[libc][darwin] add basic mutex support for darwin

libc/cmake/modules/LLVMLibCCompileOptionRules.cmake

@@ -170,6 +170,19 @@ function(_get_common_compile_options output_var flags)
           list(APPEND compile_options "-idirafter${LIBC_KERNEL_HEADERS}")
         endif()
       endif()
+      if(LIBC_TARGET_OS_IS_DARWIN)
+        execute_process(
+          COMMAND xcrun --sdk macosx --show-sdk-path
+          OUTPUT_VARIABLE MACOSX_SDK_PATH
+          RESULT_VARIABLE MACOSX_SDK_PATH_RESULT
+          OUTPUT_STRIP_TRAILING_WHITESPACE
+        )
+        if(MACOSX_SDK_PATH_RESULT EQUAL 0)
+          list(APPEND compile_options "-I" "${MACOSX_SDK_PATH}/usr/include")
+        else()
+          message(WARNING "Could not find macOS SDK path. `xcrun --sdk macosx --show-sdk-path` failed.")
+        endif()
+      endif()
     endif()
 
     if(LIBC_COMPILER_HAS_FIXED_POINT)

libc/config/darwin/aarch64/entrypoints.txt

@@ -111,6 +111,7 @@ if(LLVM_LIBC_FULL_BUILD)
     libc.src.setjmp.setjmp
     libc.src.setjmp.siglongjmp
     libc.src.setjmp.sigsetjmp
+    libc.src.stdlib._Exit
   )
 endif()
 

libc/include/llvm-libc-macros/darwin/CMakeLists.txt

@@ -0,0 +1,5 @@
+add_header(
+  time_macros
+  HDR
+    time-macros.h
+)

libc/include/llvm-libc-macros/darwin/time-macros.h

@@ -0,0 +1,14 @@
+//===-- Definition of macros from time.h ---------------------------------===//
+//
+// Part of the LLVM Project, under the Apache License v2.0 with LLVM Exceptions.
+// See https://llvm.org/LICENSE.txt for license information.
+// SPDX-License-Identifier: Apache-2.0 WITH LLVM-exception
+//
+//===----------------------------------------------------------------------===//
+
+#ifndef LLVM_LIBC_MACROS_LINUX_TIME_MACROS_H
+#define LLVM_LIBC_MACROS_LINUX_TIME_MACROS_H
+
+#include <_time.h>
+
+#endif // LLVM_LIBC_MACROS_LINUX_TIME_MACROS_H

libc/include/llvm-libc-macros/time-macros.h

@@ -7,6 +7,8 @@
 #include "linux/time-macros.h"
 #elif defined(__ELF__)
 #include "baremetal/time-macros.h"
+#elif defined(__APPLE__)
+#include "darwin/time-macros.h"
 #else
 #define CLOCKS_PER_SEC 1000000
 #endif

libc/include/llvm-libc-types/clockid_t.h

@@ -9,6 +9,12 @@
 #ifndef LLVM_LIBC_TYPES_CLOCKID_T_H
 #define LLVM_LIBC_TYPES_CLOCKID_T_H
 
+#if defined(__APPLE__)
+// Darwin provides its own defintion for clockid_t . Use that to prevent
+// redeclaration errors and correctness.
+#include <_time.h>
+#else
 typedef int clockid_t;
+#endif // __APPLE__
 
 #endif // LLVM_LIBC_TYPES_CLOCKID_T_H

libc/include/llvm-libc-types/struct_timespec.h

@@ -9,12 +9,18 @@
 #ifndef LLVM_LIBC_TYPES_STRUCT_TIMESPEC_H
 #define LLVM_LIBC_TYPES_STRUCT_TIMESPEC_H
 
+#if defined(__APPLE__)
+// Darwin provides its own definition for struct timespec. Include it directly
+// to ensure type compatibility and avoid redefinition errors.
+#include <sys/_types/_timespec.h>
+#else
 #include "time_t.h"
 
 struct timespec {
   time_t tv_sec; /* Seconds.  */
   /* TODO: BIG_ENDIAN may require padding. */
   long tv_nsec; /* Nanoseconds.  */
 };
+#endif // __APPLE__
 
