[libc-commits] [libc] [libcxx] [llvm] libcxx build test (PR #193840)

Schrodinger ZHU Yifan via libc-commits libc-commits at lists.llvm.org
Fri Apr 24 11:01:17 PDT 2026


https://github.com/SchrodingerZhu updated https://github.com/llvm/llvm-project/pull/193840

>From c98e83145a800ddb2fa3c3fef2dac6f6edb6727f Mon Sep 17 00:00:00 2001
From: Schrodinger ZHU Yifan <yifanzhu at rochester.edu>
Date: Fri, 24 Apr 2026 11:19:24 -0400
Subject: [PATCH 1/4] [libc] implement recursive mutex and fix wrong
 initializer

---
 .../include/llvm-libc-macros/pthread-macros.h | 14 +--
 libc/include/llvm-libc-types/CMakeLists.txt   |  2 +-
 libc/include/llvm-libc-types/__mutex_type.h   | 17 ++--
 libc/src/__support/threads/CMakeLists.txt     |  2 +
 libc/src/__support/threads/fork_callbacks.cpp |  4 +-
 libc/src/__support/threads/linux/barrier.cpp  |  7 +-
 libc/src/__support/threads/mutex_common.h     |  1 +
 libc/src/__support/threads/thread.cpp         |  8 +-
 libc/src/__support/threads/unix_mutex.h       | 96 ++++++++++++-------
 libc/src/pthread/pthread_mutex_init.cpp       | 38 ++++++--
 libc/src/stdlib/atexit.cpp                    |  3 +-
 libc/src/threads/mtx_init.cpp                 | 14 +--
 .../integration/src/pthread/CMakeLists.txt    |  3 +
 .../src/pthread/pthread_mutex_test.cpp        | 76 ++++++++++++++-
 .../test/integration/src/threads/mtx_test.cpp | 25 +++++
 15 files changed, 233 insertions(+), 77 deletions(-)

diff --git a/libc/include/llvm-libc-macros/pthread-macros.h b/libc/include/llvm-libc-macros/pthread-macros.h
index 58019403bb333..5fb8857ef37ab 100644
--- a/libc/include/llvm-libc-macros/pthread-macros.h
+++ b/libc/include/llvm-libc-macros/pthread-macros.h
@@ -32,16 +32,18 @@
 #ifdef __linux__
 #define PTHREAD_MUTEX_INITIALIZER                                              \
   {                                                                            \
-      /* .__timed = */ 0,      /* .__recursive = */ 0,                         \
-      /* .__robust = */ 0,     /* .__owner = */ NULL,                          \
-      /* .__lock_count = */ 0, /* .__futex_word = */ {0},                      \
+      /* .__ftxw = */ {0},           /* .__priority_inherit = */ 0,            \
+      /* .__recursive = */ 0,        /* .__robust = */ 0,                      \
+      /* .__pshared = */ 0,          /* .__owner = */ 0,                       \
+      /* .__lock_count = */ 0,                                              \
   }
 #else
 #define PTHREAD_MUTEX_INITIALIZER                                              \
   {                                                                            \
-      /* .__timed = */ 0,      /* .__recursive = */ 0,                         \
-      /* .__robust = */ 0,     /* .__owner = */ NULL,                          \
-      /* .__lock_count = */ 0,                                                 \
+      /* .__ftxw = */ {0},           /* .__priority_inherit = */ 0,            \
+      /* .__recursive = */ 0,        /* .__robust = */ 0,                      \
+      /* .__pshared = */ 0,          /* .__owner = */ 0,                       \
+      /* .__lock_count = */ 0,                                              \
   }
 #endif
 
diff --git a/libc/include/llvm-libc-types/CMakeLists.txt b/libc/include/llvm-libc-types/CMakeLists.txt
index 4cd889e4789a2..8eb9b540f6f3c 100644
--- a/libc/include/llvm-libc-types/CMakeLists.txt
+++ b/libc/include/llvm-libc-types/CMakeLists.txt
@@ -17,7 +17,7 @@ add_header(__exec_argv_t HDR __exec_argv_t.h)
 add_header(__exec_envp_t HDR __exec_envp_t.h)
 add_header(__futex_word HDR __futex_word.h)
 add_header(pid_t HDR pid_t.h)
-add_header(__mutex_type HDR __mutex_type.h DEPENDS .__futex_word .pid_t)
+add_header(__mutex_type HDR __mutex_type.h DEPENDS .__futex_word .pid_t .size_t)
 add_header(__barrier_type HDR __barrier_type.h)
 add_header(__pthread_once_func_t HDR __pthread_once_func_t.h)
 add_header(__pthread_start_t HDR __pthread_start_t.h)
diff --git a/libc/include/llvm-libc-types/__mutex_type.h b/libc/include/llvm-libc-types/__mutex_type.h
index 8355616261495..455eceb3c3955 100644
--- a/libc/include/llvm-libc-types/__mutex_type.h
+++ b/libc/include/llvm-libc-types/__mutex_type.h
@@ -10,20 +10,23 @@
 #define LLVM_LIBC_TYPES___MUTEX_TYPE_H
 
 #include "__futex_word.h"
+#include "pid_t.h"
+#include "size_t.h"
 
 typedef struct {
-  unsigned char __timed;
-  unsigned char __recursive;
-  unsigned char __robust;
-
-  void *__owner;
-  unsigned long long __lock_count;
-
 #ifdef __linux__
   __futex_word __ftxw;
 #else
 #error "Mutex type not defined for the target platform."
 #endif
+
+  unsigned int __priority_inherit : 1;
+  unsigned int __recursive : 1;
+  unsigned int __robust : 1;
+  unsigned int __pshared : 1;
+
+  pid_t __owner;
+  size_t __lock_count;
 } __mutex_type;
 
 #endif // LLVM_LIBC_TYPES___MUTEX_TYPE_H
diff --git a/libc/src/__support/threads/CMakeLists.txt b/libc/src/__support/threads/CMakeLists.txt
index b603a2cfbb0e1..0846a78bbf904 100644
--- a/libc/src/__support/threads/CMakeLists.txt
+++ b/libc/src/__support/threads/CMakeLists.txt
@@ -75,6 +75,7 @@ if(TARGET libc.src.__support.threads.${LIBC_TARGET_OS}.futex_utils)
       unix_mutex.h
     DEPENDS
       .raw_mutex
+      libc.src.__support.CPP.atomic
   )
 
   add_header_library(
@@ -162,6 +163,7 @@ if(TARGET libc.src.__support.threads.futex_utils)
       libc.src.__support.threads.sleep
       libc.src.__support.time.monotonicity
       libc.src.__support.time.abs_timeout
+      libc.src.__support.threads.identifier
   )
 endif()
 
diff --git a/libc/src/__support/threads/fork_callbacks.cpp b/libc/src/__support/threads/fork_callbacks.cpp
index 49fb41a975826..b8e6b2b1ba10a 100644
--- a/libc/src/__support/threads/fork_callbacks.cpp
+++ b/libc/src/__support/threads/fork_callbacks.cpp
@@ -34,8 +34,8 @@ class AtForkCallbackManager {
 
 public:
   constexpr AtForkCallbackManager()
-      : mtx(/*timed=*/false, /*recursive=*/false, /*robust=*/false,
-            /*pshared=*/false),
+      : mtx(/*is_priority_inherit=*/false, /*is_recursive=*/false,
+            /*is_robust=*/false, /*is_pshared=*/false),
         next_index(0) {}
 
   bool register_triple(const ForkCallbackTriple &triple) {
diff --git a/libc/src/__support/threads/linux/barrier.cpp b/libc/src/__support/threads/linux/barrier.cpp
index 80f25f8ac7a21..882f6fa61887a 100644
--- a/libc/src/__support/threads/linux/barrier.cpp
+++ b/libc/src/__support/threads/linux/barrier.cpp
@@ -28,10 +28,9 @@ int Barrier::init(Barrier *b,
   new (&b->entering) CndVar(attr ? attr->pshared : false);
   new (&b->exiting) CndVar(attr ? attr->pshared : false);
 
-  auto mutex_err = Mutex::init(&b->m, false, false, false,
-                               /*pshared=*/attr ? attr->pshared : false);
-  if (mutex_err != MutexError::NONE)
-    return EAGAIN;
+  new (&b->m) Mutex(/*is_priority_inherit=*/false, /*is_recursive=*/false,
+                    /*is_robust=*/false,
+                    /*is_pshared=*/attr ? attr->pshared : false);
 
   return 0;
 }
diff --git a/libc/src/__support/threads/mutex_common.h b/libc/src/__support/threads/mutex_common.h
index 9913f69a6a61a..1c71c5c78bc24 100644
--- a/libc/src/__support/threads/mutex_common.h
+++ b/libc/src/__support/threads/mutex_common.h
@@ -19,6 +19,7 @@ enum class MutexError : int {
   TIMEOUT,
   UNLOCK_WITHOUT_LOCK,
   BAD_LOCK_STATE,
+  OVERFLOW,
 };
 
 } // namespace LIBC_NAMESPACE_DECL
diff --git a/libc/src/__support/threads/thread.cpp b/libc/src/__support/threads/thread.cpp
index 9618d7829161a..ae179f068b88e 100644
--- a/libc/src/__support/threads/thread.cpp
+++ b/libc/src/__support/threads/thread.cpp
@@ -53,8 +53,8 @@ class TSSKeyMgr {
 
 public:
   constexpr TSSKeyMgr()
-      : mtx(/*timed=*/false, /*recursive=*/false, /*robust=*/false,
-            /*pshared=*/false) {}
+      : mtx(/*is_priority_inherit=*/false, /*is_recursive=*/false,
+            /*is_robust=*/false, /*is_pshared=*/false) {}
 
   cpp::optional<unsigned int> new_key(TSSDtor *dtor) {
     cpp::lock_guard lock(mtx);
@@ -112,8 +112,8 @@ class ThreadAtExitCallbackMgr {
 
 public:
   constexpr ThreadAtExitCallbackMgr()
-      : mtx(/*timed=*/false, /*recursive=*/false, /*robust=*/false,
-            /*pshared=*/false) {}
+      : mtx(/*is_priority_inherit=*/false, /*is_recursive=*/false,
+            /*is_robust=*/false, /*is_pshared=*/false) {}
 
   int add_callback(AtExitCallback *callback, void *obj) {
     cpp::lock_guard lock(mtx);
diff --git a/libc/src/__support/threads/unix_mutex.h b/libc/src/__support/threads/unix_mutex.h
index ac05e2528ddca..9f304c5e81159 100644
--- a/libc/src/__support/threads/unix_mutex.h
+++ b/libc/src/__support/threads/unix_mutex.h
@@ -10,9 +10,13 @@
 #define LLVM_LIBC_SRC___SUPPORT_THREADS_UNIX_MUTEX_H
 
 #include "hdr/types/pid_t.h"
+#include "hdr/types/size_t.h"
+#include "src/__support/CPP/atomic.h"
 #include "src/__support/CPP/optional.h"
 #include "src/__support/libc_assert.h"
 #include "src/__support/macros/config.h"
+#include "src/__support/macros/optimization.h"
+#include "src/__support/threads/identifier.h"
 #include "src/__support/threads/mutex_common.h"
 #include "src/__support/threads/raw_mutex.h"
 
@@ -20,37 +24,44 @@ namespace LIBC_NAMESPACE_DECL {
 
 // TODO: support shared/recursive/robust mutexes.
 class Mutex final : private RawMutex {
-  // reserved timed, may be useful when combined with other flags.
-  unsigned char timed;
-  unsigned char recursive;
-  unsigned char robust;
-  unsigned char pshared;
+  // Use bitfields to allow encoding more attributes.
+  // TODO: also track errorchecking mutex type explicitly?
+  LIBC_PREFERED_TYPE(bool) unsigned int priority_inherit : 1;
+  LIBC_PREFERED_TYPE(bool) unsigned int recursive : 1;
+  LIBC_PREFERED_TYPE(bool) unsigned int robust : 1;
+  LIBC_PREFERED_TYPE(bool) unsigned int pshared : 1;
 
   // TLS address may not work across forked processes. Use thread id instead.
-  pid_t owner;
-  unsigned long long lock_count;
+  cpp::Atomic<pid_t> owner;
+  size_t lock_count;
 
