弹出这样一个提示，有解决办法吗
// 32 x 32 bit multiplication with 32 bit result
#ifdef _PIC18
#define _Has_hardware_multiply 1
#else
#define _Has_hardware_multiply 0
#endif

#if defined(_PIC14E) || defined(_PIC14EX) || defined(_PIC18)
#define _Has_large_call_stack 1
#else
#define _Has_large_call_stack 0
#endif

unsigned long
__lmul(unsigned long multiplier, unsigned long multiplicand)
{
        unsigned long product;

#define LOWBYTE(x)  (*(unsigned char *)(&x))
#define LMIDBYTE(x) (*(((unsigned char *)(&x))+1))
#define HMIDBYTE(x) (*(((unsigned char *)(&x))+2))
#define HIGHBYTE(x) (*(((unsigned char *)(&x))+3))

#if (_Has_hardware_multiply || _Has_large_call_stack) && defined(__OPTIMIZE_SPEED__)
        {

#define USE_SHRINK

/*
a 32-bit multiply can be decomposed into the sum of ten 8-bit multiplies
             a  b  c  d
*            e  f  g  h
-----------------------
           |         dh
           |      ch  0
           |   bh  0  0
           |ah  0  0  0
           |      dg  0
           |   cg  0  0
           |bg  0  0  0
         ag| 0  0  0  0 (we ignore this intermediate product
                         because it does not affect the low 32 bits of the result)
           |   df  0  0
           |cf  0  0  0
         bf| 0  0  0  0 (ignore)
      af  0| 0  0  0  0 (ignore)
           |de  0  0  0
         ce| 0  0  0  0 (ignore)
      be  0| 0  0  0  0 (ignore)
+  ae  0  0| 0  0  0  0 (ignore)
=======================
*/
                product =  (unsigned int)LOWBYTE(multiplier) * LOWBYTE(multiplicand);

#if defined(USE_MASKS)
                product += ((unsigned long)
                             ((unsigned int)LOWBYTE(multiplier) * LMIDBYTE(multiplicand))
                             +
                             ((unsigned int)LMIDBYTE(multiplier) * LOWBYTE(multiplicand)))
                        << 8;

                product += ((unsigned long)
                            ((unsigned int)LOWBYTE(multiplier) * HMIDBYTE(multiplicand))
                            +
                            ((unsigned int)LMIDBYTE(multiplier) * LMIDBYTE(multiplicand))
                            +
                            ((unsigned int)HMIDBYTE(multiplier) * LOWBYTE(multiplicand)))
                        << 16;

                /* cast to smaller type to avoid adding high bits just to discard */
                product += ((unsigned long)
                            (unsigned char)
                            ((unsigned int)LOWBYTE(multiplier) * HIGHBYTE(multiplicand))
                            +
                            (unsigned char)
                            ((unsigned int)LMIDBYTE(multiplier) * HMIDBYTE(multiplicand))
                            +
                            (unsigned char)
                            ((unsigned int)HMIDBYTE(multiplier) * LMIDBYTE(multiplicand))
                            +
                            (unsigned char)
                            ((unsigned int)HIGHBYTE(multiplier) * LOWBYTE(multiplicand)))
                        << 24;

#elif defined(USE_SHRINK)
                /* add direct to upper bytes, rather than shift and add all bytes */
                *((unsigned short long*)(((unsigned char*)&product)+1)) +=
                        ((unsigned int)LOWBYTE(multiplier) * LMIDBYTE(multiplicand));
                *((unsigned short long*)(((unsigned char*)&product)+1)) +=
                        ((unsigned int)LMIDBYTE(multiplier) * LOWBYTE(multiplicand));


                *((unsigned int*)(((unsigned char*)&product)+2)) +=
                        ((unsigned int)LOWBYTE(multiplier) * HMIDBYTE(multiplicand));
                *((unsigned int*)(((unsigned char*)&product)+2)) +=
                        ((unsigned int)LMIDBYTE(multiplier) * LMIDBYTE(multiplicand));
                *((unsigned int*)(((unsigned char*)&product)+2)) +=
                        ((unsigned int)HMIDBYTE(multiplier) * LOWBYTE(multiplicand));

                *(((unsigned char*)&product)+3) +=
                        (unsigned char)
                        ((unsigned int)LOWBYTE(multiplier) * HIGHBYTE(multiplicand));
                *(((unsigned char*)&product)+3) +=
                        (unsigned char)
                        ((unsigned int)LMIDBYTE(multiplier) * HMIDBYTE(multiplicand));
                *(((unsigned char*)&product)+3) +=
                        (unsigned char)
                        ((unsigned int)HMIDBYTE(multiplier) * LMIDBYTE(multiplicand));
                *(((unsigned char*)&product)+3) +=
                        (unsigned char)
                        ((unsigned int)HIGHBYTE(multiplier) * LOWBYTE(multiplicand));

#else
#error No method chosen
#endif
        }
#else

        product = 0;
        do {
                if(multiplier & 1)
                        product += multiplicand;
                multiplicand <<= 1;
                multiplier >>= 1;
        } while(multiplier != 0);

#endif
        return product;
}