Access violation?

[laurasalas]

So I am trying to write a program with structs, function prototypes, references, pointers (for school).

I am able to execute this program, but after running the console and entering some info in the "Transact_AjouterUnNouveauClient(BaseDeDonnées base)" function, it stops and reads the following;

Exception thrown: read access violation.
_Pnext was 0xFFFFFFFFFFFFFFFF.


Here is my code:
https://pastebin.com/1j1nVZxW

[Duthomhas]

That is a lot of code to ask someone to debug for you.

An Access Violation (or Segfault for people using Linux) occurs when you try to dereference a pointer to memory you are not allowed to touch.

In simple terms, it means you are not being careful with your pointers.


To find out where it is happening, sprinkle some output statements throughout your function and see how many of them you get before the access violation.

void Transact_AjouterUnNouveauClient(BaseDeDonnées base)
{
std::cerr << "one\n";
    IU_FlushTampons();
    clrscr();
    int affichage_x;
    base.nombreDeClients++;
    string date;
    char c;

std::cerr << "two\n";
   
 
    base.clients[base.nombreDeClients - 1].clientDepuis = time(0);
std::cerr << "three\n";
    date = dateAString(base.clients[base.nombreDeClients - 1].clientDepuis);
std::cerr << "four\n";
...

and so on.

Keep narrowing it down until you understand where, exactly, the error is occurring.
This will also tell you which pointer has a bad value.

At this point, you can track back to see where the pointer gets its value, and you will then find the logic error that you made to get it that way.

Hope this helps.

[dutch]

Not only is it a fair amount of code, but it can only be run on Windows! (So I can't run it, for instance.)

In simple terms, it means you are not being careful with your pointers.

Or you are writing beyond the bounds of an array, either causing a segfault thereby or overwriting something that causes a segfault later. (But an array is a kind of pointer under the hood, I guess.)

I do notice that you are passing BD by value where it should presumably be passed by reference.
And I also happened to notice that you are indexing the compte array with 1, 2, 3 where it should be indexed with 0, 1, 2.

[z05DSL3A]

And I also happened to notice that you are indexing the compte array with 1, 2, 3 where it should be indexed with 0, 1, 2.

Damn, I was just going to mention that...

[Enoizat]

I’ve removed comments and now the code fits inside a forum post (just in case this code came back in the future):

#include <iostream>
#include <iomanip>
#include <conio.h>
#include <string>
#include <windows.h>
#include <time.h>
#include "../console(v1.9).h"

using namespace std;

const double MARGE_CREDIT_MAX = 10000;
const double SOLDE_COMPTE_MAX = 1000000;

const int NB_CLIENTS_MAX = 70;

const int NB_COMPTES_PAR_CLIENT_MAX = 3;

enum Commandes {
    ajouter,
    depot,
    retrait,
    virement,
    afficherInfo,
    listerClients,
    supprimer,
    quitter
};

struct Nom
{
    string prenom;
    string nom;
};

struct Adresse
{
    string noCivique;
    string rue;
    string ville;
    string codePostal;
};

struct InfoPersonnel
{
    Nom     nom;
    Adresse adresse;
    string  telephone;
    string  nas;
};

struct Compte
{
    double solde;
    double margeCredit;
};

struct Client
{
    InfoPersonnel   info;
    Compte          compte[NB_COMPTES_PAR_CLIENT_MAX];
    time_t          clientDepuis;
};

struct BaseDeDonnées
{
    int nombreDeClients;
    Client clients[NB_CLIENTS_MAX];
};

void IU_FlushTampons();
double arrondir(double v, int p);
void IU_Bip();
void IU_Bip_DialogueErreur(string message);

void IU_FlushTampons()
{
    if (cin.fail()) cin.clear();
    cin.ignore(cin.rdbuf()->in_avail());
    while (_kbhit()) _getch();
}

double arrondir(double v, int p = 2)
{
    double e = pow(10, p);
    return round(v * e) / e;
}