   // CndVar needs to access Mutex as RawMutex
   friend class CndVar;
 
-public:
-  LIBC_INLINE constexpr Mutex(bool is_timed, bool is_recursive, bool is_robust,
-                              bool is_pshared)
-      : RawMutex(), timed(is_timed), recursive(is_recursive), robust(is_robust),
-        pshared(is_pshared), owner(0), lock_count(0) {}
-
-  LIBC_INLINE static MutexError init(Mutex *mutex, bool is_timed, bool isrecur,
-                                     bool isrobust, bool is_pshared) {
-    RawMutex::init(mutex);
-    mutex->timed = is_timed;
-    mutex->recursive = isrecur;
-    mutex->robust = isrobust;
-    mutex->pshared = is_pshared;
-    mutex->owner = 0;
-    mutex->lock_count = 0;
-    return MutexError::NONE;
+  template <class LockRoutine>
+  LIBC_INLINE MutexError lock_impl(LockRoutine do_lock) {
+    if (is_recursive() && owner == internal::gettid()) {
+      if (LIBC_UNLIKELY(lock_count == cpp::numeric_limits<size_t>::max()))
+        return MutexError::OVERFLOW;
+      lock_count++;
+      return MutexError::NONE;
+    }
+
+    MutexError res = do_lock();
+    if (is_recursive() && res == MutexError::NONE) {
+      owner = internal::gettid();
+      lock_count = 1;
+    }
+    return res;
   }
 
+public:
+  LIBC_INLINE constexpr Mutex(bool is_priority_inherit, bool is_recursive,
+                              bool is_robust, bool is_pshared)
+      : RawMutex(), priority_inherit(is_priority_inherit),
+        recursive(is_recursive), robust(is_robust), pshared(is_pshared),
+        owner(0), lock_count(0) {}
+
   LIBC_INLINE static MutexError destroy(Mutex *lock) {
     LIBC_ASSERT(lock->owner == 0 && lock->lock_count == 0 &&
                 "Mutex destroyed while being locked.");
@@ -60,20 +71,33 @@ class Mutex final : private RawMutex {
 
   // TODO: record owner and lock count.
   LIBC_INLINE MutexError lock() {
-    // Since timeout is not specified, we do not need to check the return value.
-    this->RawMutex::lock(
-        /* timeout=*/cpp::nullopt, this->pshared);
-    return MutexError::NONE;
+    return lock_impl([this] {
+      // Since timeout is not specified, we do not need to check the return
+      // value.
+      // TODO: check deadlock? POSIX made it optional.
+      this->RawMutex::lock(/* timeout=*/cpp::nullopt, this->pshared);
+      return MutexError::NONE;
+    });
   }
 
   // TODO: record owner and lock count.
   LIBC_INLINE MutexError timed_lock(internal::AbsTimeout abs_time) {
-    if (this->RawMutex::lock(abs_time, this->pshared))
-      return MutexError::NONE;
-    return MutexError::TIMEOUT;
+    return lock_impl([this, abs_time] {
+      // TODO: check deadlock? POSIX made it optional.
+      if (this->RawMutex::lock(abs_time, this->pshared))
+        return MutexError::NONE;
+      return MutexError::TIMEOUT;
+    });
   }
 
   LIBC_INLINE MutexError unlock() {
+    if (is_recursive() && owner == internal::gettid()) {
+      lock_count--;
+      if (lock_count == 0)
+        owner = 0;
+      else
+        return MutexError::NONE;
+    }
     if (this->RawMutex::unlock(this->pshared))
       return MutexError::NONE;
     return MutexError::UNLOCK_WITHOUT_LOCK;
@@ -81,16 +105,20 @@ class Mutex final : private RawMutex {
 
   // TODO: record owner and lock count.
   LIBC_INLINE MutexError try_lock() {
-    if (this->RawMutex::try_lock())
-      return MutexError::NONE;
-    return MutexError::BUSY;
+    return lock_impl([this] {
+      if (this->RawMutex::try_lock())
+        return MutexError::NONE;
+      return MutexError::BUSY;
+    });
   }
 
   LIBC_INLINE bool can_be_requeued() const {
-    return !this->pshared && !this->robust;
+    return !this->pshared && !this->robust && !this->recursive &&
+           !this->priority_inherit;
   }
 
   LIBC_INLINE bool is_robust() const { return this->robust; }
+  LIBC_INLINE bool is_recursive() const { return this->recursive; }
 };
 
 } // namespace LIBC_NAMESPACE_DECL
diff --git a/libc/src/pthread/pthread_mutex_init.cpp b/libc/src/pthread/pthread_mutex_init.cpp
index 94052e53d8c0a..0fa6f80161c4d 100644
--- a/libc/src/pthread/pthread_mutex_init.cpp
+++ b/libc/src/pthread/pthread_mutex_init.cpp
@@ -9,6 +9,7 @@
 #include "pthread_mutex_init.h"
 #include "pthread_mutexattr.h"
 
+#include "src/__support/CPP/new.h"
 #include "src/__support/common.h"
 #include "src/__support/macros/config.h"
 #include "src/__support/threads/mutex.h"
@@ -17,20 +18,41 @@
 
 namespace LIBC_NAMESPACE_DECL {
 
-static_assert(sizeof(Mutex) <= sizeof(pthread_mutex_t),
-              "The public pthread_mutex_t type cannot accommodate the internal "
+static_assert(sizeof(Mutex) == sizeof(pthread_mutex_t) &&
+                  alignof(Mutex) == alignof(pthread_mutex_t),
+              "The public pthread_mutex_t type must exactly match the internal "
               "mutex type.");
 
 LLVM_LIBC_FUNCTION(int, pthread_mutex_init,
                    (pthread_mutex_t * m,
                     const pthread_mutexattr_t *__restrict attr)) {
   auto mutexattr = attr == nullptr ? DEFAULT_MUTEXATTR : *attr;
-  auto err =
-      Mutex::init(reinterpret_cast<Mutex *>(m), /*is_timed=*/true,
-                  get_mutexattr_type(mutexattr) & PTHREAD_MUTEX_RECURSIVE,
-                  get_mutexattr_robust(mutexattr) & PTHREAD_MUTEX_ROBUST,
-                  get_mutexattr_pshared(mutexattr) & PTHREAD_PROCESS_SHARED);
-  return err == MutexError::NONE ? 0 : EAGAIN;
+  bool is_recursive = false;
+  switch (get_mutexattr_type(mutexattr)) {
+  case PTHREAD_MUTEX_NORMAL:
+  case PTHREAD_MUTEX_ERRORCHECK:
+    break;
+  case PTHREAD_MUTEX_RECURSIVE:
+    is_recursive = true;
+    break;
+  }
+
+  bool is_robust = false;
+  if (get_mutexattr_robust(mutexattr) == PTHREAD_MUTEX_ROBUST)
+    is_robust = true;
+
+  bool is_pshared = false;
+  switch (get_mutexattr_pshared(mutexattr)) {
+  case PTHREAD_PROCESS_PRIVATE:
+    break;
+  case PTHREAD_PROCESS_SHARED:
+    is_pshared = true;
+    break;
+  }
+
+  new (m) Mutex(/*is_priority_inherit=*/false, /*is_recursive=*/is_recursive,
+                /*is_robust=*/is_robust, /*is_pshared=*/is_pshared);
+  return 0;
 }
 
 } // namespace LIBC_NAMESPACE_DECL
diff --git a/libc/src/stdlib/atexit.cpp b/libc/src/stdlib/atexit.cpp
index c8a15dd3cfef2..5b924be3a63ed 100644
--- a/libc/src/stdlib/atexit.cpp
+++ b/libc/src/stdlib/atexit.cpp
@@ -15,7 +15,8 @@
 namespace LIBC_NAMESPACE_DECL {
 
 constinit ExitCallbackList atexit_callbacks;
-Mutex handler_list_mtx(false, false, false, false);
+Mutex handler_list_mtx(/*is_priority_inherit=*/false, /*is_recursive=*/false,
+                       /*is_robust=*/false, /*is_pshared=*/false);
 
 extern "C" {
 
diff --git a/libc/src/threads/mtx_init.cpp b/libc/src/threads/mtx_init.cpp
index eb0ba5010584e..c6b0278c52f77 100644
--- a/libc/src/threads/mtx_init.cpp
+++ b/libc/src/threads/mtx_init.cpp
@@ -7,6 +7,7 @@
 //===----------------------------------------------------------------------===//
 
 #include "src/threads/mtx_init.h"
+#include "src/__support/CPP/new.h"
 #include "src/__support/common.h"
 #include "src/__support/macros/config.h"
 #include "src/__support/threads/mutex.h"
@@ -15,15 +16,16 @@
 
 namespace LIBC_NAMESPACE_DECL {
 
-static_assert(sizeof(Mutex) <= sizeof(mtx_t),
-              "The public mtx_t type cannot accommodate the internal mutex "
+static_assert(sizeof(Mutex) == sizeof(mtx_t) &&
+                  alignof(Mutex) == alignof(mtx_t),
+              "The public mtx_t type must exactly match the internal mutex "
               "type.");
 
 LLVM_LIBC_FUNCTION(int, mtx_init, (mtx_t * m, int type)) {
-  auto err = Mutex::init(reinterpret_cast<Mutex *>(m), type & mtx_timed,
-                         type & mtx_recursive, /* is_robust */ false,
-                         /* is_pshared */ false);
-  return err == MutexError::NONE ? thrd_success : thrd_error;
+  new (m) Mutex(/*is_priority_inherit=*/false,
+                /*is_recursive=*/static_cast<bool>(type & mtx_recursive),
+                /*is_robust=*/false, /*is_pshared=*/false);
+  return thrd_success;
 }
 
 } // namespace LIBC_NAMESPACE_DECL
diff --git a/libc/test/integration/src/pthread/CMakeLists.txt b/libc/test/integration/src/pthread/CMakeLists.txt
index 71cb039f7761e..eceebb42f18c4 100644
--- a/libc/test/integration/src/pthread/CMakeLists.txt
+++ b/libc/test/integration/src/pthread/CMakeLists.txt
@@ -15,6 +15,9 @@ add_integration_test(
     libc.src.pthread.pthread_mutex_lock
     libc.src.pthread.pthread_mutex_trylock
     libc.src.pthread.pthread_mutex_unlock
+    libc.src.pthread.pthread_mutexattr_destroy
+    libc.src.pthread.pthread_mutexattr_init
+    libc.src.pthread.pthread_mutexattr_settype
     libc.src.pthread.pthread_create
     libc.src.pthread.pthread_join
 )
diff --git a/libc/test/integration/src/pthread/pthread_mutex_test.cpp b/libc/test/integration/src/pthread/pthread_mutex_test.cpp
index 488954c0ef255..b8d71c6f48d2a 100644
--- a/libc/test/integration/src/pthread/pthread_mutex_test.cpp
+++ b/libc/test/integration/src/pthread/pthread_mutex_test.cpp
@@ -15,6 +15,9 @@
 #include "src/pthread/pthread_mutex_lock.h"
 #include "src/pthread/pthread_mutex_trylock.h"
 #include "src/pthread/pthread_mutex_unlock.h"
+#include "src/pthread/pthread_mutexattr_destroy.h"
+#include "src/pthread/pthread_mutexattr_init.h"
+#include "src/pthread/pthread_mutexattr_settype.h"
 #include "test/IntegrationTest/test.h"
 
 #include <pthread.h>
@@ -143,6 +146,73 @@ void trylock_test() {
   LIBC_NAMESPACE::pthread_mutex_destroy(&trylock_mutex);
 }
 
+void *trylock_other_thread(void *arg) {
+  auto *mutex = reinterpret_cast<pthread_mutex_t *>(arg);
+  int result = LIBC_NAMESPACE::pthread_mutex_trylock(mutex);
+  if (result == 0)
+    ASSERT_EQ(LIBC_NAMESPACE::pthread_mutex_unlock(mutex), 0);
+  return reinterpret_cast<void *>(uintptr_t(result));
+}
+
+void recursive_mutex_test() {
+  pthread_mutexattr_t attr;
+  pthread_mutex_t recursive_mutex;
+  ASSERT_EQ(LIBC_NAMESPACE::pthread_mutexattr_init(&attr), 0);
+  ASSERT_EQ(LIBC_NAMESPACE::pthread_mutexattr_settype(&attr,
+                                                      PTHREAD_MUTEX_RECURSIVE),
+            0);
+  ASSERT_EQ(LIBC_NAMESPACE::pthread_mutex_init(&recursive_mutex, &attr), 0);
+  ASSERT_EQ(LIBC_NAMESPACE::pthread_mutexattr_destroy(&attr), 0);
+
+  ASSERT_TRUE(recursive_mutex.__recursive);
+  ASSERT_EQ(recursive_mutex.__owner, 0);
+  ASSERT_EQ(recursive_mutex.__lock_count, size_t(0));
+
+  ASSERT_EQ(LIBC_NAMESPACE::pthread_mutex_lock(&recursive_mutex), 0);
+  ASSERT_EQ(LIBC_NAMESPACE::pthread_mutex_lock(&recursive_mutex), 0);
+
+  pthread_t thread;
+  ASSERT_EQ(LIBC_NAMESPACE::pthread_create(&thread, nullptr, trylock_other_thread,
+                                           &recursive_mutex),
+            0);
+  void *retval = nullptr;
+  ASSERT_EQ(LIBC_NAMESPACE::pthread_join(thread, &retval), 0);
+  ASSERT_EQ(uintptr_t(retval), uintptr_t(EBUSY));
+
+  ASSERT_EQ(LIBC_NAMESPACE::pthread_mutex_unlock(&recursive_mutex), 0);
+  ASSERT_EQ(LIBC_NAMESPACE::pthread_mutex_unlock(&recursive_mutex), 0);
+  ASSERT_EQ(recursive_mutex.__owner, 0);
+  ASSERT_EQ(recursive_mutex.__lock_count, size_t(0));
+
+  ASSERT_EQ(LIBC_NAMESPACE::pthread_mutex_trylock(&recursive_mutex), 0);
+  ASSERT_EQ(LIBC_NAMESPACE::pthread_mutex_unlock(&recursive_mutex), 0);
+  ASSERT_EQ(LIBC_NAMESPACE::pthread_mutex_destroy(&recursive_mutex), 0);
+}
+
+void initializer_acts_the_same_as_null_attr() {
+  pthread_mutex_t mutex = PTHREAD_MUTEX_INITIALIZER;
+  pthread_mutex_t mutex_from_init;
+  ASSERT_EQ(LIBC_NAMESPACE::pthread_mutex_init(&mutex_from_init, nullptr), 0);
+
+  ASSERT_EQ(mutex.__ftxw.__word, mutex_from_init.__ftxw.__word);
+  ASSERT_EQ(mutex.__priority_inherit, mutex_from_init.__priority_inherit);
+  ASSERT_EQ(mutex.__recursive, mutex_from_init.__recursive);
+  ASSERT_EQ(mutex.__robust, mutex_from_init.__robust);
+  ASSERT_EQ(mutex.__pshared, mutex_from_init.__pshared);
+  ASSERT_EQ(mutex.__owner, mutex_from_init.__owner);
+  ASSERT_EQ(mutex.__lock_count, mutex_from_init.__lock_count);
+
+  ASSERT_EQ(LIBC_NAMESPACE::pthread_mutex_lock(&mutex), 0);
+  ASSERT_EQ(LIBC_NAMESPACE::pthread_mutex_trylock(&mutex), EBUSY);
+  ASSERT_EQ(LIBC_NAMESPACE::pthread_mutex_unlock(&mutex), 0);
+  ASSERT_EQ(LIBC_NAMESPACE::pthread_mutex_destroy(&mutex), 0);
+
+  ASSERT_EQ(LIBC_NAMESPACE::pthread_mutex_lock(&mutex_from_init), 0);
+  ASSERT_EQ(LIBC_NAMESPACE::pthread_mutex_trylock(&mutex_from_init), EBUSY);
+  ASSERT_EQ(LIBC_NAMESPACE::pthread_mutex_unlock(&mutex_from_init), 0);
+  ASSERT_EQ(LIBC_NAMESPACE::pthread_mutex_destroy(&mutex_from_init), 0);
+}
+
 static constexpr int THREAD_COUNT = 10;
 static pthread_mutex_t multiple_waiter_lock;
 static pthread_mutex_t counter_lock;
@@ -199,14 +269,12 @@ void multiple_waiters() {
   LIBC_NAMESPACE::pthread_mutex_destroy(&counter_lock);
 }
 
-// Test the initializer
-[[maybe_unused]]
-static pthread_mutex_t test_initializer = PTHREAD_MUTEX_INITIALIZER;
-
 TEST_MAIN() {
   relay_counter();
   wait_and_step();
   trylock_test();
+  recursive_mutex_test();
+  initializer_acts_the_same_as_null_attr();
   multiple_waiters();
   return 0;
 }
diff --git a/libc/test/integration/src/threads/mtx_test.cpp b/libc/test/integration/src/threads/mtx_test.cpp
index 0b0a9faae24a6..18bdbc748d5fa 100644
--- a/libc/test/integration/src/threads/mtx_test.cpp
+++ b/libc/test/integration/src/threads/mtx_test.cpp
@@ -138,6 +138,30 @@ void wait_and_step() {
   LIBC_NAMESPACE::mtx_destroy(&step_lock);
 }
 
+void recursive_mutex_test() {
+  mtx_t recursive_mutex;
+  ASSERT_EQ(LIBC_NAMESPACE::mtx_init(&recursive_mutex, mtx_recursive),
+            static_cast<int>(thrd_success));
+
+  ASSERT_TRUE(recursive_mutex.__recursive);
+  ASSERT_EQ(recursive_mutex.__owner, 0);
+  ASSERT_EQ(recursive_mutex.__lock_count, size_t(0));
+
+  ASSERT_EQ(LIBC_NAMESPACE::mtx_lock(&recursive_mutex),
+            static_cast<int>(thrd_success));
+  ASSERT_EQ(LIBC_NAMESPACE::mtx_lock(&recursive_mutex),
+            static_cast<int>(thrd_success));
+
+  ASSERT_EQ(LIBC_NAMESPACE::mtx_unlock(&recursive_mutex),
+            static_cast<int>(thrd_success));
+  ASSERT_EQ(LIBC_NAMESPACE::mtx_unlock(&recursive_mutex),
+            static_cast<int>(thrd_success));
+  ASSERT_EQ(recursive_mutex.__owner, 0);
+  ASSERT_EQ(recursive_mutex.__lock_count, size_t(0));
+
+  LIBC_NAMESPACE::mtx_destroy(&recursive_mutex);
+}
+
 static constexpr int THREAD_COUNT = 10;
 static mtx_t multiple_waiter_lock;
 static mtx_t counter_lock;
@@ -197,6 +221,7 @@ void multiple_waiters() {
 TEST_MAIN() {
   relay_counter();
   wait_and_step();
+  recursive_mutex_test();
   multiple_waiters();
   return 0;
 }

>From 25b2a4ad2ea7f200eeceef5aba82db1bfee569a1 Mon Sep 17 00:00:00 2001
From: Schrodinger ZHU Yifan <yifanzhu at rochester.edu>
Date: Fri, 24 Apr 2026 11:29:45 -0400
Subject: [PATCH 2/4] fix

---
 .../src/pthread/pthread_mutex_test.cpp        | 40 +++++++++++++------
 .../test/integration/src/threads/mtx_test.cpp | 22 +++++++---
 2 files changed, 45 insertions(+), 17 deletions(-)

diff --git a/libc/test/integration/src/pthread/pthread_mutex_test.cpp b/libc/test/integration/src/pthread/pthread_mutex_test.cpp
index b8d71c6f48d2a..f45c5f1fb7d6e 100644
--- a/libc/test/integration/src/pthread/pthread_mutex_test.cpp
+++ b/libc/test/integration/src/pthread/pthread_mutex_test.cpp
@@ -18,6 +18,7 @@
 #include "src/pthread/pthread_mutexattr_destroy.h"
 #include "src/pthread/pthread_mutexattr_init.h"
 #include "src/pthread/pthread_mutexattr_settype.h"
+#include "src/string/memory_utils/inline_memcpy.h"
 #include "test/IntegrationTest/test.h"
 
 #include <pthread.h>
@@ -25,6 +26,15 @@
 constexpr int START = 0;
 constexpr int MAX = 10000;
 
+static pthread_mutex_t snapshot_mutex(const void *mutex_storage) {
+  pthread_mutex_t snapshot;
+  // The original storage may currently hold libc's internal mutex
+  // representation. Copy the bytes into pthread_mutex_t storage before
+  // inspection to avoid strict aliasing violations.
+  LIBC_NAMESPACE::inline_memcpy(&snapshot, mutex_storage, sizeof(snapshot));
+  return snapshot;
+}
+
 pthread_mutex_t mutex;
 static int shared_int = START;
 
@@ -164,9 +174,10 @@ void recursive_mutex_test() {
   ASSERT_EQ(LIBC_NAMESPACE::pthread_mutex_init(&recursive_mutex, &attr), 0);
   ASSERT_EQ(LIBC_NAMESPACE::pthread_mutexattr_destroy(&attr), 0);
 
-  ASSERT_TRUE(recursive_mutex.__recursive);
-  ASSERT_EQ(recursive_mutex.__owner, 0);
-  ASSERT_EQ(recursive_mutex.__lock_count, size_t(0));
+  pthread_mutex_t snapshot = snapshot_mutex(&recursive_mutex);
+  ASSERT_TRUE(snapshot.__recursive);
+  ASSERT_EQ(snapshot.__owner, 0);
+  ASSERT_EQ(snapshot.__lock_count, size_t(0));
 
   ASSERT_EQ(LIBC_NAMESPACE::pthread_mutex_lock(&recursive_mutex), 0);
   ASSERT_EQ(LIBC_NAMESPACE::pthread_mutex_lock(&recursive_mutex), 0);
@@ -181,8 +192,9 @@ void recursive_mutex_test() {
 
   ASSERT_EQ(LIBC_NAMESPACE::pthread_mutex_unlock(&recursive_mutex), 0);
   ASSERT_EQ(LIBC_NAMESPACE::pthread_mutex_unlock(&recursive_mutex), 0);
-  ASSERT_EQ(recursive_mutex.__owner, 0);
-  ASSERT_EQ(recursive_mutex.__lock_count, size_t(0));
+  snapshot = snapshot_mutex(&recursive_mutex);
+  ASSERT_EQ(snapshot.__owner, 0);
+  ASSERT_EQ(snapshot.__lock_count, size_t(0));
 
   ASSERT_EQ(LIBC_NAMESPACE::pthread_mutex_trylock(&recursive_mutex), 0);
   ASSERT_EQ(LIBC_NAMESPACE::pthread_mutex_unlock(&recursive_mutex), 0);
@@ -194,13 +206,17 @@ void initializer_acts_the_same_as_null_attr() {
   pthread_mutex_t mutex_from_init;
   ASSERT_EQ(LIBC_NAMESPACE::pthread_mutex_init(&mutex_from_init, nullptr), 0);
 
-  ASSERT_EQ(mutex.__ftxw.__word, mutex_from_init.__ftxw.__word);
-  ASSERT_EQ(mutex.__priority_inherit, mutex_from_init.__priority_inherit);
-  ASSERT_EQ(mutex.__recursive, mutex_from_init.__recursive);
-  ASSERT_EQ(mutex.__robust, mutex_from_init.__robust);
-  ASSERT_EQ(mutex.__pshared, mutex_from_init.__pshared);
-  ASSERT_EQ(mutex.__owner, mutex_from_init.__owner);
-  ASSERT_EQ(mutex.__lock_count, mutex_from_init.__lock_count);
+  pthread_mutex_t mutex_snapshot = snapshot_mutex(&mutex);
+  pthread_mutex_t mutex_from_init_snapshot = snapshot_mutex(&mutex_from_init);
+  ASSERT_EQ(mutex_snapshot.__ftxw.__word,
+            mutex_from_init_snapshot.__ftxw.__word);
+  ASSERT_EQ(mutex_snapshot.__priority_inherit,
+            mutex_from_init_snapshot.__priority_inherit);
+  ASSERT_EQ(mutex_snapshot.__recursive, mutex_from_init_snapshot.__recursive);
+  ASSERT_EQ(mutex_snapshot.__robust, mutex_from_init_snapshot.__robust);
+  ASSERT_EQ(mutex_snapshot.__pshared, mutex_from_init_snapshot.__pshared);
+  ASSERT_EQ(mutex_snapshot.__owner, mutex_from_init_snapshot.__owner);
+  ASSERT_EQ(mutex_snapshot.__lock_count, mutex_from_init_snapshot.__lock_count);
 
