FreeBSD/Linux Kernel Cross Reference
sys/sys/cdefs.h

     /*-
      * Copyright (c) 1991, 1993
      *      The Regents of the University of California.  All rights reserved.
      *
      * This code is derived from software contributed to Berkeley by
      * Berkeley Software Design, Inc.
      *
      * Redistribution and use in source and binary forms, with or without
      * modification, are permitted provided that the following conditions
     * are met:
     * 1. Redistributions of source code must retain the above copyright
     *    notice, this list of conditions and the following disclaimer.
     * 2. Redistributions in binary form must reproduce the above copyright
     *    notice, this list of conditions and the following disclaimer in the
     *    documentation and/or other materials provided with the distribution.
     * 4. Neither the name of the University nor the names of its contributors
     *    may be used to endorse or promote products derived from this software
     *    without specific prior written permission.
     *
     * THIS SOFTWARE IS PROVIDED BY THE REGENTS AND CONTRIBUTORS ``AS IS'' AND
     * ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE
     * IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE
     * ARE DISCLAIMED.  IN NO EVENT SHALL THE REGENTS OR CONTRIBUTORS BE LIABLE
     * FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL
     * DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS
     * OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION)
     * HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT
     * LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY
     * OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF
     * SUCH DAMAGE.
     *
     *      @(#)cdefs.h     8.8 (Berkeley) 1/9/95
     * $FreeBSD: releng/11.1/sys/sys/cdefs.h 317342 2017-04-23 20:32:46Z kib $
     */
    
    #ifndef _SYS_CDEFS_H_
    #define _SYS_CDEFS_H_
    
    /*
     * Testing against Clang-specific extensions.
     */
    #ifndef __has_attribute
    #define __has_attribute(x)      0
    #endif
    #ifndef __has_extension
    #define __has_extension         __has_feature
    #endif
    #ifndef __has_feature
    #define __has_feature(x)        0
    #endif
    #ifndef __has_include
    #define __has_include(x)        0
    #endif
    #ifndef __has_builtin
    #define __has_builtin(x)        0
    #endif
    
    #if defined(__cplusplus)
    #define __BEGIN_DECLS   extern "C" {
    #define __END_DECLS     }
    #else
    #define __BEGIN_DECLS
    #define __END_DECLS
    #endif
    
    /*
     * This code has been put in place to help reduce the addition of
     * compiler specific defines in FreeBSD code.  It helps to aid in
     * having a compiler-agnostic source tree.
     */
    
    #if defined(__GNUC__) || defined(__INTEL_COMPILER)
    
    #if __GNUC__ >= 3 || defined(__INTEL_COMPILER)
    #define __GNUCLIKE_ASM 3
    #define __GNUCLIKE_MATH_BUILTIN_CONSTANTS
    #else
    #define __GNUCLIKE_ASM 2
    #endif
    #define __GNUCLIKE___TYPEOF 1
    #define __GNUCLIKE___OFFSETOF 1
    #define __GNUCLIKE___SECTION 1
    
    #ifndef __INTEL_COMPILER
    #define __GNUCLIKE_CTOR_SECTION_HANDLING 1
    #endif
    
    #define __GNUCLIKE_BUILTIN_CONSTANT_P 1
    #if defined(__INTEL_COMPILER) && defined(__cplusplus) && \
       __INTEL_COMPILER < 800
    #undef __GNUCLIKE_BUILTIN_CONSTANT_P
    #endif
    
    #if (__GNUC_MINOR__ > 95 || __GNUC__ >= 3)
    #define __GNUCLIKE_BUILTIN_VARARGS 1
    #define __GNUCLIKE_BUILTIN_STDARG 1
    #define __GNUCLIKE_BUILTIN_VAALIST 1
    #endif
    
   #if defined(__GNUC__)
   #define __GNUC_VA_LIST_COMPATIBILITY 1
   #endif
   
   /*
    * Compiler memory barriers, specific to gcc and clang.
    */
   #if defined(__GNUC__)
   #define __compiler_membar()     __asm __volatile(" " : : : "memory")
   #endif
   
   #ifndef __INTEL_COMPILER
   #define __GNUCLIKE_BUILTIN_NEXT_ARG 1
   #define __GNUCLIKE_MATH_BUILTIN_RELOPS
   #endif
   
   #define __GNUCLIKE_BUILTIN_MEMCPY 1
   
   /* XXX: if __GNUC__ >= 2: not tested everywhere originally, where replaced */
   #define __CC_SUPPORTS_INLINE 1
   #define __CC_SUPPORTS___INLINE 1
   #define __CC_SUPPORTS___INLINE__ 1
   
