[libc-commits] [libc] [libc] Remove hardcoded sizeof in __barrier_type.h (PR #153718)

[Mikhail R. Gadelha via libc-commits]

https://github.com/mikhailramalho updated https://github.com/llvm/llvm-project/pull/153718

>From 08a3fee6380fe00d5333ff5e7d4ffa5455dbacdf Mon Sep 17 00:00:00 2001
From: "Mikhail R. Gadelha" <mikhail at igalia.com>
Date: Thu, 14 Aug 2025 21:30:21 -0300
Subject: [PATCH 1/2] Remove hardcoded sizeof

Signed-off-by: Mikhail R. Gadelha <mikhail at igalia.com>
---
 libc/include/llvm-libc-types/__barrier_type.h | 9 ++++++---
 1 file changed, 6 insertions(+), 3 deletions(-)

diff --git a/libc/include/llvm-libc-types/__barrier_type.h b/libc/include/llvm-libc-types/__barrier_type.h
index 59712619e917d..23593372af56e 100644
--- a/libc/include/llvm-libc-types/__barrier_type.h
+++ b/libc/include/llvm-libc-types/__barrier_type.h
@@ -9,13 +9,16 @@
 #ifndef LLVM_LIBC_TYPES__BARRIER_TYPE_H
 #define LLVM_LIBC_TYPES__BARRIER_TYPE_H
 
+#include "src/__support/threads/CndVar.h"
+#include "src/__support/threads/mutex.h"
+
 typedef struct __attribute__((aligned(8 /* alignof (Barrier) */))) {
   unsigned expected;
   unsigned waiting;
   bool blocking;
-  char entering[24 /* sizeof (CndVar) */];
-  char exiting[24 /* sizeof (CndVar) */];
-  char mutex[24 /* sizeof (Mutex) */];
+  char entering[sizeof(LIBC_NAMESPACE::CndVar)];
+  char exiting[sizeof(LIBC_NAMESPACE::CndVar)];
+  char mutex[sizeof(LIBC_NAMESPACE::Mutex)];
 } __barrier_type;
 
 #endif // LLVM_LIBC_TYPES__BARRIER_TYPE_H

>From 0da48fd3873eeb1c22ca55fe47373ab3189fe460 Mon Sep 17 00:00:00 2001
From: "Mikhail R. Gadelha" <mikhail at igalia.com>
Date: Fri, 15 Aug 2025 12:09:34 -0300
Subject: [PATCH 2/2] Changed static_assert

Signed-off-by: Mikhail R. Gadelha <mikhail at igalia.com>
---
 libc/include/llvm-libc-types/__barrier_type.h |  9 +++------
 libc/src/__support/threads/linux/barrier.h    | 15 ++++++++++-----
 2 files changed, 13 insertions(+), 11 deletions(-)

diff --git a/libc/include/llvm-libc-types/__barrier_type.h b/libc/include/llvm-libc-types/__barrier_type.h
index 23593372af56e..59712619e917d 100644
--- a/libc/include/llvm-libc-types/__barrier_type.h
+++ b/libc/include/llvm-libc-types/__barrier_type.h
@@ -9,16 +9,13 @@
 #ifndef LLVM_LIBC_TYPES__BARRIER_TYPE_H
 #define LLVM_LIBC_TYPES__BARRIER_TYPE_H
 
-#include "src/__support/threads/CndVar.h"
-#include "src/__support/threads/mutex.h"
-
 typedef struct __attribute__((aligned(8 /* alignof (Barrier) */))) {
   unsigned expected;
   unsigned waiting;
   bool blocking;
-  char entering[sizeof(LIBC_NAMESPACE::CndVar)];
-  char exiting[sizeof(LIBC_NAMESPACE::CndVar)];
-  char mutex[sizeof(LIBC_NAMESPACE::Mutex)];
+  char entering[24 /* sizeof (CndVar) */];
+  char exiting[24 /* sizeof (CndVar) */];
+  char mutex[24 /* sizeof (Mutex) */];
 } __barrier_type;
 
 #endif // LLVM_LIBC_TYPES__BARRIER_TYPE_H
diff --git a/libc/src/__support/threads/linux/barrier.h b/libc/src/__support/threads/linux/barrier.h
index f0655bfc52a10..d6264f7d631e8 100644
--- a/libc/src/__support/threads/linux/barrier.h
+++ b/libc/src/__support/threads/linux/barrier.h
@@ -36,15 +36,20 @@ class Barrier {
   int wait();
 };
 
-static_assert(
-    sizeof(Barrier) == sizeof(pthread_barrier_t),
-    "The public pthread_barrier_t type cannot accommodate the internal "
-    "barrier type.");
+static_assert(sizeof(Barrier) <= sizeof(pthread_barrier_t),
+              "The public pthread_barrier_t type cannot accommodate the "
+              "internal barrier type.");
 
-static_assert(alignof(Barrier) == alignof(pthread_barrier_t),
+static_assert(alignof(Barrier) <= alignof(pthread_barrier_t),
               "The public pthread_barrier_t type has a different alignment "
               "than the internal barrier type.");
 
+static_assert(sizeof(CndVar) <= 24,
+              "CndVar size exceeds the size in __barrier_type.h");
+
+static_assert(sizeof(Mutex) <= 24,
+              "Mutex size exceeds the size in __barrier_type.h");
+
 } // namespace LIBC_NAMESPACE_DECL
 
 #endif // LLVM_LIBC___SUPPORT_SRC_THREADS_LINUX_BARRIER_H