system crash after declaring global object of the class

Question

hi,
i am very new to c++. i am getting system crash (not compilation error) in doing following:

i am declaring global pointer of class.

BGiftConfigFile  *bgiftConfig;
class BGiftConfigFile : public EftBarclaysGiftConfig { }

in this class i am reading tags from xml file. it is crashing system when this pointer is used to retrieve value. i am doing coding for verifone terminal.

int referenceSetting = bgiftConfig->getreferencesetting(); //system error

getreferencesetting() is member fuction of class EftBarclaysGiftConfig

i am confused about behavior of pointer in this case. i know i am doing something wrong but couldn't rectify it.

When i declare one object of class locally it retrieves the value properly.

BGiftConfigFile  bgiftConfig1; 
int referenceSetting = bgiftConfig1.getreferencesetting(); //working

But if i declare this object global it also crashes the system.

i need to fetch values at different location in my code so i forced to use someting global.

please suggest me how to rectify this problem.

Answer 1

Your local is a stack allocated instance.

Your global is a pointer and needs to be allocated via a call to new before you start using it:

bgiftConfig = new BGiftConfigFile();

Answer 2

Firstly forward declare the class BGiftConfigFile and then declare your pointer to object of the class as follows

class BGiftConfigFile
 BGiftConfigFile  *bgiftConfig;
class BGiftConfigFile : public EftBarclaysGiftConfig { };

Then allocate space for your pointer object using new operator

bgiftConfig = new BGiftConfigFile(); // depends upon what constructors you have defined in your class

After you are done with your pointer delete it appropriated using delete operator

delete bgiftConfig;

Answer 3

i need to fetch values at different location in my code so i forced to use someting global.

No, you don't need something global. You can pass your non-global instance of this object to the code that needs it.