   #define __CC_SUPPORTS___FUNC__ 1
   #define __CC_SUPPORTS_WARNING 1
   
   #define __CC_SUPPORTS_VARADIC_XXX 1 /* see varargs.h */
   
   #define __CC_SUPPORTS_DYNAMIC_ARRAY_INIT 1
   
   #endif /* __GNUC__ || __INTEL_COMPILER */
   
   /*
    * Macro to test if we're using a specific version of gcc or later.
    */
   #if defined(__GNUC__) && !defined(__INTEL_COMPILER)
   #define __GNUC_PREREQ__(ma, mi) \
           (__GNUC__ > (ma) || __GNUC__ == (ma) && __GNUC_MINOR__ >= (mi))
   #else
   #define __GNUC_PREREQ__(ma, mi) 0
   #endif
   
   /*
    * The __CONCAT macro is used to concatenate parts of symbol names, e.g.
    * with "#define OLD(foo) __CONCAT(old,foo)", OLD(foo) produces oldfoo.
    * The __CONCAT macro is a bit tricky to use if it must work in non-ANSI
    * mode -- there must be no spaces between its arguments, and for nested
    * __CONCAT's, all the __CONCAT's must be at the left.  __CONCAT can also
    * concatenate double-quoted strings produced by the __STRING macro, but
    * this only works with ANSI C.
    *
    * __XSTRING is like __STRING, but it expands any macros in its argument
    * first.  It is only available with ANSI C.
    */
   #if defined(__STDC__) || defined(__cplusplus)
   #define __P(protos)     protos          /* full-blown ANSI C */
   #define __CONCAT1(x,y)  x ## y
   #define __CONCAT(x,y)   __CONCAT1(x,y)
   #define __STRING(x)     #x              /* stringify without expanding x */
   #define __XSTRING(x)    __STRING(x)     /* expand x, then stringify */
   
   #define __const         const           /* define reserved names to standard */
   #define __signed        signed
   #define __volatile      volatile
   #if defined(__cplusplus)
   #define __inline        inline          /* convert to C++ keyword */
   #else
   #if !(defined(__CC_SUPPORTS___INLINE))
   #define __inline                        /* delete GCC keyword */
   #endif /* ! __CC_SUPPORTS___INLINE */
   #endif /* !__cplusplus */
   
   #else   /* !(__STDC__ || __cplusplus) */
   #define __P(protos)     ()              /* traditional C preprocessor */
   #define __CONCAT(x,y)   x/**/y
   #define __STRING(x)     "x"
   
   #if !defined(__CC_SUPPORTS___INLINE)
   #define __const                         /* delete pseudo-ANSI C keywords */
   #define __inline
   #define __signed
   #define __volatile
   /*
    * In non-ANSI C environments, new programs will want ANSI-only C keywords
    * deleted from the program and old programs will want them left alone.
    * When using a compiler other than gcc, programs using the ANSI C keywords
    * const, inline etc. as normal identifiers should define -DNO_ANSI_KEYWORDS.
    * When using "gcc -traditional", we assume that this is the intent; if
    * __GNUC__ is defined but __STDC__ is not, we leave the new keywords alone.
    */
   #ifndef NO_ANSI_KEYWORDS
   #define const                           /* delete ANSI C keywords */
   #define inline
   #define signed
   #define volatile
   #endif  /* !NO_ANSI_KEYWORDS */
   #endif  /* !__CC_SUPPORTS___INLINE */
   #endif  /* !(__STDC__ || __cplusplus) */
   
   /*
    * Compiler-dependent macros to help declare dead (non-returning) and
    * pure (no side effects) functions, and unused variables.  They are
    * null except for versions of gcc that are known to support the features
    * properly (old versions of gcc-2 supported the dead and pure features
    * in a different (wrong) way).  If we do not provide an implementation
    * for a given compiler, let the compile fail if it is told to use
    * a feature that we cannot live without.
    */
   #ifdef lint
   #define __dead2
   #define __pure2
   #define __unused
   #define __packed
   #define __aligned(x)
   #define __alloc_align(x)
   #define __alloc_size(x)
   #define __section(x)
   #define __weak_symbol
   #else
   #define __weak_symbol   __attribute__((__weak__))
   #if !__GNUC_PREREQ__(2, 5) && !defined(__INTEL_COMPILER)
   #define __dead2
   #define __pure2
   #define __unused
   #endif
   #if __GNUC__ == 2 && __GNUC_MINOR__ >= 5 && __GNUC_MINOR__ < 7 && !defined(__INTEL_COMPILER)
   #define __dead2         __attribute__((__noreturn__))
   #define __pure2         __attribute__((__const__))
   #define __unused
   /* XXX Find out what to do for __packed, __aligned and __section */
   #endif
   #if __GNUC_PREREQ__(2, 7) || defined(__INTEL_COMPILER)
   #define __dead2         __attribute__((__noreturn__))
   #define __pure2         __attribute__((__const__))
   #define __unused        __attribute__((__unused__))
   #define __used          __attribute__((__used__))
   #define __packed        __attribute__((__packed__))
   #define __aligned(x)    __attribute__((__aligned__(x)))
   #define __section(x)    __attribute__((__section__(x)))
   #endif
   #if __GNUC_PREREQ__(4, 3) || __has_attribute(__alloc_size__)
   #define __alloc_size(x) __attribute__((__alloc_size__(x)))
   #else
   #define __alloc_size(x)
   #endif
   #if __GNUC_PREREQ__(4, 9) || __has_attribute(__alloc_align__)
   #define __alloc_align(x)        __attribute__((__alloc_align__(x)))
   #else
   #define __alloc_align(x)
   #endif
   #endif /* lint */
   