   ASSERT_EQ(LIBC_NAMESPACE::pthread_mutex_lock(&mutex), 0);
   ASSERT_EQ(LIBC_NAMESPACE::pthread_mutex_trylock(&mutex), EBUSY);
diff --git a/libc/test/integration/src/threads/mtx_test.cpp b/libc/test/integration/src/threads/mtx_test.cpp
index 18bdbc748d5fa..5aa2d6d1b3f50 100644
--- a/libc/test/integration/src/threads/mtx_test.cpp
+++ b/libc/test/integration/src/threads/mtx_test.cpp
@@ -12,6 +12,7 @@
 #include "src/threads/mtx_unlock.h"
 #include "src/threads/thrd_create.h"
 #include "src/threads/thrd_join.h"
+#include "src/string/memory_utils/inline_memcpy.h"
 
 #include "test/IntegrationTest/test.h"
 
@@ -20,6 +21,15 @@
 constexpr int START = 0;
 constexpr int MAX = 10000;
 
+static mtx_t snapshot_mutex(const void *mutex_storage) {
+  mtx_t snapshot;
+  // The original storage may currently hold libc's internal mutex
+  // representation. Copy the bytes into mtx_t storage before inspection to
+  // avoid strict aliasing violations.
+  LIBC_NAMESPACE::inline_memcpy(&snapshot, mutex_storage, sizeof(snapshot));
+  return snapshot;
+}
+
 mtx_t mutex;
 static int shared_int = START;
 
@@ -143,9 +153,10 @@ void recursive_mutex_test() {
   ASSERT_EQ(LIBC_NAMESPACE::mtx_init(&recursive_mutex, mtx_recursive),
             static_cast<int>(thrd_success));
 
-  ASSERT_TRUE(recursive_mutex.__recursive);
-  ASSERT_EQ(recursive_mutex.__owner, 0);
-  ASSERT_EQ(recursive_mutex.__lock_count, size_t(0));
+  mtx_t snapshot = snapshot_mutex(&recursive_mutex);
+  ASSERT_TRUE(snapshot.__recursive);
+  ASSERT_EQ(snapshot.__owner, 0);
+  ASSERT_EQ(snapshot.__lock_count, size_t(0));
 
   ASSERT_EQ(LIBC_NAMESPACE::mtx_lock(&recursive_mutex),
             static_cast<int>(thrd_success));
@@ -156,8 +167,9 @@ void recursive_mutex_test() {
             static_cast<int>(thrd_success));
   ASSERT_EQ(LIBC_NAMESPACE::mtx_unlock(&recursive_mutex),
             static_cast<int>(thrd_success));
-  ASSERT_EQ(recursive_mutex.__owner, 0);
-  ASSERT_EQ(recursive_mutex.__lock_count, size_t(0));
+  snapshot = snapshot_mutex(&recursive_mutex);
+  ASSERT_EQ(snapshot.__owner, 0);
+  ASSERT_EQ(snapshot.__lock_count, size_t(0));
 
   LIBC_NAMESPACE::mtx_destroy(&recursive_mutex);
 }

>From 62cd690365ea9fdffb2ab9f32545fa72f270aff8 Mon Sep 17 00:00:00 2001
From: Schrodinger ZHU Yifan <yifanzhu at rochester.edu>
Date: Fri, 24 Apr 2026 11:32:05 -0400
Subject: [PATCH 3/4] fix

---
 libc/include/llvm-libc-macros/pthread-macros.h   | 16 ++++++++--------
 .../src/pthread/pthread_mutex_test.cpp           | 10 +++++-----
 libc/test/integration/src/threads/mtx_test.cpp   |  2 +-
 3 files changed, 14 insertions(+), 14 deletions(-)

diff --git a/libc/include/llvm-libc-macros/pthread-macros.h b/libc/include/llvm-libc-macros/pthread-macros.h
index 5fb8857ef37ab..1619ad123d2c1 100644
--- a/libc/include/llvm-libc-macros/pthread-macros.h
+++ b/libc/include/llvm-libc-macros/pthread-macros.h
@@ -32,18 +32,18 @@
 #ifdef __linux__
 #define PTHREAD_MUTEX_INITIALIZER                                              \
   {                                                                            \
-      /* .__ftxw = */ {0},           /* .__priority_inherit = */ 0,            \
-      /* .__recursive = */ 0,        /* .__robust = */ 0,                      \
-      /* .__pshared = */ 0,          /* .__owner = */ 0,                       \
-      /* .__lock_count = */ 0,                                              \
+      /* .__ftxw = */ {0},     /* .__priority_inherit = */ 0,                  \
+      /* .__recursive = */ 0,  /* .__robust = */ 0,                            \
+      /* .__pshared = */ 0,    /* .__owner = */ 0,                             \
+      /* .__lock_count = */ 0,                                                 \
   }
 #else
 #define PTHREAD_MUTEX_INITIALIZER                                              \
   {                                                                            \
-      /* .__ftxw = */ {0},           /* .__priority_inherit = */ 0,            \
-      /* .__recursive = */ 0,        /* .__robust = */ 0,                      \
-      /* .__pshared = */ 0,          /* .__owner = */ 0,                       \
-      /* .__lock_count = */ 0,                                              \
+      /* .__ftxw = */ {0},     /* .__priority_inherit = */ 0,                  \
+      /* .__recursive = */ 0,  /* .__robust = */ 0,                            \
+      /* .__pshared = */ 0,    /* .__owner = */ 0,                             \
+      /* .__lock_count = */ 0,                                                 \
   }
 #endif
 
diff --git a/libc/test/integration/src/pthread/pthread_mutex_test.cpp b/libc/test/integration/src/pthread/pthread_mutex_test.cpp
index f45c5f1fb7d6e..7e323189431cd 100644
--- a/libc/test/integration/src/pthread/pthread_mutex_test.cpp
+++ b/libc/test/integration/src/pthread/pthread_mutex_test.cpp
@@ -168,9 +168,9 @@ void recursive_mutex_test() {
   pthread_mutexattr_t attr;
   pthread_mutex_t recursive_mutex;
   ASSERT_EQ(LIBC_NAMESPACE::pthread_mutexattr_init(&attr), 0);
-  ASSERT_EQ(LIBC_NAMESPACE::pthread_mutexattr_settype(&attr,
-                                                      PTHREAD_MUTEX_RECURSIVE),
-            0);
+  ASSERT_EQ(
+      LIBC_NAMESPACE::pthread_mutexattr_settype(&attr, PTHREAD_MUTEX_RECURSIVE),
+      0);
   ASSERT_EQ(LIBC_NAMESPACE::pthread_mutex_init(&recursive_mutex, &attr), 0);
   ASSERT_EQ(LIBC_NAMESPACE::pthread_mutexattr_destroy(&attr), 0);
 
@@ -183,8 +183,8 @@ void recursive_mutex_test() {
   ASSERT_EQ(LIBC_NAMESPACE::pthread_mutex_lock(&recursive_mutex), 0);
 
   pthread_t thread;
-  ASSERT_EQ(LIBC_NAMESPACE::pthread_create(&thread, nullptr, trylock_other_thread,
-                                           &recursive_mutex),
+  ASSERT_EQ(LIBC_NAMESPACE::pthread_create(
+                &thread, nullptr, trylock_other_thread, &recursive_mutex),
             0);
   void *retval = nullptr;
   ASSERT_EQ(LIBC_NAMESPACE::pthread_join(thread, &retval), 0);
diff --git a/libc/test/integration/src/threads/mtx_test.cpp b/libc/test/integration/src/threads/mtx_test.cpp
index 5aa2d6d1b3f50..909c4f2c5c760 100644
--- a/libc/test/integration/src/threads/mtx_test.cpp
+++ b/libc/test/integration/src/threads/mtx_test.cpp
@@ -6,13 +6,13 @@
 //
 //===----------------------------------------------------------------------===//
 
+#include "src/string/memory_utils/inline_memcpy.h"
 #include "src/threads/mtx_destroy.h"
 #include "src/threads/mtx_init.h"
 #include "src/threads/mtx_lock.h"
 #include "src/threads/mtx_unlock.h"
 #include "src/threads/thrd_create.h"
 #include "src/threads/thrd_join.h"
-#include "src/string/memory_utils/inline_memcpy.h"
 
 #include "test/IntegrationTest/test.h"
 

>From e50d3c6bc63ac78eeb84320369362d2c1324142a Mon Sep 17 00:00:00 2001
From: Schrodinger ZHU Yifan <yifanzhu at rochester.edu>
Date: Fri, 24 Apr 2026 11:52:39 -0400
Subject: [PATCH 4/4] [libc][libcxx] enable libcxx build-and-test workflow

---
 libc/config/linux/aarch64/entrypoints.txt    | 311 ++++++++++++++---
 libc/config/linux/aarch64/headers.txt        |   3 +
 libc/config/linux/riscv/entrypoints.txt      |   1 +
 libc/config/linux/x86_64/entrypoints.txt     |   3 +
 libc/include/llvm-libc-types/__thread_type.h |   4 +-
 libc/src/link/CMakeLists.txt                 |   1 +
 libc/src/link/dl_iterate_phdr.cpp            | 131 ++++++-
 libc/src/pthread/pthread_self.cpp            |   3 +-
 libc/src/threads/thrd_current.cpp            |   3 +-
 libcxx/include/__mbstate_t.h                 |   2 +
 run.sh                                       | 340 +++++++++++++++++++
 runtimes/CMakeLists.txt                      |   9 +
 12 files changed, 762 insertions(+), 49 deletions(-)
 create mode 100755 run.sh

diff --git a/libc/config/linux/aarch64/entrypoints.txt b/libc/config/linux/aarch64/entrypoints.txt
index b15edc5e3e102..27d948aa89536 100644
--- a/libc/config/linux/aarch64/entrypoints.txt
+++ b/libc/config/linux/aarch64/entrypoints.txt
@@ -18,6 +18,7 @@ set(TARGET_LIBC_ENTRYPOINTS
     libc.src.ctype.toupper
 
     # dlfcn.h entrypoints
+    libc.src.dlfcn.dladdr
     libc.src.dlfcn.dlclose
     libc.src.dlfcn.dlerror
     libc.src.dlfcn.dlopen
@@ -36,6 +37,7 @@ set(TARGET_LIBC_ENTRYPOINTS
     libc.src.poll.poll
 
     # sched.h entrypoints
+    libc.src.sched.getcpu
     libc.src.sched.sched_get_priority_max
     libc.src.sched.sched_get_priority_min
     libc.src.sched.sched_getaffinity
@@ -108,6 +110,9 @@ set(TARGET_LIBC_ENTRYPOINTS
     libc.src.inttypes.strtoimax
     libc.src.inttypes.strtoumax
 
+    # link.h entrypoints
+    libc.src.link.dl_iterate_phdr
+
     # stdbit.h entrypoints
     libc.src.stdbit.stdc_bit_ceil_uc
     libc.src.stdbit.stdc_bit_ceil_ui
@@ -181,6 +186,7 @@ set(TARGET_LIBC_ENTRYPOINTS
     libc.src.stdbit.stdc_trailing_zeros_us
 
     # stdlib.h entrypoints
+    libc.src.stdlib.a64l
     libc.src.stdlib.abs
     libc.src.stdlib.atof
     libc.src.stdlib.atoi
@@ -188,6 +194,7 @@ set(TARGET_LIBC_ENTRYPOINTS
     libc.src.stdlib.atoll
     libc.src.stdlib.bsearch
     libc.src.stdlib.div
+    libc.src.stdlib.l64a
     libc.src.stdlib.labs
     libc.src.stdlib.ldiv
     libc.src.stdlib.llabs
@@ -199,8 +206,7 @@ set(TARGET_LIBC_ENTRYPOINTS
     libc.src.stdlib.srand
     libc.src.stdlib.strfromd
     libc.src.stdlib.strfromf
-    # TODO: long double support is buggy with clang-11. Re-enable when buildbots are upgraded.
-    # libc.src.stdlib.strfroml
+    libc.src.stdlib.strfroml
     libc.src.stdlib.strtod
     libc.src.stdlib.strtof
     libc.src.stdlib.strtol
@@ -253,6 +259,9 @@ set(TARGET_LIBC_ENTRYPOINTS
     # sys/ioctl.h entrypoints
     libc.src.sys.ioctl.ioctl
 
