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Merged
julianoes merged 6 commits into from
Jul 14, 2026
+637 −553
Merged

core: switch JSON library from jsoncpp to nlohmann/json #2918

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4ad13c3
core: switch JSON library from jsoncpp to nlohmann/json
julianoes Jul 12, 2026
6242c47
mavlink_direct: represent binary char[] param fields as JSON byte arrays
julianoes Jul 13, 2026
947eaec
third_party: bump nlohmann/json to v3.12.0
julianoes Jul 13, 2026
d845979
mavlink_direct: avoid static container with destructor in binary-fiel…
julianoes Jul 13, 2026
9c61a46
third_party: use archive rather than git
julianoes Jul 13, 2026
9b89964
Merge remote-tracking branch 'origin/main' into switch-to-nlohmann-json
julianoes Jul 13, 2026
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5 changes: 3 additions & 2 deletions .github/workflows/linux.yml
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Original file line number Diff line number Diff line change
Expand Up @@ -359,7 +359,7 @@ jobs:
- name: Install dependencies
run: |
sudo apt-get update
sudo apt-get install -y liblzma-dev libtinyxml2-dev libjsoncpp-dev libcurl4-openssl-dev libssl-dev libasio-dev libfmt-dev
sudo apt-get install -y liblzma-dev libtinyxml2-dev nlohmann-json3-dev libcurl4-openssl-dev libssl-dev libasio-dev libfmt-dev
- name: Build with system dependencies
run: ./tools/build-with-system-deps.sh
- name: unit tests
Expand All @@ -385,7 +385,8 @@ jobs:
sudo apt-get update && sudo apt-get install -y \
python3-venv \
libasio-dev \
libfmt-dev
libfmt-dev \
nlohmann-json3-dev
- name: git permission workaround
run: |
git config --global --add safe.directory "$GITHUB_WORKSPACE"
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52 changes: 0 additions & 52 deletions cpp/cmake/Modules/common/Findjsoncpp.cmake
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This file was deleted.

4 changes: 2 additions & 2 deletions cpp/debian/control
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Original file line number Diff line number Diff line change
@@ -1,7 +1,7 @@
Source: mavsdk
Priority: optional
Maintainer: hcb <hcb@archaeopteryx>
Build-Depends: debhelper (>= 11), libjsoncpp-dev, libcurl4-openssl-dev, libtinyxml2-dev
Build-Depends: debhelper (>= 11), nlohmann-json3-dev, libcurl4-openssl-dev, libtinyxml2-dev
Standards-Version: 4.1.3
Section: libs
Homepage: https://mavsdk.mavlink.io/main/en/index.html
Expand All @@ -19,6 +19,6 @@ Description: MAVSDK API for Mavlink-controlled vehicles
Package: libmavsdk0
Architecture: any
Multi-Arch: same
Depends: ${shlibs:Depends}, ${misc:Depends}, libjsoncpp1, libcurl4, libtinyxml2-6a
Depends: ${shlibs:Depends}, ${misc:Depends}, libcurl4, libtinyxml2-6a
Description: MAVSDK API for Mavlink-controlled vehicles
This provides the runtime libraries for the mavsdk C++ library.
2 changes: 1 addition & 1 deletion cpp/examples/mavlink_direct_sender/sender.cpp
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Expand Up @@ -66,7 +66,7 @@ int main(int argc, char** argv)
// On 3 segments we see an obstacle, the closest is at 7m.
//
// In a real application this JSON message content would of course be
// assembled manually, or using a json library like jsoncpp or nlohmann/json.
// assembled manually, or using a json library like nlohmann/json.
obstacle_distance.fields_json = R"({
"time_usec": 12345678,
"sensor_type": 3,
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2 changes: 1 addition & 1 deletion cpp/src/MAVSDKConfig.cmake.in
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Expand Up @@ -7,7 +7,7 @@ if(NOT @BUILD_SHARED_LIBS@)
endif()