 #endif // LLVM_LIBC_TYPES_STRUCT_TIMESPEC_H

libc/include/llvm-libc-types/struct_timeval.h

@@ -12,9 +12,15 @@
 #include "suseconds_t.h"
 #include "time_t.h"
 
+#if defined(__APPLE__)
+// Darwin provides its own definition for struct timeval. Include it directly
+// to ensure type compatibility and avoid redefinition errors.
+#include <sys/_types/_timeval.h>
+#else
 struct timeval {
   time_t tv_sec;       // Seconds
   suseconds_t tv_usec; // Micro seconds
 };
+#endif // __APPLE__
 
 #endif // LLVM_LIBC_TYPES_STRUCT_TIMEVAL_H

libc/include/llvm-libc-types/suseconds_t.h

@@ -14,6 +14,12 @@
 // types...] and suseconds_t are no greater than the width of type long.
 
 // The kernel expects 64 bit suseconds_t at least on x86_64.
+#if defined(__APPLE__)
+// Darwin provides its own definition for suseconds_t. Include it directly
+// to ensure type compatibility and avoid redefinition errors.
+#include <sys/_types/_suseconds_t.h>
+#else
 typedef long suseconds_t;
+#endif // __APPLE__
 
 #endif // LLVM_LIBC_TYPES_SUSECONDS_T_H

libc/include/llvm-libc-types/time_t_32.h

@@ -9,6 +9,12 @@
 #ifndef LLVM_LIBC_TYPES_TIME_T_32_H
 #define LLVM_LIBC_TYPES_TIME_T_32_H
 
+#if defined(__APPLE__)
+// Darwin provides its own definition for time_t. Include it directly
+// to ensure type compatibility and avoid redefinition errors.
+#include <sys/_types/_time_t.h>
+#else
 typedef __INT32_TYPE__ time_t;
+#endif // __APPLE__
 
 #endif // LLVM_LIBC_TYPES_TIME_T_32_H

libc/include/llvm-libc-types/time_t_64.h

@@ -9,6 +9,12 @@
 #ifndef LLVM_LIBC_TYPES_TIME_T_64_H
 #define LLVM_LIBC_TYPES_TIME_T_64_H
 
+#if defined(__APPLE__)
+// Darwin provides its own definition for time_t. Include it directly
+// to ensure type compatibility and avoid redefinition errors.
+#include <sys/_types/_time_t.h>
+#else
 typedef __INT64_TYPE__ time_t;
+#endif // __APPLE__
 
 #endif // LLVM_LIBC_TYPES_TIME_T_64_H

libc/include/sys/syscall.h.def

@@ -9,7 +9,11 @@
 #ifndef LLVM_LIBC_SYS_SYSCALL_H
 #define LLVM_LIBC_SYS_SYSCALL_H
 
-//TODO: Handle non-linux syscalls
+#if defined(__APPLE__)
+
+#include <sys/syscall.h>
+
+#elif defined(__linux__)
 
 #include <asm/unistd.h>
 
@@ -2361,5 +2365,6 @@
 #define SYS_writev __NR_writev
 #endif
 
+#endif // __linux__
 
 #endif // LLVM_LIBC_SYS_SYSCALL_H

libc/src/__support/OSUtil/darwin/CMakeLists.txt

@@ -4,13 +4,16 @@ endif()
 
 add_subdirectory(${LIBC_TARGET_ARCHITECTURE})
 
