[libcxx-commits] [libcxx] [libcxx] Make locks available with _LIBCPP_HAS_NO_THREADS (PR #98717)

[via libcxx-commits]

llvmbot wrote:


<!--LLVM PR SUMMARY COMMENT-->

@llvm/pr-subscribers-libcxx

Author: Petr Hosek (petrhosek)

<details>
<summary>Changes</summary>

This change makes std::lock_guard, std::unique_lock, std::scoped_lock, and std::shared_lock available when _LIBCPP_HAS_NO_THREADS is set. These classes are generic and don't require threading support, and are regularly used even in environments where threading isn't available like embedded.

fixes #<!-- -->89891

---
Full diff: https://github.com/llvm/llvm-project/pull/98717.diff


4 Files Affected:

- (modified) libcxx/include/__mutex/lock_guard.h (-4) 
- (modified) libcxx/include/__mutex/unique_lock.h (-4) 
- (modified) libcxx/include/mutex (+3-3) 
- (modified) libcxx/include/shared_mutex (+7-8) 


``````````diff
diff --git a/libcxx/include/__mutex/lock_guard.h b/libcxx/include/__mutex/lock_guard.h
index 8340b9bbd4453..ef56896be9f68 100644
--- a/libcxx/include/__mutex/lock_guard.h
+++ b/libcxx/include/__mutex/lock_guard.h
@@ -16,8 +16,6 @@
 #  pragma GCC system_header
 #endif
 
-#ifndef _LIBCPP_HAS_NO_THREADS
-
 _LIBCPP_BEGIN_NAMESPACE_STD
 
 template <class _Mutex>
@@ -47,6 +45,4 @@ _LIBCPP_CTAD_SUPPORTED_FOR_TYPE(lock_guard);
 
 _LIBCPP_END_NAMESPACE_STD
 
-#endif // _LIBCPP_HAS_NO_THREADS
-
 #endif // _LIBCPP___MUTEX_LOCK_GUARD_H
diff --git a/libcxx/include/__mutex/unique_lock.h b/libcxx/include/__mutex/unique_lock.h
index 4a616ba51ee1c..5df791de4c742 100644
--- a/libcxx/include/__mutex/unique_lock.h
+++ b/libcxx/include/__mutex/unique_lock.h
@@ -22,8 +22,6 @@
 #  pragma GCC system_header
 #endif
 
-#ifndef _LIBCPP_HAS_NO_THREADS
-
 _LIBCPP_BEGIN_NAMESPACE_STD
 
 template <class _Mutex>
@@ -172,6 +170,4 @@ inline _LIBCPP_HIDE_FROM_ABI void swap(unique_lock<_Mutex>& __x, unique_lock<_Mu
 
 _LIBCPP_END_NAMESPACE_STD
 
-#endif // _LIBCPP_HAS_NO_THREADS
-
 #endif // _LIBCPP___MUTEX_UNIQUE_LOCK_H
diff --git a/libcxx/include/mutex b/libcxx/include/mutex
index 02c52dd72f02b..d4d7539240094 100644
--- a/libcxx/include/mutex
+++ b/libcxx/include/mutex
@@ -419,8 +419,9 @@ inline _LIBCPP_HIDE_FROM_ABI void lock(_L0& __l0, _L1& __l1, _L2& __l2, _L3&...
 }
 
 #  endif // _LIBCPP_CXX03_LANG
+#endif   // !_LIBCPP_HAS_NO_THREADS
 
-#  if _LIBCPP_STD_VER >= 17
+#if _LIBCPP_STD_VER >= 17
 template <class... _Mutexes>
 class _LIBCPP_TEMPLATE_VIS scoped_lock;
 
@@ -491,8 +492,7 @@ private:
 };
 _LIBCPP_CTAD_SUPPORTED_FOR_TYPE(scoped_lock);
 
-#  endif // _LIBCPP_STD_VER >= 17
-#endif   // !_LIBCPP_HAS_NO_THREADS
+#endif // _LIBCPP_STD_VER >= 17
 
 _LIBCPP_END_NAMESPACE_STD
 
diff --git a/libcxx/include/shared_mutex b/libcxx/include/shared_mutex
index 397ac290d9b2e..5918af4a214c1 100644
--- a/libcxx/include/shared_mutex
+++ b/libcxx/include/shared_mutex
@@ -122,16 +122,11 @@ template <class Mutex>
 
 */
 
-#include <__config>
-
-#ifdef _LIBCPP_HAS_NO_THREADS
-#  error "<shared_mutex> is not supported since libc++ has been configured without support for threads."
-#endif
-
 #include <__chrono/duration.h>
 #include <__chrono/steady_clock.h>
 #include <__chrono/time_point.h>
 #include <__condition_variable/condition_variable.h>
+#include <__config>
 #include <__memory/addressof.h>
 #include <__mutex/mutex.h>
 #include <__mutex/tag_types.h>
@@ -152,6 +147,8 @@ _LIBCPP_PUSH_MACROS
 
 _LIBCPP_BEGIN_NAMESPACE_STD
 
+#  ifndef _LIBCPP_HAS_NO_THREADS
+
 struct _LIBCPP_EXPORTED_FROM_ABI __shared_mutex_base {
   mutex __mut_;
   condition_variable __gate1_;
@@ -181,7 +178,7 @@ struct _LIBCPP_EXPORTED_FROM_ABI __shared_mutex_base {
   //     native_handle_type native_handle(); // See 30.2.3
 };
 
-#  if _LIBCPP_STD_VER >= 17
+#    if _LIBCPP_STD_VER >= 17
 class _LIBCPP_EXPORTED_FROM_ABI _LIBCPP_THREAD_SAFETY_ANNOTATION(__capability__("shared_mutex")) shared_mutex {
   __shared_mutex_base __base_;
 
@@ -218,7 +215,7 @@ public:
   //     typedef __shared_mutex_base::native_handle_type native_handle_type;
   //     _LIBCPP_HIDE_FROM_ABI native_handle_type native_handle() { return __base::unlock_shared(); }
 };
-#  endif
+#    endif
 
 class _LIBCPP_EXPORTED_FROM_ABI
 _LIBCPP_THREAD_SAFETY_ANNOTATION(__capability__("shared_timed_mutex")) shared_timed_mutex {
@@ -308,6 +305,8 @@ bool shared_timed_mutex::try_lock_shared_until(const chrono::time_point<_Clock,
   return true;
 }
 
+#  endif   // !_LIBCPP_HAS_NO_THREADS
+
 template <class _Mutex>
 class shared_lock {
 public:

``````````

</details>


https://github.com/llvm/llvm-project/pull/98717