Recover in C

#include <stdio.h>
#include <setjmp.h>

jmp_buf jump_buffer;

// This function simulates a panic
void may_panic() {
    printf("Simulating a panic\n");
    longjmp(jump_buffer, 1);
}

int main() {
    // setjmp sets up the jump buffer and returns 0
    if (setjmp(jump_buffer) == 0) {
        // This code will run normally
        printf("Calling may_panic()\n");
        may_panic();
        // This code will not run, because may_panic() "panics"
        printf("After may_panic()\n");
    } else {
        // This code runs if may_panic() "panics"
        printf("Recovered. Error:\n a problem\n");
    }

    return 0;
}

In C, there’s no built-in concept of panic and recover as in some other languages. However, we can simulate similar behavior using the setjmp and longjmp functions from the <setjmp.h> library.

The setjmp function saves the current execution context, and longjmp can later be used to return to this saved context, simulating a kind of error recovery mechanism.

In this example:

1. We define a global jmp_buf to store our jump buffer.

2. The may_panic() function simulates a panic by calling longjmp().

3. In main(), we use setjmp() to set up our recovery point. If setjmp() returns 0, it means we’re setting up the jump buffer for the first time.

4. We then call may_panic(), which will trigger our simulated panic.

5. If a panic occurs (simulated by longjmp()), execution jumps back to the setjmp() call, but this time it returns a non-zero value (in this case, 1).

6. We then handle the “recovered” state by printing an error message.

This approach provides a way to simulate panic and recover behavior in C, although it’s not as clean or safe as in languages with built-in support for these concepts. In practice, C programmers often use other error handling mechanisms, such as error codes or global error states.

To compile and run this program:

$ gcc -o recover recover.c
$ ./recover
Calling may_panic()
Simulating a panic
Recovered. Error:
 a problem

Note that using setjmp and longjmp can make code harder to understand and maintain, and can lead to issues with local variables. In real-world C programming, it’s often better to use more structured error handling approaches.