diff --git a/libc/Android.bp b/libc/Android.bp
index 1f54a0a..4d35592 100644
--- a/libc/Android.bp
+++ b/libc/Android.bp
@@ -1219,7 +1219,7 @@
         // so we can't include them in libc_ndk.a.
         "bionic/__cxa_thread_atexit_impl.cpp",
         "bionic/android_unsafe_frame_pointer_chase.cpp",
-        "stdlib/atexit.c",
+        "bionic/atexit.cpp",
         "bionic/fork.cpp",
     ],
 
@@ -1692,7 +1692,10 @@
 
     stubs: {
         symbol_file: "libc.map.txt",
-        versions: ["10000"],
+        versions: [
+            "29",
+            "10000",
+        ],
     },
 
     apex_available: [
diff --git a/libc/NOTICE b/libc/NOTICE
index 8245ff8..8582054 100644
--- a/libc/NOTICE
+++ b/libc/NOTICE
@@ -1,32 +1,3 @@
-   Copyright (c) 2014, ARM Limited
-   All rights Reserved.
-   Copyright (c) 2014, Linaro Ltd.
-
-   Redistribution and use in source and binary forms, with or without
-   modification, are permitted provided that the following conditions are met:
-       * Redistributions of source code must retain the above copyright
-         notice, this list of conditions and the following disclaimer.
-       * Redistributions in binary form must reproduce the above copyright
-         notice, this list of conditions and the following disclaimer in the
-         documentation and/or other materials provided with the distribution.
-       * Neither the name of the company nor the names of its contributors
-         may be used to endorse or promote products derived from this
-         software without specific prior written permission.
-
-   THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS
-   "AS IS" AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT
-   LIMITED TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR
-   A PARTICULAR PURPOSE ARE DISCLAIMED. IN NO EVENT SHALL THE COPYRIGHT
-   HOLDER OR CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL,
-   SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT
-   LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE,
-   DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY
-   THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT
-   (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE
-   OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
-
--------------------------------------------------------------------
-
    Copyright (c) 2014, Linaro Limited
    All rights reserved.
 
@@ -5225,34 +5196,6 @@
 
 -------------------------------------------------------------------
 
-Copyright (c) 2012, Linaro Limited
-   All rights reserved.
-
-   Redistribution and use in source and binary forms, with or without
-   modification, are permitted provided that the following conditions are met:
-       * Redistributions of source code must retain the above copyright
-         notice, this list of conditions and the following disclaimer.
-       * Redistributions in binary form must reproduce the above copyright
-         notice, this list of conditions and the following disclaimer in the
-         documentation and/or other materials provided with the distribution.
-       * Neither the name of the Linaro nor the
-         names of its contributors may be used to endorse or promote products
-         derived from this software without specific prior written permission.
-
-   THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS
-   "AS IS" AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT
-   LIMITED TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR
-   A PARTICULAR PURPOSE ARE DISCLAIMED. IN NO EVENT SHALL THE COPYRIGHT
-   HOLDER OR CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL,
-   SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT
-   LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE,
-   DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY
-   THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT
-   (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE
-   OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
-
--------------------------------------------------------------------
-
 Copyright (c) 2012-2013, Linaro Limited
    All rights reserved.
 
@@ -5465,33 +5408,6 @@
 
 -------------------------------------------------------------------
 
-Copyright (c) 2013-2015, Linaro Limited
-   All rights reserved.
-
-   Redistribution and use in source and binary forms, with or without
-   modification, are permitted provided that the following conditions are met:
-       * Redistributions of source code must retain the above copyright
-     notice, this list of conditions and the following disclaimer.
-       * Redistributions in binary form must reproduce the above copyright
-     notice, this list of conditions and the following disclaimer in the
-     documentation and/or other materials provided with the distribution.
-       * Neither the name of the Linaro nor the
-     names of its contributors may be used to endorse or promote products
-     derived from this software without specific prior written permission.
-
-   THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS
-   "AS IS" AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT
-   LIMITED TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR
-   A PARTICULAR PURPOSE ARE DISCLAIMED. IN NO EVENT SHALL THE COPYRIGHT
-   HOLDER OR CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL,
-   SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT
-   LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE,
-   DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY
-   THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT
-   (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE
-
--------------------------------------------------------------------
-
 Copyright (c) 2014, Intel Corporation
 All rights reserved.
 