+    # sys/ipc.h entrypoints
+    libc.src.sys.ipc.ftok
+
     # sys/mman.h entrypoints
     libc.src.sys.mman.madvise
     libc.src.sys.mman.mincore
@@ -266,6 +275,11 @@ set(TARGET_LIBC_ENTRYPOINTS
     libc.src.sys.mman.munlock
     libc.src.sys.mman.munlockall
     libc.src.sys.mman.munmap
+    libc.src.sys.mman.pkey_alloc
+    libc.src.sys.mman.pkey_free
+    libc.src.sys.mman.pkey_get
+    libc.src.sys.mman.pkey_mprotect
+    libc.src.sys.mman.pkey_set
     libc.src.sys.mman.remap_file_pages
     libc.src.sys.mman.posix_madvise
     libc.src.sys.mman.shm_open
@@ -278,6 +292,11 @@ set(TARGET_LIBC_ENTRYPOINTS
     libc.src.sys.resource.getrlimit
     libc.src.sys.resource.setrlimit
 
+    # sys/sem.h entrypoints
+    libc.src.sys.sem.semget
+    libc.src.sys.sem.semctl
+    libc.src.sys.sem.semop
+
     # sys/sendfile entrypoints
     libc.src.sys.sendfile.sendfile
 
@@ -296,6 +315,9 @@ set(TARGET_LIBC_ENTRYPOINTS
     libc.src.sys.statvfs.fstatvfs
     libc.src.sys.statvfs.statvfs
 
+    # sys/time.h entrypoints
+    libc.src.sys.time.utimes
+
     # sys/utsname.h entrypoints
     libc.src.sys.utsname.uname
 
@@ -326,6 +348,7 @@ set(TARGET_LIBC_ENTRYPOINTS
     # unistd.h entrypoints
     libc.src.unistd.access
     libc.src.unistd.chdir
+    libc.src.unistd.chown
     libc.src.unistd.close
     libc.src.unistd.dup
     libc.src.unistd.dup2
@@ -346,6 +369,7 @@ set(TARGET_LIBC_ENTRYPOINTS
     libc.src.unistd.getppid
     libc.src.unistd.getsid
     libc.src.unistd.gettid
+    libc.src.unistd.getgid
     libc.src.unistd.getuid
     libc.src.unistd.isatty
     libc.src.unistd.link
@@ -370,8 +394,42 @@ set(TARGET_LIBC_ENTRYPOINTS
     libc.src.unistd.write
 
     # wchar.h entrypoints
+    libc.src.wchar.btowc
     libc.src.wchar.wcslen
+    libc.src.wchar.wcsnlen
     libc.src.wchar.wctob
+    libc.src.wchar.wmemmove
+    libc.src.wchar.wmemset
+    libc.src.wchar.wcschr
+    libc.src.wchar.wcsncmp
+    libc.src.wchar.wcsxfrm
+    libc.src.wchar.wcscmp
+    libc.src.wchar.wcspbrk
+    libc.src.wchar.wcsrchr
+    libc.src.wchar.wcsspn
+    libc.src.wchar.wcscspn
+    libc.src.wchar.wcsdup
+    libc.src.wchar.wmemcmp
+    libc.src.wchar.wmempcpy
+    libc.src.wchar.wmemcpy
+    libc.src.wchar.wcsncpy
+    libc.src.wchar.wcscat
+    libc.src.wchar.wcsstr
+    libc.src.wchar.wcsncat
+    libc.src.wchar.wcslcat
+    libc.src.wchar.wcscpy
+    libc.src.wchar.wcslcpy
+    libc.src.wchar.wmemchr
+    libc.src.wchar.wcpcpy
+    libc.src.wchar.wcpncpy
+    libc.src.wchar.wcstod
+    libc.src.wchar.wcstof
+    libc.src.wchar.wcstok
+    libc.src.wchar.wcstol
+    libc.src.wchar.wcstold
+    libc.src.wchar.wcstoll
+    libc.src.wchar.wcstoul
+    libc.src.wchar.wcstoull
 
     # wctype.h entrypoints
     libc.src.wctype.iswalpha
@@ -469,16 +527,17 @@ set(TARGET_LIBM_ENTRYPOINTS
     libc.src.math.cosf
     libc.src.math.coshf
     libc.src.math.cospif
-    libc.src.math.daddl
-    libc.src.math.ddivl
     libc.src.math.dfmal
     libc.src.math.dmull
     libc.src.math.dsqrtl
+    libc.src.math.daddl
+    libc.src.math.ddivl
     libc.src.math.dsubl
     libc.src.math.erff
     libc.src.math.exp
     libc.src.math.exp10
     libc.src.math.exp10f
+    libc.src.math.exp10m1f
     libc.src.math.exp2
     libc.src.math.exp2f
     libc.src.math.exp2m1f
@@ -494,6 +553,10 @@ set(TARGET_LIBM_ENTRYPOINTS
     libc.src.math.fdim
     libc.src.math.fdimf
     libc.src.math.fdiml
+    libc.src.math.fdiv
+    libc.src.math.fdivl
+    libc.src.math.ffma
+    libc.src.math.ffmal
     libc.src.math.floor
     libc.src.math.floorf
     libc.src.math.floorl
@@ -687,40 +750,50 @@ endif()
 if(LIBC_TYPES_HAS_FLOAT16)
   list(APPEND TARGET_LIBM_ENTRYPOINTS
     # math.h C23 _Float16 entrypoints
+    libc.src.math.acosf16
     libc.src.math.acoshf16
+    libc.src.math.acospif16
+    libc.src.math.asinf16
+    libc.src.math.asinhf16
     libc.src.math.asinpif16
+    libc.src.math.atanf16
     libc.src.math.atan2f16
+    libc.src.math.atanhf16
+    libc.src.math.atanpif16
     libc.src.math.canonicalizef16
     libc.src.math.ceilf16
     libc.src.math.copysignf16
+    libc.src.math.cosf16
+    libc.src.math.coshf16
     libc.src.math.cospif16
     libc.src.math.erff16
     libc.src.math.erfcf16
+    libc.src.math.exp10f16
+    libc.src.math.exp10m1f16
+    libc.src.math.exp2f16
+    libc.src.math.exp2m1f16
     libc.src.math.expf16
+    libc.src.math.expm1f16
     libc.src.math.f16add
     libc.src.math.f16addf
-    # libc.src.math.f16addl
+    libc.src.math.f16addl
     libc.src.math.f16div
     libc.src.math.f16divf
-    # libc.src.math.f16divl
+    libc.src.math.f16divl
     libc.src.math.f16fma
     libc.src.math.f16fmaf
-    # libc.src.math.f16fmal
+    libc.src.math.f16fmal
     libc.src.math.f16mul
     libc.src.math.f16mulf
-    # libc.src.math.f16mull
+    libc.src.math.f16mull
     libc.src.math.f16sqrt
     libc.src.math.f16sqrtf
-    # libc.src.math.f16sqrtl
+    libc.src.math.f16sqrtl
     libc.src.math.f16sub
     libc.src.math.f16subf
-    # libc.src.math.f16subl
+    libc.src.math.f16subl
     libc.src.math.fabsf16
     libc.src.math.fdimf16
-    libc.src.math.fdiv
-    libc.src.math.fdivl
-    libc.src.math.ffma
-    libc.src.math.ffmal
     libc.src.math.floorf16
     libc.src.math.fmaf16
     libc.src.math.fmaxf16
@@ -733,11 +806,12 @@ if(LIBC_TYPES_HAS_FLOAT16)
     libc.src.math.fminimum_magf16
     libc.src.math.fminimum_numf16
     libc.src.math.fminimumf16
-    # libc.src.math.fmodf16
+    libc.src.math.fmodf16
     libc.src.math.frexpf16
     libc.src.math.fromfpf16
     libc.src.math.fromfpxf16
     libc.src.math.getpayloadf16
+    libc.src.math.hypotf16
     libc.src.math.ilogbf16
     libc.src.math.iscanonicalf16
     libc.src.math.issignalingf16
@@ -745,20 +819,20 @@ if(LIBC_TYPES_HAS_FLOAT16)
     libc.src.math.llogbf16
     libc.src.math.llrintf16
     libc.src.math.llroundf16
+    libc.src.math.log10f16
     libc.src.math.log10p1f16
+    libc.src.math.log2f16
     libc.src.math.log2p1f16
     libc.src.math.logbf16
+    libc.src.math.logf16
     libc.src.math.lrintf16
     libc.src.math.lroundf16
-    # libc.src.math.modff16
+    libc.src.math.modff16
     libc.src.math.nanf16
     libc.src.math.nearbyintf16
     libc.src.math.nextafterf16
     libc.src.math.nextdownf16
-    # Temporarily disable nexttowardf16 on aarch64 because the conversion
-    # between _Float16 and long double will crash clang-11.  This is fixed in
-    # clang-12 and after: https://godbolt.org/z/8ceT9454c
-    # libc.src.math.nexttowardf16
+    libc.src.math.nexttowardf16
     libc.src.math.nextupf16
     libc.src.math.remainderf16
     libc.src.math.remquof16
@@ -771,8 +845,13 @@ if(LIBC_TYPES_HAS_FLOAT16)
     libc.src.math.scalbnf16
     libc.src.math.setpayloadf16
     libc.src.math.setpayloadsigf16
+    libc.src.math.sinf16
+    libc.src.math.sinhf16
     libc.src.math.sinpif16
     libc.src.math.sqrtf16
+    libc.src.math.tanf16
+    libc.src.math.tanhf16
+    libc.src.math.tanpif16
     libc.src.math.totalorderf16
     libc.src.math.totalordermagf16
     libc.src.math.truncf16
@@ -780,17 +859,17 @@ if(LIBC_TYPES_HAS_FLOAT16)
     libc.src.math.ufromfpxf16
   )
 
-  # if(LIBC_TYPES_HAS_FLOAT128)
-  #   list(APPEND TARGET_LIBM_ENTRYPOINTS
-  #     # math.h C23 mixed _Float16 and _Float128 entrypoints
-  #     libc.src.math.f16addf128
-  #     libc.src.math.f16divf128
-  #     libc.src.math.f16fmaf128
-  #     libc.src.math.f16mulf128
-  #     libc.src.math.f16sqrtf128
-  #     libc.src.math.f16subf128
-  #   )
-  # endif()
+  if(LIBC_TYPES_HAS_FLOAT128)
+    list(APPEND TARGET_LIBM_ENTRYPOINTS
+      # math.h C23 mixed _Float16 and _Float128 entrypoints
+      libc.src.math.f16addf128
+      libc.src.math.f16divf128
+      libc.src.math.f16fmaf128
+      libc.src.math.f16mulf128
+      libc.src.math.f16sqrtf128
+      libc.src.math.f16subf128
+    )
+  endif()
 endif()
 
 if(LIBC_TYPES_HAS_CFLOAT128)
@@ -807,6 +886,7 @@ if(LIBC_TYPES_HAS_FLOAT128)
   list(APPEND TARGET_LIBM_ENTRYPOINTS
     # math.h C23 _Float128 entrypoints
     libc.src.math.atan2f128
+    libc.src.math.atan2l
     libc.src.math.canonicalizef128
     libc.src.math.ceilf128
     libc.src.math.copysignf128
@@ -961,8 +1041,120 @@ if(LIBC_TYPES_HAS_FLOAT128)
   )
 endif()
 
