From 0b336657b1805154373d64d00292c38b213db9dc Mon Sep 17 00:00:00 2001
From: Davis Vaughan <davis@posit.co>
Date: Mon, 17 Mar 2025 10:23:00 -0400
Subject: [PATCH] Don't negate `toff` if we've already failed

This avoids calling `-` on `not_a_offset`, which is set to `minutes::min()`, which is typically the min of `long`. Due to two's complement, calling `-` on this minimum value is undefined behavior.
---
 include/date/date.h | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/include/date/date.h b/include/date/date.h
index 79a2e9d..f70153b 100644
--- a/include/date/date.h
+++ b/include/date/date.h
@@ -7577,7 +7577,7 @@ from_stream(std::basic_istream<CharT, Traits>& is, const CharT* fmt,
                             }
                         }
                     }
-                    if (neg)
+                    if (neg && !is.fail())
                         toff = -toff;
                     checked_set(temp_offset, toff, not_a_offset, is);
                     command = nullptr;