Difference between GLIBC and Standard C library

Does anyone konw the difference between GLIBC and standard C library.
GLIBC seem to miss a few elements, for example stdarg.h .

glibc missing stdarg.h - surely some mistake.
Where did you get that from?

I am using UBUNTU, with all the development packages installed.
It's not only stdarg.h ( it's no at /usr/include ) , but some other includes as well ( some in /usr/include/sys )

Sounds like you're missing a whole bunch of stuff.
Are you sure you installed the library as well as the compiler?

yes. I have.
is libc redundent or in a LInux system you have both libc and glibc ?

glibc is an implementation of the C runtime library, along with some additional stuff required by POSIX or just thought useful by the developers.
However, some really compiler-specific parts of the CRT are not part of glibc and are instead expected to be provided by the compiler. stdarg.h is not part of glibc, but of gcc. Also, because it is compiler-specific, it is not in /usr/include, but in the gcc-version-specific include dir. On my Gentoo, that's /usr/lib/gcc/<platform>/<version>/include
That is, my GCC 3.4.6 has it here:
/usr/lib/gcc/x86_64-pc-linux-gnu/3.4.6/include/stdarg.h
whereas my GCC 4.1.1 has it here:
/usr/lib/gcc/x86_64-pc-linux-gnu/4.1.1/include/stdarg.h

The third stdarg.h in my system is some workaround for a eVC bug that STLPort uses.