Index: lib/asan/asan_posix.cc
===================================================================
--- lib/asan/asan_posix.cc
+++ lib/asan/asan_posix.cc
@@ -40,6 +40,44 @@
 
 // ---------------------- TSD ---------------- {{{1
 
+#if SANITIZER_NETBSD
+// Thread Static Data cannot be used in early init on NetBSD
+// Reuse the Asan TSD API for compatibility with existing code
+// with an alternative implementation.
+
+static bool tsd_key_inited = false;
+static void (*tsd_destructor)(void *tsd) = nullptr;
+static THREADLOCAL void *tsd_key = nullptr;
+
+void tsd_at_exit(void *unused) {
+  (*tsd_destructor)(tsd_key);
+}
+
+void AsanTSDInit(void (*destructor)(void *tsd)) {
+  CHECK(!tsd_key_inited);
+  tsd_key_inited = true;
+  tsd_destructor = destructor;
+  if (REAL(__cxa_atexit)(tsd_at_exit, 0, 0)) {
+    Printf("AddressSanitizer: failed to setup atexit callback");
+    Die();
+  }
+}
+
+void *AsanTSDGet() {
+  CHECK(tsd_key_inited);
+  return tsd_key;
+}
+
+void AsanTSDSet(void *tsd) {
+  CHECK(tsd_key_inited);
+  tsd_key = tsd;
+}
+
+void PlatformTSDDtor(void *tsd) {
+  CHECK(tsd_key_inited);
+  AsanThread::TSDDtor(tsd);
+}
+#else
 static pthread_key_t tsd_key;
 static bool tsd_key_inited = false;
 void AsanTSDInit(void (*destructor)(void *tsd)) {
@@ -67,6 +105,7 @@
   }
   AsanThread::TSDDtor(tsd);
 }
+#endif
 }  // namespace __asan
 
 #endif  // SANITIZER_POSIX