Linked List Deletion function causing program to crash *wrong pointers?*

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• How do I manipulate the contents of a stat() struct?

  I have a stat struct, and I'm looking for a way to get data out of it to be manipulated. The program will successfully run and print the desired st_mtime value, but including either of the "seg-fault" lines below causes a segmentation fault in runtime.

          struct stat buf;
          time_t time_m;
          time_t sys_time = time(0);
          if(stat(sub_dirp->d_name,&buf)==0)
                   {
                       //time_m = buf.st_mtime;                                     //seg-fault
                       //double since_last = (difftime(sys_time, buf.st_mtime)/60); //seg-fault
                       printf("%d ", (int)buf.st_mtime);                          //This works.
                   }
  

  Both lines are attempting to manipulate the buf.st_mtime value in some way.

  I've had a hard time finding any examples of the usage of stat() that do anything other than print its contents, which makes me wonder if it's even possible.

  So my question is, if it is possible, what am I missing?

  P.S. I do wish to keep st_mtime in the Unix timestamp format to make it easier to manipulate.

  Edit: After realizing that st_mtime is itself its own struct (timespec), how can I access the st_mtime.tv_sec member?

  The compiler doesn't like buf.st_mtime.tv_sec one bit.

  compiler error
• What's purpose of __linecapp in getline, when it'll auto resize?

  It's all about second parameter of getline in stdio.h,

  I'll name it 'n' or '__linecapp' below.

  According to the document:

  If the buffer is not large enough to hold the line, getline() resizes it with realloc(3), updating *lineptr and *n as necessary.

  It'll automatically update line capacity, then why should we input __linecapp?

  P.S Someone ask before, but discussion didn't explain when we need it, or how to make it useful.
• Linked list value double_up() method causing TypeError

  I am trying to implement a linked list in python and trying to create a method that doubles the value of each element in the linked list. This method updates the LinkedList object and it does not return anything.

  I'm getting a TypeError: unsupported operand type(s) for *: 'Node' and 'int'. Would anybody able to give me some tips on how to fix it?

  class Node:
      def __init__(self, data, next = None):
          self.data = data
          self.next = next
      def get_data(self):
          return self.data
      def get_next(self):
          return self.next
      def set_data(self, new_data):
          self.data = new_data
      def set_next(self, new_next):
          self.next = new_next
  class LinkedList:
      def __init__(self):
          self.head = None
          self.count = 0
      def add(self, item): 
          new_node = Node(item, self.head)
          self.head = new_node
          self.count += 1
      def is_empty(self):
          return self.count == 0
      def size(self):
          return self.count
      def search(self, item):
          current = self.head
          while current:
              if current.data == item:
                  return True
          current = current.next
          return False
      def remove(self, item): #change this method to update self.count
          found = False
          current = self.head
          previous = None
          while current is not None and not found:
              if current.data == item:
                  found = True
              else:
                  previous = current
                  current = current.next
          if found:
              if previous == None:
                  self.head= current.next
              else:
                  previous.set_next(current.next)
              self.count -= 1
      def count(self):
          return len(self)
      def __str__(self):
          new_str = ""
          if self.count != 0:
              curr = self.head
              while curr is not None:
                  new_str += str(curr.data) + " -> "
                  curr = curr.next
              new_str += "None"
          return new_str
      def remove_from_head(self):
          data = self.head.data
          self.head = self.head.next
          self.count -=1
          return data
      def double_up(self):
          while self.head.data != None:
              self.head.data = self.head.data * 2
              self.head.data = self.head.next
          
          
  fruit = LinkedList()
  fruit.add('cherry')
  fruit.add('banana')
  fruit.add('apple')
  print(fruit)
  fruit.double_up()
  print(fruit)
  

  Expected output:

  apple -> banana -> cherry -> None
  appleapple -> bananabanana -> cherrycherry -> None
  
• How can I repair this error that occurs occasionally when my code is running?

  Sometimes the code runs till the end without any errors while other times it stops in the middle and gives me this error Thread 1: EXC_BAD_ACCESS (code=EXC_I386_GPFLT) here is a picture of it (https://i.stack.imgur.com/uZDX1.png). The error is in my header file named Functions, and the compiler used in this picture is Xcode on a Mac device. I also tried another compiler "Visual Studio" on a Windows device and the code never runs till the end, it always stops in the middle of running and gives me an error in the same line of code, here is a picture of the error Visual Studio gave me Error in Visual Studio.

  #include <iostream>
  using namespace std;
  
  //products' data
  struct products{
      int ID;
      string Name;
      double Price;
      int Quantity;
  };
  
  //receipt
  struct receipt{
      string name;
      double price;
      receipt* link;
  };
  

  struct linkedListFunctions{
      //inserts node at the end of the list
      void insert(receipt** head_name_ref, string new_name, double new_price)
      {
          receipt* new_name_node = new receipt();
          receipt *last = *head_name_ref;
          new_name_node->name = new_name;
          new_name_node->price = new_price;
          new_name_node->link = NULL;
          if (*head_name_ref == NULL)
          {
              *head_name_ref = new_name_node;
              return;
          }
          while (last->link != NULL)//The error is right here
          {
              last = last->link;
          }
          last->link = new_name_node;
          return;
      }
      //prints list
      void printReceipt(receipt* n){
          while(n!=NULL){
              cout<<n->name<<": ";
              cout<<n->price<<'\t'<<" ";
              cout<<endl;
              n=n->link;
          }
      }
      //removes first node in the list
      receipt* removeFirstreceipt(struct receipt* head)
      {
          if (head == NULL)
              return NULL;
          receipt* temp = head;
          head = head->link;
          delete temp;
          return head;
      }
  };
  