   #if !__GNUC_PREREQ__(2, 95)
   #define __alignof(x)    __offsetof(struct { char __a; x __b; }, __b)
   #endif
   
   /*
    * Keywords added in C11.
    */
   
   #if !defined(__STDC_VERSION__) || __STDC_VERSION__ < 201112L || defined(lint)
   
   #if !__has_extension(c_alignas)
   #if (defined(__cplusplus) && __cplusplus >= 201103L) || \
       __has_extension(cxx_alignas)
   #define _Alignas(x)             alignas(x)
   #else
   /* XXX: Only emulates _Alignas(constant-expression); not _Alignas(type-name). */
   #define _Alignas(x)             __aligned(x)
   #endif
   #endif
   
   #if defined(__cplusplus) && __cplusplus >= 201103L
   #define _Alignof(x)             alignof(x)
   #else
   #define _Alignof(x)             __alignof(x)
   #endif
   
   #if !defined(__cplusplus) && !__has_extension(c_atomic) && \
       !__has_extension(cxx_atomic)
   /*
    * No native support for _Atomic(). Place object in structure to prevent
    * most forms of direct non-atomic access.
    */
   #define _Atomic(T)              struct { T volatile __val; }
   #endif
   
   #if defined(__cplusplus) && __cplusplus >= 201103L
   #define _Noreturn               [[noreturn]]
   #else
   #define _Noreturn               __dead2
   #endif
   
   #if !__has_extension(c_static_assert)
   #if (defined(__cplusplus) && __cplusplus >= 201103L) || \
       __has_extension(cxx_static_assert)
   #define _Static_assert(x, y)    static_assert(x, y)
   #elif __GNUC_PREREQ__(4,6)
   /* Nothing, gcc 4.6 and higher has _Static_assert built-in */
   #elif defined(__COUNTER__)
   #define _Static_assert(x, y)    __Static_assert(x, __COUNTER__)
   #define __Static_assert(x, y)   ___Static_assert(x, y)
   #define ___Static_assert(x, y)  typedef char __assert_ ## y[(x) ? 1 : -1] \
                                   __unused
   #else
   #define _Static_assert(x, y)    struct __hack
   #endif
   #endif
   
   #if !__has_extension(c_thread_local)
   /*
    * XXX: Some compilers (Clang 3.3, GCC 4.7) falsely announce C++11 mode
    * without actually supporting the thread_local keyword. Don't check for
    * the presence of C++11 when defining _Thread_local.
    */
   #if /* (defined(__cplusplus) && __cplusplus >= 201103L) || */ \
       __has_extension(cxx_thread_local)
   #define _Thread_local           thread_local
   #else
   #define _Thread_local           __thread
   #endif
   #endif
   
   #endif /* __STDC_VERSION__ || __STDC_VERSION__ < 201112L */
   
   /*
    * Emulation of C11 _Generic().  Unlike the previously defined C11
    * keywords, it is not possible to implement this using exactly the same
    * syntax.  Therefore implement something similar under the name
    * __generic().  Unlike _Generic(), this macro can only distinguish
    * between a single type, so it requires nested invocations to
    * distinguish multiple cases.
    */
   
   #if (defined(__STDC_VERSION__) && __STDC_VERSION__ >= 201112L) || \
       __has_extension(c_generic_selections)
   #define __generic(expr, t, yes, no)                                     \
           _Generic(expr, t: yes, default: no)
   #elif __GNUC_PREREQ__(3, 1) && !defined(__cplusplus)
   #define __generic(expr, t, yes, no)                                     \
           __builtin_choose_expr(                                          \
               __builtin_types_compatible_p(__typeof(expr), t), yes, no)
   #endif
   
