c++ - POD implications for a struct which holds an standard library container -

i came across this question recently. goal understand how c++ compiler views struct definitions hold standard library containers such std::vector.

ben voigt's answer linked question cites following c++0x standard:

....

a trivial class class has trivial default constructor (12.1) , trivially copyable.

[ note: in particular, trivially copyable or trivial class not have virtual functions or virtual base classes. — end note ]

a standard-layout class class that:

• has no non-static data members of type non-standard-layout class (or array of such types) or reference,

....

i'm bolded text implies following undefined behavior

struct  {     std::vector< sometype > myvec;     int myc;       a( int c ) : myc : (c) {} };  int main( void ) {     one( 1 );     two( 2 );      sometype k, z;     one.myvec.push_back( k );     two.myvec.push_back( z );      memcpy( &two, &one, sizeof( ) ); // bad juju } 

and same case any type standard library, including simpler types such std::string. due nature of library's design, given large usage of inheritance , template programming.

so, while struct a resemble of pod type, fact contains standard library type automatically invalidates category, far compiler concerned.

are assumptions correct?

no. basic assumptions flawed. "standard layout" not related templates. e.g. std::pair<t1, t2> has standard layout if , if both t1 , t2 do. same goes std::array<t,n>

however, none of containers have standard layout. whole point of allocators have advanced memory management.