Exception thrown: read access violation (Linked List)

Question

I'm making a singly Linked List called Tracks, why is it throwing exception when I try to make a ptr of type Tracks and assign head to it. It also gives same error when I assign mbidd value to node->trackRef->mbid

Test Case:

TEST(SoundCloudTesting, AlbumDatabase) { string path = "Albums.csv"; ad = Create_AD<int, string, float>(path); //function to be implemented int expected_albums[] = { 1, 2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12, 13 }; //expected abid(s) //Testing AD Data structure AD<int, string, float>* current = ad; for (int i = 0; i < 13; i++) { EXPECT_EQ(expected_albums[i], current->abid); current = current->next; } EXPECT_EQ(1, current->abid); }

Please check the error

Please post a minimal reproducible example, not just the class, but also a main that duplicates the error. — PaulMcKenzie
– PaulMcKenzie, Commented Apr 30, 2021 at 2:57
Where is your source code that uses this class? (Your input which caused the crash) — prehistoricpenguin
– prehistoricpenguin, Commented Apr 30, 2021 at 3:04

The Dark · Accepted Answer · 2021-04-30 04:11:32Z

1

The member variable trackRef is a pointer and was never initialized, but you dereferenced it here:

trackRef->mbid = 0;

I can't tell from your code where trackRef is meant to be created for each new Tracks or should be passed in to the constructor, but at the moment there is no code that sets it to anything before it is used.

edited Apr 30, 2021 at 4:11

answered Apr 30, 2021 at 3:07

The Dark

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5 Comments

Asawira Emaan Khan Over a year ago

It is still throwing exception when I assign mbidd value to node->trackRef->mbid

The Dark Over a year ago

With your updated code you set trackRef to nullptr then try to dereference it createList - if you want to dereference a pointer it must point to valid memory.

Asawira Emaan Khan Over a year ago

But I want my linked list empty at first, how should I point it to a valid memory?

The Dark Over a year ago

What is trackRef meant to be for? What does it hold? It seems to be another linked list of MMD objects, but why is it a linked list? What is in charge of this other linked list? Is there one MMD linked list per Tracks object, or do they all somehow share that linked list?

Asawira Emaan Khan Over a year ago

One node of AD (Album Database) should have a linked list of Tracks in which songs of that particular Album are listed on the basis of MBID (Music Database ID). MMD linked list have all the songs stored.

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