c++ - VS 2013 exception when using C++11 unrestricted unions -

consider code:

struct tnumeric {     bool    negative;     wstring integral;     wstring fraction; }; union tvalue {     // unnamed structs needed because otherwise compiler not accept it...     bool                bit;     struct{ tnumeric    numeric; };     struct{ wstring     text; }; };  tnumeric numeric; tnumeric &rnumeric{ numeric }; rnumeric.integral = l""; rnumeric.integral.push_back( l'x' ); //ok, no problem  tvalue value; tvalue &rvalue{ value }; rvalue.text = l""; rvalue.text.push_back( l'x' ); //ok, no problem  rvalue.numeric.integral = l""; rvalue.numeric.integral.push_back( l'x' ); // exception 

in release mode there no problem. when run in debug mode there exception @ last statement in method _adopt of class _iterator_base12 in xutility: access violation reading location 0x0000005c.

in _adopt code run when _iterator_debug_level == 2. tried with

#define _iterator_debug_level 1 

added in main program remains defined 2. there way disable check?

vs 2013 doesn't support c++11 unrestricted unions, implements unions per c++03:

an object of class non-trivial constructor (12.1), non-trivial copy constructor (12.8), non-trivial destructor (12.4), or non-trivial copy assignment operator (13.5.3, 12.8) cannot member of union

you fooled compiler using unnamed structs, doesn't solve problem: objects non-trivial, , vs2013 doesn't support that.

when switch more c++11-compliant compiler, such vs 2015, you'll have implement constructor, destructor, copy constructor etc. union in way safely constructs/destructs/copies appropriate part of union. there's example in standard (i'm quoting c++14 draft n4140 [class.union]/4):

consider object u of union type u having non-static data members m of type m , n of type n. if m has non-trivial destructor , n has non-trivial constructor (for instance, if declare or inherit virtual functions), active member of u can safely switched m n using destructor , placement new operator follows:

u.m.~m(); new (&u.n) n;