[PATCH v4 1/2] compat/mingw: allow sigaction(SIGCHLD)

From: Carlo Marcelo Arenas Belón via GitGitGadget <gitgitgadget@gmail.com>
Date: Jul 10, 2025, 19:45 UTC
Message-ID: <f21e8ff5c9df0989ce09b3d9a50c0dc81af18837.1752176743.git.gitgitgadget@gmail.com>
In-Reply-To: <pull.2002.v4.git.git.1752176743.gitgitgadget@gmail.com>

From: =?UTF-8?q?Carlo=20Marcelo=20Arenas=20Bel=C3=B3n?= <carenas@gmail.com>

A future change will start using sigaction to setup a SIGCHLD signal handler.

The current code uses signal(), which returns SIG_ERR (but doesn't seem to set errno) so instruct sigaction() to do the same.

A new SA flag will be needed, so copy the one from Cygwinr; note that the sigacgtion() implementation that is provided won't use it, so its value is otherwise irrelevant.

Signed-off-by: Carlo Marcelo Arenas Belón <carenas@gmail.com>
---
 compat/mingw-posix.h | 1 +
 compat/mingw.c       | 4 +++-
 2 files changed, 4 insertions(+), 1 deletion(-)

diff --git a/compat/mingw-posix.h b/compat/mingw-posix.h
index 88e0cf92924b..631a20868489 100644
--- a/compat/mingw-posix.h
+++ b/compat/mingw-posix.h
@@ -96,6 +96,7 @@ struct sigaction {
 	unsigned sa_flags;
 };
 #define SA_RESTART 0
+#define SA_NOCLDSTOP 1
 
 struct itimerval {
 	struct timeval it_value, it_interval;
diff --git a/compat/mingw.c b/compat/mingw.c
index 8a9972a1ca19..5d69ae32f4b9 100644
--- a/compat/mingw.c
+++ b/compat/mingw.c
@@ -2561,7 +2561,9 @@ int setitimer(int type UNUSED, struct itimerval *in, struct itimerval *out)
 
 int sigaction(int sig, struct sigaction *in, struct sigaction *out)
 {
-	if (sig != SIGALRM)
+	if (sig == SIGCHLD)
+		return -1;
+	else if (sig != SIGALRM)
 		return errno = EINVAL,
 			error("sigaction only implemented for SIGALRM");
 	if (out)

-- 
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