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From: "redi at gcc dot gnu.org" <gcc-bugzilla@gcc.gnu.org>
To: gcc-bugs@gcc.gnu.org
Subject: [Bug libstdc++/57465] New: Failed postcondition for std::function constructed with null function pointer
Date: Thu, 30 May 2013 09:49:00 -0000
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X-Bugzilla-Product: gcc
X-Bugzilla-Component: libstdc++
X-Bugzilla-Version: 4.7.3
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X-Bugzilla-Severity: normal
X-Bugzilla-Who: redi at gcc dot gnu.org
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X-Bugzilla-Priority: P3
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http://gcc.gnu.org/bugzilla/show_bug.cgi?id=57465

            Bug ID: 57465
           Summary: Failed postcondition for std::function constructed
                    with null function pointer
           Product: gcc
           Version: 4.7.3
            Status: UNCONFIRMED
          Severity: normal
          Priority: P3
         Component: libstdc++
          Assignee: unassigned at gcc dot gnu.org
          Reporter: redi at gcc dot gnu.org

#include <functional>
#include <cassert>

int main()
{
  using F = void();
  F* f = nullptr;
  std::function<F> x(f);
  assert( !x );
}

The assert should pass, but it fails with all versions.

Note that clang++ with libstdc++ headers passes the test, so this might be a
front end bug (to be filed separately) but can be fixed/worked around easily
enough in libstdc++ like so:

--- functional.orig     2013-05-30 10:48:27.081623873 +0100
+++ functional  2013-05-30 10:48:29.225370770 +0100
@@ -1964,7 +1964,7 @@

        template<typename _Tp>
          static bool
-         _M_not_empty_function(const _Tp*& __fp)
+         _M_not_empty_function(_Tp* const& __fp)
          { return __fp; }

        template<typename _Class, typename _Tp>