From c8e5fa0c16f350a8cf8d2019cbd5912f7d74ac7c Mon Sep 17 00:00:00 2001
From: Peter Stace <peterstace@gmail.com>
Date: Fri, 19 Nov 2021 06:31:17 +1100
Subject: [PATCH] Use a stub implementation of MakeValid when not supported by
 GEOS

---
 geos/entrypoints.go      | 15 +++++++++++++++
 geos/entrypoints_test.go |  3 +++
 geos/errors.go           | 20 ++++++++++++++++++++
 geos/handle.go           |  2 +-
 4 files changed, 39 insertions(+), 1 deletion(-)

diff --git a/geos/entrypoints.go b/geos/entrypoints.go
index 76238ff3..a6a8fb3b 100644
--- a/geos/entrypoints.go
+++ b/geos/entrypoints.go
@@ -4,6 +4,17 @@ package geos
 #cgo LDFLAGS: -lgeos_c
 #cgo CFLAGS: -Wall
 #include "geos_c.h"
+
+#define MAKE_VALID_MIN_VERSION "3.8.0"
+#define MAKE_VALID_MISSING ( \
+	GEOS_VERSION_MAJOR < 3 || \
+	(GEOS_VERSION_MAJOR == 3 && GEOS_VERSION_MINOR < 8) \
+)
+#if MAKE_VALID_MISSING
+// This stub implementation also fails
+GEOSGeometry *GEOSMakeValid_r(GEOSContextHandle_t handle, const GEOSGeometry* g) { return NULL; }
+#endif
+
 */
 import "C"
 
@@ -316,6 +327,10 @@ func SymmetricDifference(a, b geom.Geometry, opts ...geom.ConstructorOption) (ge
 // invalid geometry. If the input geometry is valid, then it is returned
 // unaltered.
 func MakeValid(g geom.Geometry, opts ...geom.ConstructorOption) (geom.Geometry, error) {
+	if C.MAKE_VALID_MISSING != 0 {
+		return geom.Geometry{}, unsupportedGEOSVersionError{
+			C.MAKE_VALID_MIN_VERSION, "MakeValid"}
+	}
 	result, err := unaryOpG(g, opts, func(ctx C.GEOSContextHandle_t, g *C.GEOSGeometry) *C.GEOSGeometry {
 		return C.GEOSMakeValid_r(ctx, g)
 	})
diff --git a/geos/entrypoints_test.go b/geos/entrypoints_test.go
index 43ec1a66..fef8096c 100644
--- a/geos/entrypoints_test.go
+++ b/geos/entrypoints_test.go
@@ -781,6 +781,9 @@ func TestMakeValid(t *testing.T) {
 		t.Run(strconv.Itoa(i), func(t *testing.T) {
 			in := geomFromWKT(t, tt.input, geom.DisableAllValidations)
 			gotGeom, err := MakeValid(in)
+			if _, ok := err.(unsupportedGEOSVersionError); ok {
+				t.Skip(err)
+			}
 			expectNoErr(t, err)
 			wantGeom := geomFromWKT(t, tt.wantOutput)
 			expectGeomEq(t, gotGeom, wantGeom)
diff --git a/geos/errors.go b/geos/errors.go
index ea29198d..a0cd66ad 100644
--- a/geos/errors.go
+++ b/geos/errors.go
@@ -2,9 +2,29 @@ package geos
 
 import "fmt"
 
+// #include "geos_c.h"
+import "C"
+
 func wrap(err error, format string, args ...interface{}) error {
 	if err == nil {
 		return nil
 	}
 	return fmt.Errorf(format+": %w", append(args, err)...)
 }
+
+var currentGEOSVersion = fmt.Sprintf(
+	"%d.%d.%d",
+	C.GEOS_VERSION_MAJOR,
+	C.GEOS_VERSION_MINOR,
+	C.GEOS_VERSION_PATCH,
+)
+
+type unsupportedGEOSVersionError struct {
+	requiredGEOSVersion string
+	operation           string
+}
+
+func (e unsupportedGEOSVersionError) Error() string {
+	return fmt.Sprintf("%s is unsupported in GEOS %s, requires at least GEOS %s",
+		e.operation, currentGEOSVersion, e.requiredGEOSVersion)
+}
diff --git a/geos/handle.go b/geos/handle.go
index 93845d75..c7eacc1d 100644
--- a/geos/handle.go
+++ b/geos/handle.go
@@ -22,7 +22,6 @@ char *marshal(GEOSContextHandle_t handle, const GEOSGeometry *g, size_t *size, c
 GEOSGeometry const *noop(GEOSContextHandle_t handle, const GEOSGeometry *g) {
 	return g;
 }
-
 */
 import "C"
 
@@ -62,6 +61,7 @@ func newHandle() (*handle, error) {
 		h.release()
 		return nil, errors.New("malloc failed")
 	}
+	C.memset((unsafe.Pointer)(h.errBuf), 0, 1024)
 
 	h.context = C.sf_init(unsafe.Pointer(h.errBuf))
 	if h.context == nil {