What is correct initialization for Launchpad TM4C123 button interrupts?

I cannot correctly initialize either of the buttons on the Lauchpad to connect to the GPIO interrupts PF4 or PF0.  I am using Tivaware 2.1 and CCS 5.5.  I have read multiple posts which explain the required code to use these buttons to generate interrupts which seems clear to me, but still my code does not work correctly.

The code shown for button 1 (SW1 in code) produces an immediate and constant SW1 interrupt.

When I comment out the 4 lines in GPIO_Init() which initialize the PF4 interrupt associated with button1 (SW1), the modified code executed as expected, using polling for the 2 Launchpad buttons and an additional button on a proto board, AND uses an interrupt (PC7) for another button (SWP) on the proto board !!!    This interrupt executed as expected.  It is the only one I can get to work.

I apologize for posting so basic an issue, but I have tried in vain over 3 days to identify the issue.

I have multiple clocks with interrupts,  I2c, and QEI modules running correctly but am fairly new to CCS and the Tiva parts.

I have tried removing the prototype board to eliminate any associated hardware/software issues and get similar results.  I could simply use polling to avoid the issue (as I have done for now) but NEED external interrupts for other parts of the project.

Code snippets are posted below.

Any help will be appreciated very much,

Randy

///////////////////////////////////////////////////////////////////////////////////////////////////////////////////////////////////////////////////////////////////////////////////////////////////////////

// called when the processor receives an SW1 button push interrupt, port F4

void SW1_IntHandler (void)
{
    int32_t    swp_button_active;

    printf ("SW1 interrupt\n");
    // test for button active to debounce a little
    swp_button_active = GPIOPinRead (GPIO_PORTF_BASE, GPIO_PIN_4);
    if (swp_button_active != GPIO_PIN_4)
    {
        // post sw+ semaphore
        Semaphore_post (SW1_Sem);
    }
    GPIOIntClear (GPIO_PORTF_BASE, GPIO_INT_PIN_4);

}
/************************************************************************************/

// called when the processor receives an SW2 button push interrupt, port F0

void SW2_IntHandler (void)
{
    int32_t    swp_button_active;

    GPIOIntClear (GPIO_PORTF_BASE, GPIO_INT_PIN_0);
    printf ("SW2 interrupt\n");
    // test for button active to debounce a little
    swp_button_active = GPIOPinRead (GPIO_PORTF_BASE, GPIO_PIN_0);
    if (swp_button_active != GPIO_PIN_0)
    {
        // post sw+ semaphore
        Semaphore_post (SW2_Sem);
    }
}

/************************************************************************************/

// called when the processor receives an SW+ button push interrupt, port C7

void SWP_IntHandler (void)
{
    int32_t    swp_button_active;

    GPIOIntClear (GPIO_PORTC_BASE, GPIO_INT_PIN_7);
    printf ("SWP interrupt\n");
    // test for button active to debounce a little
    swp_button_active = GPIOPinRead (GPIO_PORTC_BASE, GPIO_PIN_7);
    if (swp_button_active != GPIO_PIN_7)
    {
        // post sw+ semaphore
        Semaphore_post (SWP_Sem);
    }
}

/************************************************************************************/
// called when the processor receives an SW- button push interrupt, port C6

void SWM_IntHandler (void)
{
    int32_t    swm_button_active;

    GPIOIntClear (GPIO_PORTC_BASE, GPIO_INT_PIN_6);
    printf ("SWM interrupt\n");
    // test for button active to debounce a little
    swm_button_active = GPIOPinRead (GPIO_PORTC_BASE, GPIO_PIN_6);
    if (swm_button_active != GPIO_PIN_6)
    {
        // post sw- semaphore
        Semaphore_post (SWM_Sem);
    }
}

/***********************************************************************************************************/
void PeripheralEnableInit(Void)
{
    SysCtlPeripheralEnable(SYSCTL_PERIPH_GPIOA);
    SysCtlPeripheralEnable(SYSCTL_PERIPH_GPIOB);
    SysCtlPeripheralEnable(SYSCTL_PERIPH_GPIOC);
    SysCtlPeripheralEnable(SYSCTL_PERIPH_GPIOD);
    SysCtlPeripheralEnable(SYSCTL_PERIPH_GPIOE);
    SysCtlPeripheralEnable(SYSCTL_PERIPH_GPIOF);
}