@@ -5632,34 +5548,6 @@
 
 -------------------------------------------------------------------
 
-Copyright (c) 2017 ARM Ltd
-All rights reserved.
-
-Redistribution and use in source and binary forms, with or without
-modification, are permitted provided that the following conditions
-are met:
-1. Redistributions of source code must retain the above copyright
-   notice, this list of conditions and the following disclaimer.
-2. Redistributions in binary form must reproduce the above copyright
-   notice, this list of conditions and the following disclaimer in the
-   documentation and/or other materials provided with the distribution.
-3. The name of the company may not be used to endorse or promote
-   products derived from this software without specific prior written
-   permission.
-
-THIS SOFTWARE IS PROVIDED BY ARM LTD ``AS IS'' AND ANY EXPRESS OR IMPLIED
-WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE IMPLIED WARRANTIES OF
-MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE ARE DISCLAIMED.
-IN NO EVENT SHALL ARM LTD BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL,
-SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT LIMITED
-TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE, DATA, OR
-PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY THEORY OF
-LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT (INCLUDING
-NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE OF THIS
-SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
-
--------------------------------------------------------------------
-
 Copyright (c)1999 Citrus Project,
 All rights reserved.
 
diff --git a/libc/bionic/atexit.cpp b/libc/bionic/atexit.cpp
new file mode 100644
index 0000000..df306af
--- /dev/null
+++ b/libc/bionic/atexit.cpp
@@ -0,0 +1,263 @@
+/*
+ * Copyright (C) 2020 The Android Open Source Project
+ * All rights reserved.
+ *
+ * Redistribution and use in source and binary forms, with or without
+ * modification, are permitted provided that the following conditions
+ * are met:
+ *  * Redistributions of source code must retain the above copyright
+ *    notice, this list of conditions and the following disclaimer.
+ *  * Redistributions in binary form must reproduce the above copyright
+ *    notice, this list of conditions and the following disclaimer in
+ *    the documentation and/or other materials provided with the
+ *    distribution.
+ *
+ * THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS
+ * "AS IS" AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT
+ * LIMITED TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS
+ * FOR A PARTICULAR PURPOSE ARE DISCLAIMED. IN NO EVENT SHALL THE
+ * COPYRIGHT OWNER OR CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT,
+ * INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING,
+ * BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS
+ * OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED
+ * AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY,
+ * OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT
+ * OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF
+ * SUCH DAMAGE.
+ */
+
+#include "atexit.h"
+
+#include <errno.h>
+#include <pthread.h>
+#include <stdint.h>
+#include <stdlib.h>
+#include <string.h>
+#include <sys/mman.h>
+#include <sys/param.h>
+#include <sys/prctl.h>
+
+#include <async_safe/CHECK.h>
+#include <async_safe/log.h>
+
+#include "platform/bionic/page.h"
+
+extern "C" void __libc_stdio_cleanup();
+extern "C" void __unregister_atfork(void* dso);
+
+namespace {
+
+struct AtexitEntry {
+  void (*fn)(void*);  // the __cxa_atexit callback
+  void* arg;          // argument for `fn` callback
+  void* dso;          // shared module handle
+};
+
+class AtexitArray {
+ public:
+  size_t size() const { return size_; }
+  uint64_t total_appends() const { return total_appends_; }
+  const AtexitEntry& operator[](size_t idx) const { return array_[idx]; }
+
+  bool append_entry(const AtexitEntry& entry);
+  AtexitEntry extract_entry(size_t idx);
+  void recompact();
+
+ private:
+  AtexitEntry* array_;
+  size_t size_;
+  size_t extracted_count_;
+  size_t capacity_;
+
+  // An entry can be appended by a __cxa_finalize callback. Track the number of appends so we
+  // restart concurrent __cxa_finalize passes.
+  uint64_t total_appends_;
+
+  static size_t round_up_to_page_bytes(size_t capacity) {
+    return PAGE_END(capacity * sizeof(AtexitEntry));
+  }
+
+  static size_t next_capacity(size_t capacity) {
+    // Double the capacity each time.
+    size_t result = round_up_to_page_bytes(MAX(1, capacity * 2)) / sizeof(AtexitEntry);
+    CHECK(result > capacity);
+    return result;
+  }
+
+  // Recompact the array if it will save at least one page of memory at the end.
+  bool needs_recompaction() {
+    return round_up_to_page_bytes(size_ - extracted_count_) < round_up_to_page_bytes(size_);
+  }
+
+  void set_writable(bool writable);
+  bool expand_capacity();
+};
+
+}  // anonymous namespace
+
+bool AtexitArray::append_entry(const AtexitEntry& entry) {
+  bool result = false;
+
+  set_writable(true);
+  if (size_ < capacity_ || expand_capacity()) {
