From a417cbae4be1e18a73cb60821fe9479ec9ac906d Mon Sep 17 00:00:00 2001
From: Paul Davis <paul@linuxaudiosystems.com>
Date: Wed, 17 Nov 2021 08:58:49 -0700
Subject: [PATCH] tempo map: fix a potential bug (not seen in the wild) when
 generating the grid

the "p" variable could point to _points.end(), so we cannot indirect and use
p->sclock() value unconditionally.
---
 libs/temporal/tempo.cc | 10 +++++++++-
 1 file changed, 9 insertions(+), 1 deletion(-)

diff --git a/libs/temporal/tempo.cc b/libs/temporal/tempo.cc
index a56a1fe52b..244a582bc1 100644
--- a/libs/temporal/tempo.cc
+++ b/libs/temporal/tempo.cc
@@ -1926,7 +1926,15 @@ TempoMap::get_grid (TempoMapPoints& ret, superclock_t start, superclock_t end, u
 
 		DEBUG_TRACE (DEBUG::Grid, string_compose ("start %1 end %2 bbt %3 find first/limit with limit @ = %4\n", start, end, bbt, *p));
 
-		while (start < p->sclock() && start < end) {
+		superclock_t limit;
+
+		if (p == _points.end()) {
+			limit = end;
+		} else {
+			limit = std::min (p->sclock(), end);
+		}
+
+		while (start < limit) {
 
 			/* add point to grid, perhaps */