//************************************************************************************

void GPIO_Init (void)
{
    // Setup the LED GPIO pins used
    GPIOPinTypeGPIOOutput (GPIO_PORTF_BASE, GPIO_PIN_1); // EK_TM4C123GXL_LED_RED
    GPIOPinTypeGPIOOutput (GPIO_PORTF_BASE, GPIO_PIN_2); // EK_TM4C123GXL_LED_BLUE
    GPIOPinTypeGPIOOutput (GPIO_PORTF_BASE, GPIO_PIN_3); // EK_TM4C123GXL_LED_GREEN

    //////////////////////////////////////////////////////////////////////////////////
    // SW1, PF4

    GPIOPinTypeGPIOInput    (GPIO_PORTF_BASE, GPIO_PIN_4);
    GPIOPadConfigSet        (GPIO_PORTF_BASE, GPIO_PIN_4, GPIO_STRENGTH_4MA, GPIO_PIN_TYPE_STD_WPU);
    // interrupt setup, comment out the next 4 lines & polling & SWP interrupt work
    GPIOIntDisable            (GPIO_PORTF_BASE, GPIO_INT_PIN_4);
    GPIOIntClear            (GPIO_PORTF_BASE, GPIO_INT_PIN_4);
    GPIOIntRegister            (GPIO_PORTF_BASE, SW1_IntHandler);    // causes .vtable to exist
    GPIOIntTypeSet            (GPIO_PORTF_BASE, GPIO_INT_PIN_4, GPIO_FALLING_EDGE);

    //////////////////////////////////////////////////////////////////////////////////
    // SW2, PF0 requires unlocking before configuration

    HWREG    (GPIO_PORTF_BASE + GPIO_O_LOCK) = GPIO_LOCK_KEY;
    HWREG    (GPIO_PORTF_BASE + GPIO_O_CR) |= GPIO_PIN_0;
    //GPIOIntDisable        (GPIO_PORTF_BASE, GPIO_INT_PIN_0);
    //GPIOIntRegister        (GPIO_PORTF_BASE, SW2_IntHandler);
    //GPIOIntTypeSet        (GPIO_PORTF_BASE, GPIO_INT_PIN_0, GPIO_FALLING_EDGE);
    GPIOPinTypeGPIOInput    (GPIO_PORTF_BASE, GPIO_PIN_0);
    GPIOPadConfigSet        (GPIO_PORTF_BASE, GPIO_PIN_0, GPIO_STRENGTH_4MA, GPIO_PIN_TYPE_STD_WPU);
    HWREG    (GPIO_PORTF_BASE + GPIO_O_LOCK) = GPIO_LOCK_M;


    //////////////////////////////////////////////////////////////////////////////////
    // SWP    PC7    works

    GPIOIntDisable        (GPIO_PORTC_BASE, GPIO_INT_PIN_7);
    GPIOIntRegister        (GPIO_PORTC_BASE, SWP_IntHandler);    // causes .vtable to exist
    GPIOIntTypeSet        (GPIO_PORTC_BASE, GPIO_INT_PIN_7, GPIO_FALLING_EDGE);
    GPIOPinTypeGPIOInput(GPIO_PORTC_BASE, GPIO_PIN_7);
    GPIOPadConfigSet    (GPIO_PORTC_BASE, GPIO_PIN_7, GPIO_STRENGTH_4MA, GPIO_PIN_TYPE_STD_WPU);



    //////////////////////////////////////////////////////////////////////////////////
    // SW-    PC6
    GPIOIntDisable        (GPIO_PORTC_BASE, GPIO_INT_PIN_6);
    //GPIOIntRegister    (GPIO_PORTC_BASE, SWM_IntHandler);    // causes .vtable to exist
    //GPIOIntTypeSet    (GPIO_PORTC_BASE, GPIO_INT_PIN_6, GPIO_FALLING_EDGE);
    GPIOPinTypeGPIOInput(GPIO_PORTC_BASE, GPIO_PIN_6);  // FrontPanel Sw-
    GPIOPadConfigSet     (GPIO_PORTC_BASE, GPIO_PIN_6, GPIO_STRENGTH_4MA, GPIO_PIN_TYPE_STD_WPU);


}  // FrontPanelInitGPIO()
/**********************************************************************************************************/

Void i2c_task()
{
....

    // sw1, PF4
    GPIOIntClear     (GPIO_PORTF_BASE, GPIO_INT_PIN_4);
    GPIOIntEnable    (GPIO_PORTF_BASE, GPIO_INT_PIN_4);
////////////////////////////////////////////////////////////////////////////////////////////////////////////////////////////////////////////////////////////////////////////////////////