[Boost-users] [lexical cast] suspected bug

From: David Abrahams (dave_at_[hidden])
Date: 2007-11-28 11:53:47

If you want attention, it's always a good idea to put the library name
in the subject line.  Cheers,

on Mon Nov 26 2007, "Laurence Bunnage" <Laurence.Bunnage-AT-teraview.com> wrote:

> I am currently maintaining a project written using Borland C++ Builder version 6 build 10.166
> and boost version 1.32.
>
> I found I had a reoccuring problem in my code whereby the output from lexical_cast<string>
> (any_double) was not at the precision I was expecting.  It started off OK, but after a while it
> changed.  I have tracked it down to some of my code which I simplified to that shown below.
>
> The first cast, in the try block, works correctly with the output value d = 5.0 and no assert
>
> The second cast, in the catch statement, returns a value of d = 5.00000013628211 and asserts.
>
> With the assert removed, all subsequent calls to lexical_cast continue to give similar results.
>
> try
>
> {
>
>   double d = boost::lexical_cast<double>(boost::lexical_cast<std::string>(5.0));
>
>   assert(d == 5.0);
>
>   throw std::runtime_error("Not enough points in peak");
>
> }
>
> catch (std::exception& e)
>
> {
>
>   double d = boost::lexical_cast<double>(boost::lexical_cast<std::string>(5.0));
>
>   assert(d == 5.0);
>
> }
>
> I have searched the boost website for similar problems and have not found anything (doesn’t mean
> it’s not there, just I haven’t found it)
>
> Any help, especially a solution or work around would be greatly appreciated.
>
> NOTE at this time, due to the current state of the project, I would prefer not to have to
> upgrade to a newer version of the boost library.
>
> Laurence Bunnage
>
> Software Engineer
>
> e-mail: Laurence.Bunnage_at_[hidden]
>
> TeraView Limited
>
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>
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-- 
Dave Abrahams
Boost Consulting
http://www.boost-consulting.com