Use memset to set 0xff for a char, and then set the char and 0xff =, can they be equal?

# Include <stdio. h>
# Include <string. h>

Int main ()
{
Char;
Memset (& A, 0xff, 1 );
If (A = 0xff)
Printf ("Equal. \ n ");
Else
Printf ("not equal. \ n ");
Return 0;
}

The answer is not equal. It can be seen from GDB that the variable in the memory is indeed 0xff, because it is set using memset. However, since a is of the char type and can only be 0x7 f at the maximum, 0xff has exceeded the char semantics when = is compared, equality is not true. If a is an unsigned char, It is equal.

In programming, char * is often used to represent a piece of memory. Therefore, be sure to pay attention to the signed character of char. Otherwise, an error will occur when char is used for memory comparison. Therefore, if char * is used to represent a piece of memory rather than a string, we strongly recommend that you use unsigned char * instead!