[geos-commits] [SCM] GEOS branch main updated. d5d89d025fcd877fc96b80cd6a325b572a1b16f3

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- Log -----------------------------------------------------------------
commit d5d89d025fcd877fc96b80cd6a325b572a1b16f3
Author: Daniel Baston <dbaston at gmail.com>
Date:   Mon Jan 12 11:09:06 2026 -0500

    Fix crash in ConvexHull::preSort (#1358)
    
    * Add test for GH-1072
    
    Resolves https://github.com/libgeos/geos/issues/1072
    
    * ConvexHull: improve robustness of polarCompare

diff --git a/src/algorithm/ConvexHull.cpp b/src/algorithm/ConvexHull.cpp
index 7d8e34374..1ed617438 100644
--- a/src/algorithm/ConvexHull.cpp
+++ b/src/algorithm/ConvexHull.cpp
@@ -63,13 +63,21 @@ private:
     polarCompare(const Coordinate* o, const Coordinate* p,
                  const Coordinate* q)
     {
-        int orient = Orientation::index(*o, *p, *q);
+        // To use this comparator in std::sort it must provide a stable ordering, such that
+        // if cmp(a, b) is true then cmp(b, a) is false. Unfortunately Orientation::index may
+        // not provide this guarantee when the inputs differ by many orders of magnitude. To
+        // guard against this, we normalize the order of P and Q before calling OrientationIndex
+        // and flip the result if the inputs were flipped.
+        const bool swap = geom::CoordinateLessThan()(p, q);
+
+        const int orient = swap ? Orientation::index(*o, *q, *p) : Orientation::index(*o, *p, *q);
 
         if(orient == Orientation::COUNTERCLOCKWISE) {
-            return 1;
+            return swap ? -1 : 1;
         }
+
         if(orient == Orientation::CLOCKWISE) {
-            return -1;
+            return swap ? 1 : -1;
         }
 
         /**
@@ -102,7 +110,7 @@ public:
     RadiallyLessThen(const Coordinate* c): origin(c) {}
 
     bool
-    operator()(const Coordinate* p1, const Coordinate* p2)
+    operator()(const Coordinate* p1, const Coordinate* p2) const
     {
         return (polarCompare(origin, p1, p2) == -1);
     }
diff --git a/tests/unit/capi/GEOSMinimumBoundingCircleTest.cpp b/tests/unit/capi/GEOSMinimumBoundingCircleTest.cpp
index f535fce86..3634752e9 100644
--- a/tests/unit/capi/GEOSMinimumBoundingCircleTest.cpp
+++ b/tests/unit/capi/GEOSMinimumBoundingCircleTest.cpp
@@ -129,5 +129,20 @@ void object::test<5>
     ensure("curved geometry not supported", result_ == nullptr);
 }
 
+template<>
+template<>
+void object::test<6>
+()
+{
+    set_test_name("https://github.com/libgeos/geos/issues/1072");
+
+    geom1_ =  fromWKT("LINESTRING(7777777777777777770 7777777777777777777777777777777777777777777777777777777777777777777777777777777777777777777777777777777777777777777777777777777777777777777777777777777777777777777777777777777777777777777777777777777777777777777777777777777777777777777777777777777777777777777777777777777777777777777777777777777777770 1, 1 7 1,-2 1 2)");
+    geom2_ =  GEOSSingleSidedBuffer(geom1_, 1.0, 64, 1, 1.0, 1);
+    result_ =  GEOSMinimumBoundingCircle(geom2_, NULL, NULL);
+
+    // no segfault
+}
+
+
 } // namespace tut
 

-----------------------------------------------------------------------

Summary of changes:
 src/algorithm/ConvexHull.cpp                      | 16 ++++++++++++----
 tests/unit/capi/GEOSMinimumBoundingCircleTest.cpp | 15 +++++++++++++++
 2 files changed, 27 insertions(+), 4 deletions(-)


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