test(wasix): cover POSIX signal semantics (SA_SIGINFO, SA_RESETHAND, signal masks)

.github/ci-constants.env

@@ -1,3 +1,3 @@
 # Shared CI constants. Loaded into GITHUB_ENV by workflows that need them.
 # Pinned wasix-libc sysroot (wasix-org/wasix-libc release tag).
-WASIX_LIBC_SYSROOT_TAG=v2026-07-03.1
+WASIX_LIBC_SYSROOT_TAG=v2026-07-30.1

lib/wasix/tests/wasm_tests/signal/pthread-sigmask-inherit/main.c

@@ -0,0 +1,55 @@
+//#MinimalLibc: v2026-07-30.1
+//#ExpectedStdout: child inherited the blocked mask
+
+#include <assert.h>
+#include <pthread.h>
+#include <signal.h>
+#include <stdio.h>
+#include <string.h>
+
+// A new thread inherits its creator's signal mask, and the mask is per-thread:
+// unblocking in the child must not affect the parent.
+
+static volatile int child_saw_blocked = 0;
+static volatile int child_query_ok = 0;
+
+static void* child(void* arg) {
+  (void)arg;
+
+  sigset_t mask;
+  sigemptyset(&mask);
+  child_query_ok = (pthread_sigmask(SIG_BLOCK, NULL, &mask) == 0);
+  child_saw_blocked = sigismember(&mask, SIGUSR1);
+
+  sigset_t unblock;
+  sigemptyset(&unblock);
+  sigaddset(&unblock, SIGUSR1);
+  pthread_sigmask(SIG_UNBLOCK, &unblock, NULL);
+
+  return NULL;
+}
+
+int main() {
+  sigset_t block;
+  sigemptyset(&block);
+  sigaddset(&block, SIGUSR1);
+  assert(pthread_sigmask(SIG_BLOCK, &block, NULL) == 0);
+
+  pthread_t thread;
+  assert(pthread_create(&thread, NULL, child, NULL) == 0);
+  assert(pthread_join(thread, NULL) == 0);
+
+  assert(child_query_ok && "pthread_sigmask should succeed in the child");
+  assert(child_saw_blocked == 1 &&
+         "child should inherit the creator's blocked mask");
+
+  // The child unblocked SIGUSR1 for itself only; ours must still be blocked.
+  sigset_t mine;
+  sigemptyset(&mine);
+  assert(pthread_sigmask(SIG_BLOCK, NULL, &mine) == 0);
+  assert(sigismember(&mine, SIGUSR1) == 1 &&
+         "the mask should be per-thread, not shared");
+
+  printf("child inherited the blocked mask\n");
+  return 0;
+}

lib/wasix/tests/wasm_tests/signal/sigaction-mask-blocks-other/main.c

@@ -0,0 +1,61 @@
+//#MinimalLibc: v2026-07-30.1
+//#ExpectedStdout: usr2 deferred until handler returned
+
+#include <assert.h>
+#include <signal.h>
+#include <stdio.h>
+#include <string.h>
+
+// sa_mask names *additional* signals to block while a handler runs, not just
+// the one being delivered. A SIGUSR1 handler whose sa_mask contains SIGUSR2
+// must not be interrupted by SIGUSR2; that delivery is deferred until the
+// handler returns.
+
+static volatile sig_atomic_t usr2_calls = 0;
+static volatile sig_atomic_t usr2_seen_inside = -1;
+
+static void usr1_handler(int sig, siginfo_t* info, void* ucontext) {
+  (void)sig;
+  (void)info;
+  (void)ucontext;
+
+  raise(SIGUSR2);
+  // Sampled before returning: SIGUSR2 is in our sa_mask, so it must still be
+  // pending rather than already handled.
+  usr2_seen_inside = usr2_calls;
+}
+
+static void usr2_handler(int sig, siginfo_t* info, void* ucontext) {
+  (void)sig;
+  (void)info;
+  (void)ucontext;
+
+  usr2_calls++;
+}
+
+int main() {
+  struct sigaction sa;
+
+  memset(&sa, 0, sizeof(sa));
+  sa.sa_sigaction = usr2_handler;
+  sa.sa_flags = SA_SIGINFO;
+  sigemptyset(&sa.sa_mask);
+  assert(sigaction(SIGUSR2, &sa, NULL) == 0);
+
+  memset(&sa, 0, sizeof(sa));
+  sa.sa_sigaction = usr1_handler;
+  sa.sa_flags = SA_SIGINFO;
+  sigemptyset(&sa.sa_mask);
+  sigaddset(&sa.sa_mask, SIGUSR2);
+  assert(sigaction(SIGUSR1, &sa, NULL) == 0);
+
+  assert(raise(SIGUSR1) == 0);
+
+  assert(usr2_seen_inside == 0 &&
+         "sa_mask should keep SIGUSR2 blocked inside the SIGUSR1 handler");
+  assert(usr2_calls == 1 &&
+         "SIGUSR2 should be delivered once the SIGUSR1 handler returns");
+
+  printf("usr2 deferred until handler returned\n");
+  return 0;
+}