find_dependency(Threads REQUIRED)
find_dependency(jsoncpp REQUIRED)
find_dependency(nlohmann_json REQUIRED)
find_dependency(picosha2 REQUIRED)
find_dependency(tinyxml2 REQUIRED)
find_dependency(mav REQUIRED)
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2 changes: 1 addition & 1 deletion cpp/src/mavsdk.pc.in
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Expand Up @@ -6,6 +6,6 @@ includedir=@CMAKE_INSTALL_FULL_INCLUDEDIR@
Name: MAVSDK
Description: API and library for MAVLink compatible systems written in C++17
Version: @MAVSDK_VERSION_STRING@
Requires.private: libcurl jsoncpp tinyxml2
Requires.private: libcurl nlohmann_json tinyxml2
Libs: -L"${libdir}" -lmavsdk
Cflags: -I"${includedir}" -I"${includedir}/mavsdk"
4 changes: 2 additions & 2 deletions cpp/src/mavsdk/CMakeLists.txt
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Expand Up @@ -2,7 +2,7 @@ add_library(mavsdk)

cmake_policy(SET CMP0076 NEW)

find_package(jsoncpp REQUIRED)
find_package(nlohmann_json REQUIRED)

find_package(tinyxml2 REQUIRED)

Expand All @@ -16,7 +16,7 @@ target_link_libraries(mavsdk
PUBLIC
${CMAKE_DL_LIBS}
PRIVATE
JsonCpp::JsonCpp
nlohmann_json::nlohmann_json
tinyxml2::tinyxml2
LibEvents::LibEvents
mav::mav
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116 changes: 57 additions & 59 deletions cpp/src/mavsdk/core/libmav_conversions.cpp
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Expand Up @@ -3,7 +3,7 @@
#include "log.hpp"

#include <mav/Message.h>
#include <json/json.h>
#include <nlohmann/json.hpp>
#include <cmath>
#include <limits>
#include <vector>
Expand All @@ -12,34 +12,34 @@ namespace mavsdk {

bool json_to_libmav_message(const std::string& json_string, mav::Message& msg)
{
Json::Value json;
Json::Reader reader;
// Parse without exceptions (MAVSDK is built with -fno-exceptions); a parse
// error yields a discarded value instead of throwing.
auto json = nlohmann::json::parse(json_string, nullptr, false);

if (!reader.parse(json_string, json)) {
if (json.is_discarded() || !json.is_object()) {
LogErr("Failed to parse JSON: {}", json_string);
return false;
}

// Iterate through all JSON fields and set them in the libmav message
for (const auto& field_name : json.getMemberNames()) {
const Json::Value& field_value = json[field_name];

for (const auto& [field_name, field_value] : json.items()) {
// Convert JSON values to appropriate types and set in message
// libmav handles type casting based on field definition, so we just need to pass
// int64/uint64
if (field_value.isInt() || field_value.isInt64()) {
int64_t value = field_value.asInt64();
// int64/uint64. Check unsigned first since nlohmann stores non-negative
// integer literals as unsigned.
if (field_value.is_number_unsigned()) {
uint64_t value = field_value.get<uint64_t>();
auto result = msg.set(field_name, value);
if (result != ::mav::MessageResult::Success) {
LogWarn("Failed to set integer field {} = {}", field_name, value);
LogWarn("Failed to set unsigned integer field {} = {}", field_name, value);
}
} else if (field_value.isUInt() || field_value.isUInt64()) {
uint64_t value = field_value.asUInt64();
} else if (field_value.is_number_integer()) {
int64_t value = field_value.get<int64_t>();
auto result = msg.set(field_name, value);
if (result != ::mav::MessageResult::Success) {
LogWarn("Failed to set unsigned integer field {} = {}", field_name, value);
LogWarn("Failed to set integer field {} = {}", field_name, value);
}
} else if (field_value.isNull() || field_value.isDouble()) {
} else if (field_value.is_null() || field_value.is_number_float()) {
// Handle float/double values (including null -> NaN)
auto field_opt = msg.type().getField(field_name);
if (!field_opt) {
Expand All @@ -51,16 +51,16 @@ bool json_to_libmav_message(const std::string& json_string, mav::Message& msg)
::mav::MessageResult result = ::mav::MessageResult::FieldNotFound;

