Keep tippecanoe's own errors from being reported as protobuf errors

A tile that fails to decode is reported with EXIT_MVT, while a tile that
protozero throws on is reported with EXIT_PROTOBUF. Now that decoding
failures are raised as a tippecanoe_error rather than exiting on the
spot, the catch that was written for protozero's exceptions catches
tippecanoe's own as well, since tippecanoe_error is a std::exception:
mvt_tile::decode() throwing "Tile decompression failed" came back out as
EXIT_PROTOBUF and "PBF decoding error in tile z/x/y".

Catch tippecanoe_error first at the four places that wrap a decode in a
try. In overzoom() and in tippecanoe-decode it can be rethrown for
main() to report. In tile-join it can't: append_tile() runs on a worker
thread, where an escaping exception would call std::terminate() instead
of exiting, so report it and exit with its own status there.

Co-Authored-By: Claude Opus 5 <noreply@anthropic.com>
Claude-Session: https://claude.ai/code/session_01DuCSVGssWNUCpVEE8Yp5HT

CHANGELOG.md

@@ -8,6 +8,11 @@
   before. Along the way this fixes a leaked `z_stream` when `compress()`
   failed and two `exit()` calls that could run from a destructor or from
   `mvt_value`'s hash function.
+* Keep reporting a tile that fails to decode as `EXIT_MVT`, and report why.
+  Now that decoding failures throw, the `catch` meant for protozero's
+  exceptions was catching tippecanoe's own as well, replacing their exit
+  status and message with `EXIT_PROTOBUF` and a generic "PBF decoding
+  error".
 * Add `--drop-by-attribute-as-needed=`*attribute* to drop the features with
   the lowest values of a numeric attribute from oversized tiles, and
   `--drop-by-attribute-order=desc` to drop the highest values instead.

clip.cpp

@@ -1230,6 +1230,10 @@ std::string overzoom(std::vector<input_tile> const &tiles, int nz, int nx, int n
 			if (!tile.decode(t.tile, was_compressed)) {
 				throw_tippecanoe_error(EXIT_MVT, "Couldn't parse tile %d/%u/%u", t.z, t.x, t.y);
 			}
+		} catch (tippecanoe_error &e) {
+			// a tippecanoe_error is a std::exception, so it would
+			// otherwise be caught below and reattributed to protobuf
+			throw;
 		} catch (std::exception const &e) {
 			throw_tippecanoe_error(EXIT_PROTOBUF, "PBF decoding error in tile %d/%u/%u", t.z, t.x, t.y);
 		}

decode.cpp

@@ -102,6 +102,10 @@ void handle(std::string message, int z, unsigned x, unsigned y, std::set<std::st
 			fprintf(stderr, "Couldn't parse tile %d/%u/%u\n", z, x, y);
 			exit(EXIT_MVT);
 		}
+	} catch (tippecanoe_error &e) {
+		// a tippecanoe_error is a std::exception, so it would
+		// otherwise be caught below and reattributed to protobuf
+		throw;
 	} catch (std::exception const &e) {
 		fprintf(stderr, "PBF decoding error in tile %d/%u/%u\n", z, x, y);
 		exit(EXIT_PROTOBUF);

tile-join.cpp

@@ -108,6 +108,12 @@ void append_tile(std::string message, int z, unsigned x, unsigned y, std::map<st
 			fprintf(stderr, "Couldn't decompress tile %d/%u/%u\n", z, x, y);
 			exit(EXIT_MVT);
 		}
+	} catch (tippecanoe_error &e) {
+		// a tippecanoe_error is a std::exception, so without this it
+		// would be caught below and reattributed to protobuf. It can't
+		// be rethrown either, since this runs on a worker thread.
+		fprintf(stderr, "%s\n", e.what());
+		exit(e.exit_code);
 	} catch (std::exception const &e) {
 		fprintf(stderr, "PBF decoding error in tile %d/%u/%u\n", z, x, y);
 		exit(EXIT_MVT);
@@ -749,6 +755,11 @@ struct tileset_reader {
 				fprintf(stderr, "Couldn't parse tile %lld/%lld/%lld\n", tile.z, tile.x, tile.y);
 				exit(EXIT_MVT);
 			}
+		} catch (tippecanoe_error &e) {
+			// a tippecanoe_error is a std::exception, so without this
+			// it would be caught below and reattributed to protobuf
+			fprintf(stderr, "%s\n", e.what());
+			exit(e.exit_code);
 		} catch (std::exception const &e) {
 			fprintf(stderr, "PBF decoding error in tile %lld/%lld/%lld\n", tile.z, tile.x, tile.y);
 			exit(EXIT_PROTOBUF);