diff --git a/libc/bionic/dirent.cpp b/libc/bionic/dirent.cpp
index 3a7b5b4..74297d8 100644
--- a/libc/bionic/dirent.cpp
+++ b/libc/bionic/dirent.cpp
@@ -36,7 +36,8 @@
 #include <sys/types.h>
 #include <unistd.h>
 
-#include <private/ScopedPthreadMutexLocker.h>
+#include "private/ErrnoRestorer.h"
+#include "private/ScopedPthreadMutexLocker.h"
 
 struct DIR {
   int fd_;
@@ -108,7 +109,7 @@
 }
 
 int readdir_r(DIR* d, dirent* entry, dirent** result) {
-  int saved_errno = errno;
+  ErrnoRestorer errno_restorer;
 
   *result = NULL;
   errno = 0;
@@ -124,7 +125,6 @@
     memcpy(entry, next, next->d_reclen);
     *result = entry;
   }
-  errno = saved_errno;
   return 0;
 }
 
diff --git a/libc/bionic/pthread.c b/libc/bionic/pthread.c
index e1ace7d..bdf2b87 100644
--- a/libc/bionic/pthread.c
+++ b/libc/bionic/pthread.c
@@ -26,23 +26,12 @@
  * SUCH DAMAGE.
  */
 
-#include <assert.h>
-#include <errno.h>
-#include <fcntl.h>
-#include <limits.h>
-#include <malloc.h>
-#include <memory.h>
 #include <pthread.h>
-#include <signal.h>
-#include <stdint.h>
-#include <stdio.h>
-#include <stdlib.h>
+
+#include <errno.h>
+#include <limits.h>
 #include <sys/atomics.h>
 #include <sys/mman.h>
-#include <sys/prctl.h>
-#include <sys/stat.h>
-#include <sys/types.h>
-#include <time.h>
 #include <unistd.h>
 
 #include "bionic_atomic_inline.h"
@@ -84,23 +73,8 @@
 
 static const int kPthreadInitFailed = 1;
 
-#define PTHREAD_ATTR_FLAG_DETACHED      0x00000001
-#define PTHREAD_ATTR_FLAG_USER_STACK    0x00000002
-
-#define DEFAULT_STACKSIZE (1024 * 1024)
-
 static pthread_mutex_t mmap_lock = PTHREAD_MUTEX_INITIALIZER;
 
-
-static const pthread_attr_t gDefaultPthreadAttr = {
-    .flags = 0,
-    .stack_base = NULL,
-    .stack_size = DEFAULT_STACKSIZE,
-    .guard_size = PAGE_SIZE,
-    .sched_policy = SCHED_NORMAL,
-    .sched_priority = 0
-};
-
 __LIBC_HIDDEN__ pthread_internal_t* gThreadList = NULL;
 __LIBC_HIDDEN__ pthread_mutex_t gThreadListLock = PTHREAD_MUTEX_INITIALIZER;
 static pthread_mutex_t gDebuggerNotificationLock = PTHREAD_MUTEX_INITIALIZER;
@@ -306,7 +280,7 @@
 
     pthread_internal_t* thread = calloc(sizeof(*thread), 1);
     if (thread == NULL) {
-        return ENOMEM;
+        return EAGAIN;
     }
     thread->allocated_on_heap = true;
 
@@ -321,7 +295,7 @@
         stack = mkstack(stack_size, attr->guard_size);
         if (stack == NULL) {
             free(thread);
-            return ENOMEM;
+            return EAGAIN;
         }
     }
 
