[boost] Re: lexical_cast problem

From: Kevlin Henney (kevlin_at_[hidden])
Date: 2003-04-19 03:55:53

In article <200304181851.37221.ghost_at_[hidden]>, Vladimir Prus
<ghost_at_[hidden]> writes
>
>I've just updated my project to use boost 1.30 and also gcc 3.2 and see 
>exception which reads:
>
>   bad lexical cast: source type value could not be interpreted as target,  
>   Target=i, Source=Ss
>
>The simple reproduction recipe is: 
>
>    #include <boost/lexical_cast.hpp>
>    #include <string>
>
>   int main()
>   {
>       boost::lexical_cast<int>(std::string(" 0"));
>   }
>
>Note the space in string. The exception does not occur with gcc 2.95, but only 
>with 3.2. I wonder if this should/can be fixed? Personally, I'd expect this 
>code to work.

This is a gcc 2.95, errm, 'feature' :-> The code should not work, and
the behaviour with 3.2 is correct. It all depends on your expectation,
but according to the principle of least astonishment lexical_cast<int>("
0") should have the same success as lexical_cast<int>("0 "), which
fails. If you want leading and trailing whitespace to be removed, remove
them.

>And a related note: the exception's what() above is not quite helpfull. 

Ah, yes, the ever descriptive gcc typeid names :->

>Is it 
>possible to output the stringstream content (if source -> stringstream 
>conversion was successfull?)

This is something that I toyed with a long time ago, but eventually
decided not to put in for a couple of reasons. One is the issue that the
exception would hold a dynamically allocated string of potentially
unbounded length, rather than just a short descriptive string. I was
also concerned that the role of such an exception was more as a
debugging tool than an exception handling medium.

Kevlin
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