+    array_[size_++] = entry;
+    ++total_appends_;
+    result = true;
+  }
+  set_writable(false);
+
+  return result;
+}
+
+// Extract an entry and return it.
+AtexitEntry AtexitArray::extract_entry(size_t idx) {
+  AtexitEntry result = array_[idx];
+
+  set_writable(true);
+  array_[idx] = {};
+  ++extracted_count_;
+  set_writable(false);
+
+  return result;
+}
+
+void AtexitArray::recompact() {
+  if (!needs_recompaction()) return;
+
+  set_writable(true);
+
+  // Optimization: quickly skip over the initial non-null entries.
+  size_t src = 0, dst = 0;
+  while (src < size_ && array_[src].fn != nullptr) {
+    ++src;
+    ++dst;
+  }
+
+  // Shift the non-null entries forward, and zero out the removed entries at the end of the array.
+  for (; src < size_; ++src) {
+    const AtexitEntry entry = array_[src];
+    array_[src] = {};
+    if (entry.fn != nullptr) {
+      array_[dst++] = entry;
+    }
+  }
+
+  // If the table uses fewer pages, clean the pages at the end.
+  size_t old_bytes = round_up_to_page_bytes(size_);
+  size_t new_bytes = round_up_to_page_bytes(dst);
+  if (new_bytes < old_bytes) {
+    madvise(reinterpret_cast<char*>(array_) + new_bytes, old_bytes - new_bytes, MADV_DONTNEED);
+  }
+
+  size_ = dst;
+  extracted_count_ = 0;
+
+  set_writable(false);
+}
+
+// Use mprotect to make the array writable or read-only. Returns true on success. Making the array
+// read-only could protect against either unintentional or malicious corruption of the array.
+void AtexitArray::set_writable(bool writable) {
+  if (array_ == nullptr) return;
+  const int prot = PROT_READ | (writable ? PROT_WRITE : 0);
+  if (mprotect(array_, round_up_to_page_bytes(capacity_), prot) != 0) {
+    async_safe_fatal("mprotect failed on atexit array: %s", strerror(errno));
+  }
+}
+
+bool AtexitArray::expand_capacity() {
+  const size_t new_capacity = next_capacity(capacity_);
+  const size_t new_capacity_bytes = round_up_to_page_bytes(new_capacity);
+
+  void* new_pages;
+  if (array_ == nullptr) {
+    new_pages = mmap(nullptr, new_capacity_bytes, PROT_READ | PROT_WRITE,
+                     MAP_PRIVATE | MAP_ANONYMOUS, -1, 0);
+  } else {
+    new_pages =
+        mremap(array_, round_up_to_page_bytes(capacity_), new_capacity_bytes, MREMAP_MAYMOVE);
+  }
+  if (new_pages == MAP_FAILED) {
+    async_safe_format_log(ANDROID_LOG_WARN, "libc",
+                          "__cxa_atexit: mmap/mremap failed to allocate %zu bytes: %s",
+                          new_capacity_bytes, strerror(errno));
+    return false;
+  }
+
+  prctl(PR_SET_VMA, PR_SET_VMA_ANON_NAME, new_pages, new_capacity_bytes, "atexit handlers");
+  array_ = static_cast<AtexitEntry*>(new_pages);
+  capacity_ = new_capacity;
+  return true;
+}
+
+static AtexitArray g_array;
+static pthread_mutex_t g_atexit_lock = PTHREAD_MUTEX_INITIALIZER;
+
+static inline void atexit_lock() {
+  pthread_mutex_lock(&g_atexit_lock);
+}
+
+static inline void atexit_unlock() {
+  pthread_mutex_unlock(&g_atexit_lock);
+}
+
+// Register a function to be called either when a library is unloaded (dso != nullptr), or when the
+// program exits (dso == nullptr). The `dso` argument is typically the address of a hidden
+// __dso_handle variable. This function is also used as the backend for the atexit function.
+//
+// See https://itanium-cxx-abi.github.io/cxx-abi/abi.html#dso-dtor.
+//
+int __cxa_atexit(void (*func)(void*), void* arg, void* dso) {
+  int result = -1;
+
+  if (func != nullptr) {
+    atexit_lock();
+    if (g_array.append_entry({.fn = func, .arg = arg, .dso = dso})) {
+      result = 0;
+    }
+    atexit_unlock();
+  }
+
+  return result;
+}
+
+void __cxa_finalize(void* dso) {
+  atexit_lock();
+
+  static uint32_t call_depth = 0;
+  ++call_depth;
+
+restart:
+  const uint64_t total_appends = g_array.total_appends();
+
+  for (ssize_t i = g_array.size() - 1; i >= 0; --i) {
+    if (g_array[i].fn == nullptr || (dso != nullptr && g_array[i].dso != dso)) continue;
+
+    // Clear the entry in the array because its DSO handle will become invalid, and to avoid calling
+    // an entry again if __cxa_finalize is called recursively.
+    const AtexitEntry entry = g_array.extract_entry(i);
+
+    atexit_unlock();
+    entry.fn(entry.arg);
+    atexit_lock();
+
+    if (g_array.total_appends() != total_appends) goto restart;
+  }
+
+  // Avoid recompaction on recursive calls because it's unnecessary and would require earlier,
+  // concurrent __cxa_finalize calls to restart. Skip recompaction on program exit too
+  // (dso == nullptr), because the memory will be reclaimed soon anyway.
+  --call_depth;
+  if (call_depth == 0 && dso != nullptr) {
+    g_array.recompact();
+  }
+
+  atexit_unlock();
+
+  if (dso != nullptr) {
+    __unregister_atfork(dso);
+  } else {
+    // If called via exit(), flush output of all open files.
+    __libc_stdio_cleanup();
+  }
+}
diff --git a/libc/stdlib/atexit.h b/libc/bionic/atexit.h
similarity index 90%
rename from libc/stdlib/atexit.h
rename to libc/bionic/atexit.h
index e01bb34..8abcdc5 100644
--- a/libc/stdlib/atexit.h
+++ b/libc/bionic/atexit.h
@@ -30,5 +30,13 @@
  *
  */
 
