Compiler interpretiert falsch, überspringt z.B. if Bedingungen, was tun?

volatile unsigned char next;

bool  next = false;

ISR(TIMER0_COMPA_vect)

{

    next = true; 

}

//PWM nach mikrocontroller.net

ISR(TIMER1_COMPA_vect)

{

   /*PWM ROUTINE*/

}

void init_led_hw(void)

{

    //Init Clock

    CLKPR = 0x80;  //Freischalten des CLKPR Clock Prescaler Registers

    CLKPR = 0x00;  //Ausschalten der Clockteilung

    SET_BIT(LATCHDDR, 2);// DDRC = 0x04; /* Pin 2 von Port C auf Output schalten */

    SET_BIT(LATCH, 2); //PORTC = 0x04; /* Pint 2 von Port C auf high schalten um das Latch durchzuschalten */

    LEDS1_OFF;    //turn off the LEDs on PORT1

    LEDS2_OFF;    //turn off the LEDs on PORT2

    LED_PORT1_DDR |= 0xFF;  //set led port 1 as output

    LED_PORT2_DDR |= 0xFF;  //set led port 2 as output

    //Timer0 in Normal Mode (count from 0 to 255, reset, count from 0 to 255, ...)

    TCCR0A = TIMER0_CTC_INIT;    

  TCCR0B = TIMER_CLOCKSPEED_1024; 

  OCR0A = 249; 

    TIMSK0   |= (1 << OCIE0A); 

  //Timer1 in Normal Mode (count from 0 to 65535, reset, count from 0 to 65535, ...)

    TCCR1A = TIMER1_NORMAL_16_INIT;  

    TCCR1B = TIMER_CLOCKSPEED_FULL;  

    TIMSK1   |= (1 << OCIE1A);  

}

int main(void)

{

//lokale Variablen für das LED-Fading FADE_LED

int t[PWM_CHANNELS], i=0;

unsigned char ticker[PWM_CHANNELS], sekundentimer[PWM_CHANNELS], steps_done[PWM_CHANNELS];

  //LUFA initialization

  //SetupHardware();  

  //LEDs_SetAllLEDs(LEDMASK_USB_NOTREADY);

  //LED Dimmer initialization

  init_led_hw();

  sei();

fade_init(0, 255, 3); //led0,  zielhelligkeit 255, dauer des fades: 3 sek

fade_init(1, 255, 5); //led1,  zielhelligkeit 255, dauer des fades: 5 sek

fade_init(2, 255, 10);//led2,  zielhelligkeit 255, dauer des fades: 10 sek

pwm_update();

//MAIN PROGRAMM

for (;;)

  {

    //HID_Device_USBTask(&Generic_HID_Interface);

    //USB_USBTask();

    if(next == true)

      {  

        next=false;

        for (i=0;i<PWM_CHANNELS;i++)

          {} //end for

        pwm_update();

      } //end if

  } //end endless for

} //end void