Bug #8378: json/generator/generator.c: warning: array subscript has type 'char'

• Status: Closed
• Assignee: -
• Target version: -
• ruby -v: r40599 ruby 2.1.0dev (2013-05-07) [i386-cygwin]
• Backport: 1.9.3: UNKNOWN, 2.0.0: UNKNOWN

[akr (Akira Tanaka)]

ふと、cygwin を target とする cross-compile をしてみたところ、
以下の警告を見つけました。
(たぶん cross でなくても警告されると思います)

make[2]: Entering directory `/extdisk/chkbuild/chkbuild/tmp/build/20130507T115727Z/ruby/ext/json/generator'
compiling generator.c
generator.c: In function 'isArrayOrObject':
generator.c:897:5: warning: array subscript has type 'char' [-Wchar-subscripts]
generator.c:898:5: warning: array subscript has type 'char' [-Wchar-subscripts]
linking shared-object json/ext/generator.so

http://www.rubyist.net/~akr/chkbuild/debian/crossruby-trunk-cygwin/log/20130507T115727Z.log.html.gz

コードを見てみると以下のようになっていて、
char * を dereference した結果を isspace に渡しています。

895 char *p = RSTRING_PTR(string), *q = p + string_len - 1;
896 if (string_len < 2) return 0;
897 for (; p < q && isspace(*p); p++);
898 for (; q > p && isspace(*q); q--);
899 return (*p == '[' && *q == ']') || (*p == '{' && *q == '}');

char が signed な環境では、*p や *q は負になるかもしれないのでよろしくなくて、
*(unsigned char *)p とかにしたほうがいんじゃないでしょうか。

[naruse (Yui NARUSE)]

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

This issue was solved with changeset r40609.
Akira, thank you for reporting this issue.
Your contribution to Ruby is greatly appreciated.
May Ruby be with you.

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• ext/json/generator/generator.c (isArrayOrObject): cast char to
  unsigned char. [Bug #8378]