From 237bcacd5b5049632092c800bb1a17958a97033a Mon Sep 17 00:00:00 2001
From: Dan Baston <dbaston@gmail.com>
Date: Wed, 19 Jun 2024 21:07:40 -0400
Subject: [PATCH] GEOSConcaveHullOfPolygons: Avoid crash on zero-area input,
 references GH-1071

---
 NEWS.md                                           | 1 +
 src/algorithm/hull/ConcaveHullOfPolygons.cpp      | 2 +-
 tests/unit/capi/GEOSConcaveHullOfPolygonsTest.cpp | 9 +++++++++
 3 files changed, 11 insertions(+), 1 deletion(-)

diff --git a/NEWS.md b/NEWS.md
index 6af7744e30..017a4e2c07 100644
--- a/NEWS.md
+++ b/NEWS.md
@@ -8,6 +8,7 @@
   - GEOSLineSubstring: Fix crash on NaN length fractions (GH-1088, Dan Baston)
   - GEOSRelatePatternMatch: Fix crash on invalid DE-9IM pattern (GH-1089, Dan Baston)
   - Fix ConcaveHullOfPolygons nested shell handling (GH-1169, Martin Davis)
+  - GEOSConcaveHullOfPolygons, Avoid crash on zero-area input (GH-1071, Dan Baston)
 
 ## Changes in 3.12.2
 2024-06-05
diff --git a/src/algorithm/hull/ConcaveHullOfPolygons.cpp b/src/algorithm/hull/ConcaveHullOfPolygons.cpp
index 623a7662ab..d49b5eff1e 100644
--- a/src/algorithm/hull/ConcaveHullOfPolygons.cpp
+++ b/src/algorithm/hull/ConcaveHullOfPolygons.cpp
@@ -154,7 +154,7 @@ ConcaveHullOfPolygons::setTight(bool p_isTight)
 std::unique_ptr<Geometry>
 ConcaveHullOfPolygons::getHull()
 {
-    if (inputPolygons->isEmpty()) {
+    if (inputPolygons->isEmpty() || inputPolygons->getArea() == 0) {
         return createEmptyHull();
     }
     buildHullTris();
diff --git a/tests/unit/capi/GEOSConcaveHullOfPolygonsTest.cpp b/tests/unit/capi/GEOSConcaveHullOfPolygonsTest.cpp
index a5a485e9de..16a80299a0 100644
--- a/tests/unit/capi/GEOSConcaveHullOfPolygonsTest.cpp
+++ b/tests/unit/capi/GEOSConcaveHullOfPolygonsTest.cpp
@@ -54,6 +54,15 @@ void object::test<2>()
     ensure_geometry_equals(geom1_, expected_);
 }
 
+template<>
+template<>
+void object::test<4>()
+{
+    input_ = fromWKT("POLYGON((0 0, 0 0, 0 0))");
+    result_ = GEOSConcaveHullOfPolygons(input_, 0.7, false, false);
+    ensure(GEOSisEmpty(result_));
+}
+
 
 } // namespace tut