> --wrap symbol
> Use a wrapper function for symbol.  Any undefined reference to
> symbol will be resolved to __wrap_symbol.  Any
> undefined reference to __real_symbol will be resolved to
> symbol.
> 
> This can be used to provide a wrapper for a system function.  The
> wrapper function should be called __wrap_symbol.  If it
> wishes to call the system function, it should call
> __real_symbol.
> 
> Here is a trivial example: