singleton class misuse, c++ - explanation needed -

i came across tought wasn't possible in c++ (i learning it)

i called nonstatic function without initializing class(singleton class) object or wtf happend, im not grasping it, == null , way did -

my singleton class example:

class lightslogic {  public:     void lightslogic::request_color_shift_group_after_x_msecs(blabla);      int current_used_chase_list = 0;  // singleton class thing below private:      lightslogic() {  // constructor here !     };      lightslogic(lightslogic const&);    // don't implement. // singleton     void operator=(lightslogic const&); // don't implement // singleton  public:      static lightslogic& getinstance()  // return reference. // singleton     {         static lightslogic instance;         return instance;     }  }; 

so somewhere defined:

static lightslogic* logicofligths; 

and called method class

logicofligths->request_color_shift_group_after_x_msecs(blabla); 

now happend - method used variable:

void lightslogic::request_color_shift_group_after_x_msecs(blabla) {     current_used_chase_list; // doing variable    //but since variable defined , initialized in class header    // , == null, method cant acces variable ?! thinks can ?!    //we crash saying: first-chance exception @ 0x013f5e8b in myexe.exe: 0xc0000005: access violation reading location 0x00028d48.    // , if use check before accesing variable : if (this == null) { report("this null"); return; } //this prevent crash.  } 

now correct way of accesing method of singleton class without ruining is:

(&lightslogic::getinstance())->request_color_shift_group_after_x_msecs(blabla); //i know use lightslogic::getinstance(). im using accesing variables, more clear me , compiler should fix misery on compile ?! 

why able , doing wrong ? or isnt case of doing wrong , misused memory , getting 'undefined behaviour' ? cause first tought.

the funny part - application works if dont use variables defined in class header of method.

calling via nullpointer has undefined behavior.

anything or nothing can happen.