PREfast Warning 328 (Windows CE 5.0)
328 - <type> passed as parameter <number> when <type> is required in call to <function>.
For the is* routines, passing an argument of type char can yield unpredictable results.
An SBCS or MBCS single-byte character of type char with a value greater than 0x7F is negative. If a char is passed, the compiler might convert the value to a signed int or a signed long. This value might be sign-extended by the compiler, with unexpected results.
Example
Defective Source
char* str;
bool b1 = isdigit(*str);
Corrected Source
char* str;
bool b2 = isdigit((unsigned char)*str);
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