How to Convert CString to _TCHAR *

Maxim Zarus

Hi experts... What about this? _tcscpy(sEndDate,CurrentDate); I am using this style. Is this wrong or right way?

modified on Tuesday, May 27, 2008 7:42 AM

Rajesh R Subramanian

Umm... I'll have to agree. But you're a tough guy with that principle man. One must either know what CString is, or should not use it at all. :-D

Nobody can give you wiser advice than yourself. - Cicero .·´¯`·->Rajesh<-·´¯`·. Codeproject.com: Visual C++ MVP

CPallini · modified on Tuesday, May 27, 2008 7:42 AM

That makes a copy. It is fine sometimes (and the other times it is wrong). :)

If the Lord God Almighty had consulted me before embarking upon the Creation, I would have recommended something simpler. -- Alfonso the Wise, 13th Century King of Castile.
This is going on my arrogant assumptions. You may have a superb reason why I'm completely wrong. -- Iain Clarke

Matthew Faithfull · modified on Tuesday, May 27, 2008 7:42 AM

In general an explicit function call should be preferred over an implicit cast so it's not wrong but a GetBuffer() call would be better style and of course you should otherwise be using _tcscpy_s :-D

"The secret of happiness is freedom, and the secret of freedom, courage." Thucydides (B.C. 460-400)

Matthew Faithfull

Rajesh R Subramanian wrote:

you're a tough guy

:laugh: Not really. I certainly wouldn't apply that everywhere but CString is a bit if an exceptional case. CString abuse is so rife and so easy to fall into, and CString itself so potentially inefficient and error prone that I would say understand it or don't use it. I would not say the same for example for stl::vector or stl::map where misuse is less likely and understanding the source very much harder.

"The secret of happiness is freedom, and the secret of freedom, courage." Thucydides (B.C. 460-400)

Maxim Zarus

Sir, just tell me where it will fail? I want to clear my confusion. Thanks:confused:

CPallini

Whenever you need to actually modify CString's internal buffer. It is not a common usage, I know, but it is perfectly legal.

If the Lord God Almighty had consulted me before embarking upon the Creation, I would have recommended something simpler. -- Alfonso the Wise, 13th Century King of Castile.
This is going on my arrogant assumptions. You may have a superb reason why I'm completely wrong. -- Iain Clarke

Maxim Zarus

Thank you sir :)

CPallini

Matthew Faithfull wrote:

it's not wrong but a GetBuffer() call would be better style

I don't agree. Implicit (or explicit) cast is not the same as GetBuffer() and you shouldn't use optionally one or the other: GetBuffer returns LPTSTR, while the cast returns LPCTSTR: the added C have his significance. :)

If the Lord God Almighty had consulted me before embarking upon the Creation, I would have recommended something simpler. -- Alfonso the Wise, 13th Century King of Castile.
This is going on my arrogant assumptions. You may have a superb reason why I'm completely wrong. -- Iain Clarke

SandipG

You can even use macrs A2W and W2A for conversions from multibyte-widechar and widechar-multibyte For these macros you need to include "atlconv.h" and also you need to write USES_CONVERSION macro before using these macros inside function.

Matthew Faithfull

CPallini wrote:

the added C have his significance.

Indeed it has and although I was talking general C++ style I do think it applies in this case. The CString impilcit cast returns LPCSTR because it isn't safe for it to hand out a pointer to its internal buffer without locking it but it also isn't good C++ for it to 'silently' give you a const pointer to something that is inherently not const. It's a compromise brought on by a compromised design.

"The secret of happiness is freedom, and the secret of freedom, courage." Thucydides (B.C. 460-400)

CPallini

Well, let's try to get it from the CString's consumer point of view: (1) requesting, via (explicit) cast a pointer to a const buffer means: "OK, I need the buffer but I'll not change it". (2) requesting via GetBuffer() a pointer to the internal buffer means: "I need the buffer to make all the weirdest things I know to it". Clearly method (2) is a bit crude for a mere copy operation. :-D

If the Lord God Almighty had consulted me before embarking upon the Creation, I would have recommended something simpler. -- Alfonso the Wise, 13th Century King of Castile.
This is going on my arrogant assumptions. You may have a superb reason why I'm completely wrong. -- Iain Clarke

Rajesh R Subramanian

hi der, da getbuffr iz renamed in da latast sdk as GetBufferIKnowWhatImDoing()

Nobody can give you wiser advice than yourself. - Cicero .·´¯`·->Rajesh<-·´¯`·. Codeproject.com: Visual C++ MVP

toxcct

Jijo raj wrote:

the (LPCSTR)CurrentDate returns a constant TCHAR pointer

wrong. it returns a const char pointer. (LP-C-T-STR) returns a const TCHAR*

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toxcct

I strongly second that. GetBuffer() is really to be forbidden for cast purpose

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David Crow · modified on Tuesday, May 27, 2008 7:42 AM

Maxim Zarus wrote:

Is this wrong or right way?

It's wrong since sEndDate has no storage space; it's just a pointer (to wherever).

"Love people and use things, not love things and use people." - Unknown

"To have a respect for ourselves guides our morals; to have deference for others governs our manners." - Laurence Sterne

CPallini

Indeed! :-D

If the Lord God Almighty had consulted me before embarking upon the Creation, I would have recommended something simpler. -- Alfonso the Wise, 13th Century King of Castile.
This is going on my arrogant assumptions. You may have a superb reason why I'm completely wrong. -- Iain Clarke

Jijo Raj

Typo. :-O Actually I mean LPCTSTR. But a T means lot! :) Thanks for pointing it out. Regards, Jijo.

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Maxim Zarus

you mean, first allocate memory for sEndDate then i can use _tcscpy_s(). its ok. i agree. but is it also neccessary to allocate memory when CString::GetBuffer() has been used? because i have seen in pervious post nobody ask to allocate memory for CString::GetBuffer(). regards, Maxim... :)

Hamid Taebi

And see The Complete Guide to C++ Strings, Part II - String Wrapper Classes[^] for more info about converts. ;)