-int	__cxa_atexit(void (*)(void *), void *, void *);
-void	__cxa_finalize(void *);
+#pragma once
+
+#include <sys/cdefs.h>
+
+__BEGIN_DECLS
+
+int __cxa_atexit(void (*)(void*), void*, void*);
+void __cxa_finalize(void*);
+
+__END_DECLS
diff --git a/libc/include/bits/posix_limits.h b/libc/include/bits/posix_limits.h
index 8dfea52..452f5f6 100644
--- a/libc/include/bits/posix_limits.h
+++ b/libc/include/bits/posix_limits.h
@@ -37,7 +37,7 @@
 
 #define __BIONIC_POSIX_FEATURE_MISSING (-1)
 #define __BIONIC_POSIX_FEATURE_SINCE(level) \
-    (((__ANDROID_API__) >= level) ? _POSIX_VERSION : __BIONIC_POSIX_FEATURE_MISSING)
+    (((__ANDROID_API__) >= (level)) ? _POSIX_VERSION : __BIONIC_POSIX_FEATURE_MISSING)
 
 /* Availability macros. */
 /* See http://man7.org/linux/man-pages/man7/posixoptions.7.html for documentation. */
@@ -104,15 +104,15 @@
 #define _POSIX2_UPE                 __BIONIC_POSIX_FEATURE_MISSING
 
 #if defined(__LP64__)
-#define _POSIX_V7_ILP32_OFF32       -1
-#define _POSIX_V7_ILP32_OFFBIG      -1
+#define _POSIX_V7_ILP32_OFF32      (-1)
+#define _POSIX_V7_ILP32_OFFBIG     (-1)
 #define _POSIX_V7_LP64_OFF64         1
 #define _POSIX_V7_LPBIG_OFFBIG       1
 #else
 #define _POSIX_V7_ILP32_OFF32        1
-#define _POSIX_V7_ILP32_OFFBIG      -1
-#define _POSIX_V7_LP64_OFF64        -1
-#define _POSIX_V7_LPBIG_OFFBIG      -1
+#define _POSIX_V7_ILP32_OFFBIG     (-1)
+#define _POSIX_V7_LP64_OFF64       (-1)
+#define _POSIX_V7_LPBIG_OFFBIG     (-1)
 #endif
 
 #define _XOPEN_CRYPT                __BIONIC_POSIX_FEATURE_MISSING
diff --git a/libc/include/malloc.h b/libc/include/malloc.h
index aa046b9..ba0af3c 100644
--- a/libc/include/malloc.h
+++ b/libc/include/malloc.h
@@ -162,14 +162,14 @@
  *
  * Available since API level 27.
  */
-#define M_DECAY_TIME -100
+#define M_DECAY_TIME (-100)
 /**
  * mallopt() option to immediately purge any memory not in use. This
  * will release the memory back to the kernel. The value is ignored.
  *
  * Available since API level 28.
  */
-#define M_PURGE -101
+#define M_PURGE (-101)
 
 /**
  * [mallopt(3)](http://man7.org/linux/man-pages/man3/mallopt.3.html) modifies
diff --git a/libc/include/pthread.h b/libc/include/pthread.h
index 331e92c..8bc897a 100644
--- a/libc/include/pthread.h
+++ b/libc/include/pthread.h
@@ -68,7 +68,7 @@
 #define PTHREAD_ONCE_INIT 0
 
 #if __ANDROID_API__ >= 24
-#define PTHREAD_BARRIER_SERIAL_THREAD -1
+#define PTHREAD_BARRIER_SERIAL_THREAD (-1)
 #endif
 
 #if defined(__LP64__)
diff --git a/libc/include/sys/cdefs.h b/libc/include/sys/cdefs.h
index 9e214e5..b4556a7 100644
--- a/libc/include/sys/cdefs.h
+++ b/libc/include/sys/cdefs.h
@@ -303,7 +303,7 @@
 
