tree-wide: whenever we fork off a foreign child process reset signal mask/handlers

Also, when the child is potentially long-running make sure to set a
death signal.

Also, ignore the result of the reset operations explicitly by casting
them to (void).

src/shared/machine-pool.c

@@ -109,8 +109,8 @@ static int setup_machine_raw(uint64_t size, sd_bus_error *error) {
 
                 /* Child */
 
-                reset_all_signal_handlers();
-                reset_signal_mask();
+                (void) reset_all_signal_handlers();
+                (void) reset_signal_mask();
                 assert_se(prctl(PR_SET_PDEATHSIG, SIGTERM) == 0);
 
                 fd = safe_close(fd);

src/shared/pager.c

@@ -30,6 +30,7 @@
 #include "process-util.h"
 #include "macro.h"
 #include "terminal-util.h"
+#include "signal-util.h"
 
 static pid_t pager_pid = 0;
 
@@ -85,6 +86,9 @@ int pager_open(bool jump_to_end) {
         if (pager_pid == 0) {
                 const char* less_opts;
 
+                (void) reset_all_signal_handlers();
+                (void) reset_signal_mask();
+
                 dup2(fd[0], STDIN_FILENO);
                 safe_close_pair(fd);
 
@@ -178,6 +182,10 @@ int show_man_page(const char *desc, bool null_stdio) {
 
         if (pid == 0) {
                 /* Child */
+
+                (void) reset_all_signal_handlers();
+                (void) reset_signal_mask();
+
                 if (null_stdio) {
                         r = make_null_stdio();
                         if (r < 0) {

src/shared/pty.c

@@ -239,7 +239,7 @@ int pty_setup_child(Pty *pty) {
         assert_return(pty_is_child(pty), -EINVAL);
         assert_return(pty_is_open(pty), -EALREADY);
 
-        r = sigprocmask_many(SIG_SETMASK, -1);
+        r = reset_signal_mask();
         if (r < 0)
                 return r;
 

src/shared/util.c

@@ -2301,8 +2301,8 @@ static int do_execute(char **directories, usec_t timeout, char *argv[]) {
         /* We fork this all off from a child process so that we can
          * somewhat cleanly make use of SIGALRM to set a time limit */
 
-        reset_all_signal_handlers();
-        reset_signal_mask();
+        (void) reset_all_signal_handlers();
+        (void) reset_signal_mask();
 
         assert_se(prctl(PR_SET_PDEATHSIG, SIGTERM) == 0);
 
@@ -3344,8 +3344,8 @@ int fork_agent(pid_t *pid, const int except[], unsigned n_except, const char *pa
         /* Make sure we actually can kill the agent, if we need to, in
          * case somebody invoked us from a shell script that trapped
          * SIGTERM or so... */
-        reset_all_signal_handlers();
-        reset_signal_mask();
+        (void) reset_all_signal_handlers();
+        (void) reset_signal_mask();
 
         /* Check whether our parent died before we were able
          * to set the death signal and unblock the signals */