Problem with converting std::string to CString

Hi all,

I am experiencing a problem in converting std::string to CString, and I don't know why it occurs. I am not using MFC. I just included atlstr.h.

Here is the code I use:

string mpname = "SCCMDC.SCCM.COM";

CString sMPIP(mpname.c_str());

cout << "sMPIP: " << sMPIP << endl;

printf("Printf: &#37;s", sMPIP);
printf("Printf2: %s", &sMPIP);

cout returns something like this:

sMPIP: 000000000003046F8

While the two printfs returns something like this:

Printf: <
Printf: H=1

I am not sure if the above is causing another error: adding two CStrings.

CString sNewloc = "something" + cString1 + " something " + cString2;

printf("new loc: %s", sNewloc);



Am I converting it wrong or am I just printing it wrong? Can anyone help me with this?

Thank you!

I guess that cout is converting the CString to void *. Try casting
it to something that cout understand:

Code:

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cout << "sMPIP: " << static_cast<LPCTSTR>(sMPIP) << endl;

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I believe you meant LPCSTR, or ...

Code:

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cout << "sMPIP: " << static_cast<const char*>(sMPIP) << endl;

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Since cout is char based.

Do the same for printf("%s") parameters.

Here's how to use code-tags: http://www.codeguru.com/forum/misc.php?do=bbcode#code

gg

I'm surprised cout isn't working. But yes, printf() expects a char* for a &#37;s. While CString contains an implicit conversion to char*, it will not work in a variadic argument list like printf has.

Quote:

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Originally Posted by Lindley

I'm surprised cout isn't working.

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For wide strings, the stream to use is std::wcout. If you pass a wide string to cout, you get the addresses instead of the strings displayed.

Regards,

Paul McKenzie

Hi all, thank you all for replying.

I forgot to mention that I also tried wcout. It has the same output as in using cout.

Or does wcout not work with CStrings too?

Thank you!

Quote:

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Originally Posted by LeanA

Hi all, thank you all for replying.

I forgot to mention that I also tried wcout. It has the same output as in using cout.

Or does wcout not work with CStrings too?

Thank you!

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There are two "versions" of CString, and it depends on the build that you are producing. If it's UNICODE build, then CString will contain a wide character string, else it will contain a string that is single-byte.

That is the first issue -- sort out what build you are producing, Unicode or not Unicode. If it's Unicode, then the stream must be std::wcout when printing wide character strings, else the stream to use is std::cout.

The second issue is that operator << knows nothing about CString -- that's why you get the hex output even if you are using std::wcout and you have a Unicode string.

To tell operator << how to handle CString, the CString class has a casting operator (LPCTSTR) that returns a const char* (or const w_chart*) to operator <<, which that operator is overloaded to handle.

So you have to make two things happen -- you use the correct stream (cout or wcout), depending on the build type (Unicode, non-Unicode) and you use the LPCTSTR cast operator for CString.

Regards,

Paul McKenzie

Code:

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    CStringA a = "Hello";
    CStringW w = L"World";

    wcout << static_cast<const wchar_t*>(a) << endl; // always an error
    cout << static_cast<const char*>(w) << endl; // always an error

    wcout << static_cast<LPCTSTR>(a) << endl; // compile error, or Ok
    cout << static_cast<LPCTSTR>(w) << endl; // compile error, or operator<<(const void*) invoked

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If you cast the CString based on the stream type, you'll always catch this mistake at compile time.

gg