[Boost-bugs] [Boost C++ Libraries] #12577: Null reference in pair.hpp triggers runtime warning with -fsanitize=undefined

Subject: [Boost-bugs] [Boost C++ Libraries] #12577: Null reference in pair.hpp triggers runtime warning with -fsanitize=undefined
From: Boost C++ Libraries (noreply_at_[hidden])
Date: 2016-11-02 13:34:09

#12577: Null reference in pair.hpp triggers runtime warning with
-fsanitize=undefined
------------------------------+------------------------
 Reporter:  antoinep92@…      |      Owner:  igaztanaga
     Type:  Bugs              |     Status:  new
Milestone:  To Be Determined  |  Component:  container
  Version:  Boost 1.62.0      |   Severity:  Problem
 Keywords:                    |
------------------------------+------------------------
 I tagged 1.62 which is where I discovered the issue, but master at github
 seems affected as well.

 Consider this minimal file:
 {{{
 #include <boost/container/flat_map.hpp>
 int main() { return 0; }
 }}}

 When built with gcc 6.2 and undefined sanitizers, `g++
 -fsanitize=address`, the resulting executable triggers the following
 warning at runtime during static initialization:
 {{{
 /usr/include/boost/container/detail/pair.hpp:85:30: runtime error:
 reference binding to null pointer of type 'const struct
 piecewise_construct_t'
 }}}

 This doesn't happen with clang 3.9, so it *might* be a bug in gcc, but
 when looking at the boost code, I'd say gcc is right. Indeed, in
 `container/detail/pair.hpp` (line 85 in 1.62 and master), the static
 global variable `boost::container::piecewise_construct` is defined, of
 type `const std::piecewise_construct_t &`, and value
 `*boost::container::std_piecewise_construct_holder<0>::dummy`, defined in
 the same file, but (as far as I can tell), uninitialized.

 I'm not well positioned to assess the bug severity: either the
 null/uninitialized reference is never used, and the gcc warning can be
 ignored (although it's annoying); or there are situations the reference's
 address is dereferenced, and this can lead to crashes.

-- 
Ticket URL: <https://svn.boost.org/trac/boost/ticket/12577>
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