What actually does SFR_8BIT(address) declare?

I  am developing standard API's for MSP430G2553 Launchpad.  I have 2 different ways of setting clock source of Timer0. In both cases, i am trying to access the TA0CTL register to set the bits for selecting clock source. But the way I am trying to access is different. Below are the two ways and I get warnings in both cases:

First Method:

void set_clk_src_Timer0(unsigned short int clk_src)
{
void *ptr;
ptr=TACTL;
struct timer_control_register *TACTL_0;
TACTL_0 = (struct timer_control_register*)ptr;
TACTL_0->TSSEL = clk_src;
}

Warning : TACTL is of unsigned int type and cannot be assigned to type void*

Hence I assigned the address of TACTL in below method.

Second Method:

void set_clk_src_Timer0(unsigned short int clk_src)
{
void *ptr;
ptr=&TACTL;
struct timer_control_register *TACTL_0;
TACTL_0 = (struct timer_control_register*)ptr;
TACTL_0->TSSEL = clk_src;
}

Warning: TACTL is of type volatile unsigned int * and cannot be assigned to type void *

I see below declarations  in the MSP430G2553 header file

#define SFR_16BIT(address) extern volatile unsigned int address

#define TACTL TA0CTL

SFR_16BIT(TA0CTL)

Please explain me following doubts:

1. What actually SFR_16BIT(address) declares?

2. How the register name actually gives register address?