[Boost-bugs] [Boost C++ Libraries] #13129: bracket_and_solve_root, toms748_solve; underflow when max_iter == 0

Subject: [Boost-bugs] [Boost C++ Libraries] #13129: bracket_and_solve_root, toms748_solve; underflow when max_iter == 0
From: Boost C++ Libraries (noreply_at_[hidden])
Date: 2017-07-21 04:09:37

#13129: bracket_and_solve_root, toms748_solve; underflow when max_iter == 0
--------------------------------+--------------------------
 Reporter:  Tom C <clunietp@…>  |      Owner:  John Maddock
     Type:  Bugs                |     Status:  new
Milestone:  To Be Determined    |  Component:  math
  Version:  Boost 1.64.0        |   Severity:  Problem
 Keywords:                      |
--------------------------------+--------------------------
 ~line 295, math/tools/toms748_solve.hpp

 std::pair<T, T> toms748_solve(...)

 Parameter max_iter is boost::uintmax_t.  Line ~343 decrements count
 (--count) with no prior checks on the value of max_iter, resulting in an
 underflow if the provided max_iter==0.

 This was discovered when calling bracket_and_solve root (with
 max_iters==15), which internally calls toms748_solve with max_iter==0,
 leading to the underflow/infinite(?) loop.

 Unfortunately due to the nature of bracket_and_solve root I'm unable to
 provide a minimal repro, but to repro the underflow simply call
 toms748_solve with max_iter==0, which it does not appear to be checking
 against.

 Alternatively/additionally, bracket_and_solve root is calling
 toms748_solve with max_iter==0; I don't know if that is desired behavior.

-- 
Ticket URL: <https://svn.boost.org/trac10/boost/ticket/13129>
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