@@ -379,152 +353,6 @@
 }
 
 
-int pthread_attr_init(pthread_attr_t * attr)
-{
-    *attr = gDefaultPthreadAttr;
-    return 0;
-}
-
-int pthread_attr_destroy(pthread_attr_t * attr)
-{
-    memset(attr, 0x42, sizeof(pthread_attr_t));
-    return 0;
-}
-
-int pthread_attr_setdetachstate(pthread_attr_t * attr, int state)
-{
-    if (state == PTHREAD_CREATE_DETACHED) {
-        attr->flags |= PTHREAD_ATTR_FLAG_DETACHED;
-    } else if (state == PTHREAD_CREATE_JOINABLE) {
-        attr->flags &= ~PTHREAD_ATTR_FLAG_DETACHED;
-    } else {
-        return EINVAL;
-    }
-    return 0;
-}
-
-int pthread_attr_getdetachstate(pthread_attr_t const * attr, int * state)
-{
-    *state = (attr->flags & PTHREAD_ATTR_FLAG_DETACHED)
-           ? PTHREAD_CREATE_DETACHED
-           : PTHREAD_CREATE_JOINABLE;
-    return 0;
-}
-
-int pthread_attr_setschedpolicy(pthread_attr_t * attr, int policy)
-{
-    attr->sched_policy = policy;
-    return 0;
-}
-
-int pthread_attr_getschedpolicy(pthread_attr_t const * attr, int * policy)
-{
-    *policy = attr->sched_policy;
-    return 0;
-}
-
-int pthread_attr_setschedparam(pthread_attr_t * attr, struct sched_param const * param)
-{
-    attr->sched_priority = param->sched_priority;
-    return 0;
-}
-
-int pthread_attr_getschedparam(pthread_attr_t const * attr, struct sched_param * param)
-{
-    param->sched_priority = attr->sched_priority;
-    return 0;
-}
-
-int pthread_attr_setstacksize(pthread_attr_t * attr, size_t stack_size)
-{
-    if ((stack_size & (PAGE_SIZE - 1) || stack_size < PTHREAD_STACK_MIN)) {
-        return EINVAL;
-    }
-    attr->stack_size = stack_size;
-    return 0;
-}
-
-int pthread_attr_getstacksize(pthread_attr_t const * attr, size_t * stack_size)
-{
-    *stack_size = attr->stack_size;
-    return 0;
-}
-
-int pthread_attr_setstackaddr(pthread_attr_t * attr __attribute__((unused)),
-                               void * stack_addr __attribute__((unused)))
-{
-    // This was removed from POSIX.1-2008, and is not implemented on bionic.
-    // Needed for ABI compatibility with the NDK.
-    return ENOSYS;
-}
-
-int pthread_attr_getstackaddr(pthread_attr_t const * attr, void ** stack_addr)
-{
-    // This was removed from POSIX.1-2008.
-    // Needed for ABI compatibility with the NDK.
-    *stack_addr = (char*)attr->stack_base + attr->stack_size;
-    return 0;
-}
-
-int pthread_attr_setstack(pthread_attr_t * attr, void * stack_base, size_t stack_size)
-{
-    if ((stack_size & (PAGE_SIZE - 1) || stack_size < PTHREAD_STACK_MIN)) {
-        return EINVAL;
-    }
-    if ((uint32_t)stack_base & (PAGE_SIZE - 1)) {
-        return EINVAL;
-    }
-    attr->stack_base = stack_base;
-    attr->stack_size = stack_size;
-    return 0;
-}
-
-int pthread_attr_getstack(pthread_attr_t const * attr, void ** stack_base, size_t * stack_size)
-{
-    *stack_base = attr->stack_base;
-    *stack_size = attr->stack_size;
-    return 0;
-}
-
-int pthread_attr_setguardsize(pthread_attr_t * attr, size_t guard_size)
-{
-    if (guard_size & (PAGE_SIZE - 1) || guard_size < PAGE_SIZE) {
-        return EINVAL;
-    }
-
-    attr->guard_size = guard_size;
-    return 0;
-}
-
-int pthread_attr_getguardsize(pthread_attr_t const * attr, size_t * guard_size)
-{
-    *guard_size = attr->guard_size;
-    return 0;
-}
-
-int pthread_getattr_np(pthread_t thid, pthread_attr_t * attr)
-{
-    pthread_internal_t * thread = (pthread_internal_t *)thid;
-    *attr = thread->attr;
-    return 0;
-}
-
-int pthread_attr_setscope(pthread_attr_t *attr __attribute__((unused)), int  scope)
-{
-    if (scope == PTHREAD_SCOPE_SYSTEM)
-        return 0;
-    if (scope == PTHREAD_SCOPE_PROCESS)
-        return ENOTSUP;
-
-    return EINVAL;
-}
-
-int pthread_attr_getscope(pthread_attr_t const *attr __attribute__((unused)))
-{
-    return PTHREAD_SCOPE_SYSTEM;
-}
-
-
 /* CAVEAT: our implementation of pthread_cleanup_push/pop doesn't support C++ exceptions
  *         and thread cancelation
  */
@@ -1881,57 +1709,6 @@
     return 0;
 }
 
