kc3-lang/gnulib/doc/posix-headers/stddef.texi

• Show log

  Commit

• Hash : d7630af4
  Author :
  Date : 2023-03-16T13:45:40
  

  stddef: Define 'unreachable', for ISO C 23 compliance.
  
  * lib/verify.h (_GL_HAS_BUILTIN_UNREACHABLE): Don't define if already
  defined.
  * lib/stddef.in.h (_GL_HAS_BUILTIN_UNREACHABLE, unreachable): New
  macros.
  (abort): Declare if needed for unreachable.
  * m4/stddef_h.m4 (gl_STDDEF_H): Test for unreachable.
  * tests/test-stddef.c (test_unreachable_optimization,
  test_unreachable_noreturn): New functions, based on tests/test-verify.c.
  * doc/posix-headers/stddef.texi: Mention unreachable.
  

Download

• doc/posix-headers/stddef.texi

• @node stddef.h
  @section @file{stddef.h}
  
  POSIX specification:@* @url{https://pubs.opengroup.org/onlinepubs/9699919799/basedefs/stddef.h.html}
  
  Gnulib module: stddef
  
  Portability problems fixed by Gnulib:
  @itemize
  @item
  Some platforms fail to provide @code{unreachable}, which was added in C23:
  GCC 13, clang 15, AIX with xlc 12.1, Solaris with Sun C 5.15, and others.
  
  @item
  Some platforms fail to provide @code{max_align_t}, which was added in C11:
  NetBSD 8.0, Solaris 11.0, and others.
  
  @item
  @code{max_align_t} does not have the expected alignment on some platforms:
  NetBSD 8.0/x86, AIX 7.2 with xlc in 64-bit mode.
  
  @item
  Some old platforms fail to provide @code{wchar_t}.
  
  @item
  Some platforms provide a @code{NULL} macro that cannot be used in arbitrary
  expressions:
  NetBSD 5.0
  
  @item
  Some platforms provide a @code{NULL} macro whose value does not have the size
  of a pointer:
  AIX 7.2 with xlc in 64-bit mode.
  
  @item
  When this header file is provided by TinyCC 0.9.27 on glibc or macOS systems,
  it does not fulfil the expectations of other system header files.
  @end itemize
  
  Portability problems not fixed by Gnulib:
  @itemize
  @item
  @cindex null pointer type
  Some platforms fail to provide @code{nullptr_t},
  which Gnulib cannot usefully emulate:
  GCC 12, Clang 15, and other pre-2023 C compilers.
  
  @item
  Some platforms provide an @code{offsetof} macro that cannot be used in
  arbitrary expressions:
  Solaris 11.4
  This problem can be worked around by parenthesizing the
  @code{offsetof} expression in the unlikely case you use it with
  @code{sizeof} or @samp{[]}.
  @end itemize
  

Download