   /*
    * C99 Static array indices in function parameter declarations.  Syntax such as:
    * void bar(int myArray[static 10]);
    * is allowed in C99 but not in C++.  Define __min_size appropriately so
    * headers using it can be compiled in either language.  Use like this:
    * void bar(int myArray[__min_size(10)]);
    */
   #if !defined(__cplusplus) && \
       (defined(__clang__) || __GNUC_PREREQ__(4, 6)) && \
       (!defined(__STDC_VERSION__) || (__STDC_VERSION__ >= 199901))
   #define __min_size(x)   static (x)
   #else
   #define __min_size(x)   (x)
   #endif
   
   #if __GNUC_PREREQ__(2, 96)
   #define __malloc_like   __attribute__((__malloc__))
   #define __pure          __attribute__((__pure__))
   #else
   #define __malloc_like
   #define __pure
   #endif
   
   #if __GNUC_PREREQ__(3, 1) || (defined(__INTEL_COMPILER) && __INTEL_COMPILER >= 800)
   #define __always_inline __attribute__((__always_inline__))
   #else
   #define __always_inline
   #endif
   
   #if __GNUC_PREREQ__(3, 1)
   #define __noinline      __attribute__ ((__noinline__))
   #else
   #define __noinline
   #endif
   
   #if __GNUC_PREREQ__(3, 3)
   #define __nonnull(x)    __attribute__((__nonnull__(x)))
   #define __nonnull_all   __attribute__((__nonnull__))
   #else
   #define __nonnull(x)
   #define __nonnull_all
   #endif
   
   #if __GNUC_PREREQ__(3, 4)
   #define __fastcall      __attribute__((__fastcall__))
   #define __result_use_check      __attribute__((__warn_unused_result__))
   #else
   #define __fastcall
   #define __result_use_check
   #endif
   
   #if __GNUC_PREREQ__(4, 1)
   #define __returns_twice __attribute__((__returns_twice__))
   #else
   #define __returns_twice
   #endif
   
   #if __GNUC_PREREQ__(4, 6) || __has_builtin(__builtin_unreachable)
   #define __unreachable() __builtin_unreachable()
   #else
   #define __unreachable() ((void)0)
   #endif
   
   /* XXX: should use `#if __STDC_VERSION__ < 199901'. */
   #if !__GNUC_PREREQ__(2, 7) && !defined(__INTEL_COMPILER)
   #define __func__        NULL
   #endif
   
   #if (defined(__INTEL_COMPILER) || (defined(__GNUC__) && __GNUC__ >= 2)) && !defined(__STRICT_ANSI__) || __STDC_VERSION__ >= 199901
   #define __LONG_LONG_SUPPORTED
   #endif
   
   /* C++11 exposes a load of C99 stuff */
   #if defined(__cplusplus) && __cplusplus >= 201103L
   #define __LONG_LONG_SUPPORTED
   #ifndef __STDC_LIMIT_MACROS
   #define __STDC_LIMIT_MACROS
   #endif
   #ifndef __STDC_CONSTANT_MACROS
   #define __STDC_CONSTANT_MACROS
   #endif
   #endif
   
   /*
    * GCC 2.95 provides `__restrict' as an extension to C90 to support the
    * C99-specific `restrict' type qualifier.  We happen to use `__restrict' as
    * a way to define the `restrict' type qualifier without disturbing older
    * software that is unaware of C99 keywords.
    */
   #if !(__GNUC__ == 2 && __GNUC_MINOR__ == 95)
   #if !defined(__STDC_VERSION__) || __STDC_VERSION__ < 199901 || defined(lint)
   #define __restrict
   #else
   #define __restrict      restrict
   #endif
   #endif
   
   /*
    * GNU C version 2.96 adds explicit branch prediction so that
    * the CPU back-end can hint the processor and also so that
    * code blocks can be reordered such that the predicted path
    * sees a more linear flow, thus improving cache behavior, etc.
    *
    * The following two macros provide us with a way to utilize this
    * compiler feature.  Use __predict_true() if you expect the expression
    * to evaluate to true, and __predict_false() if you expect the
    * expression to evaluate to false.
    *
    * A few notes about usage:
    *
    *      * Generally, __predict_false() error condition checks (unless
    *        you have some _strong_ reason to do otherwise, in which case
    *        document it), and/or __predict_true() `no-error' condition
    *        checks, assuming you want to optimize for the no-error case.
    *
    *      * Other than that, if you don't know the likelihood of a test
    *        succeeding from empirical or other `hard' evidence, don't
    *        make predictions.
    *
    *      * These are meant to be used in places that are run `a lot'.
    *        It is wasteful to make predictions in code that is run
    *        seldomly (e.g. at subsystem initialization time) as the
    *        basic block reordering that this affects can often generate
    *        larger code.
    */
   #if __GNUC_PREREQ__(2, 96)
   #define __predict_true(exp)     __builtin_expect((exp), 1)
   #define __predict_false(exp)    __builtin_expect((exp), 0)
   #else
   #define __predict_true(exp)     (exp)
   #define __predict_false(exp)    (exp)
   #endif
   
