Does the default action terminate?

Challenge

Each signal has a default action; for many it is to terminate the process. Classify a signal by its default action.

Task

Implement int default_terminates(int sig) that returns 1 if sig's default action terminates the process, else 0.

Input

• sig: a signal number (compare against the <signal.h> constants).

Output

1 for SIGINT, SIGTERM, SIGKILL, SIGQUIT, SIGSEGV; else 0.

Example

default_terminates(SIGINT)    ->   1
default_terminates(SIGKILL)   ->   1
default_terminates(SIGCHLD)   ->   0   (ignored by default)

Edge cases

• Signals ignored by default (e.g. SIGCHLD): return 0.

Input format

sig: a signal number from <signal.h>.

Output format

1 for SIGINT/SIGTERM/SIGKILL/SIGQUIT/SIGSEGV, else 0.

Constraints

Match by the signal.h constants.

Starter code

#include <signal.h>

int default_terminates(int sig) {
    /* TODO */
    return 0;
}

Common mistakes

Calling non-reentrant functions (like printf or malloc) inside signal handlers; neglecting sig_atomic_t or volatile qualifier for shared flags.

Edge cases to handle

Multiple instances of the same signal queued together; signal arriving while handler is already active; interrupted system calls (EINTR).