Disable SA_RESTART for some signals on macOS

Disables the SA_RESTART behavior on macOS which causes:

> Restarting of pending calls is requested by setting the SA_RESTART bit
> in sa_flags. The affected system calls include read(2), write(2),
> sendto(2), recvfrom(2), sendmsg(2) and recvmsg(2) on a communications
> channel or a slow device (such as a terminal, but not a regular file)
> and during a wait(2) or ioctl(2).

From: https://man.openbsd.org/sigaction#SA_RESTART

This being set on macOS caused a bug where read() calls to the daemon
socket were blocking after a SIGINT was received. As a result,
checkInterrupt was never reached even though the signal was received
by the signal handler thread.

On Linux, SA_RESTART is disabled by default. This probably effects
other BSDs but I don’t have the ability to test it there right now.

1 files changed, 10 insertions, 3 deletions

diff --git a/src/libmain/shared.cc b/src/libmain/shared.cc
index 31454e49d..0ee3fe772 100644
--- a/src/libmain/shared.cc
+++ b/src/libmain/shared.cc
@@ -194,9 +194,16 @@ void initNix()
     /* HACK: on darwin, we need can’t use sigprocmask with SIGWINCH.
      * Instead, add a dummy sigaction handler, and signalHandlerThread
      * can handle the rest. */
-    struct sigaction sa;
-    sa.sa_handler = sigHandler;
-    if (sigaction(SIGWINCH, &sa, 0)) throw SysError("handling SIGWINCH");
+    act.sa_handler = sigHandler;
+    if (sigaction(SIGWINCH, &act, 0)) throw SysError("handling SIGWINCH");
+
+    // Disable SA_RESTART for interrupts, so that system calls on this thread
+    // error with EINTR like they do on Linux, and we don’t hang forever.
+    act.sa_handler = SIG_DFL;
+    if (sigaction(SIGINT, &act, 0)) throw SysError("handling SIGINT");
+    if (sigaction(SIGTERM, &act, 0)) throw SysError("handling SIGTERM");
+    if (sigaction(SIGHUP, &act, 0)) throw SysError("handling SIGHUP");
+    if (sigaction(SIGPIPE, &act, 0)) throw SysError("handling SIGPIPE");
 #endif
 
     /* Register a SIGSEGV handler to detect stack overflows. */