   #if __GNUC_PREREQ__(4, 0)
   #define __null_sentinel __attribute__((__sentinel__))
   #define __exported      __attribute__((__visibility__("default")))
   #define __hidden        __attribute__((__visibility__("hidden")))
   #else
   #define __null_sentinel
   #define __exported
   #define __hidden
   #endif
   
   /*
    * We define this here since <stddef.h>, <sys/queue.h>, and <sys/types.h>
    * require it.
    */
   #if __GNUC_PREREQ__(4, 1)
   #define __offsetof(type, field)  __builtin_offsetof(type, field)
   #else
   #ifndef __cplusplus
   #define __offsetof(type, field) \
           ((__size_t)(__uintptr_t)((const volatile void *)&((type *)0)->field))
   #else
   #define __offsetof(type, field)                                 \
     (__offsetof__ (reinterpret_cast <__size_t>                    \
                    (&reinterpret_cast <const volatile char &>     \
                     (static_cast<type *> (0)->field))))
   #endif
   #endif
   #define __rangeof(type, start, end) \
           (__offsetof(type, end) - __offsetof(type, start))
   
   /*
    * Given the pointer x to the member m of the struct s, return
    * a pointer to the containing structure.  When using GCC, we first
    * assign pointer x to a local variable, to check that its type is
    * compatible with member m.
    */
   #if __GNUC_PREREQ__(3, 1)
   #define __containerof(x, s, m) ({                                       \
           const volatile __typeof(((s *)0)->m) *__x = (x);                \
           __DEQUALIFY(s *, (const volatile char *)__x - __offsetof(s, m));\
   })
   #else
   #define __containerof(x, s, m)                                          \
           __DEQUALIFY(s *, (const volatile char *)(x) - __offsetof(s, m))
   #endif
   
   /*
    * Compiler-dependent macros to declare that functions take printf-like
    * or scanf-like arguments.  They are null except for versions of gcc
    * that are known to support the features properly (old versions of gcc-2
    * didn't permit keeping the keywords out of the application namespace).
    */
   #if !__GNUC_PREREQ__(2, 7) && !defined(__INTEL_COMPILER)
   #define __printflike(fmtarg, firstvararg)
   #define __scanflike(fmtarg, firstvararg)
   #define __format_arg(fmtarg)
   #define __strfmonlike(fmtarg, firstvararg)
   #define __strftimelike(fmtarg, firstvararg)
   #else
   #define __printflike(fmtarg, firstvararg) \
               __attribute__((__format__ (__printf__, fmtarg, firstvararg)))
   #define __scanflike(fmtarg, firstvararg) \
               __attribute__((__format__ (__scanf__, fmtarg, firstvararg)))
   #define __format_arg(fmtarg)    __attribute__((__format_arg__ (fmtarg)))
   #define __strfmonlike(fmtarg, firstvararg) \
               __attribute__((__format__ (__strfmon__, fmtarg, firstvararg)))
   #define __strftimelike(fmtarg, firstvararg) \
               __attribute__((__format__ (__strftime__, fmtarg, firstvararg)))
   #endif
   
   /* Compiler-dependent macros that rely on FreeBSD-specific extensions. */
   #if defined(__FreeBSD_cc_version) && __FreeBSD_cc_version >= 300001 && \
       defined(__GNUC__) && !defined(__INTEL_COMPILER)
   #define __printf0like(fmtarg, firstvararg) \
               __attribute__((__format__ (__printf0__, fmtarg, firstvararg)))
   #else
   #define __printf0like(fmtarg, firstvararg)
   #endif
   
   #if defined(__GNUC__) || defined(__INTEL_COMPILER)
   #ifndef __INTEL_COMPILER
   #define __strong_reference(sym,aliassym)        \
           extern __typeof (sym) aliassym __attribute__ ((__alias__ (#sym)))
   #endif
   #ifdef __STDC__
   #define __weak_reference(sym,alias)     \
           __asm__(".weak " #alias);       \
           __asm__(".equ "  #alias ", " #sym)
   #define __warn_references(sym,msg)      \
           __asm__(".section .gnu.warning." #sym); \
           __asm__(".asciz \"" msg "\"");  \
           __asm__(".previous")
   #define __sym_compat(sym,impl,verid)    \
           __asm__(".symver " #impl ", " #sym "@" #verid)
   #define __sym_default(sym,impl,verid)   \
           __asm__(".symver " #impl ", " #sym "@@" #verid)
   #else
   #define __weak_reference(sym,alias)     \
           __asm__(".weak alias");         \
           __asm__(".equ alias, sym")
   #define __warn_references(sym,msg)      \
           __asm__(".section .gnu.warning.sym"); \
           __asm__(".asciz \"msg\"");      \
           __asm__(".previous")
   #define __sym_compat(sym,impl,verid)    \
           __asm__(".symver impl, sym@verid")
   #define __sym_default(impl,sym,verid)   \
           __asm__(".symver impl, sym@@verid")
   #endif  /* __STDC__ */
   #endif  /* __GNUC__ || __INTEL_COMPILER */
   
