buffer overwrite debugging in VC++
Author
Hi, i noticed that sometimes one of the variables that I'm printing out gets a value of something like #FD. i think that this means that I'm over writing something and it's flowing into my var - is this right? How do i debug this in VC++?
Thanks.
Set a watch on the variable. It will interrupt execution whenever its value is changed, and pinpoint the code where the change is performed.
Author
Ok, the debugger said that I got an access violation and stopped at this code from the stl code:
I did it again and it was here:
what does this mean?
Thanks.
inline void __CLR_OR_THIS_CALL _Container_base::_Orphan_all() const { // orphan all iterators _Lockit _Lock(_LOCK_DEBUG); if (_Myfirstiter != _IGNORE_MYITERLIST) { for (_Iterator_base **_Pnext = (_Iterator_base **)&_Myfirstiter; *_Pnext != 0; *_Pnext = (*_Pnext)->_Mynextiter) (*_Pnext)->_Mycont = 0; *(_Iterator_base **)&_Myfirstiter = 0; } }I did it again and it was here:
// TEMPLATE FUNCTION _Destroy_rangetemplate<class _Ty, class _Alloc> inline void _Destroy_range(_Ty *_First, _Ty *_Last, _Alloc& _Al) { // destroy [_First, _Last) _Destroy_range(_First, _Last, _Al, _Ptr_cat(_First, _Last)); }what does this mean?
Thanks.
This means that the area of memory that you use does not belong to you. Either you have a pointer that points to somewhere it shouldn't, or you allocated memory, used it, deallocated it and used it again (either with new, or as part of a container).
Of course, there is still the probability that you have a non-deterministic bug in your code that randomly bombs areas of memory through overflows. Did you do that watch thing I told you about?
Of course, there is still the probability that you have a non-deterministic bug in your code that randomly bombs areas of memory through overflows. Did you do that watch thing I told you about?
Check your debugger documentation for this — I don't even know what debugger you are using, there's no way I could tell you that.
Place a breakpoint when the variable is created, select the variable name in the code, right-click and choose to watch it. Remove the program and resume the running.
You might need to evaluate the address of the variable, and watch the contents at that adress instead.
You might need to evaluate the address of the variable, and watch the contents at that adress instead.
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