Undefine a library function

[Niklaus]

Hi,
 Like the #undef for macros , do we have a way for undefining a
library function like say memset. Do we have any way(like linker) so
that my function memset(with different arguments) are used everywhere
instead of library function memset. One way would be to rename my
function memset to mymemset or #define it . But i want to know whether
there is any hack or anything so that the library is included but the
memset used is mine instead of the library version.

Regds
Nik