C++ :: Null Destination Pointer Exception
Aug 26, 2014
Here when NonlinearSolver called the constructor,
m_gradient() constructor is called to construct m_gradient, which in turns sets a variable called m_S to NULL(0), then in the assignment operator, because the m_S is NULL, Visual Studio throws an exception saying that destination pointer is null, but it's not fatal. I don't like that to happen because I have to press ignore many many times when the program is debugged, how can I fix this bug (not mine) to avoid the null destination pointer exception?
As an intermediate layer, the function calls boost unbounded array operator = which in turns calls std::copy which results in this error
Code:
NonlinearSolver(solver_type const & solver)
: m_gradient()
, m_function()
, m_projection() {
*this = solver;
[Code] .....
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Apr 9, 2014
In my raytracer-project I have the following function:
bool hitObjects(Ray &ray, std::vector<Object *> &objects, Vector3& normal, Material *mat) {
double tmin = K_HUGE_VALUE;
double t;
[Code]....
When I try to run this, I only get the message "Material pointer is null". So, somehow the pointer is null after the hitObjects-function is called, even though it isn't inside that function.
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May 17, 2014
So I'm writing a small program for class, and for some reason I keep getting an error when trying to initialize head to NULL. Even threw in the namespace just to see, nothin'.
#ifndef NUMBERLIST_H
#define NUMBERLIST_H
using namespace std;
[Code].....
There's my header file. Not sure what I'm doing wrong with the constructor.
EDIT: Got it to work with nullptr, but still curious why that isn't working
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Aug 7, 2014
In jumping into C++ it says something like this: It's not necessary but when you delete a pointer it's a good idea to reset it as a null pointer. That if your code try's to dereference the pointer after being freed, your program will crash. This happens to a lot of experienced programmers.
This could corrupt users data. delete p_int;
p_int = NULL;
1. If you can deference a pointer after the memory is freed, why can't you just delete the pointer?
2. If you can do 1, how do you delete the pointer using code?
3. Every thing I've read says that free memory is handed out in a sequenced order. I don't believe that is true at all. I may be wrong. Why can't you put the data in any number of places if it will fit. Isn't the compiler smart enough to know where bytes (bits)and pieces are stored?
4. If you storing anything in free memory must use a pointer to it?
5. Can a pointer or something similar be used with stack memory?
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Dec 9, 2013
in the below program for both class pointers pointing to null. Class contains normal function executing but class contains virtual function getting segmentation fault.
#include <cstdio>
using namespace std;
class A
{
[Code].....
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Feb 14, 2013
lets say I have a pointer p_unit of type c_unit* (c_unit is an a.b.c.)
I have a function that returns a pointer to a new c_unit object:
c_unit * man_add_unit() {
c_unit * local_p_unit;
unsigned short int local_run_code;
print_man_add_menu();
local_run_code = get_a_run_code(); // this bit just gets user input
switch (local_run_code)
[code]....
I assign that to p_unit, then add it to a vector v_units:
p_unit = man_add_unit();
v_units.push_back(p_unit);
cout << "New unit added.
";
The whole program runs on a loop, and another thing the user can do is to print out data on c_unit objects pointed to by v_units. The problem is, in that function up there ^ I give the user the option to go back to main menu without creating a unit.
Since "local_p_unit" is declared but not assigned an initial value, I'm guessing the function would return a "null" pointer (which is what's hanging me up). If I just let this run with the above code, and go to print out the unit data, the program crashes.
I tried to make an if thing with p_unit == 0 but this always returns false and doesn't catch the "bad" unit that will subsequently cause a crash.
Btw, I have considered assigning a reference to a generic c_unit object to that there local_p_unit so it won't return null, then remove pointers to that object from v_units at the end of the loop.. But I know there's got to be a better way.
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Mar 14, 2014
struct mystruct{
int n;
};
class mscope{
public:
std::vector<mystruct> mv;
[Code] .....
So I have a vector of structs and I want to traverse it, find a struct that matches a constraint and obtain a pointer to that struct. I made a function for this purpose which takes a number and an empty pointer that will store the reference. However, after function returns the pointer becomes null. What could be causing this?
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Jan 22, 2013
getting an invalid null pointer error message after a successful build. This program is supposed to ask for firstName, lastName, age and maJor and keep doing so until the age that is input is 0 and then the program closes. Here is what I have.
#include <iostream>
#include <string>
using namespace std;
[Code]....
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Apr 12, 2013
[URL] ....
Which object's draw is being called?
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May 28, 2014
Code:
#include <stdio.h>
#include <stdlib.h>
const int* const ret_con()
{
typedef const int* const cip_to_c;
}
[code]....
I have two basic questions about what is happening:
1. The return value of ret_con should be pointing to const, but instead it's pointing to a (non-const) pointer to const. Does the compiler only check the qualifiers of the end destination, why doesn't this give a warning?
