From 6d786782d455d41ce1a80a462dfc90feda3329ee Mon Sep 17 00:00:00 2001
From: "copilot-swe-agent[bot]" <198982749+Copilot@users.noreply.github.com>
Date: Wed, 24 Jun 2026 18:19:44 +0000
Subject: [PATCH 1/3] Initial plan


From fab4621078dfaac3aca5ff7c773266931093e81e Mon Sep 17 00:00:00 2001
From: "copilot-swe-agent[bot]" <198982749+Copilot@users.noreply.github.com>
Date: Wed, 24 Jun 2026 18:23:15 +0000
Subject: [PATCH 2/3] Fix invalid map step handling in path sampling

---
 src/gmt_map.c | 15 +++++++++++++++
 1 file changed, 15 insertions(+)

diff --git a/src/gmt_map.c b/src/gmt_map.c
index 373c46c9980..defae750fea 100644
--- a/src/gmt_map.c
+++ b/src/gmt_map.c
@@ -8011,6 +8011,14 @@ uint64_t gmtlib_lonpath (struct GMT_CTRL *GMT, double lon, double lat1, double l
 	/* Must do general case */
 	n = 0;
 	min_gap = 0.1 * GMT->current.setting.map_line_step;
+	if (!isfinite (GMT->current.map.dlat) || GMT->current.map.dlat <= 0.0) {	/* Guard against invalid sampling step (e.g., antipodal singularities) */
+		gmt_M_malloc2 (GMT, tlon, tlat, 2U, NULL, double);
+		tlon[0] = tlon[1] = lon;
+		tlat[0] = lat1;	tlat[1] = lat2;
+		*x = tlon;
+		*y = tlat;
+		return (2ULL);
+	}
 	if ((n_alloc = lrint (ceil (fabs (lat2 - lat1) / GMT->current.map.dlat))) == 0) return (0);
 
 	n_alloc++;	/* So n_alloc is at least 2 */
@@ -8108,6 +8116,13 @@ uint64_t gmtlib_latpath (struct GMT_CTRL *GMT, double lat, double lon1, double l
 	}
 	/* Here we try to walk along lat for small increment in longitude to make sure our steps are smaller than the line_step */
 	min_gap = 0.1 * GMT->current.setting.map_line_step;
+	if (!isfinite (GMT->current.map.dlon) || GMT->current.map.dlon <= 0.0) {	/* Guard against invalid sampling step (e.g., antipodal singularities) */
+		gmt_M_malloc2 (GMT, tlon, tlat, 2U, NULL, double);
+		tlat[0] = tlat[1] = lat;
+		tlon[0] = lon1;	tlon[1] = lon2;
+		*x = tlon;	*y = tlat;
+		return (2ULL);
+	}
 	if ((n_alloc = lrint (ceil (fabs (lon2 - lon1) / GMT->current.map.dlon))) == 0) return (0);	/* Initial guess to path length */
 
 	n_alloc++;	/* n_alloc is at least 2 */

From 9228a4f3ddcb8d794f86f6ecc644e1960cc275b2 Mon Sep 17 00:00:00 2001
From: "copilot-swe-agent[bot]" <198982749+Copilot@users.noreply.github.com>
Date: Wed, 24 Jun 2026 18:24:03 +0000
Subject: [PATCH 3/3] Polish fallback path assignments for readability

---
 src/gmt_map.c | 9 ++++++---
 1 file changed, 6 insertions(+), 3 deletions(-)

diff --git a/src/gmt_map.c b/src/gmt_map.c
index defae750fea..4fbcc82df10 100644
--- a/src/gmt_map.c
+++ b/src/gmt_map.c
@@ -8014,7 +8014,8 @@ uint64_t gmtlib_lonpath (struct GMT_CTRL *GMT, double lon, double lat1, double l
 	if (!isfinite (GMT->current.map.dlat) || GMT->current.map.dlat <= 0.0) {	/* Guard against invalid sampling step (e.g., antipodal singularities) */
 		gmt_M_malloc2 (GMT, tlon, tlat, 2U, NULL, double);
 		tlon[0] = tlon[1] = lon;
-		tlat[0] = lat1;	tlat[1] = lat2;
+		tlat[0] = lat1;
+		tlat[1] = lat2;
 		*x = tlon;
 		*y = tlat;
 		return (2ULL);
@@ -8119,8 +8120,10 @@ uint64_t gmtlib_latpath (struct GMT_CTRL *GMT, double lat, double lon1, double l
 	if (!isfinite (GMT->current.map.dlon) || GMT->current.map.dlon <= 0.0) {	/* Guard against invalid sampling step (e.g., antipodal singularities) */
 		gmt_M_malloc2 (GMT, tlon, tlat, 2U, NULL, double);
 		tlat[0] = tlat[1] = lat;
-		tlon[0] = lon1;	tlon[1] = lon2;
-		*x = tlon;	*y = tlat;
+		tlon[0] = lon1;
+		tlon[1] = lon2;
+		*x = tlon;
+		*y = tlat;
 		return (2ULL);
 	}
 	if ((n_alloc = lrint (ceil (fabs (lon2 - lon1) / GMT->current.map.dlon))) == 0) return (0);	/* Initial guess to path length */