v1-0002-Cleanup-some-signal-usage-on-Windows.patch

From ce4cbf8e720301e7ddbd2f0816c1f03c82138515 Mon Sep 17 00:00:00 2001
From: Tristan Partin <tristan@neon.tech>
Date: Thu, 6 Jul 2023 15:17:36 -0500
Subject: [PATCH v1 2/2] Cleanup some signal usage on Windows

SIGTERM can be handled the same as on a UNIX-like system. SIGINT, on the
other hand, requires special considerations. The Windows documentation
says the following:

> SIGINT is not supported for any Win32 application. When a CTRL+C
> interrupt occurs, Win32 operating systems generate a new thread to
> specifically handle that interrupt. This can cause a single-thread
> application, such as one in UNIX, to become multithreaded and cause
> unexpected behavior.

Therefore, if all the SIGINT handler does is read from memory and/or
exit, we can use the same handler. If the signal handler writes to
memory, such as setting a boolean, the original thread would never
become aware of the changed state.
---
 src/bin/initdb/initdb.c                | 17 ++++-------------
 src/bin/pg_basebackup/pg_receivewal.c  |  5 +----
 src/bin/pg_basebackup/pg_recvlogical.c |  9 ++++-----
 src/bin/pg_test_fsync/pg_test_fsync.c  |  3 ---
 4 files changed, 9 insertions(+), 25 deletions(-)

diff --git a/src/bin/initdb/initdb.c b/src/bin/initdb/initdb.c
index 3f4167682a..cac58eae2a 100644
--- a/src/bin/initdb/initdb.c
+++ b/src/bin/initdb/initdb.c
@@ -2773,26 +2773,17 @@ void
 setup_signals(void)
 {
 	/* some of these are not valid on Windows */
-#ifdef SIGHUP
-	pqsignal(SIGHUP, trapsig);
-#endif
-#ifdef SIGINT
+	pqsignal(SIGTERM, trapsig);
+
+#ifndef WIN32
 	pqsignal(SIGINT, trapsig);
-#endif
-#ifdef SIGQUIT
+	pqsignal(SIGHUP, trapsig);
 	pqsignal(SIGQUIT, trapsig);
-#endif
-#ifdef SIGTERM
-	pqsignal(SIGTERM, trapsig);
-#endif
 
 	/* Ignore SIGPIPE when writing to backend, so we can clean up */
-#ifdef SIGPIPE
 	pqsignal(SIGPIPE, SIG_IGN);
-#endif
 
 	/* Prevent SIGSYS so we can probe for kernel calls that might not work */
-#ifdef SIGSYS
 	pqsignal(SIGSYS, SIG_IGN);
 #endif
 }
diff --git a/src/bin/pg_basebackup/pg_receivewal.c b/src/bin/pg_basebackup/pg_receivewal.c
index d0a4079d50..55143c4037 100644
--- a/src/bin/pg_basebackup/pg_receivewal.c
+++ b/src/bin/pg_basebackup/pg_receivewal.c
@@ -611,14 +611,11 @@ StreamLog(void)
  * When SIGINT/SIGTERM are caught, just tell the system to exit at the next
  * possible moment.
  */
-#ifndef WIN32
-
 static void
 sigexit_handler(SIGNAL_ARGS)
 {
 	time_to_stop = true;
 }
-#endif
 
 int
 main(int argc, char **argv)
@@ -838,9 +835,9 @@ main(int argc, char **argv)
 	 * Trap signals.  (Don't do this until after the initial password prompt,
 	 * if one is needed, in GetConnection.)
 	 */
+	pqsignal(SIGTERM, sigexit_handler);
 #ifndef WIN32
 	pqsignal(SIGINT, sigexit_handler);
-	pqsignal(SIGTERM, sigexit_handler);
 #endif
 
 	/*
diff --git a/src/bin/pg_basebackup/pg_recvlogical.c b/src/bin/pg_basebackup/pg_recvlogical.c
index f3c7937a1d..1228dc03db 100644
--- a/src/bin/pg_basebackup/pg_recvlogical.c
+++ b/src/bin/pg_basebackup/pg_recvlogical.c
@@ -644,10 +644,6 @@ error:
 	conn = NULL;
 }
 
-/*
- * Unfortunately we can't do sensible signal handling on windows...
- */
-#ifndef WIN32
 
 /*
  * When SIGINT/SIGTERM are caught, just tell the system to exit at the next
@@ -659,6 +655,9 @@ sigexit_handler(SIGNAL_ARGS)
 	time_to_abort = true;
 }
 
+/* SIGHUP is not defined on Windows */
+#ifndef WIN32
+
 /*
  * Trigger the output file to be reopened.
  */
@@ -921,9 +920,9 @@ main(int argc, char **argv)
 	 * Trap signals.  (Don't do this until after the initial password prompt,
 	 * if one is needed, in GetConnection.)
 	 */
+	pqsignal(SIGTERM, sigexit_handler);
 #ifndef WIN32
 	pqsignal(SIGINT, sigexit_handler);
-	pqsignal(SIGTERM, sigexit_handler);
 	pqsignal(SIGHUP, sighup_handler);
 #endif
 
diff --git a/src/bin/pg_test_fsync/pg_test_fsync.c b/src/bin/pg_test_fsync/pg_test_fsync.c
index 2fc4b69444..263f5867a2 100644
--- a/src/bin/pg_test_fsync/pg_test_fsync.c
+++ b/src/bin/pg_test_fsync/pg_test_fsync.c
@@ -109,9 +109,6 @@ main(int argc, char *argv[])
 	pqsignal(SIGTERM, signal_cleanup);
 #ifndef WIN32
 	pqsignal(SIGALRM, process_alarm);
-#endif
-#ifdef SIGHUP
-	/* Not defined on win32 */
 	pqsignal(SIGHUP, signal_cleanup);
 #endif
 
-- 
Tristan Partin
Neon (https://neon.tech)