+if(LIBC_COMPILER_HAS_FIXED_POINT)
+  list(APPEND TARGET_LIBM_ENTRYPOINTS
+    # stdfix.h _Fract and _Accum entrypoints
+    libc.src.stdfix.abshk
+    libc.src.stdfix.abshr
+    libc.src.stdfix.absk
+    libc.src.stdfix.abslk
+    libc.src.stdfix.abslr
+    libc.src.stdfix.absr
+    libc.src.stdfix.exphk
+    libc.src.stdfix.expk
+    libc.src.stdfix.roundhk
+    libc.src.stdfix.roundhr
+    libc.src.stdfix.roundk
+    libc.src.stdfix.roundlk
+    libc.src.stdfix.roundlr
+    libc.src.stdfix.roundr
+    libc.src.stdfix.rounduhk
+    libc.src.stdfix.rounduhr
+    libc.src.stdfix.rounduk
+    libc.src.stdfix.roundulk
+    libc.src.stdfix.roundulr
+    libc.src.stdfix.roundur
+    libc.src.stdfix.sqrtuhk
+    libc.src.stdfix.sqrtuhr
+    libc.src.stdfix.sqrtuk
+    libc.src.stdfix.sqrtur
+    # libc.src.stdfix.sqrtulk
+    libc.src.stdfix.sqrtulr
+    libc.src.stdfix.uhksqrtus
+    libc.src.stdfix.uksqrtui
+    libc.src.stdfix.hrbits
+    libc.src.stdfix.uhrbits
+    libc.src.stdfix.rbits
+    libc.src.stdfix.urbits
+    libc.src.stdfix.lrbits
+    libc.src.stdfix.ulrbits
+    libc.src.stdfix.hkbits
+    libc.src.stdfix.uhkbits
+    libc.src.stdfix.kbits
+    libc.src.stdfix.ukbits
+    libc.src.stdfix.lkbits
+    libc.src.stdfix.ulkbits
+    libc.src.stdfix.bitshr
+    libc.src.stdfix.bitsr
+    libc.src.stdfix.bitslr
+    libc.src.stdfix.bitshk
+    libc.src.stdfix.bitsk
+    libc.src.stdfix.bitslk
+    libc.src.stdfix.bitsuhr
+    libc.src.stdfix.bitsur
+    libc.src.stdfix.bitsulr
+    libc.src.stdfix.bitsuhk
+    libc.src.stdfix.bitsuk
+    libc.src.stdfix.bitsulk
+    libc.src.stdfix.countlshr
+    libc.src.stdfix.countlsr
+    libc.src.stdfix.countlslr
+    libc.src.stdfix.countlshk
+    libc.src.stdfix.countlsk
+    libc.src.stdfix.countlslk
+    libc.src.stdfix.countlsuhr
+    libc.src.stdfix.countlsur
+    libc.src.stdfix.countlsulr
+    libc.src.stdfix.countlsuhk
+    libc.src.stdfix.countlsuk
+    libc.src.stdfix.countlsulk
+    libc.src.stdfix.idivr
+    libc.src.stdfix.idivlr
+    libc.src.stdfix.idivk
+    libc.src.stdfix.idivlk
+    libc.src.stdfix.idivur
+    libc.src.stdfix.idivulr
+    libc.src.stdfix.idivuk
+    libc.src.stdfix.idivulk
+    libc.src.stdfix.rdivi
+  )
+endif()
+
 if(LLVM_LIBC_FULL_BUILD)
   list(APPEND TARGET_LIBC_ENTRYPOINTS
+    # ctype.h entrypoints
+    libc.src.ctype.isalnum_l
+    libc.src.ctype.isalpha_l
+    libc.src.ctype.isblank_l
+    libc.src.ctype.iscntrl_l
+    libc.src.ctype.isdigit_l
+    libc.src.ctype.isgraph_l
+    libc.src.ctype.islower_l
+    libc.src.ctype.isprint_l
+    libc.src.ctype.ispunct_l
+    libc.src.ctype.isspace_l
+    libc.src.ctype.isupper_l
+    libc.src.ctype.isxdigit_l
+    libc.src.ctype.tolower_l
+    libc.src.ctype.toupper_l
+
+    # stdlib.h entrypoints
+    libc.src.stdlib.strtod_l
+    libc.src.stdlib.strtof_l
+    libc.src.stdlib.strtol_l
+    libc.src.stdlib.strtold_l
+    libc.src.stdlib.strtoll_l
+    libc.src.stdlib.strtoul_l
+    libc.src.stdlib.strtoull_l
+
+    # string.h entrypoints
+    libc.src.string.strcoll_l
+    libc.src.string.strxfrm_l
+
+    # strings.h entrypoints
+    libc.src.strings.strcasecmp_l
+    libc.src.strings.strncasecmp_l
+
     # assert.h entrypoints
     libc.src.assert.__assert_fail
 
@@ -1017,6 +1209,9 @@ if(LLVM_LIBC_FULL_BUILD)
     libc.src.pthread.pthread_join
     libc.src.pthread.pthread_key_create
     libc.src.pthread.pthread_key_delete
+    libc.src.pthread.pthread_barrier_init
+    libc.src.pthread.pthread_barrier_wait
+    libc.src.pthread.pthread_barrier_destroy
     libc.src.pthread.pthread_mutex_destroy
     libc.src.pthread.pthread_mutex_init
     libc.src.pthread.pthread_mutex_lock
@@ -1063,16 +1258,16 @@ if(LLVM_LIBC_FULL_BUILD)
     libc.src.sched.__sched_setcpuset
     libc.src.sched.__sched_getcpuisset
 
-    # strings.h entrypoints
-    libc.src.strings.strcasecmp_l
-    libc.src.strings.strncasecmp_l
-
     # setjmp.h entrypoints
     libc.src.setjmp.longjmp
     libc.src.setjmp.setjmp
     libc.src.setjmp.siglongjmp
     libc.src.setjmp.sigsetjmp
 
+    # ucontext.h entrypoints
+    #libc.src.ucontext.getcontext
+    #libc.src.ucontext.setcontext
+
     # stdio.h entrypoints
     libc.src.stdio.clearerr
     libc.src.stdio.clearerr_unlocked
@@ -1124,7 +1319,11 @@ if(LLVM_LIBC_FULL_BUILD)
     libc.src.stdlib.atexit
     libc.src.stdlib.exit
     libc.src.stdlib.getenv
+    libc.src.stdlib.mbstowcs
+    libc.src.stdlib.mbtowc
     libc.src.stdlib.quick_exit
+    libc.src.stdlib.wcstombs
+    libc.src.stdlib.wctomb
 
     # signal.h entrypoints
     libc.src.signal.kill
@@ -1198,11 +1397,24 @@ if(LLVM_LIBC_FULL_BUILD)
     libc.src.time.gettimeofday
     libc.src.time.gmtime
     libc.src.time.gmtime_r
+    libc.src.time.localtime
+    libc.src.time.localtime_r
     libc.src.time.mktime
     libc.src.time.nanosleep
+    libc.src.time.strftime
+    libc.src.time.strftime_l
     libc.src.time.time
     libc.src.time.timespec_get
 
+    # locale.h entrypoints
+    libc.src.locale.localeconv
+    libc.src.locale.duplocale
+    libc.src.locale.freelocale
+    libc.src.locale.localeconv
+    libc.src.locale.newlocale
+    libc.src.locale.setlocale
+    libc.src.locale.uselocale
+
     # unistd.h entrypoints
     libc.src.unistd.__llvm_libc_syscall
     libc.src.unistd._exit
@@ -1222,20 +1434,43 @@ if(LLVM_LIBC_FULL_BUILD)
     # sys/socket.h entrypoints
     libc.src.sys.socket.accept
     libc.src.sys.socket.accept4
+    libc.src.sys.socket.socket
     libc.src.sys.socket.bind
     libc.src.sys.socket.connect
     libc.src.sys.socket.getsockopt
     libc.src.sys.socket.listen
-    libc.src.sys.socket.setsockopt
     libc.src.sys.socket.shutdown
-    libc.src.sys.socket.socket
+    libc.src.sys.socket.socketpair
+    libc.src.sys.socket.setsockopt
+    libc.src.sys.socket.send
+    libc.src.sys.socket.sendto
+    libc.src.sys.socket.sendmsg
+    libc.src.sys.socket.recv
+    libc.src.sys.socket.recvfrom
+    libc.src.sys.socket.recvmsg
+
+    # wchar.h entrypoints
+    libc.src.wchar.mblen
+    libc.src.wchar.mbrlen
+    libc.src.wchar.mbsinit
+    libc.src.wchar.mbrtowc
+    libc.src.wchar.mbsrtowcs
+    libc.src.wchar.mbsnrtowcs
+    libc.src.wchar.wcrtomb
+    libc.src.wchar.wcsrtombs
+    libc.src.wchar.wcsnrtombs
+
+    # nl_types.h entrypoints
+    libc.src.nl_types.catopen 
+    libc.src.nl_types.catclose
+    libc.src.nl_types.catgets
   )
 endif()
 
 set(TARGET_LIBMVEC_ENTRYPOINTS)
 
 if(LIBC_COMPILER_HAS_EXT_VECTOR_TYPE)
-  list(APPEND TARGET_LIBMVEC_ENTRYPOINTS
+list(APPEND TARGET_LIBMVEC_ENTRYPOINTS
     libc.src.mathvec.expf
   )
 endif()
diff --git a/libc/config/linux/aarch64/headers.txt b/libc/config/linux/aarch64/headers.txt
index 4784fc5d29ddc..0e5d5c753aed1 100644
--- a/libc/config/linux/aarch64/headers.txt
+++ b/libc/config/linux/aarch64/headers.txt
@@ -20,6 +20,7 @@ set(TARGET_PUBLIC_HEADERS
     libc.include.malloc
     libc.include.math
     libc.include.netinet_in
+    libc.include.nl_types
     libc.include.poll
     libc.include.pthread
     libc.include.sched
@@ -38,12 +39,14 @@ set(TARGET_PUBLIC_HEADERS
     libc.include.sys_auxv
     libc.include.sys_epoll
     libc.include.sys_ioctl
+    libc.include.sys_ipc
     libc.include.sys_mman
     libc.include.sys_prctl
     libc.include.sys_queue
     libc.include.sys_random
     libc.include.sys_resource
     libc.include.sys_select
+    libc.include.sys_sem
     libc.include.sys_socket
     libc.include.sys_stat
     libc.include.sys_statvfs
diff --git a/libc/config/linux/riscv/entrypoints.txt b/libc/config/linux/riscv/entrypoints.txt
index 6478aed3b0391..ff82dd479665a 100644
--- a/libc/config/linux/riscv/entrypoints.txt
+++ b/libc/config/linux/riscv/entrypoints.txt
@@ -18,6 +18,7 @@ set(TARGET_LIBC_ENTRYPOINTS
     libc.src.ctype.toupper
 
     # dlfcn.h entrypoints
+    libc.src.dlfcn.dladdr
     libc.src.dlfcn.dlclose
     libc.src.dlfcn.dlerror
     libc.src.dlfcn.dlopen
diff --git a/libc/config/linux/x86_64/entrypoints.txt b/libc/config/linux/x86_64/entrypoints.txt
index 27569f0fae82b..cc2e74240dbe5 100644
--- a/libc/config/linux/x86_64/entrypoints.txt
+++ b/libc/config/linux/x86_64/entrypoints.txt
@@ -110,6 +110,9 @@ set(TARGET_LIBC_ENTRYPOINTS
     libc.src.inttypes.strtoimax
     libc.src.inttypes.strtoumax
 
+    # link.h entrypoints
+    libc.src.link.dl_iterate_phdr
+
     # stdbit.h entrypoints
     libc.src.stdbit.stdc_bit_ceil_uc
     libc.src.stdbit.stdc_bit_ceil_ui
diff --git a/libc/include/llvm-libc-types/__thread_type.h b/libc/include/llvm-libc-types/__thread_type.h
index 645573f544a99..e2f4829e9fd7f 100644
--- a/libc/include/llvm-libc-types/__thread_type.h
+++ b/libc/include/llvm-libc-types/__thread_type.h
@@ -9,8 +9,6 @@
 #ifndef LLVM_LIBC_TYPES___THREAD_TYPE_H
 #define LLVM_LIBC_TYPES___THREAD_TYPE_H
 
-typedef struct {
-  void *__attrib;
-} __thread_type;
+typedef void *__thread_type;
 
 #endif // LLVM_LIBC_TYPES___THREAD_TYPE_H
diff --git a/libc/src/link/CMakeLists.txt b/libc/src/link/CMakeLists.txt
index 55f5edfab7d93..35fe9e87c74f2 100644
--- a/libc/src/link/CMakeLists.txt
+++ b/libc/src/link/CMakeLists.txt
@@ -5,5 +5,6 @@ add_entrypoint_object(
   HDRS
     dl_iterate_phdr.h
   DEPENDS
+    libc.src.__support.OSUtil.linux.auxv
     libc.hdr.stdint_proxy
 )
diff --git a/libc/src/link/dl_iterate_phdr.cpp b/libc/src/link/dl_iterate_phdr.cpp
index 7964411598d4a..7aa2be4f497f6 100644
--- a/libc/src/link/dl_iterate_phdr.cpp
+++ b/libc/src/link/dl_iterate_phdr.cpp
@@ -8,18 +8,141 @@
 
