[thirdparty/gcc.git] / gcc / doc / gcc / known-causes-of-trouble-with-gcc / standard-libraries.rst

..
  Copyright 1988-2022 Free Software Foundation, Inc.
  This is part of the GCC manual.
  For copying conditions, see the copyright.rst file.

.. index:: Wall

.. _standard-libraries:

Standard Libraries
******************

GCC by itself attempts to be a conforming freestanding implementation.
See :ref:`standards`, for details of
what this means.  Beyond the library facilities required of such an
implementation, the rest of the C library is supplied by the vendor of
the operating system.  If that C library doesn't conform to the C
standards, then your programs might get warnings (especially when using
:option:`-Wall`) that you don't expect.

For example, the ``sprintf`` function on SunOS 4.1.3 returns
``char *`` while the C standard says that ``sprintf`` returns an
``int``.  The ``fixincludes`` program could make the prototype for
this function match the Standard, but that would be wrong, since the
function will still return ``char *``.

If you need a Standard compliant library, then you need to find one, as
GCC does not provide one.  The GNU C library (called ``glibc``)
provides ISO C, POSIX, BSD, SystemV and X/Open compatibility for
GNU/Linux and HURD-based GNU systems; no recent version of it supports
other systems, though some very old versions did.  Version 2.2 of the
GNU C library includes nearly complete C99 support.  You could also ask
your operating system vendor if newer libraries are available.
Commit	Line	Data
c63539ff ML	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
3ed1b4ce	33	your operating system vendor if newer libraries are available.