-/* This value is not exported by kernel headers, so hardcode it here */
-#define MAX_TASK_COMM_LEN	16
-#define TASK_COMM_FMT 		"/proc/self/task/%u/comm"
-
-int pthread_setname_np(pthread_t thid, const char *thname)
-{
-    size_t thname_len;
-    int saved_errno, ret;
-
-    if (thid == 0 || thname == NULL)
-        return EINVAL;
-
-    thname_len = strlen(thname);
-    if (thname_len >= MAX_TASK_COMM_LEN)
-        return ERANGE;
-
-    saved_errno = errno;
-    if (thid == pthread_self())
-    {
-        ret = prctl(PR_SET_NAME, (unsigned long)thname, 0, 0, 0) ? errno : 0;
-    }
-    else
-    {
-        /* Have to change another thread's name */
-        pthread_internal_t *thread = (pthread_internal_t *)thid;
-        char comm_name[sizeof(TASK_COMM_FMT) + 8];
-        ssize_t n;
-        int fd;
-
-        snprintf(comm_name, sizeof(comm_name), TASK_COMM_FMT, (unsigned int)thread->kernel_id);
-        fd = open(comm_name, O_RDWR);
-        if (fd == -1)
-        {
-            ret = errno;
-            goto exit;
-        }
-        n = TEMP_FAILURE_RETRY(write(fd, thname, thname_len));
-        close(fd);
-
-        if (n < 0)
-            ret = errno;
-        else if ((size_t)n != thname_len)
-            ret = EIO;
-        else
-            ret = 0;
-    }
-exit:
-    errno = saved_errno;
-    return ret;
-}
-
 /* Return the kernel thread ID for a pthread.
  * This is only defined for implementations where pthread <-> kernel is 1:1, which this is.
  * Not the same as pthread_getthreadid_np, which is commonly defined to be opaque.
diff --git a/libc/bionic/pthread_attr.cpp b/libc/bionic/pthread_attr.cpp
new file mode 100644
index 0000000..831a28e
--- /dev/null
+++ b/libc/bionic/pthread_attr.cpp
@@ -0,0 +1,165 @@
+/*
+ * Copyright (C) 2008 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 <pthread.h>
+
+#include "pthread_internal.h"
+
+#define DEFAULT_STACKSIZE (1024 * 1024)
+
+const pthread_attr_t gDefaultPthreadAttr = {
+  .flags = 0,
+  .stack_base = NULL,
+  .stack_size = DEFAULT_STACKSIZE,
+  .guard_size = PAGE_SIZE,
+  .sched_policy = SCHED_NORMAL,
+  .sched_priority = 0
+};
+
+int pthread_attr_init(pthread_attr_t* attr) {
+  *attr = gDefaultPthreadAttr;
+  return 0;
+}
+
+int pthread_attr_destroy(pthread_attr_t* attr) {
+  memset(attr, 0x42, sizeof(pthread_attr_t));
+  return 0;
+}
+
+int pthread_attr_setdetachstate(pthread_attr_t* attr, int state) {
+  if (state == PTHREAD_CREATE_DETACHED) {
+    attr->flags |= PTHREAD_ATTR_FLAG_DETACHED;
+  } else if (state == PTHREAD_CREATE_JOINABLE) {
+    attr->flags &= ~PTHREAD_ATTR_FLAG_DETACHED;
+  } else {
+    return EINVAL;
+  }
+  return 0;
+}
+
+int pthread_attr_getdetachstate(pthread_attr_t const* attr, int* state) {
+  *state = (attr->flags & PTHREAD_ATTR_FLAG_DETACHED) ? PTHREAD_CREATE_DETACHED : PTHREAD_CREATE_JOINABLE;
+  return 0;
+}
+
