Concatenation of LPWSTR strings

Question

In Visual C++, I have a

LPWSTR mystring;

which is already defined somewhere else in the code.

I want to create a new LPWSTR containing:

"hello " + mystring + " blablabla"        (i.e. a concatenation)

I'm getting mad with such a simple thing (concatenation)! Thanks a lot in advance, I'm lost!

As a Unix developer, what is `LPWSTR`!?!?! Downvoter, totally inappropriate. — Alex Chamberlain, Mar 14 '13 at 22:11
@AlexChamberlain It's a wide string type (AFAIK, Unix dev here too). Another brainless typedef from Win(cr)API. — , Mar 14 '13 at 22:13
I googled this thirty times already... of course! But I'm still unable to do this simple task... It's not as simple as it seems : because of LPWSTR, it's not very easy (for me). — Basj, Mar 14 '13 at 22:17
@JosBas You should probably have put that in the question; [tag:c++] is particularly known for downvoting! — Alex Chamberlain, Mar 14 '13 at 22:18
@AlexChamberlain What I especially hate about the Windows API (apart from the Windows API) is that they're abusing C naming conventions. What the heck is `LPWSTR` if not a preprocessor macro? Oh wait, no, it's a no-brainer typedef... Well played, Microsoft, don't even leave a small hole for obeying standards... — , Mar 14 '13 at 22:18
LPWSTR is a long pointer to a wide string, wide strings are UNICODE. — QuentinUK, Mar 14 '13 at 22:19
Wide strings aren't necessarily Unicode, that is a common misconception; in fact, they may not be wide enough depending on how you defined Unicode... See [Joel's Infamous Post](http://www.joelonsoftware.com/articles/Unicode.html). — Alex Chamberlain, Mar 14 '13 at 22:20
This has nothing to do with Visual C++ so I removed that tag and added WinAPI. — JBentley, Mar 14 '13 at 22:21
@ShmilTheCat : why did you loose 1 minute of your life to say to me "one minute Google on ..." : do you really think I haven't done it yet ? — Basj, Mar 14 '13 at 22:35

score 24 · Accepted Answer · edited Jun 08 '17 at 05:54

24

The C++ way:

std::wstring mywstring(mystring);
std::wstring concatted_stdstr = L"hello " + mywstring + L" blah";
LPCWSTR concatted = concatted_stdstr.c_str();

edited Jun 08 '17 at 05:54

ljk321

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answered Mar 14 '13 at 22:12

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One modification would be that `concatted` must be a `LPCWSTR`. – chris Mar 15 '13 at 01:02

Jacob Seleznev · Answer 2 · 2013-03-14T22:24:33.163

6

You can use StringCchCatW function

edited Mar 14 '13 at 22:24

answered Mar 14 '13 at 22:12

Jacob Seleznev

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That's not C++, or certainly shouldn't be. – Alex Chamberlain Mar 14 '13 at 22:14
@Captain He's already dealing with `LPWSTR`, so why not? This way, he avoids converting his desired type to a different type just to manipulate it, before converting it back again. I'd +1 if it weren't for "You need" (which implies no other solution). – JBentley Mar 14 '13 at 22:18
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@AlexChamberlain The question is about _Visual C++_. – Jacob Seleznev Mar 14 '13 at 22:24
@JBentley Changed _need to_ to _can_ – Jacob Seleznev Mar 14 '13 at 22:25
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@JacobSeleznev Totally irrelevant; it is not *modern* C++. – Alex Chamberlain Mar 14 '13 at 22:25
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@Alex `LPWSTR` is not modern C++, so we're already outside that domain. Why therefore limit the solution to modern C++ if a practical solution exists within the problem's domain? As I said above, he ultimately needs to convert his result back to `LPWSTR` anyway. – JBentley Mar 14 '13 at 22:27
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@JBentley Because it then becomes a question of security and clarity. – Alex Chamberlain Mar 14 '13 at 22:30

score 0 · Answer 3 · answered Sep 20 '20 at 21:54

std::wstring mystring_w(mystring);
std::wstring out_w = L"hello " + mystring_w + L" blablabla";
LPWSTR out = const_cast<LPWSTR>(out_w.c_str());

'out' is a LPWSTR wrapper for 'out_w'. So as long as 'out_w' is in scope it will be good to use. Also you don't need to delete 'out' as it's is binded to 'out_w' lifecycle.

This is pretty much the same answer 'user529758' gave, but with 'chris' proposed modification.

Concatenation of LPWSTR strings

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