulib. While a number of headers define convenience macros (usually starting _GL_ATTRIBUTE_) there are a couple of naming inconsistencies (two names used for the same attribute, typically).
I propose to move all of these definitions into a separate module, except for any definitions that need to stay as they are in order to stay in sync with glibc: $ for h in $(grep -l 'define.*_GL_ATTRIBUTE' lib/*.[hc]) ; do grep -q 'This file is part of the GNU C Library' $h || echo $h; done lib/di-set.h lib/hash.h lib/ignore-value.h lib/ino-map.h lib/openat.h lib/safe-alloc.h lib/sigpipe-die.h lib/stdio.in.h lib/stdlib.in.h lib/string.in.h lib/vasnprintf.h lib/version-etc.h lib/xalloc.h lib/xmemdup0.h lib/xprintf.h lib/xstrtol.h lib/xvasprintf.h Since this involves touching a number of files, I thought it would be useful to get some feedback on the idea in advance rather than just send a patch for review. In particular, if we keep the existing macro naming, I think the change would need to be one large patch, because many of the existing definitions of these macros are not protected by #ifndef. If it's not done in one large patch, differences in header inclusion order will mean that we'd see extra warnings about "redefinition of _GL_ATTRIBUTE_NORETURN" etc. when compiling gnulib code. While the hard work is updating all the other source files, here's an initial version of the definitions themselves, in case this helps better convey the idea: /* gcc-function-attribtues.h -- GCC-specific function attributes Copyright (C) 2011 Free Software Foundation, Inc. This program is free software: you can redistribute it and/or modify it under the terms of the GNU 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 General Public License for more details. You should have received a copy of the GNU General Public License along with this program. If not, see <http://www.gnu.org/licenses/>. */ /* Be aware that some function attributes do not work with function pointers. See http://lists.gnu.org/archive/html/bug-gnulib/2011-04/msg00007.html for details. */ #ifndef _GCC_FUNCTION_ATTRIBUTES_H #define _GCC_FUNCTION_ATTRIBUTES_H #ifndef __GNUC_PREREQ # if defined __GNUC__ && defined __GNUC_MINOR__ # define __GNUC_PREREQ(maj, min) \ ((__GNUC__ << 16) + __GNUC_MINOR__ >= ((maj) << 16) + (min)) # else # define __GNUC_PREREQ(maj, min) 0 # endif #endif /* The following attributes are currently (GCC-4.4.5) defined for functions on all targets. Where this file provides a macro for using it, the macro name is given in the second column. Attribute Macro (if implemented in this file) ------------------------------------------------------------------------------- alias aligned alloc_size _GL_ATTRIBUTE_ALLOC_SIZE(arg_num) always_inline artificial cold const constructor deprecated _GL_ATTRIBUTE_DEPRECATED destructor error externally_visible flatten format _GL_ATTRIBUTE_FORMAT(spec) _GL_ATTRIBUTE_FORMAT_PRINTF_SYSTEM(fmt,firstarg) _GL_ATTRIBUTE_FORMAT_PRINTF(fmt,firstarg) _GL_ATTRIBUTE_FORMAT_SCANF_SYSTEM(fmt,firstarg) _GL_ATTRIBUTE_FORMAT_SCANF(fmt,firstarg) format_arg gnu_inline hot malloc _GL_ATTRIBUTE_MALLOC no_instrument_function noinline nonnull _GL_ATTRIBUTE_NONNULL(args) _GL_ARG_NONNULL(args) noreturn _GL_ATTRIBUTE_NORETURN nothrow pure _GL_ATTRIBUTE_PURE returns_twice section sentinel _GL_ATTRIBUTE_SENTINEL unused used warn_unused_result _GL_ATTRIBUTE_WUR warning weak */ /* Attributes used in gnulib, but which appear to be platform-specific regparm stdcall */ /* Attributes used in gnulib with special arguments Macro Args visibility "default" */ /* The __attribute__ feature is available in gcc versions 2.5 and later. The underscored __format__ spelling of the attribute names requires 2.6.4 (we check for 2.7). */ #ifndef _GL_ATTRIBUTE_ALLOC_SIZE # if __GNUC_PREREQ(4,3) # define _GL_ATTRIBUTE_ALLOC_SIZE(arg_num) __attribute__ ((__alloc_size__ (arg_num))) # else # define _GL_ATTRIBUTE_ALLOC_SIZE(arg_num) /* unsupported */ # endif #endif #ifndef _GL_ATTRIBUTE_DEPRECATED # if __GNUC_PREREQ(3,1) # define _GL_ATTRIBUTE_DEPRECATED __attribute__ ((__deprecated__)) # else # define _GL_ATTRIBUTE_DEPRECATED /* empty */ # endif #endif #ifndef _GL_ATTRIBUTE_FORMAT # if __GNUC_PREREQ(2,7) # define _GL_ATTRIBUTE_FORMAT(spec) __attribute__ ((__format__ spec)) # else # define _GL_ATTRIBUTE_FORMAT(spec) /* unsupported */ # endif #endif #ifndef _GL_ATTRIBUTE_FORMAT_PRINTF_SYSTEM # if __GNUC_PREREQ(2,7) # define _GL_ATTRIBUTE_FORMAT_PRINTF_SYSTEM(formatstring_parameter, first_argument) \ _GL_ATTRIBUTE_FORMAT ((__printf__, formatstring_parameter, first_argument)) # else # define _GL_ATTRIBUTE_FORMAT_PRINTF_SYSTEM(spec) /* unsupported */ # endif #endif #ifndef _GL_ATTRIBUTE_FORMAT_PRINTF # if __GNUC_PREREQ(2,7) # if __GNUC_PREREQ(4,4) # define _GL_ATTRIBUTE_FORMAT_PRINTF(formatstring_parameter, first_argument) \ _GL_ATTRIBUTE_FORMAT ((__gnu_printf__, formatstring_parameter, first_argument)) # else # define _GL_ATTRIBUTE_FORMAT_PRINTF(formatstring_parameter, first_argument) \ _GL_ATTRIBUTE_FORMAT ((__printf__, formatstring_parameter, first_argument)) # endif # else # define _GL_ATTRIBUTE_FORMAT_PRINTF(spec) /* unsupported */ # endif #endif #ifndef _GL_ATTRIBUTE_FORMAT_SCANF_SYSTEM # if __GNUC_PREREQ(2,7) # define _GL_ATTRIBUTE_FORMAT_SCANF_SYSTEM(formatstring_parameter, first_argument) \ _GL_ATTRIBUTE_FORMAT ((__scanf__, formatstring_parameter, first_argument)) # else # define _GL_ATTRIBUTE_FORMAT_SCANF_SYSTEM(spec) /* unsupported */ # endif #endif #ifndef _GL_ATTRIBUTE_FORMAT_SCANF # if __GNUC_PREREQ(2,7) # if __GNUC_PREREQ(4,4) # define _GL_ATTRIBUTE_FORMAT_SCANF(formatstring_parameter, first_argument) \ _GL_ATTRIBUTE_FORMAT ((__gnu_scanf__, formatstring_parameter, first_argument)) # else # define _GL_ATTRIBUTE_FORMAT_SCANF(formatstring_parameter, first_argument) \ _GL_ATTRIBUTE_FORMAT ((__scanf__, formatstring_parameter, first_argument)) # endif # else # define _GL_ATTRIBUTE_FORMAT_SCANF(spec) /* unsupported */ # endif #endif #ifndef _GL_ATTRIBUTE_MALLOC # if __GNUC_PREREQ(3,0) # define _GL_ATTRIBUTE_MALLOC __attribute__ ((__malloc__)) # else # define _GL_ATTRIBUTE_MALLOC /* unsupported */ # endif #endif #ifndef _GL_ATTRIBUTE_NONNULL # if __GNUC_PREREQ(3,3) # define _GL_ATTRIBUTE_NONNULL(m) __attribute__ ((__nonnull__ (m))) # else # define _GL_ATTRIBUTE_NONNULL(m) /* unsupported */ # endif #endif #ifndef _GL_ARG_NONNULL /* alternative spelling used in gnulib's stdio.h */ # define _GL_ARG_NONNULL(m) _GL_ATTRIBUTE_NONNULL(m) #endif #ifndef _GL_ATTRIBUTE_NORETURN # if __GNUC_PREREQ(2,8) # define _GL_ATTRIBUTE_NORETURN __attribute__ ((__noreturn__ (m))) # else # define _GL_ATTRIBUTE_NORETURN /* unsupported */ # endif #endif #ifndef _GL_ATTRIBUTE_PURE # if __GNUC_PREREQ(2,96) # define _GL_ATTRIBUTE_PURE __attribute__ ((__pure__)) # else # define _GL_ATTRIBUTE_PURE /* unsupported */ # endif #endif #ifndef _GL_ATTRIBUTE_SENTINEL # if __GNUC_PREREQ(4,0) /* gnulib uses the __attribute__((__sentinel__)) variant, for which the argument number 0 is assumed. Arguments are counted backwards, the last being 0. */ # define _GL_ATTRIBUTE_SENTINEL(backward_arg_num) __attribute__ ((__sentinel__(backward_arg_num))) # else # define _GL_ATTRIBUTE_SENTINEL(backward_arg_num) /* unsupported */ # endif #endif #ifndef _GL_ATTRIBUTE_WUR # if __GNUC_PREREQ(3,4) # define _GL_ATTRIBUTE_WUR __attribute__ ((__warn__unused_result__)) # else # define _GL_ATTRIBUTE_WUR /* unsupported */ # endif #endif #ifndef _GL_ATTRIBUTE_RETURN_CHECK /* gnulib is inconsistent in which macro it uses; support both for now. */ # define _GL_ATTRIBUTE_RETURN_CHECK _GL_ATTRIBUTE_WUR #endif #endif /* _GCC_FUNCTION_ATTRIBUTES_H */
