File 0779-erts-Fix-overflow-when-calculating-monoton... of Package erlang

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File 0779-erts-Fix-overflow-when-calculating-monotonic-start_o.patch of Package erlang (Revision 147fb24ecc7389ec5e91cbf5b419c961)

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From db9977b988489f0ed5369dfad5d9f932a76a8f2d Mon Sep 17 00:00:00 2001
From: =?UTF-8?q?John=20H=C3=B6gberg?= <john@erlang.org>
Date: Tue, 27 Feb 2024 09:11:12 +0100
Subject: [PATCH] erts: Fix overflow when calculating monotonic start_offset

---
 erts/emulator/beam/erl_time_sup.c | 29 ++++++++++++++++++-----------
 1 file changed, 18 insertions(+), 11 deletions(-)

diff --git a/erts/emulator/beam/erl_time_sup.c b/erts/emulator/beam/erl_time_sup.c
index 0dc85edd20..f63bda3ee9 100644
--- a/erts/emulator/beam/erl_time_sup.c
+++ b/erts/emulator/beam/erl_time_sup.c
@@ -992,17 +992,24 @@ erts_init_time_sup(int time_correction, ErtsTimeWarpMode time_warp_mode)
     native_offset = erts_time_sup__.r.o.start - ERTS_MONOTONIC_BEGIN;
     abs_native_offset = native_offset;
 #else /* ARCH_64 */
-    if (ERTS_MONOTONIC_TIME_UNIT <= 10*1000*1000) {
-	erts_time_sup__.r.o.start = 0;
-	native_offset = -ERTS_MONOTONIC_BEGIN;
-	abs_native_offset = ERTS_MONOTONIC_BEGIN;
-    }
-    else {
-	erts_time_sup__.r.o.start = ((ErtsMonotonicTime) MIN_SMALL);
-	erts_time_sup__.r.o.start /= ERTS_MONOTONIC_TIME_UNIT;
-	erts_time_sup__.r.o.start *= ERTS_MONOTONIC_TIME_UNIT;
-	native_offset = erts_time_sup__.r.o.start - ERTS_MONOTONIC_BEGIN;
-	abs_native_offset = -1*native_offset;
+    {
+        /* To keep monotonic times as smalls as long as possible, we want to
+         * have a start offset as close to MIN_SMALL as possible without it
+         * overflowing a small when converted to nanoseconds. */
+        static const Uint64 nano = (1000 * 1000 * 1000);
+
+        if (ERTS_MONOTONIC_TIME_UNIT < nano) {
+            erts_time_sup__.r.o.start =
+                -(ErtsMonotonicTime)((MAX_SMALL / nano) *
+                                     ERTS_MONOTONIC_TIME_UNIT);
+        } else {
+            erts_time_sup__.r.o.start = (ErtsMonotonicTime)MIN_SMALL;
+            erts_time_sup__.r.o.start /= ERTS_MONOTONIC_TIME_UNIT;
+            erts_time_sup__.r.o.start *= ERTS_MONOTONIC_TIME_UNIT;
+        }
+
+        native_offset = erts_time_sup__.r.o.start - ERTS_MONOTONIC_BEGIN;
+        abs_native_offset = -native_offset;
     }
 #endif
 
-- 
2.35.3

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File 0779-erts-Fix-overflow-when-calculating-monotonic-start_o.patch of Package erlang (Revision 147fb24ecc7389ec5e91cbf5b419c961)

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