  The first two code boxes are in the header file named Functions.h The error is in the second code box at line 15, it has a comment next to it

  #include "Functions.h"
  
  int main(){
      struct products details[5];
      details[0] = {0, "Apple Juice", 12, 240};
      details[1] = {1,"Bread", 10, 100};
      details[2] = {2, "Chocolate", 5, 500};
      details[3] = {3, "Dates", 50, 150};
      details[4] = {4, "Eggs", 30, 360};
      
      
      linkedListFunctions list;
      
      //declaring first node in receipt linked list
      receipt* head = NULL;
      head = new receipt;
      
      //prints all products IDs and Names
      for (int i=0; i<5; i++) {
          cout<<details[i].ID<<": ";
          cout<<details[i].Name<<" ";
          cout<<details[i].Price<<"LE"<<endl;
      }
      
      char buyAgain;
      while ((buyAgain='y' && buyAgain!='n')){
      //choosing a product
          cout<<"Enter the product's ID to choose it: ";
          int chooseProduct;
          cin>>chooseProduct;
          cout<<"ID: "<<details[chooseProduct].ID<<endl
          <<"Name: "<<details[chooseProduct].Name<<endl
          <<"Price: "<<details[chooseProduct].Price<<endl
          <<"Quantity: "<<details[chooseProduct].Quantity<<endl<<"********"<<endl;
          
          //choosing the quantity
          cout<<"How much "<<details[chooseProduct].Name<<" do you want? ";
          int chooseQuantity;
          cin>>chooseQuantity;
          list.insert(&head, details[chooseProduct].Name, details[chooseProduct].Price*chooseQuantity);//
          details[chooseProduct].Quantity=details[chooseProduct].Quantity-chooseQuantity;
          cout<<details[chooseProduct].Name<<" Left: "<<details[chooseProduct].Quantity<<endl<<"********"<<endl;
              
          cout<<"Would you like to order something else? y=yes n=no";
          cin>> buyAgain;
          switch(buyAgain) {
              case 'y':
              break;
              case 'n':
                  //prints receipt
                  cout<<"***Receipt***"<<endl;
                  list.printReceipt(head);
          }
      }
      
  }
  

  The last code box is the main function
• ANTLR function to retrieve text from a single node in a parse tree

  I want to retrieve text from a parse tree's node but when i use getText(), it retrieves all the text from that node's children. I have searched but i don't find any ANTLR function that can retrieve only the node's text or a function to delete a node's children (so that i can use getText() on that node once i have deleted his children). Any help is welcomed.
• Blender Viewer Nodes showing different values for the same vectors depending on the geometry attached to them?

  In Blender (3.1.2) I tried to connect the "corresponding" points of two curve-circles with the same center (at world-origin) with cones, like the beams of a symbolic sun with the inner circle being the circumference of the sun-disc and the outer circle being the circumference of the tip of the beams. This is just an exercise to later do the same with curves of different shape, for instance between an inner circle and an outer ellipse.

  Therefore I wanted to calculate the length of the vectors between corresponding inner and outer points to scale the cones accordingly. However, I found that my simple vector math don't work as I expected.

  I created a simplified scenario without the cones to demonstrate the issue I'm facing. The upper and lower half of the Geometry-Nodes tree attached as screenshot #1 are identical. The upper part is for the outer circle with radius 2, the lower part for the inner circle with radius 1. Both circles have only 4 points for simplicity (so they appear as rhombs).

  Geometry Nodes tree

  In the 5 boxes I do the following:

  1. Create the circle-curves, convert them to points and capture the point positions.

  2. Subtract the positions of corresponding points to get the relative vectors pointing from the outer to the inner circle's points. The result should consist of a list of the 4 vectors [(1,0,0)(0,1,0)(-1,0,0)(0,-1,0)] with all having length 1 due to the radius difference of 1.

  3. Put small Ico-Spheres to the points of both circles by Instance-to-Points nodes. Here is where also the cones would be instantiated, but on just the inner circle.

  4. Group-output the geometry of the circles and ico-spheres.

  5. Here comes my issue, displayed by 4 Viewer-Nodes:

  a) The value-inputs of the two viewer-nodes in the middle are attached to the same vector array calculated in step 2. So I would expect their output to be identical in the corresponding spread-sheets, independent of the geometry the viewer nodes are attached to.

  b) The geometry-sockets of the top two viewer-nodes are attached to the ico-sphere instances on the outer circle, with the top one showing the positions of their points captured in step 1.

  c) The geometry-sockets of the bottom two viewer-nodes are attached to the ico-sphere instances on the inner circle, with the one on the very bottom showing the positions of their points also captured in step 1.

  My expectation would have been the following outputs:

  a) From the top-most viewer node (points on outer circle): (2,0,0)(0,2,0)(-2,0,0)(0,-2,0)

  b) From the bottom-most (points on inner circle): (1,0,0)(0,1,0)(-1,0,0)(0,-1,0)

  c) From the two at the center (attached to the same vector-subtract node): (1,0,0)(0,1,0)(-1,0,0)(0,-1,0)

  However, the outputs of the center viewer-nodes differ depending on which geometry is attached to them (see screenshot #2). This leads to also different length, while all 4 vectors should be of length 1 in my opinion.

  Output of the 4 viewer-nodes with unexpected different values by the center nodes

  Where is my fallacy of thinking, and how can I actually calculate the distance between corresponding points on the circles for later scaling of cones between them?

  For completnes here screenshot #3 with my entire Blender screen:

  Overview screen with geometry output

  Thank's in advance!