Configuration

This page covers C++ Fory instance configuration. Fory::builder() creates xlang payloads by default. Compatible mode is also enabled by default. Select native mode only when the payload stays in C++.

Builder Pattern

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

#include "fory/serialization/fory.h"

using namespace fory::serialization;

// Default xlang mode.
auto fory = Fory::builder().build();

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

// Same-schema optimization. Use only when every reader and writer
// always uses the same schema.
auto fory = Fory::builder()
    .compatible(false)
    .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/TypeScript, C#, Swift, Dart, Scala, and Kotlin. When false, C++ writes native-mode payloads for C++-only traffic.

Default: true

compatible(bool)

Compatible mode is enabled by default. No builder call is required for the default compatible mode. Set .compatible(false) only when every reader and writer always uses the same schema and you want faster serialization and smaller size.

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

For xlang payloads, use .compatible(false) only after verifying that every language uses the same schema, or when native types are generated from Fory schema IDL.

Default: true

track_ref(bool)

Enable/disable reference tracking for shared and circular references.

auto fory = Fory::builder()
    .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()
    .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

max_schema_versions_per_type(uint32_t)

Set the maximum accepted remote metadata versions for one logical type.

auto fory = Fory::builder()
    .max_schema_versions_per_type(10)
    .build();

Default: 10

max_type_fields(uint32_t)

Set the maximum fields accepted in one received remote struct metadata body.

auto fory = Fory::builder()
    .max_type_fields(512)
    .build();

Default: 512

max_type_meta_bytes(uint32_t)

Set the maximum encoded body bytes accepted for one received TypeDef body, excluding the 8-byte header and any extended-size varint.

auto fory = Fory::builder()
    .max_type_meta_bytes(4096)
    .build();

Default: 4096

max_average_schema_versions_per_type(uint32_t)

Set the average accepted remote metadata versions across accepted remote types. The effective global floor is 8192 schemas.

auto fory = Fory::builder()
    .max_average_schema_versions_per_type(3)
    .build();

Default: 3

check_struct_version(bool)

Enable/disable struct version checking.

auto fory = Fory::builder()
    .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().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().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	true
track_ref(bool)	Enable reference tracking	true
max_dyn_depth(uint32_t)	Maximum nesting depth for dynamic types	5
max_type_fields(uint32_t)	Max fields in one received struct metadata body	512
max_type_meta_bytes(uint32_t)	Max encoded bytes in one received metadata body	4096
max_schema_versions_per_type(uint32_t)	Max remote metadata versions for one logical type	10
max_average_schema_versions_per_type(uint32_t)	Average remote metadata versions across types	3
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) for intentional same-schema payloads.
• Keep max_dyn_depth(...) as low as your model permits to reject unexpectedly deep polymorphic graphs.
• Keep the remote schema metadata limits at their defaults unless the data is not malicious and a trusted peer sends larger metadata or many schema versions.
• 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