+int pthread_attr_setschedpolicy(pthread_attr_t* attr, int policy) {
+  attr->sched_policy = policy;
+  return 0;
+}
+
+int pthread_attr_getschedpolicy(pthread_attr_t const* attr, int* policy) {
+  *policy = attr->sched_policy;
+  return 0;
+}
+
+int pthread_attr_setschedparam(pthread_attr_t * attr, struct sched_param const* param) {
+  attr->sched_priority = param->sched_priority;
+  return 0;
+}
+
+int pthread_attr_getschedparam(pthread_attr_t const* attr, struct sched_param* param) {
+  param->sched_priority = attr->sched_priority;
+  return 0;
+}
+
+int pthread_attr_setstacksize(pthread_attr_t* attr, size_t stack_size) {
+  if ((stack_size & (PAGE_SIZE - 1) || stack_size < PTHREAD_STACK_MIN)) {
+    return EINVAL;
+  }
+  attr->stack_size = stack_size;
+  return 0;
+}
+
+int pthread_attr_getstacksize(pthread_attr_t const* attr, size_t* stack_size) {
+  *stack_size = attr->stack_size;
+  return 0;
+}
+
+int pthread_attr_setstackaddr(pthread_attr_t*, void*) {
+  // This was removed from POSIX.1-2008, and is not implemented on bionic.
+  // Needed for ABI compatibility with the NDK.
+  return ENOSYS;
+}
+
+int pthread_attr_getstackaddr(pthread_attr_t const* attr, void** stack_addr) {
+  // This was removed from POSIX.1-2008.
+  // Needed for ABI compatibility with the NDK.
+  *stack_addr = (char*)attr->stack_base + attr->stack_size;
+  return 0;
+}
+
+int pthread_attr_setstack(pthread_attr_t* attr, void* stack_base, size_t stack_size) {
+  if ((stack_size & (PAGE_SIZE - 1) || stack_size < PTHREAD_STACK_MIN)) {
+    return EINVAL;
+  }
+  if ((uint32_t)stack_base & (PAGE_SIZE - 1)) {
+    return EINVAL;
+  }
+  attr->stack_base = stack_base;
+  attr->stack_size = stack_size;
+  return 0;
+}
+
+int pthread_attr_getstack(pthread_attr_t const* attr, void** stack_base, size_t* stack_size) {
+  *stack_base = attr->stack_base;
+  *stack_size = attr->stack_size;
+  return 0;
+}
+
+int pthread_attr_setguardsize(pthread_attr_t* attr, size_t guard_size) {
+  if (guard_size & (PAGE_SIZE - 1) || guard_size < PAGE_SIZE) {
+    return EINVAL;
+  }
+  attr->guard_size = guard_size;
+  return 0;
+}
+
+int pthread_attr_getguardsize(pthread_attr_t const* attr, size_t* guard_size) {
+  *guard_size = attr->guard_size;
+  return 0;
+}
+
+int pthread_getattr_np(pthread_t thid, pthread_attr_t* attr) {
+  pthread_internal_t* thread = (pthread_internal_t*) thid;
+  *attr = thread->attr;
+  return 0;
+}
+
+int pthread_attr_setscope(pthread_attr_t* , int scope) {
+  if (scope == PTHREAD_SCOPE_SYSTEM) {
+    return 0;
+  }
+  if (scope == PTHREAD_SCOPE_PROCESS) {
+    return ENOTSUP;
+  }
+  return EINVAL;
+}
+
+int pthread_attr_getscope(pthread_attr_t const*) {
+  return PTHREAD_SCOPE_SYSTEM;
+}
diff --git a/libc/bionic/pthread_internal.h b/libc/bionic/pthread_internal.h
index 24b420c..63071d9 100644
--- a/libc/bionic/pthread_internal.h
+++ b/libc/bionic/pthread_internal.h
@@ -62,6 +62,10 @@
 
