Fix uncaught exception caused by invalid UTF-8 data

The json serializer will throw for invalid UTF-8 (e.g.
if long PS has undetected errors). Fix by catching serializer
exceptions before anything gets printed.

CHANGES.md

@@ -1,5 +1,12 @@
 # redsea changelog
 
+## 1.0.1
+
+* Fixes:
+  * Fix a crash (uncaught json exception) when attempting to serialize a string that's
+    invalid UTF-8, e.g. if long PS gets corrupted
+  * Fix build when the installed version of nlohmann-json is too old (#113)
+
 ## 1.0 (2024-06-27)
 
 * New features:

meson.build

@@ -1,5 +1,5 @@
 project('redsea', 'cpp', default_options : ['warning_level=3', 'buildtype=release', 'optimization=3'],
-        version: '1.0')
+        version: '1.0.1')
 
 # Store version number to be compiled in
 conf = configuration_data()

src/groups.cc

@@ -312,7 +312,18 @@ void Station::updateAndPrint(const Group& group, std::ostream& stream) {
     }
   }
 
-  stream << json_ << std::endl << std::flush;
+  try {
+    // nlohmann::operator<< throws if a string contains non-UTF8 data.
+    // It's better to throw while writing to a stringstream; otherwise
+    // incomplete JSON objects could get printed.
+    std::stringstream output_proxy_stream;
+    output_proxy_stream << json_;
+    stream << output_proxy_stream.str() << std::endl << std::flush;
+  } catch (const std::exception& e) {
+    nlohmann::ordered_json json_from_exception;
+    json_from_exception["debug"] = std::string(e.what());
+    stream << json_from_exception << std::endl << std::flush;
+  }
 }
 
 uint16_t Station::getPI() const {

test/unit.cc

@@ -449,3 +449,15 @@ TEST_CASE("Error detection and correction") {
     CHECK(groups.back().get(redsea::BLOCK1) == 0x0000);  // "----"
   }
 }
+
+TEST_CASE("Invalid data") {
+  redsea::Options options;
+
+  SECTION("Invalid UTF-8 is handled cleanly") {
+    REQUIRE_NOTHROW(hex2json({
+      0xE24D'4401'D02F'1942,
+      0xE24D'E400'E24D'0000,
+      0xE24D'F400'E20D'FC20
+    }, options, 0xE24D));
+  }
+}