Signal Handling

Handles signals such as SIGINT, SIGTERM, SIGQUIT, SIGUSR1, and SIGSEGV. More...

Functions
void	sig_dfl_mode ()
	Set signal handlers to default behavior.
void	sig_prog_mode ()
	Set up signal handlers for interrupt signals.
void	signal_handler (int sig_num)
	Signal handler for interrupt signals.
bool	handle_signal (int sig_num)
	Handle received signals and prompt user for action.

Detailed Description

Handles signals such as SIGINT, SIGTERM, SIGQUIT, SIGUSR1, and SIGSEGV.

This module provides functions to set up signal handlers for various signals, handle received signals, and reset signal handlers to their default behavior. It allows the program to respond to interrupt signals by prompting the user for action and ensuring proper cleanup before exiting or continuing execution.

Function Documentation

handle_signal()

bool handle_signal

(

int

sig_num

)

Handle received signals and prompt user for action.

Parameters

sig_num

The signal number received

Definition at line 147 of file sig.c.

                                {
    switch (sig_num) {
    case SIGINT:
        strnz__cpy(em1, "SIGINT - Interrupt from keyboard", MAXLEN - 1);
        break;
    case SIGTERM:
        strnz__cpy(em1, "SIGTERM - Termination signal", MAXLEN - 1);
        break;
    case SIGQUIT:
        strnz__cpy(em1, "SIGQUIT - Quit from keyboard", MAXLEN - 1);
        break;
    case SIGSEGV:
        strnz__cpy(em1, "SIGSEGV - Segmentation fault", MAXLEN - 1);
        break;
    case SIGUSR1:
        strnz__cpy(em1, "SIGUSR1 - User Signal 1", MAXLEN - 1);
        break;
    default:
        strnz__cpy(em1, "unknown signal", MAXLEN - 1);
        break;
    }
    if (!f_curses_open)
        restore_shell_tioctl();
    em0[0] = '\0';
    ssnprintf(em0, MAXLEN - 1, "Caught signal %d\n", sig_num);
#ifdef DEBUG_LOG
    write_cmenu_log(em0);
#endif
    strnz__cpy(em2, "Press 'q' or F9 to exit, any other key to continue",
               MAXLEN - 1);
    sig_received = 0;
    return true;
}

References em0, em1, em2, f_curses_open, restore_shell_tioctl(), sig_received, ssnprintf(), and strnz__cpy().

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sig_dfl_mode()

void sig_dfl_mode

(

)

Set signal handlers to default behavior.

This function sets the signal handlers for SIGINT, SIGTERM, SIGQUIT, SIGUSR1, and SIGSEGV to their default behavior. This is typically used when the program needs to exit or reset its signal handling to the default state.

Definition at line 42 of file sig.c.

                    {
    struct sigaction sa;
 
    sa.sa_handler = SIG_DFL;
    sigemptyset(&sa.sa_mask);
    sa.sa_flags = SA_RESTART;
    sigaction(SIGINT, &sa, nullptr);
    sigaction(SIGTERM, &sa, nullptr);
    sigaction(SIGQUIT, &sa, nullptr);
    sigaction(SIGUSR1, &sa, nullptr);
    sa.sa_flags = SA_SIGINFO;
    sigaction(SIGSEGV, &sa, nullptr);
}

Referenced by abend(), destroy_curses(), fork_exec(), and main().

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sig_prog_mode()

void sig_prog_mode

(

)

Set up signal handlers for interrupt signals.

Upon receiving an interrupt signal (SIGINT, SIGTERM, SIGQUIT), the program will prompt the user to either exit the program or continue execution. If the user chooses to exit, a confirmation prompt will be displayed. If the user opts to continue, the program will resume normal operation.

Definition at line 62 of file sig.c.

                     {
    struct sigaction sa;
 
    memset(&sa, 0, sizeof(sa));
    sa.sa_handler = signal_handler;
    sigemptyset(&sa.sa_mask);
    sa.sa_flags = SA_RESTART;
    if (sigaction(SIGINT, &sa, nullptr) == -1) {
        abend(-1, "sigaction SIGINT failed");
        exit(EXIT_FAILURE);
    }
    if (sigaction(SIGTERM, &sa, nullptr) == -1) {
        abend(-1, "sigaction SIGTERM failed");
        exit(EXIT_FAILURE);
    };
    if (sigaction(SIGQUIT, &sa, nullptr) == -1) {
        abend(-1, "sigaction SIGQUIT failed");
        exit(EXIT_FAILURE);
    }
    if (sigaction(SIGUSR1, &sa, nullptr) == -1) {
        abend(-1, "sigaction SIGUSR1 failed");
        exit(EXIT_FAILURE);
    }
    sa.sa_flags = SA_SIGINFO; // Set the flag to receive siginfo_t
    if (sigaction(SIGSEGV, &sa, nullptr) == -1) {
        abend(-1, "sigaction SIGSEGV failed");
        exit(EXIT_FAILURE);
    }
}

References abend(), and signal_handler().

Referenced by exec_objects(), fork_exec(), init_pick(), and main().

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signal_handler()

void signal_handler

(

int

sig_num

)

Signal handler for interrupt signals.

Parameters

sig_num

The signal number received

Definition at line 95 of file sig.c.

                                 {
    switch (sig_num) {
    case SIGINT:
        sig_received = SIGINT;
        break;
    case SIGTERM:
        sig_received = SIGTERM;
        break;
    case SIGQUIT:
        sig_received = SIGQUIT;
        break;
    case SIGSEGV:
        set_sane_tioctl(&shell_tioctl);
        char *msg1 = "\n\n\n\n\n\n\n\n\n\n\n\n\n\n\n\n\n\n\n\n\n\n\n";
        write(STDERR_FILENO, msg1, strlen(msg1));
        char *msg2 = "SIGSEGV - Segmentation fault - Stack trace\n\n";
        write(STDERR_FILENO, msg2, strlen(msg2));
        void *addrlist[MAX_FRAMES];
        char **symbols;
        int frames;
        frames = backtrace(addrlist, MAX_FRAMES);
        symbols = backtrace_symbols(addrlist, frames);
        if (symbols == nullptr) {
            abend(-1, "backtrace_symbols failed");
            exit(EXIT_FAILURE);
        }
        for (int i = 0; i < frames; i++) {
            char buf[256];
            ssnprintf(buf, sizeof(buf), "%s\n", symbols[i]);
            write(STDERR_FILENO, buf, strlen(buf));
        }
        free(symbols);
        msg2 = "\nSIGSEGV Segmentation fault - Writing core to file\n\n";
        write(STDERR_FILENO, msg2, strlen(msg2));
        struct sigaction sa;
        sa.sa_handler = SIG_DFL;
        sigemptyset(&sa.sa_mask);
        sa.sa_flags = 0;
        sigaction(SIGSEGV, &sa, NULL);
        kill(getpid(), SIGSEGV); // Re-raise the signal
        exit(EXIT_FAILURE);
    case SIGUSR1:
        sig_received = SIGUSR1;
        break;
    default:
        return;
    }
}

References abend(), set_sane_tioctl(), shell_tioctl, sig_received, and ssnprintf().

Referenced by sig_prog_mode().

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