-add_header_library(
+add_object_library(
   darwin_util
+  SRCS
+    exit.cpp
   HDRS
     io.h
     syscall.h
   DEPENDS
-    .${LIBC_TARGET_ARCHITECTURE}.darwin_util
+  .${LIBC_TARGET_ARCHITECTURE}.darwin_${LIBC_TARGET_ARCHITECTURE}_util
     libc.src.__support.common
     libc.src.__support.CPP.string_view
+    libc.include.sys_syscall
 )

libc/src/__support/OSUtil/darwin/aarch64/CMakeLists.txt

@@ -1,5 +1,5 @@
 add_header_library(
-  darwin_util
+  darwin_aarch64_util
   HDRS
     syscall.h
   DEPENDS

libc/src/__support/OSUtil/darwin/exit.cpp

@@ -0,0 +1,24 @@
+//===------------ MacOS implementation of an exit function ------*- C++ -*-===//
+//
+// Part of the LLVM Project, under the Apache License v2.0 with LLVM Exceptions.
+// See https://llvm.org/LICENSE.txt for license information.
+// SPDX-License-Identifier: Apache-2.0 WITH LLVM-exception
+//
+//===----------------------------------------------------------------------===//
+
+#include "src/__support/OSUtil/darwin/syscall.h" // syscall_impl
+#include "src/__support/common.h"
+#include "src/__support/macros/config.h"
+#include "sys/syscall.h" // For syscall numbers.
+
+namespace LIBC_NAMESPACE_DECL {
+namespace internal {
+
+[[noreturn]] void exit(int status) {
+  for (;;) {
+    LIBC_NAMESPACE::syscall_impl<long>(SYS_exit, status);
+  }
+}
+
+} // namespace internal
+} // namespace LIBC_NAMESPACE_DECL

libc/src/__support/threads/darwin/CMakeLists.txt

@@ -0,0 +1,11 @@
+if(NOT TARGET libc.src.__support.OSUtil.osutil)
+  return()
+endif()
+
+add_header_library(
+  mutex
+  HDRS
+    mutex.h
+  DEPENDS
+    libc.src.__support.threads.mutex_common
+)

