Fix some undefined behavior (#209)

* Fix some undefined behavior

* Avoid overflow in line simplification calculations

* Oops, missed a test

* Didn't mean to add that to the Makefile

* Revert "Revert "[ci] test in debug mode (#202)""

This reverts commit c95c328.

* Fix reference to out-of-scope pointer

* Fix invalid shift and out-of-bounds vector element reference

* Update changelog and version

.github/workflows/test.yml

@@ -5,7 +5,10 @@ on: [push]
 jobs:
   test:
     runs-on: ubuntu-latest
+    strategy:
+      matrix:
+        version: ['Release', 'Debug']
     steps:
       - uses: actions/checkout@v3
-      - run: uname -a; make
-      - run: make test
+      - run: uname -a; BUILDTYPE=${{ matrix.version }} make
+      - run: make test

CHANGELOG.md

@@ -1,3 +1,7 @@
+# 2.48.0
+
+* Fix some undefined behavior bugs, one of which results in slight changes to line simplification choices
+
 # 2.47.0
 
 * Stabilize feature order in tippecanoe-overzoom when --preserve-feature-order is specified but the sequence attribute is not present

clip.cpp

@@ -904,9 +904,7 @@ std::string overzoom(const mvt_tile &tile, int oz, int ox, int oy, int nz, int n
 							flush_multiplier_cluster = true;
 							feature.tags.erase(feature.tags.begin() + i, feature.tags.begin() + i + 2);
 						}
-					}
-
-					if (layer.keys[feature.tags[i]] == retain_points_multiplier_sequence) {
+					} else if (i < (ssize_t) feature.tags.size() && layer.keys[feature.tags[i]] == retain_points_multiplier_sequence) {
 						mvt_value v = layer.values[feature.tags[i + 1]];
 						feature.seq = mvt_value_to_long_long(v);
 						feature.tags.erase(feature.tags.begin() + i, feature.tags.begin() + i + 2);

geojson.cpp

@@ -105,7 +105,8 @@ int serialize_geojson_feature(struct serialization_state *sst, json_object *geom
 		if (id->type == JSON_NUMBER) {
 			if (id->value.number.number >= 0) {
 				char *err = NULL;
-				id_value = strtoull(milo::dtoa_milo(id->value.number.number).c_str(), &err, 10);
+				std::string id_number = milo::dtoa_milo(id->value.number.number);
+				id_value = strtoull(id_number.c_str(), &err, 10);
 
 				if (id->value.number.large_unsigned != 0) {
 					id_value = id->value.number.large_unsigned;

geometry.cpp

@@ -303,8 +303,15 @@ bool point_within_tile(long long x, long long y, int z) {
 double distance_from_line(long long point_x, long long point_y, long long segA_x, long long segA_y, long long segB_x, long long segB_y) {
 	long long p2x = segB_x - segA_x;
 	long long p2y = segB_y - segA_y;
-	double something = p2x * p2x + p2y * p2y;
-	double u = (0 == something) ? 0 : ((point_x - segA_x) * p2x + (point_y - segA_y) * p2y) / (something);
+
+	// These calculations must be made in integers instead of floating point
+	// to make them consistent between x86 and arm floating point implementations.
+	//
+	// Coordinates may be up to 34 bits, so their product is up to 68 bits,
+	// making their sum up to 69 bits. Downshift before multiplying to keep them in range.
+	double something = ((p2x / 4) * (p2x / 8) + (p2y / 4) * (p2y / 8)) * 32.0;
+	// likewise
+	double u = (0 == something) ? 0 : ((point_x - segA_x) / 4 * (p2x / 8) + (point_y - segA_y) / 4 * (p2y / 8)) * 32.0 / (something);
 
 	if (u >= 1) {
 		u = 1;

pool.cpp

@@ -17,7 +17,7 @@ inline int swizzlecmp(const char *a, int atype, unsigned long long ahash, const
 			return atype - btype;
 		}
 	} else {
-		return (int) ahash - (int) bhash;
+		return (int) (ahash - bhash);
 	}
 }
 

tests/ne_110m_admin_0_countries/out/-B10_-z0_--retain-points-multiplier_10_-d8_-yNAME.json

@@ -302,7 +302,7 @@
 ,
 { "type": "Feature", "properties": { "tippecanoe:retain_points_multiplier_first": true, "tippecanoe:retain_points_multiplier_sequence": 96 }, "geometry": { "type": "MultiPolygon", "coordinates": [ [ [ [ 174.375000, -40.979898 ], [ 172.968750, -44.087585 ], [ 168.750000, -47.040182 ], [ 165.937500, -46.073231 ], [ 171.562500, -40.979898 ], [ 174.375000, -40.979898 ] ] ], [ [ [ 172.968750, -34.307144 ], [ 175.781250, -37.718590 ], [ 178.593750, -37.718590 ], [ 175.781250, -42.032974 ], [ 172.968750, -34.307144 ] ] ], [ [ [ -187.031250, -35.460670 ], [ -181.406250, -37.718590 ], [ -184.218750, -42.032974 ], [ -187.031250, -35.460670 ] ] ] ] } }
 ,
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 ] }
 ] }
 ] }