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(gcc-300.info)Standard Libraries

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Standard Libraries
==================

   GCC by itself attempts to be a conforming freestanding
implementation.  Note: Language Standards Supported by GCC,
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 `-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.