Origin:
https://sourceforge.net/p/mcj/tickets/186/
https://sourceforge.net/p/mcj/fig2dev/ci/c8a87d22036e62bac0c6f7836078d8103caa6457/

--- a/fig2dev/object.h
+++ b/fig2dev/object.h
@@ -3,7 +3,7 @@
  * Copyright (c) 1991 by Micah Beck
  * Parts Copyright (c) 1985-1988 by Supoj Sutanthavibul
  * Parts Copyright (c) 1989-2015 by Brian V. Smith
- * Parts Copyright (c) 2015-2023 by Thomas Loimer
+ * Parts Copyright (c) 2015-2025 by Thomas Loimer
  *
  * Any party obtaining a copy of these files is granted, free of charge, a
  * full and unrestricted irrevocable, world-wide, paid up, royalty-free,
@@ -91,10 +91,10 @@ typedef struct f_ellipse {
 	struct f_ellipse	*next;
 } F_ellipse;
 
-#define INVALID_ELLIPSE(e)	\
+#define INVALID_ELLIPSE(e)						\
 	e->type < T_ELLIPSE_BY_RAD || e->type > T_CIRCLE_BY_DIA ||	\
-	COMMON_PROPERTIES(e) || (e->direction != 1 && e->direction != 0) || \
-	e->radiuses.x == 0 || e->radiuses.y == 0 || \
+	COMMON_PROPERTIES(e) || (e->direction != 1 && e->direction != 0) ||  \
+	e->radiuses.x == 0 || e->radiuses.y == 0 ||			\
 	e->angle < -7. || e->angle > 7.
 
 typedef struct f_arc {
@@ -121,12 +121,16 @@ typedef struct f_arc {
 	struct f_arc		*next;
 } F_arc;
 
-#define INVALID_ARC(a)	\
+#define COINCIDENT(a, b)	(a.x == b.x && a.y == b.y)
+#define INVALID_ARC(a)							\
 	a->type < T_OPEN_ARC || a->type > T_PIE_WEDGE_ARC ||		\
 	COMMON_PROPERTIES(a) || a->cap_style < 0 || a->cap_style > 2 ||	\
 	a->center.x < COORD_MIN || a->center.x > COORD_MAX ||		\
 	a->center.y < COORD_MIN || a->center.y > COORD_MAX ||		\
-	(a->direction != 0 && a->direction != 1)
+	(a->direction != 0 && a->direction != 1) ||			\
+	COINCIDENT(a->point[0], a->point[1]) ||				\
+	COINCIDENT(a->point[0], a->point[2]) ||				\
+	COINCIDENT(a->point[1], a->point[2])
 
 typedef struct f_line {
 	int			type;
--- a/fig2dev/tests/read.at
+++ b/fig2dev/tests/read.at
@@ -2,7 +2,7 @@ dnl Fig2dev: Translate Fig code to various Devices
 dnl Copyright (c) 1991 by Micah Beck
 dnl Parts Copyright (c) 1985-1988 by Supoj Sutanthavibul
 dnl Parts Copyright (c) 1989-2015 by Brian V. Smith
-dnl Parts Copyright (c) 2015-2023 by Thomas Loimer
+dnl Parts Copyright (c) 2015-2025 by Thomas Loimer
 dnl
 dnl Any party obtaining a copy of these files is granted, free of charge, a
 dnl full and unrestricted irrevocable, world-wide, paid up, royalty-free,
@@ -14,7 +14,7 @@ dnl party to do so, with the only requirement being that the above copyright
 dnl and this permission notice remain intact.
 
 dnl read.at
-dnl Author: Thomas Loimer, 2017-2020
+dnl Author: Thomas Loimer, 2017-2025
 
 
 AT_BANNER([Sanitize and harden input.])
@@ -237,6 +237,16 @@ EOF
 ])
 AT_CLEANUP
 
+AT_SETUP([reject arcs with coincident points, ticket #186])
+AT_KEYWORDS(read.c arc)
+AT_CHECK([fig2dev -L pict2e <<EOF
+FIG_FILE_TOP
+5 1 0 15 0 7 50 0 -1 0.0 1 0 0 0 0.0 0.0 1 1 1 1 2 0
+EOF
+], 1, ignore, [Invalid arc object at line 10.
+])
+AT_CLEANUP
+
 AT_SETUP([survive debian bugs #881143, #881144])
 AT_KEYWORDS([font pic tikz])
 AT_CHECK([fig2dev -L pic <<EOF