[ VM ] Fixed issue where process was suspended at exit when backgrounded.

Restoring console state when backgrounded causes SIGTTOU to be raised by
tcsetattr, which has the affect of suspending the process instead of
allowing it to complete. Blocking SIGTTOU results in tcsetattr failing
gracefully and the process running to completion.

Change-Id: I605dccbdbf311697881e5729e4fd64f1d60ed6b1
Reviewed-on: https://dart-review.googlesource.com/48823
Reviewed-by: Ben Konyi <bkonyi@google.com>
Commit-Queue: Ben Konyi <bkonyi@google.com>

Author: bkonyi

runtime/bin/platform_android.cc

@@ -47,6 +47,17 @@ bool Platform::Initialize() {
     return false;
   }
 
+  // tcsetattr raises SIGTTOU if we try to set console attributes when
+  // backgrounded, which suspends the process. Ignoring the signal prevents
+  // us from being suspended and lets us fail gracefully instead.
+  sigset_t signal_mask;
+  sigemptyset(&signal_mask);
+  sigaddset(&signal_mask, SIGTTOU);
+  if (sigprocmask(SIG_BLOCK, &signal_mask, NULL) < 0) {
+    perror("Setting signal handler failed");
+    return false;
+  }
+
   act.sa_flags = SA_SIGINFO;
   act.sa_sigaction = &segv_handler;
   if (sigemptyset(&act.sa_mask) != 0) {

runtime/bin/platform_linux.cc

@@ -47,6 +47,17 @@ bool Platform::Initialize() {
     return false;
   }
 
+  // tcsetattr raises SIGTTOU if we try to set console attributes when
+  // backgrounded, which suspends the process. Ignoring the signal prevents
+  // us from being suspended and lets us fail gracefully instead.
+  sigset_t signal_mask;
+  sigemptyset(&signal_mask);
+  sigaddset(&signal_mask, SIGTTOU);
+  if (sigprocmask(SIG_BLOCK, &signal_mask, NULL) < 0) {
+    perror("Setting signal handler failed");
+    return false;
+  }
+
   act.sa_flags = SA_SIGINFO;
   act.sa_sigaction = &segv_handler;
   if (sigemptyset(&act.sa_mask) != 0) {

runtime/bin/platform_macos.cc

@@ -54,6 +54,18 @@ bool Platform::Initialize() {
     perror("Setting signal handler failed");
     return false;
   }
+
+  // tcsetattr raises SIGTTOU if we try to set console attributes when
+  // backgrounded, which suspends the process. Ignoring the signal prevents
+  // us from being suspended and lets us fail gracefully instead.
+  sigset_t signal_mask;
+  sigemptyset(&signal_mask);
+  sigaddset(&signal_mask, SIGTTOU);
+  if (sigprocmask(SIG_BLOCK, &signal_mask, NULL) < 0) {
+    perror("Setting signal handler failed");
+    return false;
+  }
+
   act.sa_flags = SA_SIGINFO;
   act.sa_sigaction = &segv_handler;
   if (sigemptyset(&act.sa_mask) != 0) {