Subj : Re: How do I string compare two strings, one Unicode and the other
To   : borland.public.cpp.borlandcpp
From : D
Date : Thu Sep 29 2005 03:41 am


Thanks Thomas.
You have given me a much greater understanding.

maeder@glue.ch (Thomas Maeder [TeamB]) wrote:
>"D" <mr_dharris@hotmail.com> writes:
>
>> Can somebody tell me how to perform a string comparision of two
>> strings, one string is Unicode and the other a char*?
>> The following isn't working for me.
>> Am I using the correct string comparison functions?
>>   
>>   wchar_t* name = (wchar_t*) "fred";
>
>First of all, the type of "fred" is 'array of 5 char const'. Writing
>over the elements of this array isn't possible directly; doing so
>indirectly, e.g. after casting away the constness, has undefined
>behavior. You should therefore avoid having a pointer to non-const
>pointing at that array.
>
>Then the expression (wchar_t*) "fred" is equivalent to
>reinterpret_cast<wchar_t *>("fred"). The value of this expression is
>implementation-defined, and almost certainly not what you need.
>
>
>>   if (wcscmp(name, (wchar_t*) "fred") == 0)
>
>The function wcscmp is used to compare two wide character strings
>(cf. http://tinyurl.com/935o5 aka
>http://msdn.microsoft.com/library/default.asp?url=/library/en-us/vclib/html/_crt_strcmp.2c_.wcscmp.2c_._mbscmp.asp
>, which may wrap). Passing it the address of an array of no-wide
>characters is thus lying. You'll get undefined behavior; with a little
>luck on your side, the program will crash and you won't miss the
>error.
>
>
>>   {
>>     // never enters here.
>
>You are out of luck then.
>
>>   }
>
>
>You have to pass wcscmp() pointers into two arrays of wchar_t. E.g.:
>
>if (wcscmp(name,L"fred")==0)
>
>The prefix L in front of a string literal causes the literal's element
>type to be wchar_t.
>
>
>Whether this suggestion works depends on whether name and L"fred" have
>the same encoding. You write that name's encoding is Unicode. The
>encoding of L"fred" depends on the settings of the compiler and the OS
>it is run on. If it's not Unicode, you'll first have to convert L"fred"
>to Unicode.

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