libc/src/__support/threads/darwin/mutex.h

@@ -0,0 +1,132 @@
+//===--- Implementation of a Darwin mutex class ------------------*- C++
+//-*-===//
+//
+// Part of the LLVM Project, under the Apache License v2.0 with LLVM Exceptions.
+// See https://llvm.org/LICENSE.txt for license information.
+// SPDX-License-Identifier: Apache-2.0 WITH LLVM-exception
+//
+//===----------------------------------------------------------------------===//
+
+#ifndef LLVM_LIBC_SRC___SUPPORT_THREADS_DARWIN_MUTEX_H
+#define LLVM_LIBC_SRC___SUPPORT_THREADS_DARWIN_MUTEX_H
+
+#include "src/__support/libc_assert.h"
+#include "src/__support/macros/config.h"
+#include "src/__support/threads/mutex_common.h"
+#include "src/__support/threads/sleep.h" // For sleep_briefly
+#include "src/__support/time/linux/abs_timeout.h"
+
+#include <mach/mach_init.h> // For mach_thread_self
+#include <mach/mach_port.h> // For mach_port_t and MACH_PORT_NULL
+#include <os/lock.h>        // For os_unfair_lock
+#include <time.h>           // For clock_gettime
+
+namespace LIBC_NAMESPACE_DECL {
+
+// This file is an implementation of `LIBC_NAMESPACE::mutex` for Darwin-based
+// platforms. It is a wrapper around `os_unfair_lock`, which is a low-level,
+// high-performance locking primitive provided by the kernel.
+//
+// `os_unfair_lock` is a non-recursive, thread-owned lock that blocks waiters
+// efficiently in the kernel. As the name implies, it is "unfair," meaning
+// it does not guarantee the order in which waiting threads acquire the lock.
+// This trade-off allows for higher performance in contended scenarios.
+//
+// The lock must be unlocked from the same thread that locked it. Attempting
+// to unlock from a different thread will result in a runtime error.
+//
+// This implementation is suitable for simple critical sections where fairness
+// and reentrancy are not concerns.
+
+class Mutex final {
+  os_unfair_lock_s lock_val = OS_UNFAIR_LOCK_INIT;
+  mach_port_t owner = MACH_PORT_NULL;
+
+  // API compatibility fields.
+  unsigned char timed;
+  unsigned char recursive;
+  unsigned char robust;
+  unsigned char pshared;
+
+public:
+  LIBC_INLINE constexpr Mutex(bool is_timed, bool is_recursive, bool is_robust,
+                              bool is_pshared)
+      : owner(MACH_PORT_NULL), timed(is_timed), recursive(is_recursive),
+        robust(is_robust), pshared(is_pshared) {}
+
+  LIBC_INLINE constexpr Mutex()
+      : owner(MACH_PORT_NULL), timed(0), recursive(0), robust(0), pshared(0) {}
+
+  LIBC_INLINE static MutexError init(Mutex *mutex, bool is_timed, bool is_recur,
+                                     bool is_robust, bool is_pshared) {
+    mutex->lock_val = OS_UNFAIR_LOCK_INIT;
+    mutex->owner = MACH_PORT_NULL;
+    mutex->timed = is_timed;
+    mutex->recursive = is_recur;
+    mutex->robust = is_robust;
+    mutex->pshared = is_pshared;
+    return MutexError::NONE;
+  }
+
+  LIBC_INLINE static MutexError destroy(Mutex *lock) {
+    LIBC_ASSERT(lock->owner == MACH_PORT_NULL &&
+                "Mutex destroyed while locked.");
+    return MutexError::NONE;
+  }
+
+  LIBC_INLINE MutexError lock() {
+    os_unfair_lock_lock(&lock_val);
+    owner = mach_thread_self();
+    return MutexError::NONE;
+  }
+
+  LIBC_INLINE MutexError timed_lock(internal::AbsTimeout abs_time) {
+    while (true) {
+      if (try_lock() == MutexError::NONE) {
+        return MutexError::NONE;
+      }
+
+      // Manually check if the timeout has expired.
+      struct timespec now;
+      // The clock used here must match the clock used to create the
+      // absolute timeout.
+      clock_gettime(abs_time.is_realtime() ? CLOCK_REALTIME : CLOCK_MONOTONIC,
+                    &now);
+      const timespec &target_ts = abs_time.get_timespec();
+
+      if (now.tv_sec > target_ts.tv_sec || (now.tv_sec == target_ts.tv_sec &&
+                                            now.tv_nsec >= target_ts.tv_nsec)) {
+        // We might have acquired the lock between the last try_lock() and now.
+        // To avoid returning TIMEOUT incorrectly, we do one last try_lock().
+        if (try_lock() == MutexError::NONE)
+          return MutexError::NONE;
+        return MutexError::TIMEOUT;
+      }
+
+      sleep_briefly();
+    }
+  }
+
+  LIBC_INLINE MutexError unlock() {
+    // This check is crucial. It prevents both double-unlocks and unlocks
+    // by threads that do not own the mutex.
+    if (owner != mach_thread_self()) {
+      return MutexError::UNLOCK_WITHOUT_LOCK;
+    }
+    owner = MACH_PORT_NULL;
+    os_unfair_lock_unlock(&lock_val);
+    return MutexError::NONE;
+  }
+
+  LIBC_INLINE MutexError try_lock() {
+    if (os_unfair_lock_trylock(&lock_val)) {
+      owner = mach_thread_self();
+      return MutexError::NONE;
+    }
+    return MutexError::BUSY;
+  }
+};
+
+} // namespace LIBC_NAMESPACE_DECL
+
+#endif // LLVM_LIBC_SRC___SUPPORT_THREADS_DARWIN_MUTEX_H

libc/src/__support/threads/mutex.h

@@ -42,7 +42,9 @@
 
 #if defined(__linux__)
 #include "src/__support/threads/linux/mutex.h"
-#endif // __linux__
+#elif defined(__APPLE__)
+#include "src/__support/threads/darwin/mutex.h"
+#endif
 
 #elif LIBC_THREAD_MODE == LIBC_THREAD_MODE_SINGLE
 

libc/src/__support/time/darwin/CMakeLists.txt

@@ -0,0 +1,12 @@
+add_object_library(
+  clock_gettime
+  SRCS
+    clock_gettime.cpp
+  HDRS
+    ../clock_gettime.h
+  DEPENDS
+    libc.src.__support.common
+    libc.src.__support.error_or
+    libc.hdr.types.struct_timeval
+    libc.hdr.types.struct_timespec
+)