[Boost-bugs] [Boost C++ Libraries] #11669: lexical_cast crashes on certain conditions for floating point types

Subject: [Boost-bugs] [Boost C++ Libraries] #11669: lexical_cast crashes on certain conditions for floating point types
From: Boost C++ Libraries (noreply_at_[hidden])
Date: 2015-09-18 18:45:30

#11669: lexical_cast crashes on certain conditions for floating point types
--------------------------------+--------------------------
 Reporter:  alday.boost.trac@…  |      Owner:  apolukhin
     Type:  Bugs                |     Status:  new
Milestone:  To Be Determined    |  Component:  lexical_cast
  Version:  Boost 1.59.0        |   Severity:  Problem
 Keywords:                      |
--------------------------------+--------------------------
 In the presence of BOOST_LCAST_NO_COMPILE_TIME_PRECISION, there is no
 specialization of lcast_src_length<Source> for floating types, so
 lexical_converter_impl will allocate only 2 bytes and then try to do a
 sprintf, making the program crash.

 While the specialization for integral types checks for the presence of
 BOOST_NO_LIMITS_COMPILE_TIME_CONSTANTS, and ifdefs an arbitrary value or
 one calculated via std::numeric_limits, the specialization for floats gets
 wiped out completely in the presence of
 BOOST_LCAST_NO_COMPILE_TIME_PRECISION.

 Could you please do for floats what you do for integrals? I attach a patch
 that assigns an (arbitrary) max length of 156 to the representation of
 floats.

 Basically, instead of
 {{{
 #ifndef BOOST_LCAST_NO_COMPILE_TIME_PRECISION
 template<class Source>
         struct lcast_src_length<Source, BOOST_DEDUCED_TYPENAME
 boost::enable_if<boost::is_float<Source> >::type>
         {
 ...
             BOOST_STATIC_CONSTANT(std::size_t, value =5 +
 lcast_precision<Source>::value + 6);
         };
 #endif // #ifndef BOOST_LCAST_NO_COMPILE_TIME_PRECISION
 }}}

 I'd like to move the ifndef inside, as in
 {{{
  template<class Source>
         struct lcast_src_length<Source, BOOST_DEDUCED_TYPENAME
 boost::enable_if<boost::is_float<Source> >::type>
         {
 #ifndef BOOST_LCAST_NO_COMPILE_TIME_PRECISION
 ...
             BOOST_STATIC_CONSTANT(std::size_t, value =5 +
 lcast_precision<Source>::value + 6);
 #else
             BOOST_STATIC_CONSTANT(std::size_t, value = 156);
 #ifndef BOOST_LCAST_NO_COMPILE_TIME_PRECISION
 }}}

 The easiest way to reproduce it is:
 {{{
 #include <string>
 #define BOOST_LCAST_NO_COMPILE_TIME_PRECISION
 #include <boost/lexical_cast.hpp>
 int main() {
         boost::lexical_cast<std::string>(2.12345);
 }
 }}}

-- 
Ticket URL: <https://svn.boost.org/trac/boost/ticket/11669>
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