lib/wasix/tests/wasm_tests/signal/sigaction-mask-defers/main.c

@@ -0,0 +1,60 @@
+//#MinimalLibc: v2026-07-30.1
+//#ExpectedStdout: calls=5 max_depth=1
+
+#include <assert.h>
+#include <signal.h>
+#include <stdio.h>
+#include <string.h>
+
+// POSIX blocks the delivered signal for the duration of its handler (sa_mask
+// plus the signal itself, the latter unless SA_NODEFER). So a signal re-raised
+// from inside the handler is deferred and delivered once the handler returns,
+// running the handler again sequentially rather than nesting it.
+//
+// The re-raise is gated on `calls < LIMIT` in guest code, so the recursion is
+// bounded no matter how libc behaves: even with masking entirely broken this
+// nests 5 deep rather than exhausting the stack.
+//
+// Paired with sigaction-nodefer-reenters, which is the same program with
+// SA_NODEFER and therefore expects max_depth == LIMIT.
+
+#define LIMIT 5
+
+static volatile sig_atomic_t calls = 0;
+static volatile sig_atomic_t depth = 0;
+static volatile sig_atomic_t max_depth = 0;
+
+static void handler(int sig, siginfo_t* info, void* ucontext) {
+  (void)info;
+  (void)ucontext;
+
+  calls++;
+  depth++;
+  if (depth > max_depth) {
+    max_depth = depth;
+  }
+  if (calls < LIMIT) {
+    raise(sig);
+  }
+  depth--;
+}
+
+int main() {
+  struct sigaction sa;
+  memset(&sa, 0, sizeof(sa));
+  sa.sa_sigaction = handler;
+  sa.sa_flags = SA_SIGINFO;
+  sigfillset(&sa.sa_mask);
+  assert(sigaction(SIGUSR1, &sa, NULL) == 0);
+
+  // Every deferred delivery is drained before the raise that triggered the
+  // first one returns, so no further syscall is needed to observe them.
+  assert(raise(SIGUSR1) == 0);
+
+  assert(calls == LIMIT && "handler should run once per raise");
+  assert(max_depth == 1 && "a blocked signal must not re-enter its handler");
+  assert(depth == 0 && "every invocation should have returned");
+
+  printf("calls=%d max_depth=%d\n", (int)calls, (int)max_depth);
+  return 0;
+}

lib/wasix/tests/wasm_tests/signal/sigaction-nodefer-reenters/main.c

@@ -0,0 +1,57 @@
+//#MinimalLibc: v2026-07-30.1
+//#ExpectedStdout: calls=5 max_depth=5
+
+#include <assert.h>
+#include <signal.h>
+#include <stdio.h>
+#include <string.h>
+
+// SA_NODEFER opts out of adding the delivered signal to the mask for the
+// duration of its handler, so a signal re-raised from inside the handler
+// re-enters it immediately instead of being deferred.
+//
+// sa_mask must be empty here: it is applied on top of SA_NODEFER, so a
+// sigfillset() mask would block SIGUSR1 anyway and defeat the opt-out.
+//
+// The re-raise is gated on `calls < LIMIT` in guest code, bounding the nesting
+// to 5 frames. Paired with sigaction-mask-defers, the same program without
+// SA_NODEFER, which expects max_depth == 1.
+
+#define LIMIT 5
+
+static volatile sig_atomic_t calls = 0;
+static volatile sig_atomic_t depth = 0;
+static volatile sig_atomic_t max_depth = 0;
+
+static void handler(int sig, siginfo_t* info, void* ucontext) {
+  (void)info;
+  (void)ucontext;
+
+  calls++;
+  depth++;
+  if (depth > max_depth) {
+    max_depth = depth;
+  }
+  if (calls < LIMIT) {
+    raise(sig);
+  }
+  depth--;
+}
+
+int main() {
+  struct sigaction sa;
+  memset(&sa, 0, sizeof(sa));
+  sa.sa_sigaction = handler;
+  sa.sa_flags = SA_SIGINFO | SA_NODEFER;
+  sigemptyset(&sa.sa_mask);
+  assert(sigaction(SIGUSR1, &sa, NULL) == 0);
+
+  assert(raise(SIGUSR1) == 0);
+
+  assert(calls == LIMIT && "handler should run once per raise");
+  assert(max_depth == LIMIT && "SA_NODEFER should allow the handler to nest");
+  assert(depth == 0 && "every invocation should have returned");
+
+  printf("calls=%d max_depth=%d\n", (int)calls, (int)max_depth);
+  return 0;
+}