void IU_Bip() { cout << "\a"; }

void IU_Bip_DialogueErreur(string message)
{
    IU_Bip();
    MessageBoxA( NULL, message.c_str(), "ERREUR", MB_OK|MB_ICONSTOP|MB_SYSTEMMODAL );
}

string dateAString(time_t date)
{
    string date_en_lettres;
    tm ltm;
    localtime_s(&ltm, &date);

    date_en_lettres = to_string(ltm.tm_mday) + "/" + to_string(1 + ltm.tm_mon) + "/" + to_string(1900 + ltm.tm_year);

    return date_en_lettres;
}

void IU_AfficherMenuPrincipal()
{
    gotoxy(16, 0); cout << "Compagnie 420-B21";
    gotoxy(16, 4); cout << "1. Ajouter un client";
    gotoxy(16, 6); cout << "2. Dépôt";
    gotoxy(16, 8); cout << "3. Retrait";
    gotoxy(16, 10); cout << "4. Virement";
    gotoxy(16, 12); cout << "5. Afficher les informations d'un client";
    gotoxy(16, 14); cout << "6. Lister les clients et leur crédit actuel";
    gotoxy(16, 16); cout << "7. Supprimer un client";
    gotoxy(16, 18); cout << "8. Quitter";
    gotoxy(16, 24); cout << "Entrez votre choix: ";
}

Commandes IU_LireUnChoixValideDuMenuPrincipal()
{
    Commandes cmd = quitter;
    COORD choixCoord = { wherex(),wherey() };
    bool choixValide = false;
    int choix;
    char lettre_choix;
    do
    {
        clreol();
        IU_FlushTampons();
        gotoxy(choixCoord.X, choixCoord.Y);
        choix = _getch();

        if (isdigit(choix))
        {
            choix = choix - '0';
            choixValide = true;
            cout << choix;
        }
        else {
            lettre_choix = choix;
            cout << lettre_choix;
        }

    } while (choix < 1 || choix > 8 || !choixValide);

    switch (choix)
    {
    case 1:
        cmd = ajouter;
        break;
    case 2:
        cmd = depot;
        break;
    case 3:
        cmd = retrait;
        break;
    case 4:
        cmd = virement;
        break;
    case 5:
        cmd = afficherInfo;
        break;
    case 6:
        cmd = listerClients;
        break;
    case 7:
        cmd = supprimer;
        break;
    case 8:
        cmd = quitter;
    }
    return cmd;
}

void IU_MessageDeFinDuProgramme()
{

}

int IU_LireUnNoDeClient(int max);
int IU_LireUnNoDeCompteValide();
double IU_LireUnMontantValide(double max);
void IU_AfficherLesInformationsDuClient(Client client);
Client UI_LireLesInfosNouveauClient();

void Transact_AjouterUnNouveauClient(BaseDeDonnées base)
{

    IU_FlushTampons();
    clrscr();
    int affichage_x;
    base.nombreDeClients++;
    string date;
    char c;

    base.clients[base.nombreDeClients - 1].clientDepuis = time(0);
    date = dateAString(base.clients[base.nombreDeClients - 1].clientDepuis);

    gotoxy(0, 0); cout << "Transaction: ajouter un nouveau client";
    gotoxy(0, 2); cout << "Création du client #" << base.nombreDeClients;

    gotoxy(0, 4); cout << left << setw(21) << "Prénom" << ": ";
    cin >> base.clients[base.nombreDeClients - 1].info.nom.prenom;
    gotoxy(0, 5); cout << left << setw(21) << "Nom" << ": ";
    cin >> base.clients[base.nombreDeClients - 1].info.nom.nom;

