diff --git a/libc/include/bits/posix_limits.h b/libc/include/bits/posix_limits.h
index c498c69..db09bd7 100644
--- a/libc/include/bits/posix_limits.h
+++ b/libc/include/bits/posix_limits.h
@@ -31,20 +31,22 @@
 
 #include <sys/cdefs.h>
 
+#define __BIONIC_POSIX_FEATURE_SINCE(level) (((__ANDROID_API__) >= level) ? 200809L : -1)
+
 /* Any constant values here other than -1 or 200809L are explicitly specified by POSIX.1-2008. */
 /* Keep this list sorted by name. */
-#define _POSIX_ADVISORY_INFO        200809L
+#define _POSIX_ADVISORY_INFO __BIONIC_POSIX_FEATURE_SINCE(23) /* posix_memadvise arrived late. */
 #define _POSIX_AIO_LISTIO_MAX       2
 #define _POSIX_AIO_MAX              1
 #define _POSIX_ARG_MAX              4096
 #define _POSIX_ASYNCHRONOUS_IO      -1  /* not implemented */
-#define _POSIX_BARRIERS             200809L
+#define _POSIX_BARRIERS __BIONIC_POSIX_FEATURE_SINCE(24)
 #define _POSIX_CHILD_MAX            25
 #define _POSIX_CHOWN_RESTRICTED     1  /* yes, chown requires appropriate privileges */
 #define _POSIX_CLOCK_SELECTION      200809L
 #define _POSIX_CPUTIME              0  /* Use sysconf to detect support at runtime. */
 #define _POSIX_DELAYTIMER_MAX       32
-#define _POSIX_FSYNC                200809L  /* fdatasync() supported */
+#define _POSIX_FSYNC 200809L
 #define _POSIX_HOST_NAME_MAX        255
 #define _POSIX_IPV6                 200809L
 #define _POSIX_JOB_CONTROL          1  /* job control is a Linux feature */
@@ -53,8 +55,8 @@
 #define _POSIX_MAPPED_FILES         200809L  /* mmap-ed files supported */
 #define _POSIX_MAX_CANON            255
 #define _POSIX_MAX_INPUT            255
-#define _POSIX_MEMLOCK              200809L
-#define _POSIX_MEMLOCK_RANGE        200809L
+#define _POSIX_MEMLOCK __BIONIC_POSIX_FEATURE_SINCE(17) /* mlockall. */
+#define _POSIX_MEMLOCK_RANGE        200809L /* mlock. */
 #define _POSIX_MEMORY_PROTECTION    200809L
 #define _POSIX_MESSAGE_PASSING      -1  /* not implemented */
 #define _POSIX_MONOTONIC_CLOCK      0  /* the monotonic clock may be available; ask sysconf */
@@ -81,7 +83,7 @@
 #define _POSIX_SHELL                1   /* system() supported */
 #define _POSIX_SIGQUEUE_MAX         32
 #define _POSIX_SPAWN                -1  /* not implemented */
-#define _POSIX_SPIN_LOCKS           200809L
+#define _POSIX_SPIN_LOCKS __BIONIC_POSIX_FEATURE_SINCE(24)
 #define _POSIX_SPORADIC_SERVER      -1  /* not implemented */
 #define _POSIX_SSIZE_MAX            32767
 #define _POSIX_STREAM_MAX           8
@@ -103,7 +105,7 @@
 #define _POSIX_THREAD_SAFE_FUNCTIONS 200809L
 #define _POSIX_THREAD_SPORADIC_SERVER -1  /* not implemented */
 #define _POSIX_THREAD_THREADS_MAX   64
-#define _POSIX_TIMEOUTS             200809L
+#define _POSIX_TIMEOUTS __BIONIC_POSIX_FEATURE_SINCE(21) /* pthread_mutex_timedlock arrived late. */
 #define _POSIX_TIMERS               200809L  /* Posix timers are supported */
 #define _POSIX_TIMER_MAX            32
 #define _POSIX_TRACE                -1  /* not implemented */
diff --git a/libc/include/bits/pthread_types.h b/libc/include/bits/pthread_types.h
index 7fc379b..a173e3c 100644
--- a/libc/include/bits/pthread_types.h
+++ b/libc/include/bits/pthread_types.h
@@ -44,6 +44,7 @@
 #endif
 } pthread_attr_t;
 
+#if __ANDROID_API__ >= __ANDROID_API_N__
 typedef struct {
 #if defined(__LP64__)
   int64_t __private[4];
@@ -51,8 +52,11 @@
   int32_t __private[8];
 #endif
 } pthread_barrier_t;
+#endif
 
+#if __ANDROID_API__ >= __ANDROID_API_N__
 typedef int pthread_barrierattr_t;
+#endif
 
 typedef struct {
 #if defined(__LP64__)
@@ -88,6 +92,7 @@
 
 typedef long pthread_rwlockattr_t;
 
