linking behavior for CGT 7.3.1 for C6657

we are using CGT 7.3.1 with CCS5.1 and sysBios 6.33.6.50. We could define our own memset, memcpy and memcmp in c file with additional address checking, and the application built without any problem. But when we tried to define open, we got linking error that open is defined already.

Why do we see this different behavior? Are memset/memcpy/memcmp and open in different libraries? Is there a way for us to define not to link some function from runtime lib? Is there a way for us to replace library?

thanks

Weichun