   #define __GLOBL1(sym)   __asm__(".globl " #sym)
   #define __GLOBL(sym)    __GLOBL1(sym)
   
   #if defined(__GNUC__) || defined(__INTEL_COMPILER)
   #define __IDSTRING(name,string) __asm__(".ident\t\"" string "\"")
   #else
   /*
    * The following definition might not work well if used in header files,
    * but it should be better than nothing.  If you want a "do nothing"
    * version, then it should generate some harmless declaration, such as:
    *    #define   __IDSTRING(name,string) struct __hack
    */
   #define __IDSTRING(name,string) static const char name[] __unused = string
   #endif
   
   /*
    * Embed the rcs id of a source file in the resulting library.  Note that in
    * more recent ELF binutils, we use .ident allowing the ID to be stripped.
    * Usage:
    *      __FBSDID("$FreeBSD: releng/11.1/sys/sys/cdefs.h 317342 2017-04-23 20:32:46Z kib $");
    */
   #ifndef __FBSDID
   #if !defined(lint) && !defined(STRIP_FBSDID)
   #define __FBSDID(s)     __IDSTRING(__CONCAT(__rcsid_,__LINE__),s)
   #else
   #define __FBSDID(s)     struct __hack
   #endif
   #endif
   
   #ifndef __RCSID
   #ifndef NO__RCSID
   #define __RCSID(s)      __IDSTRING(__CONCAT(__rcsid_,__LINE__),s)
   #else
   #define __RCSID(s)      struct __hack
   #endif
   #endif
   
   #ifndef __RCSID_SOURCE
   #ifndef NO__RCSID_SOURCE
   #define __RCSID_SOURCE(s)       __IDSTRING(__CONCAT(__rcsid_source_,__LINE__),s)
   #else
   #define __RCSID_SOURCE(s)       struct __hack
   #endif
   #endif
   
   #ifndef __SCCSID
   #ifndef NO__SCCSID
   #define __SCCSID(s)     __IDSTRING(__CONCAT(__sccsid_,__LINE__),s)
   #else
   #define __SCCSID(s)     struct __hack
   #endif
   #endif
   
   #ifndef __COPYRIGHT
   #ifndef NO__COPYRIGHT
   #define __COPYRIGHT(s)  __IDSTRING(__CONCAT(__copyright_,__LINE__),s)
   #else
   #define __COPYRIGHT(s)  struct __hack
   #endif
   #endif
   
   #ifndef __DECONST
   #define __DECONST(type, var)    ((type)(__uintptr_t)(const void *)(var))
   #endif
   
   #ifndef __DEVOLATILE
   #define __DEVOLATILE(type, var) ((type)(__uintptr_t)(volatile void *)(var))
   #endif
   
   #ifndef __DEQUALIFY
   #define __DEQUALIFY(type, var)  ((type)(__uintptr_t)(const volatile void *)(var))
   #endif
   
   /*-
    * The following definitions are an extension of the behavior originally
    * implemented in <sys/_posix.h>, but with a different level of granularity.
    * POSIX.1 requires that the macros we test be defined before any standard
    * header file is included.
    *
    * Here's a quick run-down of the versions:
    *  defined(_POSIX_SOURCE)              1003.1-1988
    *  _POSIX_C_SOURCE == 1                1003.1-1990
    *  _POSIX_C_SOURCE == 2                1003.2-1992 C Language Binding Option
    *  _POSIX_C_SOURCE == 199309           1003.1b-1993
    *  _POSIX_C_SOURCE == 199506           1003.1c-1995, 1003.1i-1995,
    *                                      and the omnibus ISO/IEC 9945-1: 1996
    *  _POSIX_C_SOURCE == 200112           1003.1-2001
    *  _POSIX_C_SOURCE == 200809           1003.1-2008
    *
    * In addition, the X/Open Portability Guide, which is now the Single UNIX
    * Specification, defines a feature-test macro which indicates the version of
    * that specification, and which subsumes _POSIX_C_SOURCE.
    *
    * Our macros begin with two underscores to avoid namespace screwage.
    */
   
