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ccross-platformmemcmpstrncmp

What will happen we pass -1 as value for 3rd parameter in strncmp() ie. n number bytes of bytes to compare?

I have three questions,

  1. What will happen we pass -1 as value for 3rd parameter in strncmp() ie. n number bytes of bytes to compare?
  2. Why the output differs in ARM and PPC? ie. if which one correct?

  3. If I use memcmp instead of strncmp, I m getting "inside else" output in both ARM and PPC. How and why?

    char str[10];

memset(str,'\0',sizeof(str));

printf("str:%s ,len:%d\n\r",str,strlen(str));

if(strncmp(str,"Maximum",(strlen(str)-1)) == 0)    
{         
    printf("inside if\n\r");     
}   
else    
{    
    printf("inside else\n\r");    
}

Output in ppc

str: ,len:0
inside else

Output in arm

str: ,len:0
inside if
Solution

  • What will happen we pass -1 as value for 3rd parameter in strncmp()

    Assuming the 3rd parameter is defined a being of size_tand furthermore assuming size_t is defined as unsigned integer, passing in -1 will result in a "wrap-around" and the function will receiving the value of SIZE_MAX. On a 32bit system this probably would be 0xffffffff.