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| author | shyouhei <shyouhei@b2dd03c8-39d4-4d8f-98ff-823fe69b080e> | 2018-11-12 01:08:35 +0000 |
|---|---|---|
| committer | shyouhei <shyouhei@b2dd03c8-39d4-4d8f-98ff-823fe69b080e> | 2018-11-12 01:08:35 +0000 |
| commit | 199c5cc18506f0f92e2b76f76e08608f7a09e5ca (patch) | |
| tree | 8422fde996a19ba10833c33ecac7ef57a3664439 /lib/irb.rb | |
| parent | 623ecdace6c9201aec8ae5dca88770cee6c85a37 (diff) | |
~(unsigned char) is not unsigned char
The unary ~ operator excercises integer promotion of the operand
_before_ actually applying bitwise complement (cf: ISO/IEC 9899:1990
section 6.3.3.3). Which means `~buf[i]` is in fact
`(int)~(int)buf[i]`.
The problem is, when buf[i] is 0xFF:
buf[i] 0xFF
(int)buf[i] 0x0000_00FF
~(int)buf[i] 0xFFFF_FF00 This is -256, out of unsigned char range.
The proposed fix is to change the char signed. By doing so,
buf[i] 0xFF
(signed char)buf[i] 0xFF
(int)(signed char)buf[i] 0xFFFF_FFFF
~(int)(signed char)buf[i] 0x0000_0000 This is 0, does not overflow.
git-svn-id: svn+ssh://ci.ruby-lang.org/ruby/trunk@65675 b2dd03c8-39d4-4d8f-98ff-823fe69b080e
Diffstat (limited to 'lib/irb.rb')
0 files changed, 0 insertions, 0 deletions