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[2/3] std::latch: reduce internal implementation from ptrdiff_t to int

Message ID 20210305182128.2071822-3-thiago.macieira@intel.com
State New
Headers show
Series Uncontroversial improvements to C++20 wait-related implementation | expand

Commit Message

Thiago Macieira March 5, 2021, 6:21 p.m. UTC 
ints can be used as futex on Linux. ptrdiff_t on 64-bit Linux can't.

libstdc++-v3/ChangeLog:

        * include/std/latch: Use int instead of ptrdiff_t
---
 libstdc++-v3/include/std/latch | 4 ++--
 1 file changed, 2 insertions(+), 2 deletions(-)
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Patch

diff --git a/libstdc++-v3/include/std/latch b/libstdc++-v3/include/std/latch
index ef8c301e5e9..f3f73360618 100644
--- a/libstdc++-v3/include/std/latch
+++ b/libstdc++-v3/include/std/latch
@@ -48,7 +48,7 @@  _GLIBCXX_BEGIN_NAMESPACE_VERSION
   public:
     static constexpr ptrdiff_t
     max() noexcept
-    { return __gnu_cxx::__int_traits<ptrdiff_t>::__max; }
+    { return __gnu_cxx::__int_traits<int>::__max; }
 
     constexpr explicit latch(ptrdiff_t __expected) noexcept
       : _M_a(__expected) { }
@@ -85,7 +85,7 @@  _GLIBCXX_BEGIN_NAMESPACE_VERSION
     }
 
   private:
-    alignas(__alignof__(ptrdiff_t)) ptrdiff_t _M_a;
+    alignas(4) int _M_a;	// kernel requires 4-byte alignment
   };
 _GLIBCXX_END_NAMESPACE_VERSION
 } // namespace