 /* Intended for use in evaluated contexts. */
 #define __bos_dynamic_check_impl_and(bos_val, op, index, cond) \
-  (bos_val == __BIONIC_FORTIFY_UNKNOWN_SIZE ||                 \
+  ((bos_val) == __BIONIC_FORTIFY_UNKNOWN_SIZE ||                 \
    (__builtin_constant_p(index) && bos_val op index && (cond)))
 
 #define __bos_dynamic_check_impl(bos_val, op, index) \
diff --git a/libc/platform/bionic/reserved_signals.h b/libc/platform/bionic/reserved_signals.h
index 4ac6455..3c5bc02 100644
--- a/libc/platform/bionic/reserved_signals.h
+++ b/libc/platform/bionic/reserved_signals.h
@@ -47,9 +47,9 @@
 // If you change this, also change __ndk_legacy___libc_current_sigrtmin
 // in <android/legacy_signal_inlines.h> to match.
 
-#define BIONIC_SIGNAL_DEBUGGER __SIGRTMIN + 3
-#define BIONIC_SIGNAL_PROFILER __SIGRTMIN + 4
-#define BIONIC_SIGNAL_FDTRACK __SIGRTMIN + 7
+#define BIONIC_SIGNAL_DEBUGGER (__SIGRTMIN + 3)
+#define BIONIC_SIGNAL_PROFILER (__SIGRTMIN + 4)
+#define BIONIC_SIGNAL_FDTRACK (__SIGRTMIN + 7)
 
 #define __SIGRT_RESERVED 8
 static inline __always_inline sigset64_t filter_reserved_signals(sigset64_t sigset, int how) {
diff --git a/libc/platform/bionic/tls_defines.h b/libc/platform/bionic/tls_defines.h
index 92f707a..78099b3 100644
--- a/libc/platform/bionic/tls_defines.h
+++ b/libc/platform/bionic/tls_defines.h
@@ -80,8 +80,8 @@
 // [1] "Addenda to, and Errata in, the ABI for the ARM Architecture". Section 3.
 // http://infocenter.arm.com/help/topic/com.arm.doc.ihi0045e/IHI0045E_ABI_addenda.pdf
 
