Difference between std::quick_exit and std::abort in C++

By Brijesh Kumar

In this tutorial, you will learn the difference between std::quick_exit and std::abort in C++. Before understanding the difference between std::quick_exit() and std::abort() in C++, first lets understands both individually.

std::quick_exit()

The quick_exit() function causes a program to terminate normally without actually entirely cleansing its resources.

Syntax :

void quick_exit(int exit_code) no except;

The quick_exit() function exits the program with cleanup on the authority of at_quick_exit().

The function std::quick_exit() terminates the application by first calls all functions that are registered at_quick_exit() then it terminates the application.

Above all, functions registered to at_quick_exit() function called in their backward order of registrations.

Syntax for at_quick_exit() :

int at_quick_exit( void (*func)(void) );

Hence, at_quick_exit() declares the func which pointer to a function and it is called on a quick program termination. The at_quick_exit() function returns 0(zero) if registration succeeds otherwise non-zero.

//use of at_quick_exit() and quick_exit()
#include <cstdlib>
void atexitf()
{
  cout << "Inside quick exit function.";
}
int main()
{
  at_quick_exit(atexitf);
  cout << " Inside the main function.";
  quick_exit(0);
  cout << "End of the main function"; 
  return 0;
}

Above program demonstrated functionality of both exit functions. Where at_quick_exit() function calls atexitf(), thereby prints “Inside main function”.

Output :

Inside quick exit function.
Inside the main function.

Then the next statement i.e., “Inside the main function” prints on the console. And hence the program terminates.

std::abort() 

The std::abort() function basically aborts the program. By aborting a program it might force to strike on some systems.

Syntax :

void abort();

The abort function terminates the program instantly. Above all, it has no parameters, no return type, and no exceptions.

// use of abort()
#include <cstdlib>
int main ()
{
  FILE *filepointer;
  filepointer = fopen("somefile.txt", "r");
  if (filepointer== NULL)
  {
    fputs("Error in opening the file \n", stderr);
    abort();
  }
  fclose(filepointer);
  return 0;
}

The above program works as follows if the file somefile.txt is not able to open in reading mode. Then the file pointer will contain a NULL value. And thereby displays the error messages. And then it calls the abort() function which in turn terminates the program.

Conclusion: Difference between std::quick_exit and std::abort

Here we will understand the difference between std::quick_exit() and std::abort() in C++ as well as its resemblances.

Resemblances: Both functions used for termination of the program still unique. Both functions defined in the cstdlib header. They have no parameters, exceptions and no return value.

Differences: The std::quick_exit() terminates all function registered with at_quick_exit(). The std::abort() function terminates the program in which the functions is either registered to at_quick_exit() or not. The std::abort() function terminates without actually executing the remaining program and not removing the remaining input/output.

 

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