   /* Deal with IEEE Std. 1003.1-1990, in which _POSIX_C_SOURCE == 1. */
   #if defined(_POSIX_C_SOURCE) && _POSIX_C_SOURCE == 1
   #undef _POSIX_C_SOURCE          /* Probably illegal, but beyond caring now. */
   #define _POSIX_C_SOURCE         199009
   #endif
   
   /* Deal with IEEE Std. 1003.2-1992, in which _POSIX_C_SOURCE == 2. */
   #if defined(_POSIX_C_SOURCE) && _POSIX_C_SOURCE == 2
   #undef _POSIX_C_SOURCE
   #define _POSIX_C_SOURCE         199209
   #endif
   
   /* Deal with various X/Open Portability Guides and Single UNIX Spec. */
   #ifdef _XOPEN_SOURCE
   #if _XOPEN_SOURCE - 0 >= 700
   #define __XSI_VISIBLE           700
   #undef _POSIX_C_SOURCE
   #define _POSIX_C_SOURCE         200809
   #elif _XOPEN_SOURCE - 0 >= 600
   #define __XSI_VISIBLE           600
   #undef _POSIX_C_SOURCE
   #define _POSIX_C_SOURCE         200112
   #elif _XOPEN_SOURCE - 0 >= 500
   #define __XSI_VISIBLE           500
   #undef _POSIX_C_SOURCE
   #define _POSIX_C_SOURCE         199506
   #endif
   #endif
   
   /*
    * Deal with all versions of POSIX.  The ordering relative to the tests above is
    * important.
    */
   #if defined(_POSIX_SOURCE) && !defined(_POSIX_C_SOURCE)
   #define _POSIX_C_SOURCE         198808
   #endif
   #ifdef _POSIX_C_SOURCE
   #if _POSIX_C_SOURCE >= 200809
   #define __POSIX_VISIBLE         200809
   #define __ISO_C_VISIBLE         1999
   #elif _POSIX_C_SOURCE >= 200112
   #define __POSIX_VISIBLE         200112
   #define __ISO_C_VISIBLE         1999
   #elif _POSIX_C_SOURCE >= 199506
   #define __POSIX_VISIBLE         199506
   #define __ISO_C_VISIBLE         1990
   #elif _POSIX_C_SOURCE >= 199309
   #define __POSIX_VISIBLE         199309
   #define __ISO_C_VISIBLE         1990
   #elif _POSIX_C_SOURCE >= 199209
   #define __POSIX_VISIBLE         199209
   #define __ISO_C_VISIBLE         1990
   #elif _POSIX_C_SOURCE >= 199009
   #define __POSIX_VISIBLE         199009
   #define __ISO_C_VISIBLE         1990
   #else
   #define __POSIX_VISIBLE         198808
   #define __ISO_C_VISIBLE         0
   #endif /* _POSIX_C_SOURCE */
   #else
   /*-
    * Deal with _ANSI_SOURCE:
    * If it is defined, and no other compilation environment is explicitly
    * requested, then define our internal feature-test macros to zero.  This
    * makes no difference to the preprocessor (undefined symbols in preprocessing
    * expressions are defined to have value zero), but makes it more convenient for
    * a test program to print out the values.
    *
    * If a program mistakenly defines _ANSI_SOURCE and some other macro such as
    * _POSIX_C_SOURCE, we will assume that it wants the broader compilation
    * environment (and in fact we will never get here).
    */
   #if defined(_ANSI_SOURCE)       /* Hide almost everything. */
   #define __POSIX_VISIBLE         0
   #define __XSI_VISIBLE           0
   #define __BSD_VISIBLE           0
   #define __ISO_C_VISIBLE         1990
   #define __EXT1_VISIBLE          0
   #elif defined(_C99_SOURCE)      /* Localism to specify strict C99 env. */
   #define __POSIX_VISIBLE         0
   #define __XSI_VISIBLE           0
   #define __BSD_VISIBLE           0
   #define __ISO_C_VISIBLE         1999
   #define __EXT1_VISIBLE          0
   #elif defined(_C11_SOURCE)      /* Localism to specify strict C11 env. */
   #define __POSIX_VISIBLE         0
   #define __XSI_VISIBLE           0
   #define __BSD_VISIBLE           0
   #define __ISO_C_VISIBLE         2011
   #define __EXT1_VISIBLE          0
   #else                           /* Default environment: show everything. */
   #define __POSIX_VISIBLE         200809
   #define __XSI_VISIBLE           700
   #define __BSD_VISIBLE           1
   #define __ISO_C_VISIBLE         2011
   #define __EXT1_VISIBLE          1
   #endif
   #endif
   
