Configuration

This page covers C++ runtime configuration. Fory::builder() creates xlang payloads by default, and omitted compatible mode resolves to compatible mode in xlang. Native mode is selected explicitly with .xlang(false) and defaults to schema-consistent payloads.

Builder Pattern

Use Fory::builder() to construct Fory instances with custom configuration:

#include "fory/serialization/fory.h"

using namespace fory::serialization;

// Xlang mode with compatible schema evolution.
auto fory = Fory::builder().xlang(true).build();

// Schema-consistent xlang payloads.
auto fory = Fory::builder()
    .xlang(true)
    .compatible(false)
    .build();

// Native mode for C++-only traffic.
auto fory = Fory::builder()
    .xlang(false)
    .build();

// Native mode with compatible schema evolution.
auto fory = Fory::builder()
    .xlang(false)
    .track_ref(true)
    .max_dyn_depth(10)
    .compatible(true)
    .build();

Configuration

xlang(bool)

Select the wire mode.

auto fory = Fory::builder()
    .xlang(false)
    .build();

When true, C++ writes the xlang wire format used by Java, Python, Go, Rust, JavaScript, C#, Swift, and Dart. When false, C++ writes native-mode payloads for C++-only traffic.

Default: true

compatible(bool)

Enable compatible schema evolution.

auto fory = Fory::builder()
    .xlang(true)
    .compatible(true)
    .build();

When enabled, supports reading data serialized with different schema versions. When omitted, xlang mode defaults to compatible mode. Native mode defaults to schema-consistent mode and uses compatible mode only when this option is set.

Default: true in xlang mode; false in native mode

track_ref(bool)

Enable/disable reference tracking for shared and circular references.

auto fory = Fory::builder()
    .xlang(true)
    .track_ref(true)  // Enable reference tracking
    .build();

When enabled, avoids duplicating shared objects and handles cycles.

Default: true

max_dyn_depth(uint32_t)

Set maximum allowed nesting depth for dynamically-typed objects.

auto fory = Fory::builder()
    .xlang(true)
    .max_dyn_depth(10)  // Allow up to 10 levels
    .build();

This limits the maximum depth for nested polymorphic object serialization (e.g., shared_ptr<Base>, unique_ptr<Base>). This prevents stack overflow from deeply nested structures in dynamic serialization scenarios.

Default: 5

When to adjust:

• Increase: For legitimate deeply nested data structures
• Decrease: For stricter security requirements or shallow data structures

check_struct_version(bool)

Enable/disable struct version checking.

auto fory = Fory::builder()
    .xlang(true)
    .compatible(false)
    .check_struct_version(true)  // Enable version checking
    .build();

When enabled, validates type hashes to detect schema mismatches.

Default: false

Thread-Safe vs Single-Threaded

Single-Threaded (Fastest)

auto fory = Fory::builder().xlang(true).build();  // Returns Fory

Single-threaded Fory is the fastest option, but NOT thread-safe. Use one instance per thread.

Thread-Safe

auto fory = Fory::builder().xlang(true).build_thread_safe();  // Returns ThreadSafeFory

ThreadSafeFory uses a pool of Fory instances to provide thread-safe serialization. Slightly slower due to pool overhead, but safe to use from multiple threads concurrently.

Configuration Summary

Option	Description	Default
xlang(bool)	Use xlang mode	true
compatible(bool)	Enable schema evolution	xlang: true; native: false
track_ref(bool)	Enable reference tracking	true
max_dyn_depth(uint32_t)	Maximum nesting depth for dynamic types	5
check_struct_version(bool)	Enable struct version checking	false

Security

Security-related configuration:

• Register all structs and polymorphic implementations before deserializing untrusted payloads.
• Use check_struct_version(true) with compatible(false) when exact schema matching is required.
• Keep max_dyn_depth(...) as low as your model permits to reject unexpectedly deep polymorphic graphs.
• Prefer concrete fields over broad polymorphic fields for untrusted input.

Related Topics

• Basic Serialization - Using configured Fory
• Xlang Serialization - xlang mode details
• Type Registration - Registering types