Razones por las que falla un programa en C++

A veces nos encontramos con bloqueos anormales de programas C++. A continuación se presentan algunas razones posibles que pueden causar que C++ se bloquee de manera anormal.

• Segmentation Fault: It is the major reason for program to crash. These are may be the reasons for the such cause:
  • Attempting to access memory location that doesn’t exist in our system.
  • There may be an attempt to write on a read only memory location.

    // CPP program to demonstrate int main() {    char *str;         /* Stored in read only part of data segment */    str = "GfG";             /* Problem:  trying to modify read only memory */    *(str+1) = 'n';     return 0; }

    Output :

    Segmentation fault (core dumped)

  • There may be an attempt to access protected memory location such as kernel memory
  • Stack Overflow: There may case of non terminating recursion with memory location.

    // C program to demonstrate stack overflow // by creating a non-terminating recursive // function. #include<stdio.h>    void fun(int x) {     if (x == 1)        return;     x = 6;     fun(x); }    int main() {    int x = 5;    fun(x); }

    Output :

    Segmentation fault (core dumped)

• Buffer Overflow: It is an anomaly where a program, while writing data to a buffer, overruns the buffer’s boundary and overwrites adjacent memory locations.

  • Consider below C++ program.

    // C++ code to demonstrate buffer // overflow. #include <bits/stdc++.h> using namespace std;    // driver code int main() {     char A[8] = "";     unsigned short B = 1979;     strcpy(A, "excessive");     return 0; }

    Output :

    *** stack smashing detected ***: /home/gfg/a terminated
    Aborted (core dumped)

    The program has two variables which are adjacent in memory: an 8-byte-long string buffer, A, and a two-byte big-endian integer, B.

    char A[8] = “”;
    unsigned short B = 1979;

    Initially, A contains nothing but zero bytes, and B contains the number 1979.
    
    Now, the program attempts to store the null-terminated string “excessive” with ASCII encoding in the A buffer.

    strcpy(A, “excessive”);

    This string is of 9 characters long and encodes to 10 bytes including the null terminator, but A can take only 8 bytes. By failing to check the length of the string, it also overwrites the value of B:

    

    B’s value has now been inadvertently replaced by a number formed from part of the character string. In this example “e” followed by a zero byte would become 25856.

    This overflow is called buffer buffer overflow.

• Fuga de memoria:
  Si asignamos algo de memoria por algún programa y lo dejamos como está. Después de un tiempo, habrá una gran cantidad de memoria asignada pero no utilizada, por lo que faltará memoria después de un tiempo. Y así el programa comienza a fallar.

  // C program to demonstrate heap overflow // by continuously allocating memory #include<stdio.h>     int main() {     for (int i=0; i<10000000; i++)     {        // Allocating memory without freeing it        int *ptr = (int *)malloc(sizeof(int));     } }

• Excepciones
  • Dividir entre cero.

    // C++ code to demonstrate divide by 0. #include <bits/stdc++.h> using namespace std;    // driver code int main() {     int x = 10;     int y = 0;     cout << x/y;     return 0; }

    Producción :

    Floating point exception (core dumped)