stringstream not working on esp32

[LeonB]

I'm using ArduinoJson on an esp32.

This works:

    DynamicJsonDocument doc(1024);
    doc["reading"] = "test";

    String s;
    serializeJson(doc, s);
    Serial.println(s);

This works:

    DynamicJsonDocument doc(1024);
    doc["reading"] = "test";

    std::string s;
    serializeJson(doc, s);
    Serial.println(s.c_str());

But as soon as I try to use std::stringstream I get a compile error:

    DynamicJsonDocument doc(1024);
    doc["reading"] = "test";

    std::stringstream ss();
    serializeJson(doc, ss);

libraries/ArduinoJson/src/ArduinoJson/Json/TextFormatter.hpp:129:13:   required from 'void ArduinoJson6130_000001::TextFormatter<TWriter>::writeRaw(const char*) [with TWriter = ArduinoJson6130_000001::Writer<std::__cxx11::basic_stringstream<char>(), void>]'
libraries/ArduinoJson/src/ArduinoJson/Json/JsonSerializer.hpp:80:5:   required from 'void ArduinoJson6130_000001::JsonSerializer<TWriter>::visitNull() [with TWriter = ArduinoJson6130_000001::Writer<std::__cxx11::basic_stringstream<char>(), void>]'
libraries/ArduinoJson/src/ArduinoJson/Variant/VariantFunctions.hpp:16:5:   required from 'void ArduinoJson6130_000001::variantAccept(const ArduinoJson6130_000001::VariantData*, Visitor&) [with Visitor = ArduinoJson6130_000001::JsonSerializer<ArduinoJson6130_000001::Writer<std::__cxx11::basic_stringstream<char>(), void> >]'
libraries/ArduinoJson/src/ArduinoJson/Variant/VariantRef.hpp:352:18:   required from 'void ArduinoJson6130_000001::VariantConstRef::accept(Visitor&) const [with Visitor = ArduinoJson6130_000001::JsonSerializer<ArduinoJson6130_000001::Writer<std::__cxx11::basic_stringstream<char>(), void> >]'
libraries/ArduinoJson/src/ArduinoJson/Document/JsonDocument.hpp:20:39:   required from 'void ArduinoJson6130_000001::JsonDocument::accept(Visitor&) const [with Visitor = ArduinoJson6130_000001::JsonSerializer<ArduinoJson6130_000001::Writer<std::__cxx11::basic_stringstream<char>(), void> >]'
libraries/ArduinoJson/src/ArduinoJson/Serialization/serialize.hpp:15:3:   required from 'size_t ArduinoJson6130_000001::doSerialize(const TSource&, TWriter) [with TSerializer = ArduinoJson6130_000001::JsonSerializer; TSource = ArduinoJson6130_000001::BasicJsonDocument<ArduinoJson6130_000001::DefaultAllocator>; TWriter = ArduinoJson6130_000001::Writer<std::__cxx11::basic_stringstream<char>(), void>; size_t = unsigned int]'
libraries/ArduinoJson/src/ArduinoJson/Serialization/serialize.hpp:23:34:   required from 'size_t ArduinoJson6130_000001::serialize(const TSource&, TDestination&) [with TSerializer = ArduinoJson6130_000001::JsonSerializer; TSource = ArduinoJson6130_000001::BasicJsonDocument<ArduinoJson6130_000001::DefaultAllocator>; TDestination = std::__cxx11::basic_stringstream<char>(); size_t = unsigned int]'
libraries/ArduinoJson/src/ArduinoJson/Json/JsonSerializer.hpp:102:35:   required from 'size_t ArduinoJson6130_000001::serializeJson(const TSource&, TDestination&) [with TSource = ArduinoJson6130_000001::BasicJsonDocument<ArduinoJson6130_000001::DefaultAllocator>; TDestination = std::__cxx11::basic_stringstream<char>(); size_t = unsigned int]'
src/Server.ino:92:26:   required from here
libraries/ArduinoJson/src/ArduinoJson/Serialization/Writer.hpp:22:29: error: request for member 'write' in '*((ArduinoJson6130_000001::Writer<std::__cxx11::basic_stringstream<char>(), void>*)this)->ArduinoJson6130_000001::Writer<std::__cxx11::basic_stringstream<char>(), void>::_dest', which is of non-class type 'std::__cxx11::basic_stringstream<char>()'
     return _dest->write(s, n);
                             ^
libraries/ArduinoJson/src/ArduinoJson/Serialization/Writer.hpp: In instantiation of 'size_t ArduinoJson6130_000001::Writer<TDestination, Enable>::write(uint8_t) [with TDestination = std::__cxx11::basic_stringstream<char>(); Enable = void; size_t = unsigned int; uint8_t = unsigned char]':
libraries/ArduinoJson/src/ArduinoJson/Json/TextFormatter.hpp:146:13:   required from 'void ArduinoJson6130_000001::TextFormatter<TWriter>::writeRaw(char) [with TWriter = ArduinoJson6130_000001::Writer<std::__cxx11::basic_stringstream<char>(), void>]'
