Segmentation Fault (Core Dumped) in C and C++

Segmentation Fault (Core Dumped) in C and C++

by

Programming languages like C and C++ manage the memory in a more direct way than other programming languages like Java, C#, Python, etc. When an application tries to access the memory area that it does not belong to it Segmentation Fault occurs. Generally, the segmentation fault resulted in the core being dumped which is saving the error memory area into a file for later investigation. There are different reasons for the “Segmentation Fault”/”Core Dumped” error like below.

  • Modifying String Literal
  • Accessing Freed Address
  • Accessing Out Of Array Index Bounds
  • Improper useof scanf() Function
  • Stackoverflow
  • Dereferencing Uninitialized Pointer

Modifying String Literal

String literals are stored in a read-only part of the application. String literals can not be edited as they are located in the read-only part of memory. When the string literal is tried to be changed the segmentation fault occurs and the core is dumped with the Abnormal termination of program .

int main()
{
   char *s;

   /* Stored in read only part of application memory */
   s = "wt";	

   /* Problem: trying to modify read only memory */
   *(s+1) = 'x';

   return 0;
}

Accessing Freed Address

Pointers are used to allocated memory parts with memory addresses. After usage, the memory areas or addresses are freed and the freed address range can not be used. If the application tries to access the free address locations the “core dump” error occurs.

int main()
{
   char* s= (int*) malloc(8*sizeof(int));

   *s = 10;

   //s memory area is freed
   free(s);

   //Try to access free memory are 
   *s = 20;

   return 0;
}

Accessing Out Of Array Index Bounds

C and C++ programming languages provide arrays in order to store multiple characters and values inside a single variable. The size of the arrays should be set during initialization and the memory area is allocated according to its size. If the application tries to access of range memory area of the array the “core dump” error occurs.

int main()
{
   char s[3]="abc";

   s[5]="d";

   return 0;
}

Improper useof scanf() Function

The scanf() function is used to read user input from the standard input interactively. The scanf() function requires the memory address of a variable in order to store read value If the address is not provided properly or read-only.

int main()
{
   char s[3];

   scanf("%s",&s+1)

   return 0;
}

StackOverflow

Every application has a limited memory area called the stack. The stack area is used to store data temporarily during the execution of the application when functions are called. When the stack area is filled and there is no free area the StackOverflow occurs. The stack overflow generally occurs in error-prone algorithms like using recursive functions infinitely.

int main()
{
    rec();
}

int rec()
{
   int a = 5;

   rec();
}

Dereferencing Uninitialized Pointer

Pointers are used to point to specific memory addresses. In order to use a pointer, it should be initialized before accessing or dereferencing it. Without initialization, the pointer does not point to any memory area or data which can not be used.

int main()
{
   int* a;
   
   printf("%d",*a);

   return 0;
}

Leave a Comment