[core] Report conversion errors using std::string

char* increases the risk of pointing to a invalid reference. Qt had
to use a static variable as retainer to workaround.

2 files changed, 5 insertions, 11 deletions

diff --git a/platform/qt/src/qmapboxgl.cpp b/platform/qt/src/qmapboxgl.cpp
index 71264faed7..d9eb43cf05 100644
--- a/platform/qt/src/qmapboxgl.cpp
+++ b/platform/qt/src/qmapboxgl.cpp
@@ -628,7 +628,7 @@ void QMapboxGL::addSource(const QString& sourceID, const QVariant& value)
 
     Result<std::unique_ptr<Source>> source = convert<std::unique_ptr<Source>>(value, sourceID.toStdString());
     if (!source) {
-        qWarning() << "Unable to add source:" << source.error().message;
+        qWarning() << "Unable to add source:" << source.error().message.c_str();
         return;
     }
 
@@ -665,7 +665,7 @@ void QMapboxGL::addLayer(const QVariant& value)
 
     Result<std::unique_ptr<Layer>> layer = convert<std::unique_ptr<Layer>>(value);
     if (!layer) {
-        qWarning() << "Unable to add layer:" << layer.error().message;
+        qWarning() << "Unable to add layer:" << layer.error().message.c_str();
         return;
     }
 
@@ -692,7 +692,7 @@ void QMapboxGL::setFilter(const QString& layer_, const QVariant& filter_)
 
     Result<Filter> converted = convert<Filter>(filter_);
     if (!converted) {
-        qWarning() << "Error parsing filter:" << converted.error().message;
+        qWarning() << "Error parsing filter:" << converted.error().message.c_str();
         return;
     }
     filter = std::move(*converted);
diff --git a/platform/qt/src/qt_geojson.hpp b/platform/qt/src/qt_geojson.hpp
index ff7ee2eada..fd2b689fed 100644
--- a/platform/qt/src/qt_geojson.hpp
+++ b/platform/qt/src/qt_geojson.hpp
@@ -29,22 +29,16 @@ Result<GeoJSON> convertGeoJSON(const QVariant& value) {
         d.Parse<0>(value.toByteArray().constData());
     }
 
-    // Needed to keep the error message alive
-    // when we go out of this scope.
-    static std::string error;
-
     if (d.HasParseError()) {
         std::stringstream message;
         message << d.GetErrorOffset() << " - " << rapidjson::GetParseError_En(d.GetParseError());
 
-        error = message.str();
-        return Error { error.c_str() };
+        return Error { message.str() };
     }
 
     conversion::Result<GeoJSON> geoJSON = conversion::convertGeoJSON<JSValue>(d);
     if (!geoJSON) {
-        error = geoJSON.error().message;
-        return Error { error.c_str() };
+        return Error { geoJSON.error().message };
     }
 
     return geoJSON;