Switching from ArduinoJson 6 to 7 leads to a random assertion failure at runtime: const VariantPoolList.hpp:98 (poolIndex < count_
#2034
Comments
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Hi @mathieucarbou, This looks like a corrupted The stack trace shows a Best regards, |
Hello, Yes that's what I am thinking: I discovered yesterday that the library I use is not thread safe and is calling this |
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@bblanchon : I have to re-open it... I have removed any potential concurrent access: now, the generateLayout method is only called once from the async_http task (websocket handler) and nowhere else.. Also, the json document reads data that is initialised once, stays as references in private fields in a static class, and this data is not modified concrurently. While the json document is building, I have this error again, and constantly: It also also fails at the place: This line matches JsonObject doc = root.to<JsonObject>();
doc["command"] = changes_only ? "update:components" : "update:layout:next";
for (int i = 0; i < cards.Size(); i++) {So it is like a document becomes unusable after being cleared. If I do not use We can see in the logs above that the first call to send() works, then the document is cleared for re-use and it crashes. Here is part of the code: // generates the layout JSON string to the frontend
void ESPDash::generateLayoutJSON(AsyncWebSocketClient* client, bool changes_only, Card* onlyCard) {
#if ARDUINOJSON_VERSION_MAJOR == 6
DynamicJsonDocument root(DASH_JSON_SIZE);
#else
JsonDocument root;
#endif
// preparing layout
{
JsonObject doc = root.to<JsonObject>();
if (!changes_only) {
doc["command"] = "update:layout:begin";
// OTHER DOC SETTERS
} else {
doc["command"] = "update:components";
}
// Generate Tab JSON
for (int i = 0; i < tabs.Size(); i++) {
// [...]
doc["tabs"][i]["id"] = t->_id;
// [...]
// OTHER DOC SETTERS
}
if (!changes_only || doc["tabs"].as<JsonArray>().size() > 0) {
send(client, doc);
}
}
// Generate JSON for all Cards
{
JsonObject doc = root.to<JsonObject>();
doc["command"] = changes_only ? "update:components" : "update:layout:next";
for (int i = 0; i < cards.Size(); i++) {
// [...]
// Generate JSON
#if ARDUINOJSON_VERSION_MAJOR == 6
JsonObject obj = doc["cards"].createNestedObject();
#else
JsonObject obj = doc["cards"].add<JsonObject>();
#endif
generateComponentJSON(obj, c, changes_only);
if (overflowed(root)) {
doc["cards"].as<JsonArray>().remove(doc["cards"].as<JsonArray>().size() - 1);
send(client, doc);
doc = root.to<JsonObject>();
doc["command"] = changes_only ? "update:components" : "update:layout:next";
i--;
continue;
}
// [...]
}
if (doc["cards"].as<JsonArray>().size() > 0)
send(client, doc);
}
// Generate JSON for all Charts
{
JsonObject doc = root.to<JsonObject>();
doc["command"] = changes_only ? "update:components" : "update:layout:next";
for (int i = 0; i < charts.Size(); i++) {
// [...]
// Generate JSON
#if ARDUINOJSON_VERSION_MAJOR == 7
JsonObject obj = doc["charts"].add<JsonObject>();
#else
JsonObject obj = doc["charts"].createNestedObject();
#endif
generateComponentJSON(obj, c, changes_only);
if (overflowed(root)) {
doc["charts"].as<JsonArray>().remove(doc["charts"].as<JsonArray>().size() - 1);
send(client, doc);
doc = root.to<JsonObject>();
doc["command"] = changes_only ? "update:components" : "update:layout:next";
i--;
continue;
}
// [...]
}
if (doc["charts"].as<JsonArray>().size() > 0)
send(client, doc);
}
// Generate JSON for all Statistics
{
JsonObject doc = root.to<JsonObject>();
doc["command"] = changes_only ? "update:components" : "update:layout:next";
int idx = 0;
// Check if default statistics are needed
if (default_stats_enabled) {
if (!changes_only) {
// OTHER DOC SETTERS
}
// Loop through user defined stats
for (int i = 0; i < statistics.Size(); i++, idx++) {
// [...]
// OTHER DOC SETTERS
if (overflowed(root)) {
doc["stats"].as<JsonArray>().remove(idx);
send(client, doc);
doc = root.to<JsonObject>();
doc["command"] = changes_only ? "update:components" : "update:layout:next";
i--;
idx = 0;
continue;
}
// Clear change flags
if (changes_only) {
s->_changed = false;
}
}
if (doc["stats"].as<JsonArray>().size() > 0)
send(client, doc);
}
}
void ESPDash::send(AsyncWebSocketClient* client, JsonObject& doc) {
const size_t len = measureJson(doc);
auto buffer = std::make_shared<std::vector<uint8_t>>(len);
if (!buffer) {
doc.clear();
return;
}
serializeJson(doc, buffer->data(), len);
#ifdef DASH_DEBUG
Serial.printf("T %12u %-10.10s (%u) ESP-DASH client=%u, measureJson=%u\r\n", static_cast<uint32_t>(esp_timer_get_time() >> 10), pcTaskGetName(NULL), xPortGetCoreID(), (client == nullptr ? -1 : client->id()), len);
#endif
if (client != nullptr) {
client->text(buffer);
} else {
_ws->textAll(buffer);
}
doc.clear();
}
bool ESPDash::overflowed(JsonDocument& json) {
return json.overflowed() || measureJson(json.as<JsonObject>()) > DASH_JSON_SIZE;
} |
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Ok so there is definitely something wrong with reusing a Json doc after a clear(). I've implemented a new version which is creating a new JsonDocument each time, and it works. |
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Could you provide an MCVE? |
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We have a big internet outage here but as soon as I can, yes. |
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Here is a simple #include <ArduinoJson.h>
void fill(JsonObject &obj) {
obj["foo-bar-baz"] = "foo-bar-baz-foo-bar-baz";
}
void send(JsonObject &obj) {
serializeJson(obj, Serial);
Serial.println("");
obj.clear();
}
void setup() {
Serial.begin(115200);
JsonDocument doc;
{
JsonObject obj = doc.to<JsonObject>();
obj["command"] = "update:components";
obj["tabs"][0]["id"] = "0";
send(obj);
}
{
JsonObject obj = doc.to<JsonObject>();
obj["command"] = "update:components";
JsonObject card = doc["cards"].add<JsonObject>();
fill(card);
send(obj);
}
}
void loop() { }Please note that if I comment out the void send(JsonObject &obj) {
serializeJson(obj, Serial);
Serial.println("");
//obj.clear();
}logs: What is the recommandation for such usage: use only one My assumption was that destroying and creating a new JsonDocument each time would be slower, so that is why I've tried to reuse it with |
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Thank you very much for this code. ❤️
I recommend short lifetimes to release memory as soon as possible and reduce the cognitive load.
Calling |
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Thanks for the advices, and glad I was able to help :-) |
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The fix was published in ArduinoJson 7.0.2. |
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I cannot use the the Arduino Json Troubleshooter since the issue happens when building a json document, when allocating memory.
I do not use any custom allocator.
Board is the standard ESP32 NodePCU Dev Kit from AZ-Delivery.
I have no idea what to do or how to troubleshoot this...
How I am using the JsonDocument:
Stack trace:
The text was updated successfully, but these errors were encountered: