CString will not go to cout

[evenstar]

CString st1;
st1.Format(_T("%s"),"010210002022E803E903"); 
printf_s("%s\n",st1);//output:010210002022E803E903
//wcout<<st1.GetString()<<endl;            //error,why? 
 
 
 
CString st=_T("010210002022E803E903");
printf_s("%s\n",st);//output:0,why?
wcout<<st.GetString()<<endl;//output:010210002022E803E903 

in Visual Studio 2008

[Banfa]

Because %s in printf (and similar functions) indicates a parameter on the stack that points to a c string, that is a zero terminated array of characters. Your variable, st is an object of type CString not a pointer to a c string. You can however cast it to a constant pointer to a c string

(LPCSTR)st

because the CString object implements an operator for this so

printf_s("%s\n",(LPCSTR)st);

should work for you.

[evenstar]

CString st=_T("010210002022E803E903"); 
printf_s("%s\n",(LPCTSTR)st);

I've tried this method.But I still get the output:0

[Banfa]

Sorry the other thing is that CString deals with what ever character type Windows is using. This is normally unicode.

printf (and related functions) however still use a straight ASCII string.

To printf a CString you will need to convert the characters from Unicode to ASCII.

There should be plenty of information about this available either through google or msdn.

[evenstar]

Thank you very much for your help,but I pulzzed

CString st1; 
st1.Format(_T("%s"),"010210002022E803E903"); //output:010210002022E803E903  
printf_s("%s\n",st1);

st1 has a string of Unicode,but,printf_s alao can output in correct.

[JosAH]

I didn't even know the ostream class had an overloaded << operator for that CString class; why don't you use the string class? Every implementation understands that.

kind regards,

Jos

[Banfa]

@JosAH
It doesn't have an overload operator for CString, the wcout call is made on the return of a CString member function that returns a pointer to the CStrings buffer.

I assume that if the OP is using a CString then they are using MFC in general. In my experience MFC classes do not play particularly nicely with classes from other libraries including the stl.

[Banfa]

@evenstar
It isn't clear if you mean "printf_s also outputs it correctly" or "printf_s outputs it incorrect" which have opposite meanings.

Try calling wprintf_s, the wide character version of printf_s or use the format specifier %ls or %ws both of which indicate wide character strings.

[evenstar]

sorry,I mean printf_s also outputs it correctly

CString st1;
st1.Format(_T("%s"),"010210002022E803E903");
printf_s("%s\n",st1); //output:010210002022E803E90

CString st2;
st2=_T("010210002022E803E903");
printf_s("%ws\n",st2); //also output:010210002022E803E90

CString st3;
st3=_T("010210002022E803E903");
printf_s("%s\n",st2); //output:0

I think there are some differents between "="operator and "format()".
"st2=_T("010210002022E803E903");" will make string be saved as "%ws" in st2? So "printf_s("%s\n",st2) "only output 0,I guessed.
And I find another problem that

int _t main(int argc, _TCHAR* argv[])
{
CString st1;  
st1.Format(_T("%s"),"010210002022E803E903");  
printf_s("%ws\n",st1);
 
return 0;
}

only output:"pess any key to continue..."
there is no compile error or runtime error,but the code is not be executed

[weaknessforcats]

No one has mentioned that the OP code is not TCHAR compliant.

That is, in TCHAR code you cannot use standard C functions directly since the program must be able to switch between ASCII and Unicode by means of a compiler switch.

That means all of your functions must switch automatically. The ASCII strlen must change to the Unicode wcslen without making any program changes.

That means you must use the TCHAR macros.

Which you are not. Hence, the garbage.

_tprintf is the TCHAR macro you want.

BTW: CString is ASCII only. That means you should not be using this directly in TCHAR programs. Instead, use PTCHAR only. Then assign to this pointer the results of a macro that on the ASCII side is a PCHAR from CString and on the Unicode side is a PWCHAR obtained by converting your CString into a LPWSTR string.

Personally, I never use CString. Instead I use the C++ string and wstring:

[Banfa]

CString reference (admittedly from Visual C++ 6.0 but getting at any CString documentation is hard nowa days as MS seem to have deleted all the links to its documentation).

CString is based on the TCHAR data type.

And therefore CString is not ASCII only although I was surprised when I found this out about a week ago.

[evenstar]

Thank you all for your attention

[weaknessforcats]

And therefore CString is not ASCII only although I was surprised when I found this out about a week ago.

I am surprised too. I did not know MSDN supported TCHAR. I can see this TCHAR support was added after thge original release since several code examples where methods use LPCTSTR don't work since ASCII is hard-coded in the examples. This tells me MS just tested with ASCII and not UNICODE.

I wonder how MS gets this to work with libraries where CString is compiled with UNICODE undefined and the library is used in an ASCII program. You need two libraries?