Read Access Violation in ouster::sensor::parse_config

[Misamag]

Description

When calling

ouster::sensor::sensor_config config;
if (!ouster::sensor::get_config(hostname, config))
...

from my application, I get a read access violation in

static sensor_config parse_config(const Json::Value& root) {
    sensor_config config{};

    if (!root["udp_dest"].empty()) {
        config.udp_dest = root["udp_dest"].asString();

The config read in client.cpp:285 auto res = sensor_http->get_config_params(active) is a valid JSON string.

It looks like the parsing in types.cpp:659 if (!Json::parseFromStream(builder, ss, &root, &errors)) { results in an invalid root. The ss argument contains the JSON string but root or root["udp_dest"], after this call, just contain garbage.

Platform

• OS2
• Ouster Firmware Version? 2.5.2
• Programming Language? C++
• Operating System? Windows 10 22H2
• Machine Architecture? x64
• git commit hash 9d0971107f6f9c95e16afd727fa2534d01a0fe4e

Note

• I upgraded from an older version of the API and followed up the docs here: https://static.ouster.dev/sdk-docs/cpp/building.html
• Application using API is compiled for c++20 using VS build tools for 2019 from within VS 2022.
• Using Qt libs 5.4 as well.
• Using mtp_client_example, it all works.

[twslankard]

Thanks for the detailed report, @Misamag.

There may be an issue with how ouster-sdk is interacting with JsonCpp here.

If possible, could you provide

1. the contents of the JSON string you obtained when this issue occurred,
2. the version of JsonCpp you're using,
3. whether you're building a Debug build or Release build

Best Regards,

Tom Staff Engineer Ouster Inc.

[Misamag]

@twslankard,

this is the JSON string:

{"phase_lock_offset": 0, "udp_profile_lidar": "LEGACY", "nmea_baud_rate": "BAUD_9600", "udp_port_imu": 53510, "udp_dest": "239.83.104.101", "sync_pulse_out_angle": 360, "nmea_leap_seconds": 0, "sync_pulse_out_polarity": "ACTIVE_HIGH", "udp_port_lidar": 53509, "lidar_mode": "2048x10", "timestamp_mode": "TIME_FROM_INTERNAL_OSC", "sync_pulse_out_pulse_width": 0, "signal_multiplier": 3, "operating_mode": "NORMAL", "sync_pulse_out_frequency": 1, "sync_pulse_in_polarity": "ACTIVE_HIGH", "phase_lock_enable": false, "multipurpose_io_mode": "OFF", "nmea_in_polarity": "ACTIVE_HIGH", "azimuth_window": [300000, 50000], "udp_profile_imu": "LEGACY", "nmea_ignore_valid_char": 0, "columns_per_packet": 16}

JsonCpp: 1.9.5

Issue persiststs in Debug build. In Release build, it parses correctly.

Thanks, Marvin

[Misamag]

I have just noticed something: when I switch the language version in the cmake file from 14 to 17, I do not get any errors. The following is just a guess as I have not made much of reverse-engineering:

• My calling application (which is C++17) is using the sensor_config and interprets the optional values as std::optional
• The lib, as compiled with C++14 support uses nonstd::optional during build
• no binary compatibility between those types => corruption

[Samahu]

@Misamag this is the same issue as #483 and yes it happens when the nonstd::optional is compiled with different cxx standards. The fix to this problem lies within the application embedding ouster client. You just need to make sure the cxx standard is set before ouster client is included.

[Misamag]

@Samahu thanks, I see. It would be handy to have such information available in the starting guide at https://static.ouster.dev/sdk-docs/cpp/building.html. Like the required C++ version, mandatory defines (like EIGEN_MAX_ALIGN_BYTES=32) an so on.