2. The original variable from ret_con (ci) is a local automatic, shouldn't its lifetime have expired when you leave the scope?
I also checked this with C++ compiler (taking out the auto keyword), it gave no warnings either.
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Feb 24, 2015
I want to examine every packet of a pcap trace file and if packet n+1 source address == packet n destination address && packet n+1 destination address == packet n source address i want to get the time between those 2 packages.
Problem: I can't compare the ipv6 adresses of src and destination.
comparing src and src is no problem. dst with dst as well
Code: ....
handle = pcap_open_offline(argv[fnum], errbuf);
while (packet = pcap_next(handle,&header))
{
...
struct ip6_hdr *ip_hdr = (struct ip6_hdr *)packet;
if (memcmp(&(ip_hdr->ip6_dst),ipv6_src,sizeof(ip_hdr->ip6_dst)))
{
.....
[code]....
if i try to compare these adresses i will never get a match. But i use a trace file with much matches. Do i need a offset in pkt_ptr? I saw some examples which deals with it.
Code:
uint32_t* test = (uint32_t*)ipv6_dst;
for (uint32_t j=0;j<sizeof(ip_hdr->ip6_dst);j++)
{
printf ("%x", *(test+j));
}
printf ("
[Code] ......
with given addresses:
Source: 2001:6f8:1c2c:2000:54c2:b056:f097:2830
Destination: 2a01:238:43f5:d900:2bf:784a:e3f8:9cd7
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Jan 25, 2014
VS 2012 / Windows 7 64 bit
class
class myclass {
public:
myclass(){/*stuff here*/}
myclass(int* p) {MyPointer = p; myclass()}
[Code] ....
it works until the myclass(int* p) calls myclass()
then the MyPointer will become CCCCCCCC (NULL value)!
is there a way to stop the second constructor from resetting the pointer value to null?
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Feb 18, 2014
I am looking at one of the functions of an exercise:
void escape(char * s, char * t) {
int i, j;
i = j = 0;
while ( t[i] ) {
/* Translate the special character, if we have one */
switch( t[i] ) {
[code]...
Notice the while loop evaluates the current value in t to true or false. When we hit the null terminator, does that get evaluated as 0 and hence evaluates as a falsy value so the while loop exits?
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Mar 31, 2015
When you login to my site my loginservice which is done by ajax and json make a session called context.Session["Name"]. With BreakPoints it shows that everything is good and the variables are in place. However when I use Session["Name"] it comes out as null.
I will add my code at the bottem not
using System;
using System.Collections.Generic;
using System.Linq;
[Code].....
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Jan 30, 2014
My perceptron's train function seems to materialize my BadInput exception object out of nowhere. Yet, everything works fine.
And when I put an forever loop in main to validate the output with many different inputs, I get a bad_alloc exception and a call to terminate().
BadInput.hpp
Code:
#ifndef BADINPUT_HPP
#define BADINPUT_HPP
class BadInput {
public:
BadInput(int val):difference(val) {
[Code] ....
I cannot figure out why train() is throwing an exception...feedforward didn't, as it's error message never printed.
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Feb 14, 2013
I catch an exception and want to log it on the console. This works as exepcted, but Valgrind shows me a set of invalid reads.
Here the code of the catch-block:
} catch(HGL::IOException &e) {
logError(e);
}
The signature of the logDebug is: BasicLogger &operator<<(const std::exception &e);
Now valgrind shows me 4 errors like that:
==20943== Invalid read of size 1
==20943== at 0x402C658: strlen (in /usr/lib/valgrind/vgpreload_memcheck-x86-linux.so)
==20943== by 0x41554DD: std::basic_ostream<wchar_t, std::char_traits<wchar_t> >& std::operator<< <wchar_t, std::char_traits<wchar_t> >(std::basic_ostream<wchar_t, std::char_traits<wchar_t> >&, char const*) (in /usr/lib/i386-linux-gnu/libstdc++.so.6.0.16)
[Code] .....
Generally I dislike invalid read in my code, even if they are harmless like in that case.
If I don't pass a reference, but a copy of the exception, I don't get this invalid reads, but also loose all information, because of the implicit upcasting.
Why I get the illegal read, resp. why std::wstring is deleting it on the way to the <<-operator?
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Oct 25, 2014
I know how exception handling works, but how should I actually use it in action? Let's say I have something like this:
Class X
{
public:
X();
//Pre-condition: example can't be 3.
void number(int example);
[code]......
If I know that the exception can only happen at the beginning of the function, is it okay to catch it right away?