lib/wasix/tests/wasm_tests/signal/sigaction-resethand/main.c

@@ -0,0 +1,47 @@
+//#MinimalLibc: v2026-07-30.1
+//#ExpectedStdout: resethand ok
+
+#include <assert.h>
+#include <signal.h>
+#include <stdio.h>
+#include <string.h>
+
+// POSIX resets a handler installed with SA_RESETHAND to SIG_DFL on entry, so
+// re-raising the same signal from inside the handler takes the default action
+// instead of re-entering the handler. Node's `SignalExit` relies on exactly
+// that: it re-raises to let the default disposition terminate the process.
+// Without the reset it recurses until the stack is exhausted.
+//
+// The reset is asserted directly rather than by re-raising, because unbounded
+// re-entry exhausts the host stack and would take the test process down with
+// it instead of failing this one test.
+
+static volatile sig_atomic_t calls = 0;
+
+static void handler(int sig, siginfo_t* info, void* ucontext) {
+  (void)sig;
+  (void)info;
+  (void)ucontext;
+  calls++;
+}
+
+int main() {
+  struct sigaction sa;
+  memset(&sa, 0, sizeof(sa));
+  sa.sa_sigaction = handler;
+  sa.sa_flags = SA_SIGINFO | SA_RESETHAND;
+  sigfillset(&sa.sa_mask);
+  assert(sigaction(SIGUSR1, &sa, NULL) == 0);
+
+  assert(raise(SIGUSR1) == 0);
+  assert(calls == 1 && "handler should have run once");
+
+  struct sigaction old;
+  memset(&old, 0, sizeof(old));
+  assert(sigaction(SIGUSR1, NULL, &old) == 0);
+  assert(old.sa_handler == SIG_DFL &&
+         "SA_RESETHAND should reset the disposition to SIG_DFL");
+
+  printf("resethand ok\n");
+  return 0;
+}

lib/wasix/tests/wasm_tests/signal/sigaction-siginfo/main.c

@@ -0,0 +1,58 @@
+//#MinimalLibc: v2026-07-30.1
+//#ExpectedStdout: plain handler ok
+//#ExpectedStdout: siginfo handler ok
+
+#include <assert.h>
+#include <signal.h>
+#include <stdio.h>
+#include <string.h>
+
+// A handler installed through `sa_sigaction` with `SA_SIGINFO` takes three
+// arguments, while one installed through `sa_handler` takes a single one. On
+// wasm these are distinct function types, so dispatching a three-argument
+// handler through a one-argument `call_indirect` traps with "indirect call
+// type mismatch" and kills the instance. Cover both dispatch forms.
+
+static volatile sig_atomic_t plain_calls = 0;
+static volatile sig_atomic_t info_calls = 0;
+static volatile sig_atomic_t info_signo = 0;
+static volatile sig_atomic_t info_arg_ok = 0;
+
+static void plain_handler(int sig) {
+  (void)sig;
+  plain_calls++;
+}
+
+static void info_handler(int sig, siginfo_t* info, void* ucontext) {
+  (void)ucontext;
+  info_calls++;
+  info_signo = sig;
+  info_arg_ok = (info != NULL && info->si_signo == sig);
+}
+
+int main() {
+  struct sigaction sa;
+
+  memset(&sa, 0, sizeof(sa));
+  sa.sa_handler = plain_handler;
+  sigfillset(&sa.sa_mask);
+  assert(sigaction(SIGUSR1, &sa, NULL) == 0);
+
+  assert(raise(SIGUSR1) == 0);
+  assert(plain_calls == 1 && "one-argument handler should have run");
+  printf("plain handler ok\n");
+
+  memset(&sa, 0, sizeof(sa));
+  sa.sa_sigaction = info_handler;
+  sa.sa_flags = SA_SIGINFO;
+  sigfillset(&sa.sa_mask);
+  assert(sigaction(SIGUSR2, &sa, NULL) == 0);
+
+  assert(raise(SIGUSR2) == 0);
+  assert(info_calls == 1 && "three-argument handler should have run");
+  assert(info_signo == SIGUSR2 && "handler should receive the signal number");
+  assert(info_arg_ok && "handler should receive a populated siginfo_t");
+  printf("siginfo handler ok\n");
+
+  return 0;
+}