libraries/ArduinoJson/src/ArduinoJson/Json/TextFormatter.hpp:69:15:   required from 'void ArduinoJson6130_000001::TextFormatter<TWriter>::writeFloat(T) [with T = float; TWriter = ArduinoJson6130_000001::Writer<std::__cxx11::basic_stringstream<char>(), void>]'
libraries/ArduinoJson/src/ArduinoJson/Json/JsonSerializer.hpp:56:5:   required from 'void ArduinoJson6130_000001::JsonSerializer<TWriter>::visitFloat(ArduinoJson6130_000001::Float) [with TWriter = ArduinoJson6130_000001::Writer<std::__cxx11::basic_stringstream<char>(), void>; ArduinoJson6130_000001::Float = float]'
libraries/ArduinoJson/src/ArduinoJson/Variant/VariantData.hpp:30:51:   required from 'void ArduinoJson6130_000001::VariantData::accept(Visitor&) const [with Visitor = ArduinoJson6130_000001::JsonSerializer<ArduinoJson6130_000001::Writer<std::__cxx11::basic_stringstream<char>(), void> >]'
libraries/ArduinoJson/src/ArduinoJson/Variant/VariantFunctions.hpp:14:5:   required from 'void ArduinoJson6130_000001::variantAccept(const ArduinoJson6130_000001::VariantData*, Visitor&) [with Visitor = ArduinoJson6130_000001::JsonSerializer<ArduinoJson6130_000001::Writer<std::__cxx11::basic_stringstream<char>(), void> >]'
libraries/ArduinoJson/src/ArduinoJson/Variant/VariantRef.hpp:352:18:   required from 'void ArduinoJson6130_000001::VariantConstRef::accept(Visitor&) const [with Visitor = ArduinoJson6130_000001::JsonSerializer<ArduinoJson6130_000001::Writer<std::__cxx11::basic_stringstream<char>(), void> >]'
libraries/ArduinoJson/src/ArduinoJson/Document/JsonDocument.hpp:20:39:   required from 'void ArduinoJson6130_000001::JsonDocument::accept(Visitor&) const [with Visitor = ArduinoJson6130_000001::JsonSerializer<ArduinoJson6130_000001::Writer<std::__cxx11::basic_stringstream<char>(), void> >]'
libraries/ArduinoJson/src/ArduinoJson/Serialization/serialize.hpp:15:3:   required from 'size_t ArduinoJson6130_000001::doSerialize(const TSource&, TWriter) [with TSerializer = ArduinoJson6130_000001::JsonSerializer; TSource = ArduinoJson6130_000001::BasicJsonDocument<ArduinoJson6130_000001::DefaultAllocator>; TWriter = ArduinoJson6130_000001::Writer<std::__cxx11::basic_stringstream<char>(), void>; size_t = unsigned int]'
libraries/ArduinoJson/src/ArduinoJson/Serialization/serialize.hpp:23:34:   required from 'size_t ArduinoJson6130_000001::serialize(const TSource&, TDestination&) [with TSerializer = ArduinoJson6130_000001::JsonSerializer; TSource = ArduinoJson6130_000001::BasicJsonDocument<ArduinoJson6130_000001::DefaultAllocator>; TDestination = std::__cxx11::basic_stringstream<char>(); size_t = unsigned int]'
libraries/ArduinoJson/src/ArduinoJson/Json/JsonSerializer.hpp:102:35:   required from 'size_t ArduinoJson6130_000001::serializeJson(const TSource&, TDestination&) [with TSource = ArduinoJson6130_000001::BasicJsonDocument<ArduinoJson6130_000001::DefaultAllocator>; TDestination = std::__cxx11::basic_stringstream<char>(); size_t = unsigned int]'
src/Server.ino:92:26:   required from here
libraries/ArduinoJson/src/ArduinoJson/Serialization/Writer.hpp:18:26: error: request for member 'write' in '*((ArduinoJson6130_000001::Writer<std::__cxx11::basic_stringstream<char>(), void>*)this)->ArduinoJson6130_000001::Writer<std::__cxx11::basic_stringstream<char>(), void>::_dest', which is of non-class type 'std::__cxx11::basic_stringstream<char>()'
     return _dest->write(c);
                          ^

I've defined ARDUINOJSON_ENABLE_STD_STREAM:

#define ARDUINOJSON_ENABLE_STD_STREAM 1

In the tests I see std::stringstream is used. What is going wrong here? I'm using the makeEspArduino makefile.

[bblanchon]

Hi @LeonB,

Are you sure you defined ARDUINOJSON_ENABLE_STD_STREAM before including ArduinoJson.h?
If you have multiple compilation units, make sure you use the same settings, the best is to set the defines in the Makefile.

Meanwhile, I'll add some code to auto-enable support std::stream base on the new __has_header directive introduced in C++17.

Best regards,
Benoit.