[libc-commits] [libc] Libc/gcc bug (PR #95600)

[Schrodinger ZHU Yifan via libc-commits]

https://github.com/SchrodingerZhu created https://github.com/llvm/llvm-project/pull/95600

None

>From aa8fe4eb559c5ad9eee916ba07453948dba546cc Mon Sep 17 00:00:00 2001
From: Yifan Zhu <yifzhu at nvidia.com>
Date: Fri, 14 Jun 2024 13:48:53 -0700
Subject: [PATCH 1/2] [libc] fix preferred_type attribute detection

---
 libc/src/__support/macros/attributes.h | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/libc/src/__support/macros/attributes.h b/libc/src/__support/macros/attributes.h
index 7e8e2ddfac9b1..c6474673de85a 100644
--- a/libc/src/__support/macros/attributes.h
+++ b/libc/src/__support/macros/attributes.h
@@ -42,7 +42,7 @@
 #define LIBC_CONSTINIT
 #endif
 
-#ifdef __clang__
+#if defined(__clang__) && __has_attribute(preferred_type)
 #define LIBC_PREFERED_TYPE(TYPE) [[clang::preferred_type(TYPE)]]
 #else
 #define LIBC_PREFERED_TYPE(TYPE)

>From a6e874ae1ab69a6fe1c599382aa1b93b4ec38fd2 Mon Sep 17 00:00:00 2001
From: Yifan Zhu <yifzhu at nvidia.com>
Date: Fri, 14 Jun 2024 14:03:22 -0700
Subject: [PATCH 2/2] [libc] workaround gcc bitfield assignment warning

---
 libc/src/__support/threads/linux/rwlock.h | 5 +++--
 1 file changed, 3 insertions(+), 2 deletions(-)

diff --git a/libc/src/__support/threads/linux/rwlock.h b/libc/src/__support/threads/linux/rwlock.h
index 5db0590fd6aa0..1778995cf3766 100644
--- a/libc/src/__support/threads/linux/rwlock.h
+++ b/libc/src/__support/threads/linux/rwlock.h
@@ -370,8 +370,9 @@ class RwLock {
 public:
   LIBC_INLINE constexpr RwLock(Role preference = Role::Reader,
                                bool is_pshared = false)
-      : is_pshared(is_pshared), preference(static_cast<unsigned>(preference)),
-        state(0), writer_tid(0), queue() {}
+      : is_pshared(is_pshared),
+        preference(static_cast<unsigned>(preference) & 1u), state(0),
+        writer_tid(0), queue() {}
 
   [[nodiscard]]
   LIBC_INLINE LockResult try_read_lock() {