makefile 学习之__fls 测试

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#include <stdio.h>
#include<string.h>
#define BITS_PER_LONG 32
unsigned long __fls(unsigned long word)
{
   int num = BITS_PER_LONG - 1;

   if (!(word & (~0ul << (BITS_PER_LONG-16)))) {
       num -= 16;
       word <<= 16;
              printf("word = [%d],num=[%d] (~0ul << (BITS_PER_LONG-16))=[%x]\n",word,num,(~0ul << (BITS_PER_LONG-16)));
   }
   if (!(word & (~0ul << (BITS_PER_LONG-8)))) {
       num -= 8;
       word <<= 8;
       printf("word = [%d],num=[%d] (~0ul << (BITS_PER_LONG-8))=[%x]\n",word,num,(~0ul << (BITS_PER_LONG-8)));
   }

   if (!(word & (~0ul << (BITS_PER_LONG-4)))) {
       num -= 4;
       word <<= 4;
       printf("word = [%d],num=[%d] (~0ul << (BITS_PER_LONG-4))=[%x]\n",word,num,(~0ul << (BITS_PER_LONG-4)));
   }
   if (!(word & (~0ul << (BITS_PER_LONG-2)))) {
       num -= 2;
       word <<= 2;
       printf("word = [%d],num=[%d] (~0ul << (BITS_PER_LONG-2))=[%x]\n",word,num,(~0ul << (BITS_PER_LONG-2)));
   }
   if (!(word & (~0ul << (BITS_PER_LONG-1))))
   {
       num -= 1;
       printf("word = [%d],num=[%d] (~0ul << (BITS_PER_LONG-1))=[%x]\n",word,num,(~0ul << (BITS_PER_LONG-1)));
   }

   return num;
}

int main(int argc, char **argv)
{
        printf("fls = [%d]\n",__fls(0X1010));
        printf("aa = [%x]\n",~0ul);
        return 0;

}

makefile 如下：加了一个新文件Makefile。填入下面的内容，然后输入make就可以编译了

test:he.c
gcc he.c -o hello

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