 __LIBC_HIDDEN__ void pthread_key_clean_all(void);
 
+#define PTHREAD_ATTR_FLAG_DETACHED      0x00000001
+#define PTHREAD_ATTR_FLAG_USER_STACK    0x00000002
+
+extern __LIBC_HIDDEN__ const pthread_attr_t gDefaultPthreadAttr;
 extern pthread_internal_t* gThreadList;
 extern pthread_mutex_t gThreadListLock;
 
diff --git a/libc/bionic/pthread_key.cpp b/libc/bionic/pthread_key.cpp
index 00dacba..b01f9bd 100644
--- a/libc/bionic/pthread_key.cpp
+++ b/libc/bionic/pthread_key.cpp
@@ -26,33 +26,10 @@
  * SUCH DAMAGE.
  */
 
-#include <assert.h>
-#include <errno.h>
-#include <fcntl.h>
-#include <limits.h>
-#include <malloc.h>
-#include <memory.h>
 #include <pthread.h>
-#include <signal.h>
-#include <stdint.h>
-#include <stdio.h>
-#include <stdlib.h>
-#include <sys/atomics.h>
-#include <sys/mman.h>
-#include <sys/prctl.h>
-#include <sys/stat.h>
-#include <sys/types.h>
-#include <time.h>
-#include <unistd.h>
 
-#include "bionic_atomic_inline.h"
-#include "bionic_futex.h"
-#include "bionic_pthread.h"
-#include "bionic_ssp.h"
 #include "bionic_tls.h"
-#include "debug_format.h"
 #include "pthread_internal.h"
-#include "thread_private.h"
 
 /* A technical note regarding our thread-local-storage (TLS) implementation:
  *
diff --git a/libc/bionic/pthread_setname_np.cpp b/libc/bionic/pthread_setname_np.cpp
new file mode 100644
index 0000000..88b86ec
--- /dev/null
+++ b/libc/bionic/pthread_setname_np.cpp
@@ -0,0 +1,79 @@
+/*
+ * Copyright (C) 2008 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 <pthread.h>
+
+#include <fcntl.h>
+#include <stdio.h> // For snprintf.
+#include <sys/prctl.h>
+#include <sys/stat.h>
+#include <sys/types.h>
+#include <unistd.h>
+
+#include "pthread_internal.h"
+#include "private/ErrnoRestorer.h"
+
+// This value is not exported by kernel headers.
+#define MAX_TASK_COMM_LEN 16
+#define TASK_COMM_FMT "/proc/self/task/%u/comm"
+
+int pthread_setname_np(pthread_t thread, const char* thread_name) {
+  ErrnoRestorer errno_restorer;
+
+  if (thread == 0 || thread_name == NULL) {
+    return EINVAL;
+  }
+
+  size_t thread_name_len = strlen(thread_name);
+  if (thread_name_len >= MAX_TASK_COMM_LEN) {
+    return ERANGE;
+  }
+
+  // Changing our own name is an easy special case.
+  if (thread == pthread_self()) {
+    return prctl(PR_SET_NAME, (unsigned long)thread_name, 0, 0, 0) ? errno : 0;
+  }
+
+  // Have to change another thread's name.
+  pthread_internal_t* t = reinterpret_cast<pthread_internal_t*>(thread);
+  char comm_name[sizeof(TASK_COMM_FMT) + 8];
+  snprintf(comm_name, sizeof(comm_name), TASK_COMM_FMT, (unsigned int) t->kernel_id);
+  int fd = open(comm_name, O_RDWR);
+  if (fd == -1) {
+    return errno;
+  }
+  ssize_t n = TEMP_FAILURE_RETRY(write(fd, thread_name, thread_name_len));
+  close(fd);
+
+  if (n < 0) {
+    return errno;
+  } else if ((size_t)n != thread_name_len) {
+    return EIO;
+  }
+  return 0;
+}
diff --git a/libc/bionic/pthread_sigmask.cpp b/libc/bionic/pthread_sigmask.cpp
index 9c9dc3e..e4e1b2b 100644
--- a/libc/bionic/pthread_sigmask.cpp
+++ b/libc/bionic/pthread_sigmask.cpp
@@ -30,12 +30,13 @@
 #include <pthread.h>
 #include <signal.h>
 
