c++ - Double free or corruption, why does this appear? -

-

i've finished smart pointer (i know...) uploaded univerity's website runs number of automated tests on code. there 2 things wrong number of tests:

  • memory or time limit exceeded
  • memory access problem (ie. null pointer)

the thing don't know kind of tests being excecuted. able read automated tests' stdout did, written there:

in instantiation of ‘my_pointer<t>::my_pointer() [with t = tester]’: error: no matching function call ‘tester::tester()’ note: candidates are: tester::tester(my_pointer<tester>) candidate expects 1 argument, 0 provided tester::tester(const tester&) candidate expects 1 argument, 0 provided

so i'm guessing odd reason won't invoke my_pointer() constructor? smart pointer class:

template<class t> class my_pointer {     t* raw_pointer;  public:     my_pointer() {         raw_pointer = new t();         raw_pointer->increfcnt();     }      my_pointer(t *obj) : raw_pointer(obj) {         if(raw_pointer != null) raw_pointer->increfcnt();     }      my_pointer(const my_pointer<t>& smart_pointer) : raw_pointer(smart_pointer.raw_pointer) {         if(raw_pointer != null) raw_pointer->increfcnt();     }      t& operator*() {         return *raw_pointer;     }      t* operator->() {         return raw_pointer;     }      operator t*() {         return raw_pointer;     }      my_pointer<t> &operator=(const my_pointer<t> &smart_pointer) {         if(this != &smart_pointer && raw_pointer != null) {             /** if last reference given memory address */             if (raw_pointer->decrefcnt() == 0) {             delete raw_pointer;                                 }              raw_pointer = smart_pointer.raw_pointer;             raw_pointer->increfcnt();         }          return *this;     }      bool operator== (const t* pointer) {         return raw_pointer == pointer;     }      bool operator!= (const t* pointer) {         return raw_pointer != pointer;     }      bool operator== (const my_pointer<t> &smart_pointer) {         return raw_pointer == smart_pointer.raw_pointer;     }      bool operator!= (const my_pointer<t> &smart_pointer) {         return raw_pointer != smart_pointer.raw_pointer;     }      ~my_pointer() {        if(raw_pointer->decrefcnt() == 0 && raw_pointer != null) {            delete raw_pointer;         }     } };

this class, in references can counted:

class refcounted { private:     int count; public:     refcounted() : count(0) { }      int increfcnt() {         return ++count;     }      int decrefcnt() {         return --count;     } };

can see problems code? in advance!

you unconditionally deleting raw pointer in destructor. wrong. must decrement reference count, , delete if becomes zero.

you call raw_pointer->increfcnt(); in several places without checking whether raw_pointer null.


Comments

Post a Comment

Popular posts from this blog

javascript - Slick Slider width recalculation -

-
i'm trying add slide in panel on slick container css. carousel works except new width not being calculated when space has been added. recalibrate once advance next slide i'd happen each time panel opened or closed. i've tried adding both margin , padding, neither makes difference. ideas? https://jsfiddle.net/mhigley/dpf7mlpl/ html: <button type="button" id="button"><i class="fa fa-arrow-right"></i></button> <aside> <h2>slide in panel</h2> <ol> <li>list item</li> <li>list item</li> <li>list item</li> <li>list item</li> <li>list item</li> </ol> </aside> <main role="main"> <div class="sections"> <section> <article> <h2>first slide</h2> <p>lorem ipsum d...
Read more

jsf - PrimeFaces Datatable - What is f:facet actually doing? -

-
looking through primefaces code in app noticed following line: <f:facet name="header">#{trainsearch.traincount} trains</f:facet> it looks overriding header, makes sense, can explain me in little more detail? what happening line of code? complete code listed below: <p:datatable id = "results" value = "#{trainsearch.trains}" var = "train" rendered="#{not empty trainsearch.trains}" styleclass = "train-search-table horizontal-border"> <f:facet name="header">#{trainsearch.traincount} trains</f:facet> <p:column headertext = "train id"> <p:panelgrid columns="1" styleclass = "train-id-grid" layout = "grid"> <h:outputtext styleclass = "train-id-label" value="#{train.traini}"/> <h:outputtex...
Read more

angular2 services - Angular 2 RC 4 Http post not firing -

-
i trying fire post request app , it's not working, tried multiple ways. don't see request being fired under network tab in chrome. not sure problem is, appreciated. import { injectable } '@angular/core'; import { http, headers } '@angular/http'; @injectable() export class userservice{ private _url="users"; constructor(private _http: http){ } checkifusernameexists(username){ return this._http.get(this._url+"/"+username) .map(response => response.json()) } createuser(user){ let headers = new headers(); headers.append('content-type', 'application/json') console.log(json.stringify(user)); return this._http.post(this._url, json.stringify(user),{headers: headers}) .map(response => response.json()) } } first need capture error , solve error: this._http.post(this._url, json.stringify(user),{headers: headers}) .subscribe( ...
Read more