 #include "dl_iterate_phdr.h"
 
+#include "hdr/sys_auxv_macros.h"
+#include "src/__support/OSUtil/linux/auxv.h"
 #include "src/__support/common.h"
 #include "src/__support/macros/config.h"
 
+#include <elf.h>
+
+extern "C" {
+[[gnu::weak]] extern const char __ehdr_start;
+[[gnu::weak]] extern const char __executable_start;
+}
+
 namespace LIBC_NAMESPACE_DECL {
 
+namespace {
+
+LIBC_INLINE bool is_valid_elf(const ElfW(Ehdr) *ehdr) {
+  if (ehdr == nullptr)
+    return false;
+
+  return ehdr->e_ident[EI_MAG0] == ELFMAG0 &&
+         ehdr->e_ident[EI_MAG1] == ELFMAG1 &&
+         ehdr->e_ident[EI_MAG2] == ELFMAG2 &&
+         ehdr->e_ident[EI_MAG3] == ELFMAG3;
+}
+
+LIBC_INLINE const ElfW(Ehdr) *get_executable_ehdr() {
+  const ElfW(Ehdr) *ehdr = nullptr;
+
+  if (&__ehdr_start != nullptr)
+    ehdr = reinterpret_cast<const ElfW(Ehdr) *>(&__ehdr_start);
+  else if (&__executable_start != nullptr)
+    ehdr = reinterpret_cast<const ElfW(Ehdr) *>(&__executable_start);
+
+  return is_valid_elf(ehdr) ? ehdr : nullptr;
+}
+
+LIBC_INLINE ElfW(Addr) get_executable_load_bias(const ElfW(Ehdr) *ehdr,
+                                                const ElfW(Phdr) *phdr_table,
+                                                ElfW(Half) phnum) {
+  if (phdr_table != nullptr) {
+    const uintptr_t runtime_phdr = reinterpret_cast<uintptr_t>(phdr_table);
+    for (ElfW(Half) i = 0; i < phnum; ++i) {
+      if (phdr_table[i].p_type == PT_PHDR)
+        return static_cast<ElfW(Addr)>(runtime_phdr - phdr_table[i].p_vaddr);
+    }
+  }
+
+  // For PIE binaries the ELF header is mapped at the load bias. ET_EXEC uses
+  // absolute virtual addresses, so report zero there.
+  if (ehdr != nullptr && ehdr->e_type == ET_DYN)
+    return reinterpret_cast<ElfW(Addr)>(ehdr);
+
+  return 0;
+}
+
+LIBC_INLINE int call_with_executable(__dl_iterate_phdr_callback_t callback,
+                                     void *arg) {
+  const ElfW(Ehdr) *ehdr = get_executable_ehdr();
+  if (ehdr == nullptr)
+    return -1;
+
+  cpp::optional<unsigned long> aux_phdr_val = auxv::get(AT_PHDR);
+  cpp::optional<unsigned long> aux_phnum_val = auxv::get(AT_PHNUM);
+  auto *aux_phdr = reinterpret_cast<const ElfW(Phdr) *>(
+      aux_phdr_val ? *aux_phdr_val : 0);
+  const auto aux_phnum = static_cast<ElfW(Half)>(aux_phnum_val ? *aux_phnum_val
+                                                               : 0);
+
+  const ElfW(Phdr) *phdr =
+      aux_phdr != nullptr ? aux_phdr
+                          : reinterpret_cast<const ElfW(Phdr) *>(
+                                reinterpret_cast<uintptr_t>(ehdr) + ehdr->e_phoff);
+  const ElfW(Half) phnum = aux_phnum != 0 ? aux_phnum : ehdr->e_phnum;
+
+  dl_phdr_info exe_info = {};
+  exe_info.dlpi_addr = get_executable_load_bias(ehdr, phdr, phnum);
+  exe_info.dlpi_name = nullptr;
+  exe_info.dlpi_phdr = phdr;
+  exe_info.dlpi_phnum = phnum;
+  exe_info.dlpi_adds = 0;
+  exe_info.dlpi_subs = 0;
+  exe_info.dlpi_tls_modid = 0;
+  exe_info.dlpi_tls_data = nullptr;
+  return callback(&exe_info, sizeof(exe_info), arg);
+}
+
+LIBC_INLINE int call_with_vdso(__dl_iterate_phdr_callback_t callback,
+                               void *arg) {
+  cpp::optional<unsigned long> aux_vdso = auxv::get(AT_SYSINFO_EHDR);
+  auto *ehdr_vdso =
+      reinterpret_cast<const ElfW(Ehdr) *>(aux_vdso ? *aux_vdso : 0);
+  if (!is_valid_elf(ehdr_vdso))
+    return 0;
+
+  auto *phdr = reinterpret_cast<const ElfW(Phdr) *>(
+      reinterpret_cast<uintptr_t>(ehdr_vdso) + ehdr_vdso->e_phoff);
+
+  dl_phdr_info vdso_info = {};
+  vdso_info.dlpi_name = nullptr;
+  vdso_info.dlpi_phdr = phdr;
+  vdso_info.dlpi_phnum = ehdr_vdso->e_phnum;
+  vdso_info.dlpi_adds = 0;
+  vdso_info.dlpi_subs = 0;
+  vdso_info.dlpi_tls_modid = 0;
+  vdso_info.dlpi_tls_data = nullptr;
+
+  for (ElfW(Half) i = 0; i < ehdr_vdso->e_phnum; ++i) {
+    if (phdr[i].p_type == PT_LOAD) {
+      vdso_info.dlpi_addr = reinterpret_cast<ElfW(Addr)>(ehdr_vdso) -
+                            static_cast<ElfW(Addr)>(phdr[i].p_vaddr);
+      break;
+    }
+  }
+
+  return callback(&vdso_info, sizeof(vdso_info), arg);
+}
+
+} // namespace
+
 LLVM_LIBC_FUNCTION(int, dl_iterate_phdr,
                    (__dl_iterate_phdr_callback_t callback, void *arg)) {
-  // FIXME: For pure static linking, this can report just the executable with
-  // info from __ehdr_start or AT_{PHDR,PHNUM} decoding, and its PT_TLS; and it
-  // could report the vDSO.
-  (void)callback, (void)arg;
+#if defined(LIBC_TARGET_ARCH_IS_X86_64) || defined(LIBC_TARGET_ARCH_IS_AARCH64)
+  if (callback == nullptr)
+    return -1;
+
+  int rc = call_with_executable(callback, arg);
+  if (rc != 0)
+    return rc;
+  return call_with_vdso(callback, arg);
+#else
+  (void)callback;
+  (void)arg;
   return 0;
+#endif
 }
 
 } // namespace LIBC_NAMESPACE_DECL
diff --git a/libc/src/pthread/pthread_self.cpp b/libc/src/pthread/pthread_self.cpp
index c3169ec1ca5c4..e810b033170cb 100644
--- a/libc/src/pthread/pthread_self.cpp
+++ b/libc/src/pthread/pthread_self.cpp
@@ -20,8 +20,7 @@ static_assert(sizeof(pthread_t) == sizeof(LIBC_NAMESPACE::Thread),
               "Mismatch between pthread_t and internal Thread.");
 
 LLVM_LIBC_FUNCTION(pthread_t, pthread_self, ()) {
-  pthread_t th;
-  th.__attrib = self.attrib;
+  pthread_t th = self.attrib;
   return th;
 }
 
diff --git a/libc/src/threads/thrd_current.cpp b/libc/src/threads/thrd_current.cpp
index 634159712b629..29a0de13ef85e 100644
--- a/libc/src/threads/thrd_current.cpp
+++ b/libc/src/threads/thrd_current.cpp
@@ -19,8 +19,7 @@ static_assert(sizeof(thrd_t) == sizeof(LIBC_NAMESPACE::Thread),
               "Mismatch between thrd_t and internal Thread.");
 
 LLVM_LIBC_FUNCTION(thrd_t, thrd_current, ()) {
-  thrd_t th;
-  th.__attrib = self.attrib;
+  thrd_t th = self.attrib;
   return th;
 }
 
