From 9d240e90f87bf8b53bd5d92b623e33419db64717 Mon Sep 17 00:00:00 2001 From: Alvaro Herrera Date: Mon, 1 Jul 2024 10:41:06 +0200 Subject: [PATCH v2] Fix alignment of variable in pg_atomic_monotonic_advance_u64 Reported-by: Alexander Lakhin Discussion: https://postgr.es/m/36796438-a718-cf9b-2071-b2c1b947c1b5@gmail.com --- src/include/port/atomics.h | 24 ++++++++++++++++-------- 1 file changed, 16 insertions(+), 8 deletions(-) diff --git a/src/include/port/atomics.h b/src/include/port/atomics.h index 78987f3154..964732e660 100644 --- a/src/include/port/atomics.h +++ b/src/include/port/atomics.h @@ -580,30 +580,38 @@ pg_atomic_sub_fetch_u64(volatile pg_atomic_uint64 *ptr, int64 sub_) static inline uint64 pg_atomic_monotonic_advance_u64(volatile pg_atomic_uint64 *ptr, uint64 target_) { - uint64 currval; + /* + * On 32-bit machines, declaring a bare uint64 variable doesn't promise + * the alignment we need, so coerce the compiler this way. + */ + union + { + uint64 u64; + double force_align_d; + } currval; #ifndef PG_HAVE_ATOMIC_U64_SIMULATION AssertPointerAlignment(ptr, 8); #endif - currval = pg_atomic_read_u64_impl(ptr); - if (currval >= target_) + currval.u64 = pg_atomic_read_u64_impl(ptr); + if (currval.u64 >= target_) { pg_memory_barrier(); - return currval; + return currval.u64; } #ifndef PG_HAVE_ATOMIC_U64_SIMULATION - AssertPointerAlignment(&currval, 8); + AssertPointerAlignment(&currval.u64, 8); #endif - while (currval < target_) + while (currval.u64 < target_) { - if (pg_atomic_compare_exchange_u64_impl(ptr, &currval, target_)) + if (pg_atomic_compare_exchange_u64_impl(ptr, &currval.u64, target_)) break; } - return Max(target_, currval); + return Max(target_, currval.u64); } #undef INSIDE_ATOMICS_H -- 2.39.2