gcc/doc/gcc/known-causes-of-trouble-with-gcc/standard-libraries.rst

   1 ..
   2   Copyright 1988-2022 Free Software Foundation, Inc.
   3   This is part of the GCC manual.
   4   For copying conditions, see the copyright.rst file.
   5
   6 .. index:: Wall
   7
   8 .. _standard-libraries:
   9
  10 Standard Libraries
  11 ******************
  12
  13 GCC by itself attempts to be a conforming freestanding implementation.
  14 See :ref:`standards`, for details of
  15 what this means.  Beyond the library facilities required of such an
  16 implementation, the rest of the C library is supplied by the vendor of
  17 the operating system.  If that C library doesn't conform to the C
  18 standards, then your programs might get warnings (especially when using
  19 :option:`-Wall`) that you don't expect.
  20
  21 For example, the ``sprintf`` function on SunOS 4.1.3 returns
  22 ``char *`` while the C standard says that ``sprintf`` returns an
  23 ``int``.  The ``fixincludes`` program could make the prototype for
  24 this function match the Standard, but that would be wrong, since the
  25 function will still return ``char *``.
  26
  27 If you need a Standard compliant library, then you need to find one, as
  28 GCC does not provide one.  The GNU C library (called ``glibc``)
  29 provides ISO C, POSIX, BSD, SystemV and X/Open compatibility for
  30 GNU/Linux and HURD-based GNU systems; no recent version of it supports
  31 other systems, though some very old versions did.  Version 2.2 of the
  32 GNU C library includes nearly complete C99 support.  You could also ask
  33 your operating system vendor if newer libraries are available.