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)
| Code Block |
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unsigned aaa; |
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char zzs; |
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signed char ss; |
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ss= zzs = |
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0xF0; aaa = ss ; //expected aaa, but 0xFFFF FFF0 |
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aaa = zzs ; |
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//expect aaa <= 0xF0, but it has different value depending on compiler option |
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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
it depends on compiler option.
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for (char depth = 3; |
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depth >= 0 |
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; --depth) |
char has 3 types
char : not allowed to use as number
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