diff --git a/libc/bionic/sigaction.cpp b/libc/bionic/sigaction.cpp
index 1cdb021..a84886b 100644
--- a/libc/bionic/sigaction.cpp
+++ b/libc/bionic/sigaction.cpp
@@ -39,26 +39,25 @@
 extern "C" int __rt_sigaction(int, const struct __kernel_sigaction*, struct __kernel_sigaction*, size_t);
 
 int sigaction(int signal, const struct sigaction* bionic_new_action, struct sigaction* bionic_old_action) {
-  __kernel_sigaction kernel_new_action;
+  __kernel_sigaction kernel_new_action = {};
   if (bionic_new_action != nullptr) {
     kernel_new_action.sa_flags = bionic_new_action->sa_flags;
     kernel_new_action.sa_handler = bionic_new_action->sa_handler;
     // Don't filter signals here; if the caller asked for everything to be blocked, we should obey.
     kernel_new_action.sa_mask = bionic_new_action->sa_mask;
-#if defined(SA_RESTORER)
+#if defined(__x86_64__)
+    // riscv64 doesn't have sa_restorer. For arm64 and 32-bit x86, unwinding
+    // works best if you just let the kernel supply the default restorer
+    // from [vdso]. gdb doesn't care, but libgcc needs the nop that the
+    // kernel includes before the actual code. (We could add that ourselves,
+    // but why bother?)
+    // TODO: why do arm32 and x86-64 need this to unwind through signal handlers?
     kernel_new_action.sa_restorer = bionic_new_action->sa_restorer;
-#if defined(__aarch64__)
-    // arm64 has sa_restorer, but unwinding works best if you just let the
-    // kernel supply the default restorer from [vdso]. gdb doesn't care, but
-    // libgcc needs the nop that the kernel includes before the actual code.
-    // (We could add that ourselves, but why bother?)
-#else
     if (!(kernel_new_action.sa_flags & SA_RESTORER)) {
       kernel_new_action.sa_flags |= SA_RESTORER;
       kernel_new_action.sa_restorer = &__restore_rt;
     }
 #endif
-#endif
   }
 
   __kernel_sigaction kernel_old_action;
@@ -90,10 +89,11 @@
 // by extracting the implementation of sigaction64 to a static function.
 static int __sigaction64(int signal, const struct sigaction64* bionic_new,
                          struct sigaction64* bionic_old) {
-  struct sigaction64 kernel_new;
+  struct sigaction64 kernel_new = {};
   if (bionic_new) {
     kernel_new = *bionic_new;
-#if defined(SA_RESTORER)
+#if defined(__arm__)
+    // (See sa_restorer comment in sigaction() above.)
     if (!(kernel_new.sa_flags & SA_RESTORER)) {
       kernel_new.sa_flags |= SA_RESTORER;
       kernel_new.sa_restorer = (kernel_new.sa_flags & SA_SIGINFO) ? &__restore_rt : &__restore;
@@ -110,9 +110,8 @@
 int sigaction(int signal, const struct sigaction* bionic_new, struct sigaction* bionic_old) {
   // The 32-bit ABI is broken. struct sigaction includes a too-small sigset_t,
   // so we have to translate to struct sigaction64 first.
-  struct sigaction64 kernel_new;
+  struct sigaction64 kernel_new = {};
   if (bionic_new) {
-    kernel_new = {};
     kernel_new.sa_flags = bionic_new->sa_flags;
     kernel_new.sa_handler = bionic_new->sa_handler;
 #if defined(SA_RESTORER)