https://github.com/openstreetmap/merkaartor/issues/314
https://github.com/openstreetmap/merkaartor/commit/9949b586afb914ffac7b17d1f2b90f6300b8e2ca
https://github.com/openstreetmap/merkaartor/commit/41ea3a2215a64f3cfc465e8aaf481fc29a6a3abc

From 9949b586afb914ffac7b17d1f2b90f6300b8e2ca Mon Sep 17 00:00:00 2001
From: =?UTF-8?q?Ladislav=20L=C3=A1ska?= <krakonos@krakonos.org>
Date: Tue, 21 Oct 2025 10:04:10 +0200
Subject: [PATCH] Fixed compilation errors introduced by gdal 3.12.

Some API calls now return const pointers. We've annotated our types as
such, since we use them in const manny anyway.

Thanks to @gdt at Github for submitting a patch in issue #314.
--- a/src/ImportExport/ImportExportGdal.cpp
+++ b/src/ImportExport/ImportExportGdal.cpp
@@ -337,7 +337,7 @@ bool ImportExportGdal::importGDALDataset(GDALDataset* poDS, Layer* aLayer, bool
     qDebug(lc_importExportGdal) << "Layers #" << poDS->GetLayerCount();
     OGRLayer  *poLayer = poDS->GetLayer(0);
 
-    OGRSpatialReference * theSrs = poLayer->GetSpatialRef(); // Note: Contrary to other OGR objects, the spatial ref must NOT be released by our code!
+    const OGRSpatialReference * theSrs = poLayer->GetSpatialRef(); // Note: Contrary to other OGR objects, the spatial ref must NOT be released by our code!
     toWGS84 = NULL;
 
     if (theSrs) {
@@ -390,7 +390,7 @@ bool ImportExportGdal::importGDALDataset(GDALDataset* poDS, Layer* aLayer, bool
                 Feature* F = parseGeometry(aLayer, poGeometry);
                 if (F) {
                     for (int i=0; i<poFeature->GetFieldCount(); ++i) {
-                        OGRFieldDefn  *fd = poFeature->GetFieldDefnRef(i);
+                        const OGRFieldDefn  *fd = poFeature->GetFieldDefnRef(i);
                         QString k = QString::fromUtf8(fd->GetNameRef());
                         if (k == "osm_id") {
                             F->setId(IFeature::FId(F->getType(), (qint64)poFeature->GetFieldAsDouble(i)));
From 41ea3a2215a64f3cfc465e8aaf481fc29a6a3abc Mon Sep 17 00:00:00 2001
From: =?UTF-8?q?Ladislav=20L=C3=A1ska?= <krakonos@krakonos.org>
Date: Tue, 21 Oct 2025 10:05:37 +0200
Subject: [PATCH] Fixed memory management in ImportExportGDAL

The affected OGRSpatialReference is fetched from OGRLayer and by
documentation should not be released manually.

Thanks to @gdt at Github for submitting a patch in issue #314.
--- a/src/ImportExport/ImportExportGdal.cpp
+++ b/src/ImportExport/ImportExportGdal.cpp
@@ -351,7 +351,6 @@ bool ImportExportGdal::importGDALDataset(GDALDataset* poDS, Layer* aLayer, bool
                 qDebug("GDAL: couldn't initialise EPSG:27700: %d: %s", ogrError, CPLGetLastErrorMsg());
                 the27700Srs->Release();
             } else {
-                theSrs->Release();
                 theSrs = the27700Srs;
             }
         }