RE: [boost] lexical_cast warnings in MS VC7.1 (was: (no subject))

From: Reece Dunn (msclrhd_at_[hidden])
Date: 2004-01-01 16:23:23

Kris Braun wrote:

>When compiling a lexical_cast< int >( foo ) call using MSVC 7.1 with /W4, I 
>get a
>C4701 "unreferenced variable" warning. This is because the compiler doesn't 
>know that
>the throw_exception function never returns. This warning can be fixed by 
>adding
>"__declspec( noreturn )" before "void throw_exception". I would generate a 
>patch,
>but I'm unsure how long noreturn has been supported by the compiler, so I 
>don't know what kind of conditional to use.

I get 3 types of warnings:

[1] C4511: copy constructor could not be generated; C4512 assignment 
operator could not be generated
   at lexical_cast.hpp(181)

This is fixample by replacing line 125 with:
+ class lexical_stream: public boost::noncopyable
- class lexical_stream

and adding
+ #include <boost/noncopyable.hpp>
at the top of the file.

[2] C4701: local variable 'result' may be used without having been 
initialized
   at lexical_cast.hpp(191)

This is the warning I think you are referring to. I don't understand your 
fix -- adding __declspec(noreturn) to the throw_exception function does 
nothing. The warning is referring to the line:
   Target result;
where the variable result has not been given a value.
   Target result = Target();
will remove the warning (since Target result(); results in a function 
decleration, not variable initialization!)

[3] C4127: conditional expression is constant
   at lexical_cast.hpp(131)
   at lexical_cast.hpp(133)

The only way around this one is to wrap the lines around the following:

#if defined(BOOST_MSVC)
#   pragma warning( push )
#   pragma warning( disable : 4127 ) // conditional expression is constant
#endif

   // ...

#if defined(BOOST_MSVC)
#   pragma warning( pop )
#endif

HTH,
Reece

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