+#if __ANDROID_API__ >= __ANDROID_API_N__
 typedef struct {
 #if defined(__LP64__)
   int64_t __private;
@@ -95,6 +100,7 @@
   int32_t __private[2];
 #endif
 } pthread_spinlock_t;
+#endif
 
 typedef long pthread_t;
 
diff --git a/libc/include/pthread.h b/libc/include/pthread.h
index 20fd566..ae4fdce 100644
--- a/libc/include/pthread.h
+++ b/libc/include/pthread.h
@@ -69,7 +69,9 @@
 
 #define PTHREAD_ONCE_INIT 0
 
+#if __ANDROID_API__ >= __ANDROID_API_N__
 #define PTHREAD_BARRIER_SERIAL_THREAD -1
+#endif
 
 #if defined(__LP64__)
 #define PTHREAD_STACK_MIN (4 * PAGE_SIZE)
@@ -178,23 +180,29 @@
 int pthread_rwlock_unlock(pthread_rwlock_t* _Nonnull);
 int pthread_rwlock_wrlock(pthread_rwlock_t* _Nonnull);
 
+#if __ANDROID_API__ >= __ANDROID_API_N__
 int pthread_barrierattr_init(pthread_barrierattr_t* _Nonnull attr) __INTRODUCED_IN(24);
 int pthread_barrierattr_destroy(pthread_barrierattr_t* _Nonnull attr) __INTRODUCED_IN(24);
 int pthread_barrierattr_getpshared(const pthread_barrierattr_t* _Nonnull attr,
                                    int* _Nonnull pshared) __INTRODUCED_IN(24);
 int pthread_barrierattr_setpshared(pthread_barrierattr_t* _Nonnull attr, int pshared)
   __INTRODUCED_IN(24);
+#endif
 
+#if __ANDROID_API__ >= __ANDROID_API_N__
 int pthread_barrier_init(pthread_barrier_t* _Nonnull, const pthread_barrierattr_t*, unsigned)
   __INTRODUCED_IN(24);
 int pthread_barrier_destroy(pthread_barrier_t* _Nonnull) __INTRODUCED_IN(24);
 int pthread_barrier_wait(pthread_barrier_t* _Nonnull) __INTRODUCED_IN(24);
+#endif
 
+#if __ANDROID_API__ >= __ANDROID_API_N__
 int pthread_spin_destroy(pthread_spinlock_t* _Nonnull) __INTRODUCED_IN(24);
 int pthread_spin_init(pthread_spinlock_t* _Nonnull, int) __INTRODUCED_IN(24);
 int pthread_spin_lock(pthread_spinlock_t* _Nonnull) __INTRODUCED_IN(24);
 int pthread_spin_trylock(pthread_spinlock_t* _Nonnull) __INTRODUCED_IN(24);
 int pthread_spin_unlock(pthread_spinlock_t* _Nonnull) __INTRODUCED_IN(24);
+#endif
 
 pthread_t pthread_self(void) __attribute_const__;
 
diff --git a/linker/linker.cpp b/linker/linker.cpp
index a05cd3b..4b00f80 100644
--- a/linker/linker.cpp
+++ b/linker/linker.cpp
@@ -1673,6 +1673,8 @@
     root = root->get_local_group_root();
   }
 
+  ScopedTrace trace((std::string("unload ") + root->get_realpath()).c_str());
+
   if (!root->can_unload()) {
     TRACE("not unloading \"%s\" - the binary is flagged with NODELETE", root->get_realpath());
     return;
@@ -1999,6 +2001,7 @@
               const char* sym_ver,
               const void* caller_addr,
               void** symbol) {
+  ScopedTrace trace("dlsym");
 #if !defined(__LP64__)
   if (handle == nullptr) {
     DL_ERR("dlsym failed: library handle is null");
@@ -2074,6 +2077,7 @@
 }
 
 int do_dlclose(void* handle) {
+  ScopedTrace trace("dlclose");
   ProtectedDataGuard guard;
   soinfo* si = soinfo_from_handle(handle);
   if (si == nullptr) {
diff --git a/linker/linker_soinfo.cpp b/linker/linker_soinfo.cpp
index 15f2502..1d59dbb 100644
--- a/linker/linker_soinfo.cpp
+++ b/linker/linker_soinfo.cpp
@@ -426,7 +426,8 @@
   if (!constructors_called) {
     return;
   }
-  TRACE("\"%s\": calling destructors", get_realpath());
+
+  ScopedTrace trace((std::string("calling destructors: ") + get_realpath()).c_str());
 
   // DT_FINI_ARRAY must be parsed in reverse order.
   call_array("DT_FINI_ARRAY", fini_array_, fini_array_count_, true, get_realpath());