C++ Boolean Variables Changing -

i have c++ class; class follows:

first, header:

class pagetableentry { public:      pagetableentry(bool modified = true);     virtual ~pagetableentry();      bool modified();     void setmodified(bool modified);  private:     pagetableentry(pagetableentry &existing);     pagetableentry &operator=(pagetableentry &rhs);      bool _modified; }; 

and .cpp file

#include "pagetableentry.h"  pagetableentry::pagetableentry(bool modified) {     _modified = modified; }  pagetableentry::~pagetableentry() {}  bool pagetableentry::modified() {     return _modified; } void pagetableentry::setmodified(bool modified) {     _modified = modified; } 

i set breakpoint on 3 lines in .cpp file involving _modified can see being set/changed/read. sequence goes follows:

1. breakpoint in constructor triggered. _modified variable confirmed set true
2. breakpoint in accessor triggered. _modified variable false!

this occurs every instance of pagetableentry. class not changing variable - else is. unfortunately, don't know what. class created dynamically using new , passed around (as pointers) various stl structures, including vector , map. mutator never called own code (i haven't gotten point yet) , stl structures shouldn't able to, , since breakpoint never called on mutator can assume aren't.

clearly there's "gotcha" private variables can, under circumstances, changed without going through class's mutator, triggered who-knows-what situation, can't imagine be. thoughts?

update: value of this @ each stage:
constructor 1: 0x100100210
constructor 2: 0x100100400
accessor 1: 0x1001003f0
accessor 2: 0x100100440

update2:
(code showing pagetableentry accessed)

// in constructor:     _tableentries = std::map<unsigned int, pagetableentry *>();  // entry in table (body of testaddr() function, address unsigned int:     std::map<unsigned int, pagetableentry *>::iterator it;     = _tableentries.find(address);     if (it == _tableentries.end()) {         return null;     }     return (pagetableentry *)&(*it);  // create new entry:     pagetableentry *entry = testaddr(address);     if (!entry) {         entry = new pagetableentry(_currentprocessid, 0, true, kstoragetypedoesnotexist);         _tableentries.insert(std::pair<unsigned int, pagetableentry *>(address, entry));     } 

those points @ pagetableentry objects stored , retrieved stl structures in order cause issue. other functions utilize testaddr() function retrieve entries.

unrelated: since c++ has 65663 questions, , far 164 have been asked today, means only today number of c++ tagged questions exceeded 16-bit unsigned integer. useful? no. interesting? yes. :)

either debugger isn't reporting value correctly (not unheard of, , expected in optimized builds) or have memory corruption elsewhere in program. code you've shown more-or-less fine , should behave expect.

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edit corresponding 'update2':
problem in line:

return (pagetableentry *)&(*it); 

the type of *it std::pair<unsigned const, pagetableentry*>&, you're reinterpret-casting std::pair<unsigned const, pagetableentry*>* pagetableentry*. change line to:

return it->second; 

keep eye out other casts in codebase. needing cast in first place code smell, , result of doing cast incorrectly can undefined behavior, including manifesting memory corruption you're seeing here. using c++-style casts instead of c-style casts makes trivial find casts occur in codebase can reviewed (hint, hint).