Standard Libraries#
GCC by itself attempts to be a conforming freestanding implementation.
See 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.