CCS: warning about function declared implicitly

Tool/software: Code Composer Studio

I opened a new "empty_EK_TM4C129EXL_TI_TivaTM4C129ENCPDT" project.

I get a warning in empty.c about "function declared implicitly" for the GPIOPinRead and GPIOPinWrite functions below (I wrote them in). 

This function gets triggered from ledoggleClk.

#include <ti/drivers/GPIO.h>  // This include in also in the file.  This file is listed as an extern.  I could not find any other reference for those functions.  How to I resolve this warning? 

Thanks very much, George

void GPIO_Toggle_Pin(void);

void GPIO_Toggle_Pin(void)

{

int8_t port_data;

port_data = GPIOPinRead(SYSCTL_PERIPH_GPION, Board_LED0);

port_data = port_data ^ Board_LED0;

GPIOPinWrite(SYSCTL_PERIPH_GPION, Board_LED0, port_data);

}