    gotoxy(0, 7); cout << left << setw(21) << "Numéro civique" << ": ";
    cin >> base.clients[base.nombreDeClients - 1].info.adresse.noCivique;
    gotoxy(0, 8); cout << left << setw(21) << "Rue" << ": ";
    cin >> base.clients[base.nombreDeClients - 1].info.adresse.rue;
    gotoxy(0, 9); cout << left << setw(21) << "Ville" << ": ";
    cin >> base.clients[base.nombreDeClients - 1].info.adresse.ville;
    gotoxy(0, 10); cout << left << setw(21) << "Code postal" << ": ";
    cin >> base.clients[base.nombreDeClients - 1].info.adresse.codePostal;
    gotoxy(0, 11); cout << left << setw(21) << "Téléphone" << ": ";
    cin >> base.clients[base.nombreDeClients - 1].info.telephone;

    gotoxy(0, 13); cout << left << setw(21) << "Numéro d'assurance sociale" << ": ";
    cin >> base.clients[base.nombreDeClients - 1].info.nas;

    gotoxy(0, 15); cout << "Marge de crédit du compte #1 (Max de " << fixed << setprecision(2) << MARGE_CREDIT_MAX << " $)" << ": "; affichage_x = wherex();
    cin >> base.clients[base.nombreDeClients - 1].compte[1].margeCredit;
    gotoxy(affichage_x, 15); cout << base.clients[base.nombreDeClients - 1].compte[1].margeCredit;

    gotoxy(0, 16); cout << "Marge de crédit du compte #2 (Max de " << fixed << setprecision(2) << MARGE_CREDIT_MAX << " $)" << ": "; affichage_x = wherex();
    cin >> base.clients[base.nombreDeClients - 1].compte[2].margeCredit;
    gotoxy(affichage_x, 16); cout << base.clients[base.nombreDeClients - 1].compte[2].margeCredit;

    gotoxy(0, 17); cout << "Marge de crédit du compte #3 (Max de " << fixed << setprecision(2) << MARGE_CREDIT_MAX << " $)" << ": "; affichage_x = wherex();
    cin >> base.clients[base.nombreDeClients - 1].compte[3].margeCredit;
    gotoxy(affichage_x, 17); cout << base.clients[base.nombreDeClients - 1].compte[3].margeCredit;

    gotoxy(0, 19); cout << "Date de création de ce dossier: " << date;

    gotoxy(0, 22); cout << "Appuyez sur une touche pour continuer";
    c = _getch();
}

void Transact_FaireUnDepot(  )
{

}

void Transact_FaireUnRetrait(  )
{

}

void Transact_FaireUnVirement(  )
{

}

void Transact_AfficherTouteslesInfosDuClient(  )
{

}

void Transact_ListerLesClientsEtLeurCréditActuel(  )
{

}

void Transact_SupprimerUnClient(  )
{

}

void main()
{

    SetConsoleCP(1252);
    SetConsoleOutputCP(1252);

    BaseDeDonnées BD;
    BD.nombreDeClients = 0;
    Commandes cmd;
    do
    {
        IU_AfficherMenuPrincipal();
        cmd = IU_LireUnChoixValideDuMenuPrincipal();

        switch (cmd)
        {
        case ajouter: Transact_AjouterUnNouveauClient(BD); break;
        case depot: Transact_FaireUnDepot(); break;
        case retrait: Transact_FaireUnRetrait(); break;
        case virement: Transact_FaireUnVirement(); break;
        case afficherInfo: Transact_AfficherTouteslesInfosDuClient(); break;
        case listerClients: Transact_ListerLesClientsEtLeurCréditActuel(); break;
        case supprimer: Transact_SupprimerUnClient(); break;
        case quitter: IU_MessageDeFinDuProgramme(); break;
        }

    } while(cmd != quitter );
    _getch();
}

[olybobo]

while (_kbhit()) _getch();

What is the while statement meant to do. I think might be 2-steps behind..Hence, I am just trying to understand the code

[George P]

_kbhit() : checks the console for keyboard input
https://docs.microsoft.com/en-us/cpp/c-runtime-library/reference/kbhit?view=vs-2019

_getch() : gets a character from the console without echo
https://docs.microsoft.com/en-us/cpp/c-runtime-library/reference/getch-getwch?view=vs-2019

[olybobo]

thx