-#define MIN_TLS_SLOT              -1 // update this value when reserving a slot
-#define TLS_SLOT_BIONIC_TLS       -1
+#define MIN_TLS_SLOT            (-1) // update this value when reserving a slot
+#define TLS_SLOT_BIONIC_TLS     (-1)
 #define TLS_SLOT_DTV              0
 #define TLS_SLOT_THREAD_ID        1
 #define TLS_SLOT_APP              2 // was historically used for errno
diff --git a/libc/stdlib/atexit.c b/libc/stdlib/atexit.c
deleted file mode 100644
index 0efb118..0000000
--- a/libc/stdlib/atexit.c
+++ /dev/null
@@ -1,200 +0,0 @@
-/*	$OpenBSD: atexit.c,v 1.20 2014/07/11 09:51:37 kettenis Exp $ */
-/*
- * Copyright (c) 2002 Daniel Hartmeier
- * All rights reserved.
- *
- * Redistribution and use in source and binary forms, with or without
- * modification, are permitted provided that the following conditions
- * are met:
- *
- *    - Redistributions of source code must retain the above copyright
- *      notice, this list of conditions and the following disclaimer.
- *    - Redistributions in binary form must reproduce the above
- *      copyright notice, this list of conditions and the following
- *      disclaimer in the documentation and/or other materials provided
- *      with the distribution.
- *
- * THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS
- * "AS IS" AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT
- * LIMITED TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS
- * FOR A PARTICULAR PURPOSE ARE DISCLAIMED. IN NO EVENT SHALL THE
- * COPYRIGHT HOLDERS OR CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT,
- * INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING,
- * BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES;
- * LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER
- * CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT
- * LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN
- * ANY WAY OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE
- * POSSIBILITY OF SUCH DAMAGE.
- *
- */
-
-#include "atexit.h"
-
-#include <pthread.h>
-#include <stdlib.h>
-#include <string.h>
-#include <unistd.h>
-#include <sys/mman.h>
-#include <sys/prctl.h>
-#include <sys/types.h>
-
-static pthread_mutex_t g_atexit_lock = PTHREAD_MUTEX_INITIALIZER;
-#define _ATEXIT_LOCK() pthread_mutex_lock(&g_atexit_lock)
-#define _ATEXIT_UNLOCK() pthread_mutex_unlock(&g_atexit_lock)
-
-struct atexit {
-	struct atexit *next;		/* next in list */
-	int ind;			/* next index in this table */
-	int max;			/* max entries >= ATEXIT_SIZE */
-	struct atexit_fn {
-		void (*fn_ptr)(void *);
-		void *fn_arg;		/* argument for CXA callback */
-		void *fn_dso;		/* shared module handle */
-	} fns[1];			/* the table itself */
-};
-
-static struct atexit *__atexit;
-static int restartloop;
-
-/* BEGIN android-changed: __unregister_atfork is used by __cxa_finalize */
-extern void __unregister_atfork(void* dso);
-/* END android-changed */
-
-/*
- * Function pointers are stored in a linked list of pages. The list
- * is initially empty, and pages are allocated on demand. The first
- * function pointer in the first allocated page (the last one in
- * the linked list) is reserved for the cleanup function.
- *
- * Outside the following functions, all pages are mprotect()'ed
- * to prevent unintentional/malicious corruption.
- */
-
-/*
- * Register a function to be performed at exit or when a shared object
- * with the given dso handle is unloaded dynamically.  Also used as
- * the backend for atexit().  For more info on this API, see:
- *
- *	http://www.codesourcery.com/cxx-abi/abi.html#dso-dtor
- */
-int
-__cxa_atexit(void (*func)(void *), void *arg, void *dso)
-{
-	struct atexit_fn *fnp;
-	size_t pgsize = getpagesize();
-	int ret = -1;
-
-	if (pgsize < sizeof(struct atexit))
-		return (-1);
-	_ATEXIT_LOCK();
-	struct atexit *p = __atexit;
-	if (p != NULL) {
-		if (p->ind + 1 >= p->max)
-			p = NULL;
-		else if (mprotect(p, pgsize, PROT_READ | PROT_WRITE))
-			goto unlock;
-	}
-	if (p == NULL) {
-		p = mmap(NULL, pgsize, PROT_READ | PROT_WRITE,
-		    MAP_ANON | MAP_PRIVATE, -1, 0);
-		if (p == MAP_FAILED)
-			goto unlock;
-/* BEGIN android-changed */
-		prctl(PR_SET_VMA, PR_SET_VMA_ANON_NAME, p, pgsize,
-		    "atexit handlers");
-/* END android-changed */
-		if (__atexit == NULL) {
-			memset(&p->fns[0], 0, sizeof(p->fns[0]));
-			p->ind = 1;
-		} else
-			p->ind = 0;
-		p->max = (pgsize - ((char *)&p->fns[0] - (char *)p)) /
-		    sizeof(p->fns[0]);
-		p->next = __atexit;
-		__atexit = p;
-	}
-	fnp = &p->fns[p->ind++];
-	fnp->fn_ptr = func;
-	fnp->fn_arg = arg;
-	fnp->fn_dso = dso;
-	if (mprotect(p, pgsize, PROT_READ))
-		goto unlock;
-	restartloop = 1;
-	ret = 0;
-unlock:
-	_ATEXIT_UNLOCK();
-	return (ret);
-}
-
-/*
- * Call all handlers registered with __cxa_atexit() for the shared
- * object owning 'dso'.
- * Note: if 'dso' is NULL, then all remaining handlers are called.
- */
-void
-__cxa_finalize(void *dso)
-{
-	struct atexit *p, *q;
-	struct atexit_fn fn;
-	int n, pgsize = getpagesize();
-	static int call_depth;
-
-	_ATEXIT_LOCK();
-	call_depth++;
-
-restart:
-	restartloop = 0;
-	for (p = __atexit; p != NULL; p = p->next) {
-		for (n = p->ind; --n >= 0;) {
-			if (p->fns[n].fn_ptr == NULL)
-				continue;	/* already called */
-			if (dso != NULL && dso != p->fns[n].fn_dso)
-				continue;	/* wrong DSO */
-
-			/*
-			 * Mark handler as having been already called to avoid
-			 * dupes and loops, then call the appropriate function.
-			 */
-			fn = p->fns[n];
-			if (mprotect(p, pgsize, PROT_READ | PROT_WRITE) == 0) {
-				p->fns[n].fn_ptr = NULL;
-				mprotect(p, pgsize, PROT_READ);
-			}
-			_ATEXIT_UNLOCK();
-			(*fn.fn_ptr)(fn.fn_arg);
-			_ATEXIT_LOCK();
-			if (restartloop)
-				goto restart;
-		}
-	}
-
-	call_depth--;
-
-	/*
-	 * If called via exit(), unmap the pages since we have now run
-	 * all the handlers.  We defer this until calldepth == 0 so that
-	 * we don't unmap things prematurely if called recursively.
-	 */
-	if (dso == NULL && call_depth == 0) {
-		for (p = __atexit; p != NULL; ) {
-			q = p;
-			p = p->next;
-			munmap(q, pgsize);
-		}
-		__atexit = NULL;
-	}
-	_ATEXIT_UNLOCK();
-
-	/* If called via exit(), flush output of all open files. */
-	if (dso == NULL) {
-		extern void __libc_stdio_cleanup(void);
-		__libc_stdio_cleanup();
-	}
-
-  /* BEGIN android-changed: call __unregister_atfork if dso is not null */
-  if (dso != NULL) {
-    __unregister_atfork(dso);
-  }
-  /* END android-changed */
-}
diff --git a/libdl/Android.bp b/libdl/Android.bp
index 59f1937..f431e84 100644
--- a/libdl/Android.bp
+++ b/libdl/Android.bp
@@ -29,6 +29,11 @@
     sanitize: {
         never: true,
     },
+
+    apex_available: [
+        "//apex_available:platform",
+        "com.android.runtime",
+    ],
 }
 