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Jul 18, 2014
I'm trying to do some operator overloading, the function is supposed to add the values at index [i] of two vectors and place the result in the returning vector. The problem is I keep getting a vector out of range. This is the overloaded operator I'm working with (relatively new to these):
vector<float> operator+(const vector<float>& a, const vector<float>& b){
unsigned long size;
vector<float> temp;
if(a.size() >= b.size())
size = a.size();
[Code] .....
and then I would do something like this in the main:
vector<float> v, v1, v2;
v1.push_back(9.1);
...
v2.push_back(8);
...
v = v1 + v2;
but when I try to output the vector v I just get a vector out of range exception.
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Feb 24, 2013
I'm making an "improved" array for my programing class. It's currently unfinished, so you might see some commented out code. I'm trying to debug what I have.
I keep getting these errors when I try to complile my main.cpp:
In file included from main.cpp:3:0:
array.h:107:43: error: expected type-specifier before ‘out_of_range’
array.h:107:43: error: expected ‘)’ before ‘out_of_range’
array.h:107:43: error: expected initializer before ‘out_of_range’
array.h:121:55: error: expected type-specifier before ‘out_of_range’
array.h:121:55: error: expected ‘)’ before ‘out_of_range’
array.h:121:55: error: expected initializer before ‘out_of_range’
My main file:
#include <iostream>
#include <stdexcept>
#include "array.h"
using namespace std;
using namespace ArrayNameSpace;
int main()
{
Array<int> testSubject(5);
return 0;
}//End main
aannnd my Array.h file:
//ADD CONSTS TO METHODS
//CURRENTLY WORKING ON EXCEPTIONS AND BRACKET[] OVERLOADS. I HAVE TO FIGURE OUT SOLUTIONS FOR REACHING
//INDEXES FOR CHARS AND ENUMS
#ifndef __array_H__
#define __array_H__
#include <stdexcept>
namespace ArrayNameSpace
{
[code]....
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Sep 21, 2013
I have been assigned to create a search function in text file, but I received this error when I run the program and try to search: Error message: Unhandled exception at 0x0f85d442 (msvcr100d.dll) in Ticket.exe: 0xC0000005: Access violation reading location 0xcccccd08.
I don't know what is the exactly problem. So I just copy everything and paste here. Please don't fear of these codes, I have 2 files only, but I will paste 3 files here, the one is prototypes.h, then the main.cpp, the last one is part of my function that can working well alone, but when I put them into main.cpp I will get the error message like I mentioned before.
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Feb 17, 2015
write a program as described below: program that reads in two integers (age, social security number). You should write functions that throw an out-of-range exception forage (no negative numbers)SSN (must be a 9-digit integer) My code is written below:
#include "std_lib_facilities_4.h"
int main(){
int age = 0;
int ssn = 0;
[Code].....
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Apr 14, 2012
If a class A contains an array of objects of another class B.. And in the constructor of A, while constructing objects of B, any one object throws an exception, then how can we guarantee to release all the memory acquired.. so that there is no memory leak..
class B{};
class A{
public:
B Array[100];
...
};
In the above code, if in constructor of A, suppose 99 objects of B are constructed successfully, but 100th object throws exception, then how can we guarantee to release all the memory acquired by the other 99 objects?
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Mar 12, 2014
I have one problem deleting a file with boost. The file is opened in another application and cannot be deleted. I am supposed to received an exception error but I don't get it.
Here is my piece of code, very simple:
bool delete_file(const string &path) {
boost::filesystem::path bpath(path);
try {
if (boost::filesystem::remove(bath)) return true;
[Code] ....
I have put a breakpoint inside the catch part but it does not come to this point. Instead, the the output window of visual studio, I got these lines:
First-chance exception at 0x00007FFD2E575A88 in site_server.exe: Microsoft C++ exception: boost::filesystem::filesystem_error at memory location 0x00000070F8E3E920.
Unhandled exception at at 0x00007FFD2E575A88 in site_server.exe: Microsoft C++ exception: boost::filesystem::filesystem_error at memory location 0x00000070F8E3E920.
How to manage this situation?
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Sep 9, 2012
I'm getting Unhandled exception when try to run option 3.
This my code below.
Code:
#include <iostream>
#include <string>
using namespace std;
struct Vet {
string name;
int numOfAnimals;
string phoneNum;
[code]....
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Feb 12, 2015
It is advisable not to throw the exception from destructor. Because if exception happens stack unwinding happens. suppose the destructor again throws the exception then on part of first exception again one exception is thrown and exceptions can not be handled at same time. This is what i read from stack over flow.
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Jun 9, 2012
I'm out of track how to realize one point in exercise condition wording :
Give the OutOfBoundsException class a constructor with an int as argument that indicates the erroneous array index and store it in a data member.
How should I change the code below .
Code:
//array.h
#ifndef Array_H
#define Array_H
#include "point.h"
#include <string>
using namespace std;
class Array {
private:
Point* m_data; // Dynamic Array of Point pointers
[code]....
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