diff --git a/libcxx/include/__mbstate_t.h b/libcxx/include/__mbstate_t.h
index d331ba622d37f..d7ff5b8dd4adc 100644
--- a/libcxx/include/__mbstate_t.h
+++ b/libcxx/include/__mbstate_t.h
@@ -39,6 +39,8 @@
 #  define __NEED_mbstate_t
 #  include <bits/alltypes.h>
 #  undef __NEED_mbstate_t
+#elif __has_include(<llvm-libc-types/mbstate_t.h>)
+#  include <llvm-libc-types/mbstate_t.h>
 #elif __has_include(<bits/types/mbstate_t.h>)
 #  include <bits/types/mbstate_t.h> // works on most Unixes
 #elif __has_include(<sys/_types/_mbstate_t.h>)
diff --git a/run.sh b/run.sh
new file mode 100755
index 0000000000000..748565f0ac573
--- /dev/null
+++ b/run.sh
@@ -0,0 +1,340 @@
+#!/usr/bin/env bash
+set -euo pipefail
+
+repo="$(cd -- "$(dirname -- "${BASH_SOURCE[0]}")" && pwd)"
+build="${BUILD_DIR:-$repo/build-libcxx-llvm}"
+base_c_compiler="${CC:-/usr/bin/clang}"
+base_compiler="${CXX:-/usr/bin/clang++}"
+lit_jobs="${LIT_JOBS:-4}"
+host_arch="$(uname -m)"
+multiarch_triple=""
+configure_c_flags="${CFLAGS:-}"
+configure_cxx_flags="${CXXFLAGS:-}"
+compiler_is_clang=0
+
+case "$host_arch" in
+  x86_64)
+    compiler_rt_arch=x86_64
+    ;;
+  aarch64|arm64)
+    compiler_rt_arch=aarch64
+    ;;
+  *)
+    compiler_rt_arch="$host_arch"
+    ;;
+esac
+
+if "$base_compiler" -dM -E -x c++ /dev/null 2>/dev/null | grep -q '__clang__'; then
+  compiler_is_clang=1
+fi
+
+cd "$repo"
+
+for candidate in \
+  "$(
+    case "$host_arch" in
+      x86_64) echo x86_64-linux-gnu ;;
+      aarch64|arm64) echo aarch64-linux-gnu ;;
+      riscv64) echo riscv64-linux-gnu ;;
+      *) ;;
+    esac
+  )" \
+  "$("$base_c_compiler" -print-multiarch 2>/dev/null || true)" \
+  "$("$base_compiler" -print-multiarch 2>/dev/null || true)" \
+  "$("$base_c_compiler" -dumpmachine 2>/dev/null || true)" \
+  "$("$base_compiler" -dumpmachine 2>/dev/null || true)"; do
+  if [[ -n "$candidate" && -d "/usr/include/$candidate" ]]; then
+    multiarch_triple="$candidate"
+    break
+  fi
+done
+
+if [[ -z "$multiarch_triple" ]]; then
+  multiarch_triple="$(find /usr/include -mindepth 1 -maxdepth 1 -type d -name '*-linux-gnu' -exec test -d '{}/asm' ';' -print -quit | xargs -r basename)"
+fi
+
+if [[ -n "$multiarch_triple" ]]; then
+  configure_c_flags="${configure_c_flags:+$configure_c_flags }-idirafter/usr/include/$multiarch_triple"
+  configure_cxx_flags="${configure_cxx_flags:+$configure_cxx_flags }-idirafter/usr/include/$multiarch_triple"
+fi
+
+if [[ ! -f "$build/CMakeCache.txt" ]]; then
+  mkdir -p "$build"
+  cmake \
+    -S "$repo/runtimes" \
+    -B "$build" \
+    -G Ninja \
+    -DCMAKE_BUILD_TYPE=Release \
+    -DCMAKE_C_COMPILER="$base_c_compiler" \
+    -DCMAKE_CXX_COMPILER="$base_compiler" \
+    -DCMAKE_C_FLAGS="$configure_c_flags" \
+    -DCMAKE_CXX_FLAGS="$configure_cxx_flags" \
+    -DCMAKE_C_COMPILER_LAUNCHER= \
+    -DCMAKE_CXX_COMPILER_LAUNCHER= \
+    -DLIBUNWIND_ENABLE_SHARED=OFF \
+    -DLIBUNWIND_ENABLE_STATIC=ON \
+    -DLIBCXXABI_ENABLE_SHARED=OFF \
+    -DLIBCXXABI_ENABLE_STATIC=ON \
+    -DLIBCXXABI_ENABLE_STATIC_UNWINDER=ON \
+    -DLIBCXX_ENABLE_SHARED=OFF \
+    -DLIBCXX_ENABLE_STATIC=ON \
+    -DLIBCXX_ENABLE_STATIC_ABI_LIBRARY=ON \
+    -DLIBCXX_ENABLE_FILESYSTEM=OFF \
+    -DLIBCXX_ENABLE_WIDE_CHARACTERS=OFF \
+    -DLLVM_LIBC_INCLUDE_SCUDO=ON \
+    -DCOMPILER_RT_BUILD_SCUDO_STANDALONE_WITH_LLVM_LIBC=ON \
+    -DCOMPILER_RT_BUILD_GWP_ASAN=OFF \
+    -DCOMPILER_RT_SCUDO_STANDALONE_BUILD_SHARED=OFF \
+    -DRUNTIMES_USE_LIBC=llvm-libc \
+    -DLLVM_ENABLE_RUNTIMES="libc;compiler-rt;libunwind;libcxxabi;libcxx" \
+    -DLIBCXX_INCLUDE_TESTS=ON \
+    -DLIBCXX_INCLUDE_BENCHMARKS=OFF
+fi
+
+builtins_target="clang_rt.builtins-$compiler_rt_arch"
+builtins_target_candidates="$(ninja -C "$build" -t targets all | sed -n 's/:.*//; /^clang_rt\.builtins-/p; /^libclang_rt\.builtins-.*\.a$/p')"
+if ! grep -qx "$builtins_target" <<<"$builtins_target_candidates"; then
+  alt_target="libclang_rt.builtins-$compiler_rt_arch.a"
+  if grep -qx "$alt_target" <<<"$builtins_target_candidates"; then
+    builtins_target="$alt_target"
+  else
+    builtins_target="$(head -n 1 <<<"$builtins_target_candidates")"
+    if [[ -z "$builtins_target" ]]; then
+      echo "unable to locate a compiler-rt builtins target in $build" >&2
+      exit 1
+    fi
+  fi
+fi
+
+root="$(mktemp -d "$build/run-sandbox.XXXXXX")"
+launcher_shims="$root/shims"
+sysroot="$root/sysroot"
+wrapper="$root/clang++-llvm-libc"
+lit_wrapper="$root/llvm-lit-fork"
+empty_include="$root/empty-usr-local-include"
+fortify_shim_c="$root/fortify-shim.c"
+fortify_shim_o="$root/fortify-shim.o"
+multiarch_include_dir=""
+asm_source_dir=""
+
+cleanup() {
+  rm -rf "$root"
+}
+trap cleanup EXIT
+
+mkdir -p "$launcher_shims"
+cat > "$launcher_shims/sccache" <<'EOF'
+#!/usr/bin/env bash
+exec "$@"
+EOF
+chmod +x "$launcher_shims/sccache"
+export PATH="$launcher_shims:$PATH"
+
+if (($# == 0)); then
+  targets=("$build/libcxx/test")
+else
+  targets=("$@")
+fi
+
+ninja -C "$build" \
+  libc/include/generate-libc-headers \
+  crt1.o \
+  libc.a \
+  libm.a \
+  lib/libunwind.a \
+  "$builtins_target" \
+  cxx-test-depends
+
+builtins="$build/compiler-rt/lib/linux/libclang_rt.builtins-$compiler_rt_arch.a"
+if [[ ! -f "$builtins" ]]; then
+  builtins="$(find "$build/compiler-rt/lib" -name "libclang_rt.builtins-$compiler_rt_arch.a" -print -quit)"
+fi
+if [[ -z "${builtins:-}" || ! -f "$builtins" ]]; then
+  builtins="$(find "$build/compiler-rt/lib" -name 'libclang_rt.builtins-*.a' -print -quit)"
+  if [[ -z "${builtins:-}" ]]; then
+    echo "unable to locate compiler-rt builtins archive under $build/compiler-rt/lib" >&2
+    exit 1
+  fi
+fi
+
+mkdir -p "$sysroot/usr/include" "$empty_include"
+
+# Preserve Linux UAPI headers, but do not copy libc++ into /usr/include.
+if [[ -d /usr/include/linux ]]; then
+  cp -a /usr/include/linux "$sysroot/usr/include/"
+fi
+if [[ -d /usr/include/asm-generic ]]; then
+  cp -a /usr/include/asm-generic "$sysroot/usr/include/"
+fi
+if [[ -n "$multiarch_triple" ]]; then
+  multiarch_include_dir="$sysroot/usr/include/$multiarch_triple"
+  mkdir -p "$multiarch_include_dir"
+fi
+if [[ -n "$multiarch_triple" && -d "/usr/include/$multiarch_triple/asm" ]]; then
+  asm_source_dir="$(readlink -f "/usr/include/$multiarch_triple/asm")"
+elif [[ -d /usr/include/asm ]]; then
+  asm_source_dir="$(readlink -f /usr/include/asm)"
+fi
+if [[ -n "$asm_source_dir" ]]; then
+  mkdir -p "${multiarch_include_dir:-$sysroot/usr/include}/asm"
+  cp -a "$asm_source_dir/." "${multiarch_include_dir:-$sysroot/usr/include}/asm/"
+fi
+cp -a "$build/libc/include/." "$sysroot/usr/include/"
+
+crtbegin="$("$base_compiler" --print-file-name=crtbeginT.o)"
+crtend="$("$base_compiler" --print-file-name=crtend.o)"
+
+cat > "$fortify_shim_c" <<'EOF'
+typedef __SIZE_TYPE__ size_t;
+
+__attribute__((noreturn)) static void __llvm_libcxx_test_chk_fail(void) {
+  __builtin_trap();
+}
+
+static void *__llvm_libcxx_test_memcpy(void *dst, const void *src, size_t len) {
+  unsigned char *out = (unsigned char *)dst;
+  const unsigned char *in = (const unsigned char *)src;
+  for (size_t i = 0; i < len; ++i)
+    out[i] = in[i];
+  return dst;
+}
+
+static void *__llvm_libcxx_test_memmove(void *dst, const void *src, size_t len) {
+  unsigned char *out = (unsigned char *)dst;
+  const unsigned char *in = (const unsigned char *)src;
+  if (out == in || len == 0)
+    return dst;
+  if (out < in || out >= in + len) {
+    for (size_t i = 0; i < len; ++i)
+      out[i] = in[i];
+  } else {
+    for (size_t i = len; i != 0; --i)
+      out[i - 1] = in[i - 1];
+  }
+  return dst;
+}
+
+static void *__llvm_libcxx_test_memset(void *dst, int value, size_t len) {
+  unsigned char *out = (unsigned char *)dst;
+  unsigned char byte = (unsigned char)value;
+  for (size_t i = 0; i < len; ++i)
+    out[i] = byte;
+  return dst;
+}
+
+void *__memcpy_chk(void *dst, const void *src, size_t len, size_t dstlen) {
+  if (len > dstlen)
+    __llvm_libcxx_test_chk_fail();
+  return __llvm_libcxx_test_memcpy(dst, src, len);
+}
+
+void *__memmove_chk(void *dst, const void *src, size_t len, size_t dstlen) {
+  if (len > dstlen)
+    __llvm_libcxx_test_chk_fail();
+  return __llvm_libcxx_test_memmove(dst, src, len);
+}
+
+void *__memset_chk(void *dst, int value, size_t len, size_t dstlen) {
+  if (len > dstlen)
+    __llvm_libcxx_test_chk_fail();
+  return __llvm_libcxx_test_memset(dst, value, len);
+}
+EOF
+
+"$base_compiler" \
+  -c \
+  -x c \
+  -fno-stack-protector \
+  -ffreestanding \
+  "$fortify_shim_c" \
+  -o "$fortify_shim_o"
+
+cat > "$wrapper" <<EOF
+#!/usr/bin/env bash
+set -euo pipefail
+
+base_compiler=$base_compiler
+sysroot=$sysroot
+repo=$repo
+build=$build
+crtbegin=$crtbegin
+crtend=$crtend
+builtins=$builtins
+fortify_shim_o=$fortify_shim_o
+multiarch_include_dir=$multiarch_include_dir
+compiler_is_clang=$compiler_is_clang
+
+linking=1
+for arg in "\$@"; do
+  case "\$arg" in
+    -c|-E|-S|-fsyntax-only|-emit-ast)
+      linking=0
+      ;;
+  esac
+done
+
+common_args=(
+  -nostdlibinc
+  -isystem "\$sysroot/usr/include"
+  -fno-stack-protector
+  -Wno-missing-braces
+)
+if (( compiler_is_clang )); then
+  # The sandboxed sysroot setup can trigger Clang's GCC-install-dir warning,
+  # and libc++'s config probes use -Werror while checking -std= flags.
+  common_args+=(-Wno-unknown-warning-option -Wno-gcc-install-dir-libstdcxx)
+fi
+if [[ -n "\$multiarch_include_dir" ]]; then
+  common_args+=(-isystem "\$multiarch_include_dir")
+fi
+
+if (( linking )); then
+  exec "\$base_compiler" \
+    "\$@" \
+    "\${common_args[@]}" \
+    -nodefaultlibs \
+    -nostartfiles \
+    -static \
+    "$build/libc/startup/linux/crt1.o" \
+    "\$crtbegin" \
+    -L "$build/libc/lib" \
+    -lunwind \
+    -lc \
+    -lm \
+    "\$fortify_shim_o" \
+    "\$builtins" \
+    "\$crtend"
+else
+  exec "\$base_compiler" "\$@" "\${common_args[@]}"
+fi
+EOF
+
+chmod +x "$wrapper"
+
+cat > "$lit_wrapper" <<EOF
+#!/usr/bin/env python3
+import multiprocessing as mp
+import runpy
+import sys
+
+mp.set_start_method("fork")
+sys.argv[0] = "$build/bin/llvm-lit"
+runpy.run_path("$build/bin/llvm-lit", run_name="__main__")
+EOF
+
+chmod +x "$lit_wrapper"
+
+bwrap \
+  --ro-bind / / \
+  --bind "$repo" "$repo" \
+  --dev-bind /dev /dev \
+  --proc /proc \
+  --tmpfs /tmp \
+  --chdir "$repo" \
+  --ro-bind "$sysroot/usr/include" /usr/include \
+  --ro-bind "$empty_include" /usr/local/include \
+  "$lit_wrapper" \
+  -sv \
+  "-j$lit_jobs" \
+  --param "compiler=$wrapper" \
+  "${targets[@]}"
diff --git a/runtimes/CMakeLists.txt b/runtimes/CMakeLists.txt
index 75551ba0c651a..61a43356694f3 100644
--- a/runtimes/CMakeLists.txt
+++ b/runtimes/CMakeLists.txt
@@ -59,6 +59,15 @@ foreach(proj ${LLVM_ENABLE_RUNTIMES})
   endif()
 endforeach()
 
+# The in-tree LLVM libc only provides a complete public C header set in
+# full-build mode. Consumers like libc++, libc++abi, and libunwind need those
+# headers to avoid falling back to the host libc in overlay mode.
+if(DEFINED RUNTIMES_USE_LIBC AND RUNTIMES_USE_LIBC STREQUAL "llvm-libc")
+  message(STATUS "Enabling LLVM_LIBC_FULL_BUILD because RUNTIMES_USE_LIBC=llvm-libc")
+  set(LLVM_LIBC_FULL_BUILD ON CACHE BOOL
+      "Build and test LLVM libc as if it is the full libc" FORCE)
+endif()
+
 function(runtime_register_component name)
   set_property(GLOBAL APPEND PROPERTY SUB_COMPONENTS ${name})
 endfunction()



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