Executing fork call gives exit status 0x3 for Linux

Debugging a Fork Call Resulting in Exit Status 0x3 for Linux:

In this technical blog post, we'll delve into a specific issue encountered when executing a fork call, resulting in an exit status of 0x3 on a Linux system. We'll analyze the provided code snippet and identify a critical bug that leads to this error.

Code Analysis:

current_cnt = 0;

if (current_cnt > 0) // can NOT reach below
{
  // Start child process.
  pid_t rc;
  if ((rc = fork()) < 0) {
    // There was an error.
    abort();
  } else if (rc == 0) {
    // Run the i'th process.
    printf("%d\n", execv(argv[cnt - current_cnt], &argv[cnt]));
    exit(0);
  }
}

The provided code attempts to create a child process using the fork() system call and then execute a specific program using the execv() function. However, due to a bug in the code, the fork() and execv() calls are never reached, resulting in the exit status 0x3.

Bug Identification:

The critical bug lies in the initialization of the current_cnt variable. It is set to 0 at the beginning of the code, which means that the if (current_cnt > 0) condition will always evaluate to false. Consequently, the code inside the if block, including the fork() and execv() calls, is never executed.

Solution:

To fix the issue, you need to move the line current_cnt = 0; to the end of the if block. This ensures that the variable is only reset to 0 after the fork() and execv() calls have been executed successfully.

Checking for Errors:

Additionally, it's essential to check the return value of the fork() call to handle any potential errors. If fork() returns a negative value, it indicates an error occurred. In such cases, you can use the errno variable to obtain the specific error code and take appropriate actions.

pid = wait(&status);
int err = errno;
printf("Error: %s\n", strerror(err));  // Error: No child processes

By incorporating these modifications and handling errors appropriately, you can ensure that the fork() call executes successfully and the desired program is executed as expected.