一个关于微软的_toupper的ｂｕｇ！

最近在使用　 _toupper　这个函数时，发现了一个微软的一个非常低级的ｂｕｇ，带入如下：

 

char toUpper = _toupper('t');
 char upper = _toupper('T');

 

结果确是：　toUpper is T, upper is 4.

看来， _toupper这个函数的实现可能比较笨，只要是传进来，就直接进行减0x20操作，不管你传的是否是小写。

 

 

ＭＳＤＮ的帮助如下：

int toupper(
   int c 
);
int _toupper(
   int c 
);
int towupper(
   wint_t c 
);
int _toupper_l(
   int c ,
   _locale_t locale
);
int _towupper_l(
   wint_t c ,
   _locale_t locale
);

 Parameters

c

Character to convert.

locale

Locale to use.

 Return Value

Each of these routines converts a copy of c, if possible, and returns the result.

If c is a wide character for which iswlower is nonzero and there is a corresponding wide character for which iswupper is nonzero, towupper returns the corresponding wide character; otherwise, towupper returns c unchanged.

There is no return value reserved to indicate an error.

In order for toupper to give the expected results, __isascii and islower must both return nonzero.

 

也没有说使用的注意事项。　可以看出，这应该是一个ｂｕｇ！ 希望看到此文章的人，能够注意这个函数，以防用错！

Linux 系统的说明很清楚,APP应该保证传入的是大写字母。NAME _toupper - transliterate lowercase characters to uppercaseSYNOPSIS #include int _toupper(int c);DESCRIPTION The _toupper() macro shall be equivalent to toupper() except that the application shall ensure that the argument c is a lowercase letter.