From 20b6a57af64506a4152b145b031aad2946a37ca8 Mon Sep 17 00:00:00 2001
From: Ron Yorston <rmy@pobox.com>
Date: Tue, 23 May 2023 10:57:56 +0100
Subject: win32: crtl-c interrupts non-console applications

Commit 9db9b34ad (win32: ignore ctrl-c in parent of execve(2))
prevented a parent process from reacting to Ctrl-C while it was
waiting for its child to complete.  This avoids the problem where
a shell and an interactive child end up competing for input after
a Ctrl-C.

However, a child process which isn't attached to the console
(a GUI application, for example) can't then be killed by Ctrl-C.

Instead of completely ignoring Ctrl-C give the parent a handler
which detects if its child is attached to the console.  If so it's
left to handle Ctrl-C itself and the parent ignores the interrupt.
If not the parent terminates the child and all its children as if
by SIGINT.

Costs 200 bytes.
---
 include/mingw.h |  1 +
 win32/process.c | 37 ++++++++++++++++++++++++++++++++++++-
 2 files changed, 37 insertions(+), 1 deletion(-)

diff --git a/include/mingw.h b/include/mingw.h
index f94804d91..13adf9017 100644
--- a/include/mingw.h
+++ b/include/mingw.h
@@ -540,6 +540,7 @@ int mingw_execve(const char *cmd, char *const *argv, char *const *envp);
 
 #define has_dos_drive_prefix(path) (isalpha(*(path)) && (path)[1] == ':')
 
+BOOL WINAPI kill_child_ctrl_handler(DWORD dwCtrlType);
 int kill_signal_by_handle(HANDLE process, int sig);
 int FAST_FUNC is_valid_signal(int number);
 
diff --git a/win32/process.c b/win32/process.c
index ebc006d4e..6abc329da 100644
--- a/win32/process.c
+++ b/win32/process.c
@@ -369,11 +369,46 @@ mingw_spawn_proc(const char **argv)
 	return mingw_spawnvp(P_NOWAIT, argv[0], (char *const *)argv);
 }
 
+BOOL WINAPI kill_child_ctrl_handler(DWORD dwCtrlType)
+{
+	static pid_t child_pid = 0;
+	DWORD dummy, *procs, count, rcount, i;
+
+	if (child_pid == 0) {
+		// First call sets child pid
+		child_pid = dwCtrlType;
+		return FALSE;
+	}
+
+	if (dwCtrlType == CTRL_C_EVENT || dwCtrlType == CTRL_BREAK_EVENT) {
+		count = GetConsoleProcessList(&dummy, 1) + 16;
+		procs = malloc(sizeof(DWORD) * count);
+		rcount = GetConsoleProcessList(procs, count);
+		if (rcount != 0 && rcount <= count) {
+			for (i = 0; i < rcount; i++) {
+				if (procs[i] == child_pid) {
+					// Child is attached to our console
+					break;
+				}
+			}
+			if (i == rcount) {
+				// Kill non-console child; console children can
+				// handle Ctrl-C as they see fit.
+				kill(-child_pid, SIGINT);
+			}
+		}
+		free(procs);
+		return TRUE;
+	}
+	return FALSE;
+}
+
 static NORETURN void wait_for_child(HANDLE child)
 {
 	DWORD code;
 
-	SetConsoleCtrlHandler(NULL, TRUE);
+	kill_child_ctrl_handler(GetProcessId(child));
+	SetConsoleCtrlHandler(kill_child_ctrl_handler, TRUE);
 	WaitForSingleObject(child, INFINITE);
 	GetExitCodeProcess(child, &code);
 	exit((int)code);
-- 
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