typedef unsigned __int16 OpCode;
class CInstruction
{public:
CInstruction(OpCode Code);
CInstruction(OpCode Code, const char* Data, size_t DataSize); // new constructor
~CInstruction();
OpCode Code() const {return _Code;}
const char* Data() const {return _Data;}
CInstruction& operator=(const CInstruction& Other);
private:
OpCode _Code;
char* _Data;
};
//////////////////////////////////////////////
CInstruction::CInstruction(OpCode Code)
{ _Code = Code;
_Data = NULL;
}
CInstruction::CInstruction(OpCode Code, const char* Data, size_t DataSize)
{ _Code = Code;
_Data = new char[DataSize];
memcpy(_Data, Data, DataSize);
}
CInstruction::~CInstruction()
{ cout << "Instruction starting destruction.\n";
delete _Data; // After this line, it never returns to my own code
_Data = NULL;
cout << "Instruction destroyed.\n";
}
///////////////////////////////////////
typedef std::vector<CInstruction> InstrList;
void main()
{ char* text = "This is some text";
size_t textsize = strlen(text) + 1;
CVirtualMachine vm;
CScript::InstrList iList;
iList.push_back(CInstruction(op_Print));
iList.push_back(CInstruction(op_Print, text, textsize)); // This line never completes
}
Pushing pointers into a std::vector
Author
I'm currently stuck on "Creating a Scripting System in C++ - Part 2". I managed to get part 1 up and running without any problems, but with the addition of the second constructor and the memcpy() function, it compiles, but an assertion fails within dbgdel.cpp (it breaks on the line "_ASSERTE(_BLOCK_TYPE_IS_VALID(pHead->nBlockUse));").
A bit of code might help (I'll post the parts involved).
The first iList.push_back succeeds, but the second fails in the destructor, just as delete is called. The debugger reveals that CInstruction::_Data, points to garbage. Any suggestions?
If it matters, I'm using Visual Studio .NET.
[EDIT] Fixed some screwed-up HTML [/EDIT]
You allocate memory using new[] and free it with delete. That may cause your problem, use delete[] _Data;
Make sure that _Data isn't NULL when deleting. In the destructor try: if( _Data ) delete _Data;
Quote:Original post by nyStagmus
Make sure that _Data isn't NULL when deleting. In the destructor try: if( _Data ) delete _Data;
No, deleting pointers to 0 is safe. "if" isn't necessary.
This looks like a class Rule of Three problem: you need to define a copy constructor and assignment operator for your class. The default copy constructor just copies the pointer value for your _Data pointer, which means if you create a temporary object and copy that, the _Data pointer will be deleted when the temp object goes out of scope, and you are creating a temp object in your call to push_back().
Author
I see...I always thought vectors pushed the original into the list, but I suppose it would be easier for them to push a copy instead (just build it where you want it rather than move the original). I guess I get to go back to my books and learn copy constructors. Shouldn't be too hard [smile]
Author
Thanks for the help, guys (I'm assuming...)! Once I added the copy constructor, it didn't give me any more problems). This is why I like this site - lots of helpful information from helpful people. Thanks again!
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