_sys_exit和_ttywrch，explicit type is missing (“int“ assumed)

报错

..\SYSTEM\usart\usart.c(64): error:  #260-D: explicit type is missing ("int" assumed)
  _sys_exit(int x) 
..\SYSTEM\usart\usart.c(69): error:  #260-D: explicit type is missing ("int" assumed)
  _ttywrch(int ch)

原本

_sys_exit(int x) 
{ 
	x = x; 
} 

_ttywrch(int ch)
{
    ch=ch;
}

修改

void _sys_exit(int x) 
{ 
	x = x; 
} 

void _ttywrch(int ch)
{
    ch=ch;
}