The software might also feature a handler, tasked with capturing the SIGABRT signal and then returning control back to the main environment. Failure to intercept the signal results in an irregular program shutdown.
Note: When the program's termination is not normal, the user will be unable to use atexit functions.
The developer also has the option to employ a handler by utilizing the abort function. This handler is implemented to manage the SIGABRT signal subsequent to its activation. The signal will be retriggered if the programs return the handler for any default action. The code encounters the handle solely on one occasion, even during the resetting of the handler.
Similarly, if the handler neglects the signal, it will result in the program being terminated.
The program's end can still be prevented following the execution of the abort function if the handler catches the SIGABRT signal or if it is left unhandled. There are multiple techniques available within your program to prevent exiting from the handler, such as swiftly exiting the handler itself.
Utilize the provided functions to exit from the handler:
-
- setjmp
-
- longjmp
Declaring the abort function
Declaring the abort function follows the typical syntax of any other function. It commences with specifying the return type, then proceeds with the function name, in this case, abort. Finally, the function may include parameters enclosed within parentheses.
Therefore, the function does not necessitate any input parameters and it also does not yield any output.
value. So for both, we use the datatype void.
Implementing abort in C:
Let's explore a scenario where we demonstrate the utilization of the abort function:
#include <stdio.h>
#include <stdlib.h>
int main ()
{
FILE *fileptr;
printf("The program will open the thisfile.txt\n");
fileptr = fopen( "thisfile.txt","r" );
if(fileptr == NULL) {
printf("If this condition is met, user would abort the program\n");
abort();
}
printf("Once the file is used close thisfile.txt\n");
fclose(fileptr);
return(0);
}
Output:
The program will open the thisfile.txt
If this condition is met, user would abort the program
Once the file is used close thisfile.txt
After the aforementioned steps, the program will yield the following outcome:
The program attempts to open the specified thisfile.txt file, but since no file with that name exists, the file opening operation fails. Consequently, the code execution is halted.
The steps are as follows:
- Open the thisfile.txt
- Abort the program
- Dump the core.
Difference between abort and exit
The exit function guarantees a proper termination of the program by closing all files opened within its execution, clearing the buffer, and invoking the functions registered in atexit.
When the abort function is called, it triggers a SIGABRT signal that halts the program unless it is intercepted by a signal handler within the program. If the handler successfully catches the signal, it can avert the program termination. The termination process under these circumstances is atypical, potentially leaving files open or temporary files unremoved that were generated during program execution.
On using exit, the functions that are registered with atexit cannot be implemented. If the user wants to clear the stream buffer, it is better to use the exit function, or the programmer should include a handler for SIGABRT in the code.