1) assign signed or char type variable, which has smaller bit size, into unsigned variable (Sign extension problem)
ex) 32bit unsigned = 8bit / 16bit signed ,, (occur sing extension)
ex) 32bit unsigned = char (worse! It depends on compiler option)
unsigned aaa;
char zzs;
signed char ss;
ss= zzs = 0xF0;
aaa = ss ; //expected aaa, but 0xFFFF FFF0
aaa = zzs ; //expect aaa <= 0xF0, but it has different value depending on compiler option
For gcc, the default is signed, but you can modify that with -funsigned-char. note: for gcc in Android NDK, the default is unsigned. You can also explicitly ask for signed characters with -fsigned-char.
2) when compare char variables, it has different values depending on signed or unsigned
depends on compiler option
for (char depth = 3; depth >= 0 ; --depth)
char has 3 types
char : not allowed to use as number
signed char : -128 ~ 127
unsigned char : 0 ~ 255
Ie, this is error when you compare with char variables
=> It is fine when you use signed char or unsigned char
Add Comment