-#include <private/kernel_sigset_t.h>
+#include "private/ErrnoRestorer.h"
+#include "private/kernel_sigset_t.h"
 
 extern "C" int __rt_sigprocmask(int, const kernel_sigset_t*, kernel_sigset_t*, size_t);
 
 int pthread_sigmask(int how, const sigset_t* iset, sigset_t* oset) {
-  int old_errno = errno;
+  ErrnoRestorer errno_restorer;
 
   // 'in_set_ptr' is the second parameter to __rt_sigprocmask. It must be NULL
   // if 'set' is NULL to ensure correct semantics (which in this case would
@@ -48,15 +49,13 @@
   }
 
   kernel_sigset_t out_set;
-  int result = __rt_sigprocmask(how, in_set_ptr, &out_set, sizeof(out_set));
-  if (result < 0) {
-    result = errno;
+  if (__rt_sigprocmask(how, in_set_ptr, &out_set, sizeof(out_set)) == -1) {
+    return errno;
   }
 
   if (oset != NULL) {
     *oset = out_set.bionic;
   }
 
-  errno = old_errno;
-  return result;
+  return 0;
 }
diff --git a/libc/bionic/strerror_r.cpp b/libc/bionic/strerror_r.cpp
index 646cc52..81120ec 100644
--- a/libc/bionic/strerror_r.cpp
+++ b/libc/bionic/strerror_r.cpp
@@ -7,6 +7,8 @@
 #include <stdio.h>
 #include <string.h>
 
+#include "private/ErrnoRestorer.h"
+
 struct Pair {
   int code;
   const char* msg;
@@ -42,7 +44,7 @@
 }
 
 int strerror_r(int error_number, char* buf, size_t buf_len) {
-  int saved_errno = errno;
+  ErrnoRestorer errno_restorer;
   size_t length;
 
   const char* error_name = __strerror_lookup(error_number);
@@ -52,11 +54,10 @@
     length = snprintf(buf, buf_len, "Unknown error %d", error_number);
   }
   if (length >= buf_len) {
-    errno = ERANGE;
+    errno_restorer.override(ERANGE);
     return -1;
   }
 
-  errno = saved_errno;
   return 0;
 }
 
diff --git a/libc/bionic/stubs.cpp b/libc/bionic/stubs.cpp
index 3f24d1b..8ddc326 100644
--- a/libc/bionic/stubs.cpp
+++ b/libc/bionic/stubs.cpp
@@ -31,15 +31,17 @@
 #include <grp.h>
 #include <mntent.h>
 #include <netdb.h>
-#include <private/android_filesystem_config.h>
-#include <private/debug_format.h>
-#include <private/logd.h>
 #include <pthread.h>
 #include <pwd.h>
 #include <stdio.h>
 #include <stdlib.h>
 #include <unistd.h>
 