   /* User override __EXT1_VISIBLE */
   #if defined(__STDC_WANT_LIB_EXT1__)
   #undef  __EXT1_VISIBLE
   #if __STDC_WANT_LIB_EXT1__
   #define __EXT1_VISIBLE          1
   #else
   #define __EXT1_VISIBLE          0
   #endif
   #endif /* __STDC_WANT_LIB_EXT1__ */
   
   #if defined(__mips) || defined(__powerpc64__) || defined(__riscv__)
   #define __NO_TLS 1
   #endif
   
   /*
    * Old versions of GCC use non-standard ARM arch symbols; acle-compat.h
    * translates them to __ARM_ARCH and the modern feature symbols defined by ARM.
    */
   #if defined(__arm__) && !defined(__ARM_ARCH)
   #include <machine/acle-compat.h>
   #endif
   
   /*
    * Nullability qualifiers: currently only supported by Clang.
    */
   #if !(defined(__clang__) && __has_feature(nullability))
   #define _Nonnull
   #define _Nullable
   #define _Null_unspecified
   #define __NULLABILITY_PRAGMA_PUSH
   #define __NULLABILITY_PRAGMA_POP
   #else
   #define __NULLABILITY_PRAGMA_PUSH _Pragma("clang diagnostic push")      \
           _Pragma("clang diagnostic ignored \"-Wnullability-completeness\"")
   #define __NULLABILITY_PRAGMA_POP _Pragma("clang diagnostic pop")
   #endif
   
   /*
    * Type Safety Checking
    *
    * Clang provides additional attributes to enable checking type safety
    * properties that cannot be enforced by the C type system. 
    */
   
   #if __has_attribute(__argument_with_type_tag__) && \
       __has_attribute(__type_tag_for_datatype__) && !defined(lint)
   #define __arg_type_tag(arg_kind, arg_idx, type_tag_idx) \
               __attribute__((__argument_with_type_tag__(arg_kind, arg_idx, type_tag_idx)))
   #define __datatype_type_tag(kind, type) \
               __attribute__((__type_tag_for_datatype__(kind, type)))
   #else
   #define __arg_type_tag(arg_kind, arg_idx, type_tag_idx)
   #define __datatype_type_tag(kind, type)
   #endif
   
   /*
    * Lock annotations.
    *
    * Clang provides support for doing basic thread-safety tests at
    * compile-time, by marking which locks will/should be held when
    * entering/leaving a functions.
    *
    * Furthermore, it is also possible to annotate variables and structure
    * members to enforce that they are only accessed when certain locks are
    * held.
    */
   
   #if __has_extension(c_thread_safety_attributes)
   #define __lock_annotate(x)      __attribute__((x))
   #else
   #define __lock_annotate(x)
   #endif
   
   /* Structure implements a lock. */
   #define __lockable              __lock_annotate(lockable)
   
   /* Function acquires an exclusive or shared lock. */
   #define __locks_exclusive(...) \
           __lock_annotate(exclusive_lock_function(__VA_ARGS__))
   #define __locks_shared(...) \
           __lock_annotate(shared_lock_function(__VA_ARGS__))
   
   /* Function attempts to acquire an exclusive or shared lock. */
   #define __trylocks_exclusive(...) \
           __lock_annotate(exclusive_trylock_function(__VA_ARGS__))
   #define __trylocks_shared(...) \
           __lock_annotate(shared_trylock_function(__VA_ARGS__))
   
   /* Function releases a lock. */
   #define __unlocks(...)          __lock_annotate(unlock_function(__VA_ARGS__))
   
   /* Function asserts that an exclusive or shared lock is held. */
   #define __asserts_exclusive(...) \
           __lock_annotate(assert_exclusive_lock(__VA_ARGS__))
   #define __asserts_shared(...) \
           __lock_annotate(assert_shared_lock(__VA_ARGS__))
   
   /* Function requires that an exclusive or shared lock is or is not held. */
   #define __requires_exclusive(...) \
           __lock_annotate(exclusive_locks_required(__VA_ARGS__))
   #define __requires_shared(...) \
           __lock_annotate(shared_locks_required(__VA_ARGS__))
   #define __requires_unlocked(...) \
           __lock_annotate(locks_excluded(__VA_ARGS__))
   
   /* Function should not be analyzed. */
   #define __no_lock_analysis      __lock_annotate(no_thread_safety_analysis)
   
   /* Guard variables and structure members by lock. */
   #define __guarded_by(x)         __lock_annotate(guarded_by(x))
   #define __pt_guarded_by(x)      __lock_annotate(pt_guarded_by(x))
   
   #endif /* !_SYS_CDEFS_H_ */

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