src: do not alias new and old signal masks

In recent gcc, -Wrestrict warns when an argument passed to a
restrict-qualified parameter aliases with another argument.

PR-URL: #24810
Reviewed-By: Richard Lau <riclau@uk.ibm.com>

Author: sam-github

src/inspector_agent.cc

@@ -110,7 +110,9 @@ static int StartDebugSignalHandler() {
   sigset_t sigmask;
   // Mask all signals.
   sigfillset(&sigmask);
-  CHECK_EQ(0, pthread_sigmask(SIG_SETMASK, &sigmask, &sigmask));
+  sigset_t savemask;
+  CHECK_EQ(0, pthread_sigmask(SIG_SETMASK, &sigmask, &savemask));
+  sigmask = savemask;
   pthread_t thread;
   const int err = pthread_create(&thread, &attr,
                                  StartIoThreadMain, nullptr);

src/node_watchdog.cc

@@ -187,7 +187,9 @@ int SigintWatchdogHelper::Start() {
 
   sigset_t sigmask;
   sigfillset(&sigmask);
-  CHECK_EQ(0, pthread_sigmask(SIG_SETMASK, &sigmask, &sigmask));
+  sigset_t savemask;
+  CHECK_EQ(0, pthread_sigmask(SIG_SETMASK, &sigmask, &savemask));
+  sigmask = savemask;
   int ret = pthread_create(&thread_, nullptr, RunSigintWatchdog, nullptr);
   CHECK_EQ(0, pthread_sigmask(SIG_SETMASK, &sigmask, nullptr));
   if (ret != 0) {