 cc_library {
@@ -111,7 +116,10 @@
 
     stubs: {
         symbol_file: "libdl.map.txt",
-        versions: ["10000"],
+        versions: [
+            "29",
+            "10000",
+        ],
     },
 
     apex_available: [
diff --git a/libdl/libdl.cpp b/libdl/libdl.cpp
index 1ee4012..a56a5ab 100644
--- a/libdl/libdl.cpp
+++ b/libdl/libdl.cpp
@@ -138,16 +138,4 @@
   return __loader_android_get_application_target_sdk_version();
 }
 
-#if defined(__arm__)
-// An arm32 unwinding table has an R_ARM_NONE relocation to
-// __aeabi_unwind_cpp_pr0. This shared library will never invoke the unwinder,
-// so it doesn't actually need the routine. Define a dummy version here,
-// because the real version calls libc functions (e.g. memcpy, abort), which
-// would create a dependency cycle with libc.so.
-__attribute__((visibility("hidden")))
-void __aeabi_unwind_cpp_pr0() {
-  __builtin_trap();
-}
-#endif
-
 } // extern "C"
diff --git a/libdl/libdl_android.cpp b/libdl/libdl_android.cpp
index 77b3bf8..47a164a 100644
--- a/libdl/libdl_android.cpp
+++ b/libdl/libdl_android.cpp
@@ -115,16 +115,4 @@
   return __loader_android_get_exported_namespace(name);
 }
 
-#if defined(__arm__)
-// An arm32 unwinding table has an R_ARM_NONE relocation to
-// __aeabi_unwind_cpp_pr0. This shared library will never invoke the unwinder,
-// so it doesn't actually need the routine. Define a dummy version here,
-// because the real version calls libc functions (e.g. memcpy, abort), which
-// would create a dependency cycle with libc.so.
-__attribute__((visibility("hidden")))
-void __aeabi_unwind_cpp_pr0() {
-  __builtin_trap();
-}
-#endif
-
 } // extern "C"
diff --git a/libm/Android.bp b/libm/Android.bp
index d4cdd7b..1c4fe55 100644
--- a/libm/Android.bp
+++ b/libm/Android.bp
@@ -499,7 +499,10 @@
 
     stubs: {
         symbol_file: "libm.map.txt",
-        versions: ["10000"],
+        versions: [
+            "29",
+            "10000",
+        ],
     },
 
     apex_available: [
diff --git a/linker/Android.bp b/linker/Android.bp
index 4be080b..3190870 100644
--- a/linker/Android.bp
+++ b/linker/Android.bp
@@ -98,6 +98,7 @@
     static_libs: [
         "libziparchive",
         "libbase",
+        "libdl", // libbase uses dlsym
         "libz",
 
         "libasync_safe",
diff --git a/linker/ld_android.cpp b/linker/ld_android.cpp
index 152c2e2..0239c30 100644
--- a/linker/ld_android.cpp
+++ b/linker/ld_android.cpp
@@ -58,15 +58,3 @@
 __strong_alias(__loader_dl_unwind_find_exidx, __internal_linker_error);
 #endif
 __strong_alias(rtld_db_dlactivity, __internal_linker_error);
-
-#if defined(__arm__)
-// An arm32 unwinding table has an R_ARM_NONE relocation to
-// __aeabi_unwind_cpp_pr0. This shared library will never invoke the unwinder,
-// so it doesn't actually need the routine. Define a dummy version here,
-// because the real version calls libc functions (e.g. memcpy, abort), which
-// would create a dependency cycle with libc.so.
-__attribute__((visibility("hidden")))
-extern "C" void __aeabi_unwind_cpp_pr0() {
-  __builtin_trap();
-}
-#endif
diff --git a/linker/linker_debug.h b/linker/linker_debug.h
index 738ff6f..477b009 100644
--- a/linker/linker_debug.h
+++ b/linker/linker_debug.h
@@ -58,7 +58,7 @@
 #include <async_safe/log.h>
 #include <async_safe/CHECK.h>
 