+#include "private/android_filesystem_config.h"
+#include "private/debug_format.h"
+#include "private/ErrnoRestorer.h"
+#include "private/logd.h"
+
 // Thread-specific state for the non-reentrant functions.
 static pthread_once_t stubs_once = PTHREAD_ONCE_INIT;
 static pthread_key_t stubs_key;
@@ -58,7 +60,7 @@
                       passwd** result) {
   // getpwnam_r and getpwuid_r don't modify errno, but library calls we
   // make might.
-  int old_errno = errno;
+  ErrnoRestorer errno_restorer;
   *result = NULL;
 
   // Our implementation of getpwnam(3) and getpwuid(3) use thread-local
@@ -69,9 +71,7 @@
   // POSIX allows failure to find a match to be considered a non-error.
   // Reporting success (0) but with *result NULL is glibc's behavior.
   if (src == NULL) {
-    int rc = (errno == ENOENT) ? 0 : errno;
-    errno = old_errno;
-    return rc;
+    return (errno == ENOENT) ? 0 : errno;
   }
 
   // Work out where our strings will go in 'buf', and whether we've got
@@ -84,13 +84,11 @@
   dst->pw_shell = buf + required_byte_count;
   required_byte_count += strlen(src->pw_shell) + 1;
   if (byte_count < required_byte_count) {
-    errno = old_errno;
     return ERANGE;
   }
 
   // Copy the strings.
-  snprintf(buf, byte_count, "%s%c%s%c%s",
-           src->pw_name, 0, src->pw_dir, 0, src->pw_shell);
+  snprintf(buf, byte_count, "%s%c%s%c%s", src->pw_name, 0, src->pw_dir, 0, src->pw_shell);
 
   // pw_passwd is non-POSIX and unused (always NULL) in bionic.
   // pw_gecos is non-POSIX and missing in bionic.
@@ -101,7 +99,6 @@
   dst->pw_uid = src->pw_uid;
 
   *result = dst;
-  errno = old_errno;
   return 0;
 }
 
diff --git a/libc/bionic/sysconf.cpp b/libc/bionic/sysconf.cpp
index f4845e1..869faef 100644
--- a/libc/bionic/sysconf.cpp
+++ b/libc/bionic/sysconf.cpp
@@ -306,7 +306,7 @@
       return _POSIX_THREAD_DESTRUCTOR_ITERATIONS;
 
     case _SC_THREAD_KEYS_MAX:
-      return (BIONIC_TLS_SLOTS - TLS_SLOT_FIRST_USER_SLOT);
+      return (BIONIC_TLS_SLOTS - TLS_SLOT_FIRST_USER_SLOT - GLOBAL_INIT_THREAD_LOCAL_BUFFER_COUNT);
 
     case _SC_THREAD_STACK_MIN:    return SYSTEM_THREAD_STACK_MIN;
     case _SC_THREAD_THREADS_MAX:  return SYSTEM_THREAD_THREADS_MAX;
diff --git a/libc/bionic/tmpfile.cpp b/libc/bionic/tmpfile.cpp
index b97cc6c..8419ff5 100644
--- a/libc/bionic/tmpfile.cpp
+++ b/libc/bionic/tmpfile.cpp
@@ -38,6 +38,8 @@
 #include <sys/types.h>
 #include <unistd.h>
 
+#include "private/ErrnoRestorer.h"
+
 class ScopedSignalBlocker {
  public:
   ScopedSignalBlocker() {
@@ -77,9 +79,8 @@
     struct stat sb;
     int rc = fstat(fd, &sb);
     if (rc == -1) {
-      int old_errno = errno;
+      ErrnoRestorer errno_restorer;
       close(fd);
-      errno = old_errno;
       return NULL;
     }
   }
@@ -91,9 +92,8 @@
   }
 
   // Failure. Clean up. We already unlinked, so we just need to close.
-  int old_errno = errno;
+  ErrnoRestorer errno_restorer;
   close(fd);
-  errno = old_errno;
   return NULL;
 }