From 3a4ff2d02eef18921eee766c81c1a96335764020 Mon Sep 17 00:00:00 2001
From: Syrus Akbary <me@syrusakbary.com>
Date: Sun, 16 Aug 2026 20:02:57 -0700
Subject: [PATCH] fix(signal): terminate without raising SIGABRT

---
 libc-top-half/musl/src/signal/sigaction.c |  9 +++-
 test/wasix/c_signals/CMakeLists.txt       |  4 ++
 test/wasix/c_signals/main.c               | 54 +++++++++++++++++++++++
 test/wasix/c_signals/test.sh              | 41 +++++++++++++++++
 4 files changed, 106 insertions(+), 2 deletions(-)
 create mode 100644 test/wasix/c_signals/CMakeLists.txt
 create mode 100644 test/wasix/c_signals/main.c
 create mode 100755 test/wasix/c_signals/test.sh

diff --git a/libc-top-half/musl/src/signal/sigaction.c b/libc-top-half/musl/src/signal/sigaction.c
index 5adc7420b..7bd50c42a 100644
--- a/libc-top-half/musl/src/signal/sigaction.c
+++ b/libc-top-half/musl/src/signal/sigaction.c
@@ -1,5 +1,6 @@
 #include <signal.h>
 #include <errno.h>
+#include <stdlib.h>
 #include <string.h>
 #include <sysexits.h>
 #include "syscall.h"
@@ -31,8 +32,12 @@ static void core_handler(int sig) {
 
 _Noreturn
 static void terminate_handler(int sig) {
-    fprintf(stderr, "Program recieved termination signal: %s\n", strsignal(sig));
-    abort();
+    /* A terminating signal is not an abort. Calling abort() here raises
+     * SIGABRT while the original signal is still being dispatched, which can
+     * recursively re-enter the default signal path on runtimes that deliver
+     * the nested signal immediately. POSIX termination is silent; report it
+     * through the conventional shell status instead. */
+    _Exit(128 + sig);
 }
 
 _Noreturn
diff --git a/test/wasix/c_signals/CMakeLists.txt b/test/wasix/c_signals/CMakeLists.txt
new file mode 100644
index 000000000..a973015e0
--- /dev/null
+++ b/test/wasix/c_signals/CMakeLists.txt
@@ -0,0 +1,4 @@
+cmake_minimum_required(VERSION 3.5.0)
+project(c_signals C)
+
+add_executable(main main.c)
diff --git a/test/wasix/c_signals/main.c b/test/wasix/c_signals/main.c
new file mode 100644
index 000000000..1b6473677
--- /dev/null
+++ b/test/wasix/c_signals/main.c
@@ -0,0 +1,54 @@
+#include <signal.h>
+#include <stdio.h>
+#include <string.h>
+
+static volatile sig_atomic_t handled;
+
+static void siginfo_handler(int sig, siginfo_t *info, void *context)
+{
+    if (sig == SIGUSR1 && info != NULL && info->si_signo == SIGUSR1 &&
+        context == NULL) {
+        handled++;
+    }
+}
+
+static int install_siginfo_handler(int flags)
+{
+    struct sigaction action;
+    memset(&action, 0, sizeof(action));
+    action.sa_sigaction = siginfo_handler;
+    action.sa_flags = SA_SIGINFO | flags;
+    sigemptyset(&action.sa_mask);
+    return sigaction(SIGUSR1, &action, NULL);
+}
+
+int main(int argc, char **argv)
+{
+    if (argc != 2) return 2;
+
+    if (strcmp(argv[1], "siginfo") == 0) {
+        if (install_siginfo_handler(0) != 0) return 3;
+        if (raise(SIGUSR1) != 0) return 4;
+        return handled == 1 ? 0 : 5;
+    }
+
+    if (strcmp(argv[1], "reset") == 0) {
+        if (install_siginfo_handler(SA_RESETHAND) != 0) return 6;
+        if (raise(SIGUSR1) != 0) return 7;
+        if (handled != 1) return 8;
+        raise(SIGUSR1);
+        return 9;
+    }
+
+    if (strcmp(argv[1], "terminate") == 0) {
+        struct sigaction action;
+        memset(&action, 0, sizeof(action));
+        action.sa_handler = SIG_DFL;
+        sigemptyset(&action.sa_mask);
+        if (sigaction(SIGTERM, &action, NULL) != 0) return 10;
+        raise(SIGTERM);
+        return 12;
+    }
+
+    return 11;
+}
diff --git a/test/wasix/c_signals/test.sh b/test/wasix/c_signals/test.sh
new file mode 100755
index 000000000..e83768694
--- /dev/null
+++ b/test/wasix/c_signals/test.sh
@@ -0,0 +1,41 @@
+#!/usr/bin/env bash
+
+set -u
+
+stderr_file=$(mktemp)
+trap 'rm -f "$stderr_file"' EXIT
+
+wasmer run --enable-all ./main siginfo
+RESULT=$?
+if [ "$RESULT" != "0" ]; then
+    echo "SA_SIGINFO test failed: different exit code ($RESULT vs. 0)" >&2
+    exit 1
+fi
+
+wasmer run --enable-all ./main reset 2>"$stderr_file"
+RESULT=$?
+if [ "$RESULT" != "138" ]; then
+    echo "SA_RESETHAND test failed: different exit code ($RESULT vs. 138)" >&2
+    cat "$stderr_file" >&2
+    exit 1
+fi
+if grep -q "fatal signal: Aborted" "$stderr_file"; then
+    echo "SA_RESETHAND test failed: default termination recursed into SIGABRT" >&2
+    cat "$stderr_file" >&2
+    exit 1
+fi
+
+wasmer run --enable-all ./main terminate 2>"$stderr_file"
+RESULT=$?
+if [ "$RESULT" != "143" ]; then
+    echo "default SIGTERM test failed: different exit code ($RESULT vs. 143)" >&2
+    cat "$stderr_file" >&2
+    exit 1
+fi
+if [ -s "$stderr_file" ]; then
+    echo "default SIGTERM test failed: default termination wrote to stderr" >&2
+    cat "$stderr_file" >&2
+    exit 1
+fi
+
+echo "c_signals test passed"