[Boost-bugs] [Boost C++ Libraries] #8700: multiprecision : Trying to cast to unsigned from cpp_int > 19 bits causes crash

Subject: [Boost-bugs] [Boost C++ Libraries] #8700: multiprecision : Trying to cast to unsigned from cpp_int > 19 bits causes crash
From: Boost C++ Libraries (noreply_at_[hidden])
Date: 2013-06-16 01:53:50

#8700: multiprecision : Trying to cast to unsigned from cpp_int > 19 bits causes
crash
--------------------------------------------+----------------------------
 Reporter:  danq@…                          |      Owner:  johnmaddock
     Type:  Bugs                            |     Status:  new
Milestone:  To Be Determined                |  Component:  multiprecision
  Version:  Boost 1.53.0                    |   Severity:  Showstopper
 Keywords:  crash cast multiprecision dump  |
--------------------------------------------+----------------------------
 The code segment below shows an iteration through a list of fields.  Each
 field will be filled with a sub-set of the cpp_int number.

 If the cpp_int number is 20-bits or larger, the second line of the 'for'
 loop (where the cast to unsigned occurs) crashes bit-time.

 When I comment out the cast, the code works file.  If I reduce the size of
 the cpp_int 'i_addr' to 19 bits or less, it works fine.

 20 bits or more causes a complete crash.

 Ticket #8423 comments about a similar crash and that it was fixed for the
 next release.  I was unable to find the fix.  Note that in that example,
 the 32-bit value crashes while the 16-bit one does not.

 Very similar to my case, so I suspect it is the same bug.

 Can someone please confirm this?



 Mingw 10.2 -
 GCC 4.8.1 - Boost 1.53.0 - FreeType 2.4.12, libogg 1.3.1, PCRE 8.33,
 pngcrush 1.7.60.


 //-----------------------------------------------------------//

 typedef boost :: multiprecision :: cpp_int Bit_Reg ;

 Bit_Reg i_addr ;    // This is incremented elsewhere, but used in this
 loop

 for (auto * i_field : table->i_field_list)
 {
   Bit_Reg i_value = i_addr >> i_field->bits.lsb ;

   i_field->value  = i_value.template convert_to <unsigned> () ;
 }

-- 
Ticket URL: <https://svn.boost.org/trac/boost/ticket/8700>
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