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TCLAP std::wstring issue. Hello All,

I am using TCLAP(command line parsing utility). It has worked well so far until I ran into issues with wstring processing capability.

I have the below line to parse code for an UnlabeledValueArg 

std::wstring defaultValue; 

UnlabeledValueArg<std::wstring>
serverName("COMPUTERNAME", "List all scheduled tasks of computer", false,
           defaultValue, "string" );

I run into compile time issues ( Visual Studio spits out incredulous amounts of issues.). My question is have anyone tried using std::wstring with TCLAP. If yes can you post the solution or the approach to it. Thanks.

Edit - The compiler warnings I get is -

C:\DevProjects\MyProjects\nttoolkit\trunk\external\tclap/StandardTraits.h(187) : error C2679: binary '=' : no operator found which takes a right-hand operand of type 'const std::string' (or there is no acceptable conversion)

    c:\Program Files (x86)\Microsoft Visual Studio

9.0\VC\include\xstring(914): could be 'std::basic_string<_Elem,_Traits,_Ax>

&std::basic_string<_Elem,_Traits,_Ax>::operator

=(const std::basic_string<_Elem,_Traits,_Ax> &)' with [ _Elem=wchar_t, _Traits=std::char_traits, _Ax=std::allocator ]

    c:\Program Files (x86)\Microsoft Visual Studio

9.0\VC\include\xstring(919): or 'std::basic_string<_Elem,_Traits,_Ax> &std::basic_string<_Elem,_Traits,_Ax>::operator =(const _Elem *)' with [ _Elem=wchar_t, _Traits=std::char_traits, _Ax=std::allocator ]

    c:\Program Files (x86)\Microsoft Visual Studio

9.0\VC\include\xstring(924): or 'std::basic_string<_Elem,_Traits,_Ax> &std::basic_string<_Elem,_Traits,_Ax>::operator =(_Elem)' with [ _Elem=wchar_t, _Traits=std::char_traits, _Ax=std::allocator ] while trying to match the argument list '(std::wstring, const std::string)'

    C:\DevProjects\MyProjects\nttoolkit\trunk\external\tclap/Arg.h(446)

: see reference to function template instantiation 'void TCLAP::SetString(T &,const std::string &)' being compiled with [ T=std::wstring ]

    C:\DevProjects\MyProjects\nttoolkit\trunk\external\tclap/ValueArg.h(391)

: see reference to function template instantiation 'void TCLAP::ExtractValue(T &,const std::string &,TCLAP::StringLike)' being compiled with [ T=std::wstring ]

    C:\DevProjects\MyProjects\nttoolkit\trunk\external\tclap/ValueArg.h(389)

: while compiling class template member function 'void TCLAP::ValueArg::_extractValue(const std::string &)' with [ T=std::wstring ]

    C:\DevProjects\MyProjects\nttoolkit\trunk\external\tclap/ValueArg.h(325)

: while compiling class template member function 'bool TCLAP::ValueArg::processArg(int *,std::vector<_Ty> &)' with [ T=std::wstring, _Ty=std::string ]

    C:\DevProjects\MyProjects\nttoolkit\trunk\external\tclap/UnlabeledValueArg.h(44)

: see reference to class template

instantiation 'TCLAP::ValueArg' being compiled with [ T=std::wstring ]

    C:\DevProjects\MyProjects\nttoolkit\trunk\tasksecure\src\main.cpp(26)

: see reference to class template instantiation 'TCLAP::UnlabeledValueArg' being compiled with [ T=std::wstring ]

TaskSecure - 1 error(s), 6 warning(s)

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  • What are the errors VS is giving you? Commented May 12, 2011 at 16:35
  • I've just edited and added the compiler warnings. Thanks. Commented May 18, 2011 at 14:49

2 Answers 2

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I downloaded the source and built your example. The UnlabeledValueArg does take std::string, so apologies. The StandardTraits.h:202 shows dst = src. It is trying to set std::string to a std::wstring and there is no conversion. Apparently, TCLAP does not support std::wstring. The src should be std::wstring.

One work around might be to use std::string instead, and UTF-8 encode your program's arguments before using TCLAP.

Another option is to ask the owner of TCLAP to extend it to support either wide and narrow arguments.

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5 Comments

When in doubt kindly add it as a comment. Also try having a look at the method signature before posting replies.
@Eternal Learner - the method signature indicates: no operator found which takes a right-hand operand of type 'const std::string'. To me, that looks like you should be using wide strings.
Maybe having a look at this might give you a better idea. - tclap.sourceforge.net/html/annotated.html . Have a look at the UnlabeledValueArg class constructor.
@Eternal Learner - I downloaded the source and built your example. The UnlabeledValueArg does take std::string, so apologies. The StandardTraits.h:202 shows dst = src. It is trying to set std::string to a std::wstring and there is no conversion. Apparently, TCLAP does not support std::wstring. The src should be std::wstring. A work around might be to use std::string instead, and UTF-8 encode your program's arguments before using TCLAP.
Thanks for your suggestion. Yes I am looking into that now and trying to add support to std::wstring. I don't know much about UTF-8 encoding. Thanks will look into it. Kindly edit your answer so that I can remove my down-vote(thanks for taking time off and undergoing the pain of downloading the source).
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I also had a problem with TCLAP trying to process Unicode in command lines. I solved it by modifying TCLAP to use wchar_t and std::wstring. So I've made WTCLAP (Wide Templatized Command Line Argument Parser - https://github.com/vasyutin/wtclap). Maybe it will be useful for you, too. You can even use TCLAP and WTCLAP together in platform independent code.

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