1 files changed, 142 insertions, 0 deletions
diff --git a/libc-bottom-half/signal/signal.c b/libc-bottom-half/signal/signal.c
new file mode 100644
index 0000000..290d6b2
--- /dev/null
+++ b/libc-bottom-half/signal/signal.c
@@ -0,0 +1,142 @@
+// Userspace emulation of `raise` and `signal`.
+//
+// WebAssembly doesn't support asynchronous signal delivery, so we can't
+// support it in WASI libc. But we can make things like `raise` work.
+
+#define _WASI_EMULATED_SIGNAL
+#define _ALL_SOURCE
+#define _GNU_SOURCE
+#include <signal.h>
+#include <stdio.h>
+#include <stdlib.h>
+#include <errno.h>
+#include <string.h>
+#include <assert.h>
+
+void __SIG_IGN(int sig) {
+    // do nothing
+}
+
+_Noreturn
+void __SIG_ERR(int sig) {
+    __builtin_trap();
+}
+
+_Noreturn
+static void core_handler(int sig) {
+    fprintf(stderr, "Program received fatal signal: %s\n", strsignal(sig));
+    abort();
+}
+
+_Noreturn
+static void terminate_handler(int sig) {
+    fprintf(stderr, "Program recieved termination signal: %s\n", strsignal(sig));
+    abort();
+}
+
+_Noreturn
+static void stop_handler(int sig) {
+    fprintf(stderr, "Program recieved stop signal: %s\n", strsignal(sig));
+    abort();
+}
+
+static void continue_handler(int sig) {
+    // do nothing
+}
+
+static const sighandler_t default_handlers[_NSIG] = {
+    // Default behavior: "core".
+    [SIGABRT] = core_handler,
+    [SIGBUS] = core_handler,
+    [SIGFPE] = core_handler,
+    [SIGILL] = core_handler,
+#if SIGIOT != SIGABRT
+    [SIGIOT] = core_handler,
+#endif
+    [SIGQUIT] = core_handler,
+    [SIGSEGV] = core_handler,
+    [SIGSYS] = core_handler,
+    [SIGTRAP] = core_handler,
+    [SIGXCPU] = core_handler,
+    [SIGXFSZ] = core_handler,
+#if defined(SIGUNUSED) && SIGUNUSED != SIGSYS
+    [SIGUNUSED] = core_handler,
+#endif
+
+    // Default behavior: ignore.
+    [SIGCHLD] = SIG_IGN,
+#if defined(SIGCLD) && SIGCLD != SIGCHLD
+    [SIGCLD] = SIG_IGN,
+#endif
+    [SIGURG] = SIG_IGN,
+    [SIGWINCH] = SIG_IGN,
+
+    // Default behavior: "continue".
+    [SIGCONT] = continue_handler,
+
+    // Default behavior: "stop".
+    [SIGSTOP] = stop_handler,
+    [SIGTSTP] = stop_handler,
+    [SIGTTIN] = stop_handler,
+    [SIGTTOU] = stop_handler,
+
+    // Default behavior: "terminate".
+    [SIGHUP] = terminate_handler,
+    [SIGINT] = terminate_handler,
+    [SIGKILL] = terminate_handler,
+    [SIGUSR1] = terminate_handler,
+    [SIGUSR2] = terminate_handler,
+    [SIGPIPE] = terminate_handler,
+    [SIGALRM] = terminate_handler,
+    [SIGTERM] = terminate_handler,
+    [SIGSTKFLT] = terminate_handler,
+    [SIGVTALRM] = terminate_handler,
+    [SIGPROF] = terminate_handler,
+    [SIGIO] = terminate_handler,
+#if SIGPOLL != SIGIO
+    [SIGPOLL] = terminate_handler,
+#endif
+    [SIGPWR] = terminate_handler,
+};
+
+static sighandler_t handlers[_NSIG];
+
+int raise(int sig) {
+    if (sig < 0 || sig >= _NSIG) {
+        errno = EINVAL;
+        return -1;
+    }
+
+    sighandler_t func = handlers[sig];
+
+    if (func == NULL) {
+        default_handlers[sig](sig);
+    } else {
+        func(sig);
+    }
+
+    return 0;
+}
+
+void (*signal(int sig, void (*func)(int)))(int) {
+    assert(SIG_DFL == NULL);
+
+    if (sig < 0 || sig >= _NSIG) {
+        errno = EINVAL;
+        return SIG_ERR;
+    }
+
+    if (sig == SIGKILL || sig == SIGSTOP) {
+        errno = EINVAL;
+        return SIG_ERR;
+    }
+
+    sighandler_t old = handlers[sig];
+
+    handlers[sig] = func;
+
+    return old;
+}
+
+extern __typeof(signal) bsd_signal __attribute__((weak, alias("signal")));
+extern __typeof(signal) __sysv_signal __attribute__((weak, alias("signal")));