Core Dump (Segmentation fault) in C/C++

Core Dump/Segmentation fault is a specific kind of error caused by accessing memory that “does not belong to you.”

• When a piece of code tries to do read and write operation in a read only location in memory or freed block of memory, it is known as core dump.
• It is an error indicating memory corruption.

Common segmentation fault scenarios:

• Modifying a string literal :
  The below program may crash (gives segmentation fault error) because the line *(str+1) = ‘n’ tries to write a read only memory.
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  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; }

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  Abnormal termination of program.
  

  Refer Storage for Strings in C for details

• Accessing an address that is freed :
  Here in the below code, the pointer p is dereferenced after freeing the memory block, which is not allowed by the compiler. So it produces the error segment fault or abnormal program termination at runtime.
  Example:
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  // C program to illustrate // Core Dump/Segmentation fault #include <stdio.h> #include<alloc.h> int main(void) {     // allocating memory to p     int* p = malloc(8);     *p = 100;            // deallocated the space allocated to p     free(p);            // core dump/segmentation fault     //  as now this statement is illegal     *p = 110;            return 0; }

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  Output:

  
  
  

  Abnormal termination of program.
  

• Accessing out of array index bounds :
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  // C++ program to demonstrate segmentation // fault when array out of bound is accessed. #include <iostream> using namespace std;    int main()  {    int arr[2];    arr[3] = 10;  // Accessing out of bound    return 0; }

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  Output:

  Abnormal termination of program.
  

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