if (field.type.base_type == ::mav::FieldType::BaseType::FLOAT) {
if (field_value.isNull()) {
if (field_value.is_null()) {
result = msg.set(field_name, std::numeric_limits<float>::quiet_NaN());
} else {
result = msg.set(field_name, static_cast<float>(field_value.asFloat()));
result = msg.set(field_name, field_value.get<float>());
}
} else if (field.type.base_type == ::mav::FieldType::BaseType::DOUBLE) {
if (field_value.isNull()) {
if (field_value.is_null()) {
result = msg.set(field_name, std::numeric_limits<double>::quiet_NaN());
} else {
result = msg.set(field_name, field_value.asDouble());
result = msg.set(field_name, field_value.get<double>());
}
} else {
LogWarn("Field {} is not a float or double field", field_name);
Expand All @@ -71,14 +71,15 @@ bool json_to_libmav_message(const std::string& json_string, mav::Message& msg)
LogWarn(
"Failed to set float/double field {} = {}",
field_name,
(field_value.isNull() ? "null" : std::to_string(field_value.asDouble())));
(field_value.is_null() ? "null" : std::to_string(field_value.get<double>())));
}
} else if (field_value.isString()) {
auto result = msg.setString(field_name, field_value.asString());
} else if (field_value.is_string()) {
auto value = field_value.get<std::string>();
auto result = msg.setString(field_name, value);
if (result != ::mav::MessageResult::Success) {
LogWarn("Failed to set string field {} = {}", field_name, field_value.asString());
LogWarn("Failed to set string field {} = {}", field_name, value);
}
} else if (field_value.isArray()) {
} else if (field_value.is_array()) {
// Handle array fields with proper type detection
auto array_size = field_value.size();

