[Boost-users] suspected bug

From: Laurence Bunnage (Laurence.Bunnage_at_[hidden])
Date: 2007-11-26 06:39:19

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prefer not to have to upgrade to a newer version of the boost library.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]
<mailto:Laurence.Bunnage_at_[hidden]> 

 

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