From: Jonathan Wakely <jwakely@redhat.com>
Date: Fri, 4 Oct 2024 17:11:06 +0000 (+0100)
Subject: libstdc++: Fix -Wsign-compare in std::latch::count_down
X-Git-Tag: basepoints/gcc-16~5344
X-Git-Url: http://git.ipfire.org/?a=commitdiff_plain;h=f5021ce9aa6be524beca99e0bbd0180b4e53029b;p=thirdparty%2Fgcc.git

libstdc++: Fix -Wsign-compare in std::latch::count_down

Also add assertions for the precondition on the parameter's value.

libstdc++-v3/ChangeLog:

	* include/std/latch (latch::count_down): Add assertions for
	preconditions. Cast parameter to avoid -Wsign-compare on some
	targets.
---

diff --git a/libstdc++-v3/include/std/latch b/libstdc++-v3/include/std/latch
index 146e1860979..1d254aa2581 100644
--- a/libstdc++-v3/include/std/latch
+++ b/libstdc++-v3/include/std/latch
@@ -63,9 +63,11 @@ _GLIBCXX_BEGIN_NAMESPACE_VERSION
     _GLIBCXX_ALWAYS_INLINE void
     count_down(ptrdiff_t __update = 1)
     {
+      __glibcxx_assert(__update >= 0);
       auto const __old = __atomic_impl::fetch_sub(&_M_a,
 				    __update, memory_order::release);
-      if (__old == __update)
+      __glibcxx_assert(__update >= 0);
+      if (__old == static_cast<__detail::__platform_wait_t>(__update))
 	__atomic_impl::notify_all(&_M_a);
     }
 
@@ -88,6 +90,8 @@ _GLIBCXX_BEGIN_NAMESPACE_VERSION
     }
 
   private:
+    // This alignas is not redundant, it increases the alignment for
+    // long long on x86.
     alignas(__alignof__(__detail::__platform_wait_t)) __detail::__platform_wait_t _M_a;
   };
 _GLIBCXX_END_NAMESPACE_VERSION