Expand All @@ -101,91 +102,89 @@ bool json_to_libmav_message(const std::string& json_string, mav::Message& msg)
case ::mav::FieldType::BaseType::UINT8: {
std::vector<uint8_t> vec;
vec.reserve(array_size);
for (Json::ArrayIndex i = 0; i < array_size; ++i) {
const auto& elem = field_value[i];
vec.push_back(elem.isNumeric() ? static_cast<uint8_t>(elem.asUInt()) : 0);
for (const auto& elem : field_value) {
vec.push_back(
elem.is_number() ? static_cast<uint8_t>(elem.get<uint64_t>()) : 0);
}
result = msg.set(field_name, vec);
break;
}
case ::mav::FieldType::BaseType::UINT16: {
std::vector<uint16_t> vec;
vec.reserve(array_size);
for (Json::ArrayIndex i = 0; i < array_size; ++i) {
const auto& elem = field_value[i];
vec.push_back(elem.isNumeric() ? static_cast<uint16_t>(elem.asUInt()) : 0);
for (const auto& elem : field_value) {
vec.push_back(
elem.is_number() ? static_cast<uint16_t>(elem.get<uint64_t>()) : 0);
}
result = msg.set(field_name, vec);
break;
}
case ::mav::FieldType::BaseType::UINT32: {
std::vector<uint32_t> vec;
vec.reserve(array_size);
for (Json::ArrayIndex i = 0; i < array_size; ++i) {
const auto& elem = field_value[i];
vec.push_back(elem.isNumeric() ? static_cast<uint32_t>(elem.asUInt()) : 0);
for (const auto& elem : field_value) {
vec.push_back(
elem.is_number() ? static_cast<uint32_t>(elem.get<uint64_t>()) : 0);
}
result = msg.set(field_name, vec);
break;
}
case ::mav::FieldType::BaseType::UINT64: {
std::vector<uint64_t> vec;
vec.reserve(array_size);
for (Json::ArrayIndex i = 0; i < array_size; ++i) {
const auto& elem = field_value[i];
for (const auto& elem : field_value) {
vec.push_back(
elem.isNumeric() ? static_cast<uint64_t>(elem.asUInt64()) : 0);
elem.is_number() ? static_cast<uint64_t>(elem.get<uint64_t>()) : 0);
}
result = msg.set(field_name, vec);
break;
}
case ::mav::FieldType::BaseType::INT8: {
std::vector<int8_t> vec;
vec.reserve(array_size);
for (Json::ArrayIndex i = 0; i < array_size; ++i) {
const auto& elem = field_value[i];
vec.push_back(elem.isNumeric() ? static_cast<int8_t>(elem.asInt()) : 0);
for (const auto& elem : field_value) {
vec.push_back(
elem.is_number() ? static_cast<int8_t>(elem.get<int64_t>()) : 0);
}
result = msg.set(field_name, vec);
break;
}
case ::mav::FieldType::BaseType::INT16: {
std::vector<int16_t> vec;
vec.reserve(array_size);
for (Json::ArrayIndex i = 0; i < array_size; ++i) {
const auto& elem = field_value[i];
vec.push_back(elem.isNumeric() ? static_cast<int16_t>(elem.asInt()) : 0);
for (const auto& elem : field_value) {
vec.push_back(
elem.is_number() ? static_cast<int16_t>(elem.get<int64_t>()) : 0);
}
result = msg.set(field_name, vec);
break;
}
case ::mav::FieldType::BaseType::INT32: {
std::vector<int32_t> vec;
vec.reserve(array_size);
for (Json::ArrayIndex i = 0; i < array_size; ++i) {
const auto& elem = field_value[i];
vec.push_back(elem.isNumeric() ? static_cast<int32_t>(elem.asInt()) : 0);
for (const auto& elem : field_value) {
vec.push_back(
elem.is_number() ? static_cast<int32_t>(elem.get<int64_t>()) : 0);
}
result = msg.set(field_name, vec);
break;
}
case ::mav::FieldType::BaseType::INT64: {
std::vector<int64_t> vec;
vec.reserve(array_size);
for (Json::ArrayIndex i = 0; i < array_size; ++i) {
const auto& elem = field_value[i];
vec.push_back(elem.isNumeric() ? static_cast<int64_t>(elem.asInt64()) : 0);
for (const auto& elem : field_value) {
vec.push_back(
elem.is_number() ? static_cast<int64_t>(elem.get<int64_t>()) : 0);
}
result = msg.set(field_name, vec);
break;
}
case ::mav::FieldType::BaseType::FLOAT: {
std::vector<float> vec;
vec.reserve(array_size);
for (Json::ArrayIndex i = 0; i < array_size; ++i) {
const auto& elem = field_value[i];
if (elem.isNumeric()) {
vec.push_back(static_cast<float>(elem.asFloat()));
for (const auto& elem : field_value) {
if (elem.is_number()) {
vec.push_back(elem.get<float>());
} else {
// For non-numeric values (including null), use NaN
vec.push_back(std::numeric_limits<float>::quiet_NaN());
Expand All @@ -197,10 +196,9 @@ bool json_to_libmav_message(const std::string& json_string, mav::Message& msg)
case ::mav::FieldType::BaseType::DOUBLE: {
std::vector<double> vec;
vec.reserve(array_size);
for (Json::ArrayIndex i = 0; i < array_size; ++i) {
const auto& elem = field_value[i];
if (elem.isNumeric()) {
vec.push_back(elem.asDouble());
for (const auto& elem : field_value) {
if (elem.is_number()) {
vec.push_back(elem.get<double>());
} else {
// For non-numeric values (including null), use NaN
vec.push_back(std::numeric_limits<double>::quiet_NaN());
Expand All @@ -212,9 +210,9 @@ bool json_to_libmav_message(const std::string& json_string, mav::Message& msg)
case ::mav::FieldType::BaseType::CHAR: {
std::vector<char> vec;
vec.reserve(array_size);
for (Json::ArrayIndex i = 0; i < array_size; ++i) {
const auto& elem = field_value[i];
vec.push_back(elem.isNumeric() ? static_cast<char>(elem.asInt()) : 0);
for (const auto& elem : field_value) {
vec.push_back(
elem.is_number() ? static_cast<char>(elem.get<int64_t>()) : 0);
}
result = msg.set(field_name, vec);
break;
Expand Down
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