-#define LINKER_VERBOSITY_PRINT  -1
+#define LINKER_VERBOSITY_PRINT (-1)
 #define LINKER_VERBOSITY_INFO   0
 #define LINKER_VERBOSITY_TRACE  1
 #define LINKER_VERBOSITY_DEBUG  2
diff --git a/tests/Android.bp b/tests/Android.bp
index b840f36..f39aff0 100644
--- a/tests/Android.bp
+++ b/tests/Android.bp
@@ -83,6 +83,7 @@
     defaults: ["bionic_tests_defaults"],
     srcs: [
         "__aeabi_read_tp_test.cpp",
+        "__cxa_atexit_test.cpp",
         "alloca_test.cpp",
         "android_get_device_api_level.cpp",
         "arpa_inet_test.cpp",
diff --git a/tests/__cxa_atexit_test.cpp b/tests/__cxa_atexit_test.cpp
new file mode 100644
index 0000000..6a122d1
--- /dev/null
+++ b/tests/__cxa_atexit_test.cpp
@@ -0,0 +1,77 @@
+/*
+ * Copyright (C) 2020 The Android Open Source Project
+ * All rights reserved.
+ *
+ * Redistribution and use in source and binary forms, with or without
+ * modification, are permitted provided that the following conditions
+ * are met:
+ *  * Redistributions of source code must retain the above copyright
+ *    notice, this list of conditions and the following disclaimer.
+ *  * Redistributions in binary form must reproduce the above copyright
+ *    notice, this list of conditions and the following disclaimer in
+ *    the documentation and/or other materials provided with the
+ *    distribution.
+ *
+ * THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS
+ * "AS IS" AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT
+ * LIMITED TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS
+ * FOR A PARTICULAR PURPOSE ARE DISCLAIMED. IN NO EVENT SHALL THE
+ * COPYRIGHT OWNER OR CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT,
+ * INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING,
+ * BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS
+ * OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED
+ * AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY,
+ * OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT
+ * OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF
+ * SUCH DAMAGE.
+ */
+
+#include <cxxabi.h>
+#include <gtest/gtest.h>
+
+TEST(__cxa_atexit, simple) {
+  int counter = 0;
+
+  __cxxabiv1::__cxa_atexit([](void* arg) { ++*static_cast<int*>(arg); }, &counter, &counter);
+
+  __cxxabiv1::__cxa_finalize(&counter);
+  ASSERT_EQ(counter, 1);
+
+  // The handler won't be called twice.
+  __cxxabiv1::__cxa_finalize(&counter);
+  ASSERT_EQ(counter, 1);
+}
+
+TEST(__cxa_atexit, order) {
+  static std::vector<int> actual;
+
+  char handles[2];
+
+  auto append_to_actual = [](void* arg) {
+    int* idx = static_cast<int*>(arg);
+    actual.push_back(*idx);
+    delete idx;
+  };
+
+  for (int i = 0; i < 500; ++i) {
+    __cxxabiv1::__cxa_atexit(append_to_actual, new int{i}, &handles[i % 2]);
+  }
+
+  __cxxabiv1::__cxa_finalize(&handles[0]);
+
+  for (int i = 500; i < 750; ++i) {
+    __cxxabiv1::__cxa_atexit(append_to_actual, new int{i}, &handles[1]);
+  }
+
+  __cxxabiv1::__cxa_finalize(&handles[1]);
+
+  std::vector<int> expected;
+  for (int i = 498; i >= 0; i -= 2) expected.push_back(i);
+  for (int i = 749; i >= 500; --i) expected.push_back(i);
+  for (int i = 499; i >= 1; i -= 2) expected.push_back(i);
+
+  ASSERT_EQ(expected.size(), actual.size());
+  for (size_t i = 0; i < expected.size(); ++i) {
+    ASSERT_EQ(expected[i], actual[i]) << "index=" << i;
+  }
+}
diff --git a/tests/malloc_test.cpp b/tests/malloc_test.cpp
index 5944414..a2f310e 100644
--- a/tests/malloc_test.cpp
+++ b/tests/malloc_test.cpp
@@ -1225,7 +1225,6 @@
 #if defined(__BIONIC__) && defined(__aarch64__) && defined(ANDROID_EXPERIMENTAL_MTE)
   if (!(getauxval(AT_HWCAP2) & HWCAP2_MTE)) {
     GTEST_SKIP() << "requires MTE support";
-    return;
   }
 
   std::unique_ptr<int[]> p = std::make_unique<int[]>(4);
diff --git a/tests/sys_stat_test.cpp b/tests/sys_stat_test.cpp
index 71591c0..8f1437b 100644
--- a/tests/sys_stat_test.cpp
+++ b/tests/sys_stat_test.cpp
@@ -109,7 +109,6 @@
   int rc = statx(AT_FDCWD, "/proc/version", AT_STATX_SYNC_AS_STAT, STATX_ALL, &sx);
   if (rc == -1 && errno == ENOSYS) {
     GTEST_SKIP() << "statx returned ENOSYS";
-    return;
   }
   ASSERT_EQ(0, rc);
   struct stat64 sb;