Bug #10078: String#count() returns wrong count under specific conditions

• Status: Closed
• Assignee: -
• Target version: -
• ruby -v: ruby 2.0.0p481 (2014-05-08) [i386-mingw32]
• Backport: 2.0.0: DONE, 2.1: DONE

[nazy (Hiroki Najima)]

以下の条件の場合、String#countが誤った文字数を返します。

• 文字コードがWindows-31J (文字コード体系が違うせいか、UTF_8, ISO2022_JP, EUC_JPでは再現せず)
• countの引数が1バイト文字一つのみ
• Stringにcountに指定された文字と一致する文字コードが含まれる。

異常な例: 和は0x9861, aは0x61

>ruby -ve "puts 'a-和'.count('a')"
ruby 2.0.0p481 (2014-05-08) [i386-mingw32]
2

正常な例: countに2バイト以上与えると動作が正しくなります。
'a-a'などtr由来のcountの動作も的確ですが、'a-a'と'a'は等価なはずなのに異常な例と結果が異なります。

>ruby -ve "puts 'a-和'.count('a-a')"
ruby 2.0.0p481 (2014-05-08) [i386-mingw32]
1

>ruby -ve "puts 'a-和'.count('ab')"
ruby 2.0.0p481 (2014-05-08) [i386-mingw32]
1

[nobu (Nobuyoshi Nakada)]

• Status changed from Open to Closed
• % Done changed from 0 to 100

Applied in changeset r46896.

---

string.c: fix wrong single-byte optimization

• string.c (rb_str_count): fix wrong single-byte optimization.
  7bit ascii can be a trailing byte in Shift_JIS.
  [ruby-dev:48442] [Bug #10078]

[nagachika (Tomoyuki Chikanaga)]

• Backport changed from 2.0.0: UNKNOWN, 2.1: UNKNOWN to 2.0.0: REQUIRED, 2.1: REQUIRED

[nagachika (Tomoyuki Chikanaga)]

• Backport changed from 2.0.0: REQUIRED, 2.1: REQUIRED to 2.0.0: REQUIRED, 2.1: DONE

Backported into ruby_2_1 branch at r47255.

[usa (Usaku NAKAMURA)]

• Backport changed from 2.0.0: REQUIRED, 2.1: DONE to 2.0.0: DONE, 2.1: DONE

backported into ruby_2_0_0 at r47401.