Update MentOs code to the latest development version.

programs/tests/t_sigmask.c

@@ -0,0 +1,50 @@
+///                MentOS, The Mentoring Operating system project
+/// @file t_sigmask.c
+/// @brief
+/// @copyright (c) 2014-2021 This file is distributed under the MIT License.
+/// See LICENSE.md for details.
+
+#include <sys/unistd.h>
+#include <signal.h>
+#include <stdlib.h>
+#include <stdio.h>
+#include <string.h>
+#include <strerror.h>
+#include <sys/wait.h>
+
+void sigusr1_handler(int sig)
+{
+    printf("handler(sig: %d) : Starting handler.\n", sig);
+    printf("handler(sig: %d) : Ending handler.\n", sig);
+}
+
+int main(int argc, char *argv[])
+{
+    int ret;
+    sigaction_t action;
+    memset(&action, 0, sizeof(action));
+    action.sa_handler = sigusr1_handler;
+    if (sigaction(SIGUSR1, &action, NULL) == -1) {
+        printf("Failed to set signal handler (%d, %s).\n", SIGUSR1, strerror(errno));
+        return 1;
+    }
+
+    printf("main : Blocking signal (%d).\n", SIGUSR1);
+    sigset_t mask;
+    sigemptyset(&mask);
+    sigaddset(&mask, SIGUSR1);
+    sigprocmask(SIG_BLOCK, &mask, NULL);
+
+    printf("main : Calling handler (%d).\n", SIGUSR1);
+    ret = kill(getpid(), SIGUSR1);
+    printf("main : Returning from handler (%d): %d.\n", SIGUSR1, ret);
+
+    printf("main : Unblocking signal (%d).\n", SIGUSR1);
+    sigprocmask(SIG_UNBLOCK, &mask, NULL);
+
+    printf("main : Calling handler (%d).\n", SIGUSR1);
+    ret = kill(getpid(), SIGUSR1);
+    printf("main : Returning from handler (%d): %d.\n", SIGUSR1, ret);
+
+    return 0;
+}